1
   2
   3
   4
   5
   6
   7
   8
   9
  10
  11
  12
  13
  14
  15
  16
  17
  18
  19
  20
  21
  22
  23
  24
  25
  26
  27
  28
  29
  30
  31
  32
  33
  34
  35
  36
  37
  38
  39
  40
  41
  42
  43
  44
  45
  46
  47
  48
  49
  50
  51
  52
  53
  54
  55
  56
  57
  58
  59
  60
  61
  62
  63
  64
  65
  66
  67
  68
  69
  70
  71
  72
  73
  74
  75
  76
  77
  78
  79
  80
  81
  82
  83
  84
  85
  86
  87
  88
  89
  90
  91
  92
  93
  94
  95
  96
  97
  98
  99
 100
 101
 102
 103
 104
 105
 106
 107
 108
 109
 110
 111
 112
 113
 114
 115
 116
 117
 118
 119
 120
 121
 122
 123
 124
 125
 126
 127
 128
 129
 130
 131
 132
 133
 134
 135
 136
 137
 138
 139
 140
 141
 142
 143
 144
 145
 146
 147
 148
 149
 150
 151
 152
 153
 154
 155
 156
 157
 158
 159
 160
 161
 162
 163
 164
 165
 166
 167
 168
 169
 170
 171
 172
 173
 174
 175
 176
 177
 178
 179
 180
 181
 182
 183
 184
 185
 186
 187
 188
 189
 190
 191
 192
 193
 194
 195
 196
 197
 198
 199
 200
 201
 202
 203
 204
 205
 206
 207
 208
 209
 210
 211
 212
 213
 214
 215
 216
 217
 218
 219
 220
 221
 222
 223
 224
 225
 226
 227
 228
 229
 230
 231
 232
 233
 234
 235
 236
 237
 238
 239
 240
 241
 242
 243
 244
 245
 246
 247
 248
 249
 250
 251
 252
 253
 254
 255
 256
 257
 258
 259
 260
 261
 262
 263
 264
 265
 266
 267
 268
 269
 270
 271
 272
 273
 274
 275
 276
 277
 278
 279
 280
 281
 282
 283
 284
 285
 286
 287
 288
 289
 290
 291
 292
 293
 294
 295
 296
 297
 298
 299
 300
 301
 302
 303
 304
 305
 306
 307
 308
 309
 310
 311
 312
 313
 314
 315
 316
 317
 318
 319
 320
 321
 322
 323
 324
 325
 326
 327
 328
 329
 330
 331
 332
 333
 334
 335
 336
 337
 338
 339
 340
 341
 342
 343
 344
 345
 346
 347
 348
 349
 350
 351
 352
 353
 354
 355
 356
 357
 358
 359
 360
 361
 362
 363
 364
 365
 366
 367
 368
 369
 370
 371
 372
 373
 374
 375
 376
 377
 378
 379
 380
 381
 382
 383
 384
 385
 386
 387
 388
 389
 390
 391
 392
 393
 394
 395
 396
 397
 398
 399
 400
 401
 402
 403
 404
 405
 406
 407
 408
 409
 410
 411
 412
 413
 414
 415
 416
 417
 418
 419
 420
 421
 422
 423
 424
 425
 426
 427
 428
 429
 430
 431
 432
 433
 434
 435
 436
 437
 438
 439
 440
 441
 442
 443
 444
 445
 446
 447
 448
 449
 450
 451
 452
 453
 454
 455
 456
 457
 458
 459
 460
 461
 462
 463
 464
 465
 466
 467
 468
 469
 470
 471
 472
 473
 474
 475
 476
 477
 478
 479
 480
 481
 482
 483
 484
 485
 486
 487
 488
 489
 490
 491
 492
 493
 494
 495
 496
 497
 498
 499
 500
 501
 502
 503
 504
 505
 506
 507
 508
 509
 510
 511
 512
 513
 514
 515
 516
 517
 518
 519
 520
 521
 522
 523
 524
 525
 526
 527
 528
 529
 530
 531
 532
 533
 534
 535
 536
 537
 538
 539
 540
 541
 542
 543
 544
 545
 546
 547
 548
 549
 550
 551
 552
 553
 554
 555
 556
 557
 558
 559
 560
 561
 562
 563
 564
 565
 566
 567
 568
 569
 570
 571
 572
 573
 574
 575
 576
 577
 578
 579
 580
 581
 582
 583
 584
 585
 586
 587
 588
 589
 590
 591
 592
 593
 594
 595
 596
 597
 598
 599
 600
 601
 602
 603
 604
 605
 606
 607
 608
 609
 610
 611
 612
 613
 614
 615
 616
 617
 618
 619
 620
 621
 622
 623
 624
 625
 626
 627
 628
 629
 630
 631
 632
 633
 634
 635
 636
 637
 638
 639
 640
 641
 642
 643
 644
 645
 646
 647
 648
 649
 650
 651
 652
 653
 654
 655
 656
 657
 658
 659
 660
 661
 662
 663
 664
 665
 666
 667
 668
 669
 670
 671
 672
 673
 674
 675
 676
 677
 678
 679
 680
 681
 682
 683
 684
 685
 686
 687
 688
 689
 690
 691
 692
 693
 694
 695
 696
 697
 698
 699
 700
 701
 702
 703
 704
 705
 706
 707
 708
 709
 710
 711
 712
 713
 714
 715
 716
 717
 718
 719
 720
 721
 722
 723
 724
 725
 726
 727
 728
 729
 730
 731
 732
 733
 734
 735
 736
 737
 738
 739
 740
 741
 742
 743
 744
 745
 746
 747
 748
 749
 750
 751
 752
 753
 754
 755
 756
 757
 758
 759
 760
 761
 762
 763
 764
 765
 766
 767
 768
 769
 770
 771
 772
 773
 774
 775
 776
 777
 778
 779
 780
 781
 782
 783
 784
 785
 786
 787
 788
 789
 790
 791
 792
 793
 794
 795
 796
 797
 798
 799
 800
 801
 802
 803
 804
 805
 806
 807
 808
 809
 810
 811
 812
 813
 814
 815
 816
 817
 818
 819
 820
 821
 822
 823
 824
 825
 826
 827
 828
 829
 830
 831
 832
 833
 834
 835
 836
 837
 838
 839
 840
 841
 842
 843
 844
 845
 846
 847
 848
 849
 850
 851
 852
 853
 854
 855
 856
 857
 858
 859
 860
 861
 862
 863
 864
 865
 866
 867
 868
 869
 870
 871
 872
 873
 874
 875
 876
 877
 878
 879
 880
 881
 882
 883
 884
 885
 886
 887
 888
 889
 890
 891
 892
 893
 894
 895
 896
 897
 898
 899
 900
 901
 902
 903
 904
 905
 906
 907
 908
 909
 910
 911
 912
 913
 914
 915
 916
 917
 918
 919
 920
 921
 922
 923
 924
 925
 926
 927
 928
 929
 930
 931
 932
 933
 934
 935
 936
 937
 938
 939
 940
 941
 942
 943
 944
 945
 946
 947
 948
 949
 950
 951
 952
 953
 954
 955
 956
 957
 958
 959
 960
 961
 962
 963
 964
 965
 966
 967
 968
 969
 970
 971
 972
 973
 974
 975
 976
 977
 978
 979
 980
 981
 982
 983
 984
 985
 986
 987
 988
 989
 990
 991
 992
 993
 994
 995
 996
 997
 998
 999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
# $Id: nodes.py 8592 2020-12-15 23:06:26Z milde $
# Author: David Goodger <goodger@python.org>
# Maintainer: docutils-develop@lists.sourceforge.net
# Copyright: This module has been placed in the public domain.

"""
Docutils document tree element class library.

Classes in CamelCase are abstract base classes or auxiliary classes. The one
exception is `Text`, for a text (PCDATA) node; uppercase is used to
differentiate from element classes.  Classes in lower_case_with_underscores
are element classes, matching the XML element generic identifiers in the DTD_.

The position of each node (the level at which it can occur) is significant and
is represented by abstract base classes (`Root`, `Structural`, `Body`,
`Inline`, etc.).  Certain transformations will be easier because we can use
``isinstance(node, base_class)`` to determine the position of the node in the
hierarchy.

.. _DTD: http://docutils.sourceforge.net/docs/ref/docutils.dtd
"""
from __future__ import print_function
from collections import Counter

__docformat__ = 'reStructuredText'

import sys
import os
import re
import warnings
import unicodedata

if sys.version_info >= (3, 0):
    unicode = str  # noqa
    basestring = str  # noqa

class _traversal_list(list):
    # auxiliary class to report a FutureWarning
    done = False
    def _warning_decorator(fun):
        msg = ("\n   The iterable returned by Node.traverse()"
               "\n   will become an iterator instead of a list in "
               "Docutils > 0.16.")
        def wrapper(self, *args, **kwargs):
            if not self.done:
                warnings.warn(msg, FutureWarning, stacklevel=2)
            self.done = True
            return fun(self, *args, **kwargs)
        return wrapper

    __add__ = _warning_decorator(list.__add__)
    __contains__ = _warning_decorator(list.__contains__)
    __getitem__ = _warning_decorator(list.__getitem__)
    __reversed__ = _warning_decorator(list.__reversed__)
    __setitem__ = _warning_decorator(list.__setitem__)
    append = _warning_decorator(list.append)
    count = _warning_decorator(list.count)
    extend = _warning_decorator(list.extend)
    index = _warning_decorator(list.index)
    insert = _warning_decorator(list.insert)
    pop = _warning_decorator(list.pop)
    reverse = _warning_decorator(list.reverse)


# ==============================
#  Functional Node Base Classes
# ==============================

class Node(object):

    """Abstract base class of nodes in a document tree."""

    parent = None
    """Back-reference to the Node immediately containing this Node."""

    source = None
    """Path or description of the input source which generated this Node."""

    line = None
    """The line number (1-based) of the beginning of this Node in `source`."""

    _document = None

    @property
    def document(self):
        """
        Return the `document` node at the root of the tree containing this Node.
        """
        try:
            return self._document or self.parent.document
        except AttributeError:
            return None

    @document.setter
    def document(self, value):
        self._document = value

    def __bool__(self):
        """
        Node instances are always true, even if they're empty.  A node is more
        than a simple container.  Its boolean "truth" does not depend on
        having one or more subnodes in the doctree.

        Use `len()` to check node length.  Use `None` to represent a boolean
        false value.
        """
        return True

    if sys.version_info < (3, 0):
        __nonzero__ = __bool__

    if sys.version_info < (3, 0):
        # on 2.x, str(node) will be a byte string with Unicode
        # characters > 255 escaped; on 3.x this is no longer necessary
        def __str__(self):
            return unicode(self).encode('raw_unicode_escape')

    def asdom(self, dom=None):
        """Return a DOM **fragment** representation of this Node."""
        if dom is None:
            import xml.dom.minidom as dom
        domroot = dom.Document()
        return self._dom_node(domroot)

    def pformat(self, indent='    ', level=0):
        """
        Return an indented pseudo-XML representation, for test purposes.

        Override in subclasses.
        """
        raise NotImplementedError

    def copy(self):
        """Return a copy of self."""
        raise NotImplementedError

    def deepcopy(self):
        """Return a deep copy of self (also copying children)."""
        raise NotImplementedError

    def astext(self):
        """Return a string representation of this Node."""
        raise NotImplementedError

    def setup_child(self, child):
        child.parent = self
        if self.document:
            child.document = self.document
            if child.source is None:
                child.source = self.document.current_source
            if child.line is None:
                child.line = self.document.current_line

    def walk(self, visitor):
        """
        Traverse a tree of `Node` objects, calling the
        `dispatch_visit()` method of `visitor` when entering each
        node.  (The `walkabout()` method is similar, except it also
        calls the `dispatch_departure()` method before exiting each
        node.)

        This tree traversal supports limited in-place tree
        modifications.  Replacing one node with one or more nodes is
        OK, as is removing an element.  However, if the node removed
        or replaced occurs after the current node, the old node will
        still be traversed, and any new nodes will not.

        Within ``visit`` methods (and ``depart`` methods for
        `walkabout()`), `TreePruningException` subclasses may be raised
        (`SkipChildren`, `SkipSiblings`, `SkipNode`, `SkipDeparture`).

        Parameter `visitor`: A `NodeVisitor` object, containing a
        ``visit`` implementation for each `Node` subclass encountered.

        Return true if we should stop the traversal.
        """
        stop = False
        visitor.document.reporter.debug(
            'docutils.nodes.Node.walk calling dispatch_visit for %s'
            % self.__class__.__name__)
        try:
            try:
                visitor.dispatch_visit(self)
            except (SkipChildren, SkipNode):
                return stop
            except SkipDeparture:           # not applicable; ignore
                pass
            children = self.children
            try:
                for child in children[:]:
                    if child.walk(visitor):
                        stop = True
                        break
            except SkipSiblings:
                pass
        except StopTraversal:
            stop = True
        return stop

    def walkabout(self, visitor):
        """
        Perform a tree traversal similarly to `Node.walk()` (which
        see), except also call the `dispatch_departure()` method
        before exiting each node.

        Parameter `visitor`: A `NodeVisitor` object, containing a
        ``visit`` and ``depart`` implementation for each `Node`
        subclass encountered.

        Return true if we should stop the traversal.
        """
        call_depart = True
        stop = False
        visitor.document.reporter.debug(
            'docutils.nodes.Node.walkabout calling dispatch_visit for %s'
            % self.__class__.__name__)
        try:
            try:
                visitor.dispatch_visit(self)
            except SkipNode:
                return stop
            except SkipDeparture:
                call_depart = False
            children = self.children
            try:
                for child in children[:]:
                    if child.walkabout(visitor):
                        stop = True
                        break
            except SkipSiblings:
                pass
        except SkipChildren:
            pass
        except StopTraversal:
            stop = True
        if call_depart:
            visitor.document.reporter.debug(
                'docutils.nodes.Node.walkabout calling dispatch_departure '
                'for %s' % self.__class__.__name__)
            visitor.dispatch_departure(self)
        return stop

    def _fast_traverse(self, cls):
        """Return iterator that only supports instance checks."""
        if isinstance(self, cls):
            yield self
        for child in self.children:
            for subnode in child._fast_traverse(cls):
                yield subnode

    def _all_traverse(self):
        """Return iterator that doesn't check for a condition."""
        yield self
        for child in self.children:
            for subnode in child._all_traverse():
                yield subnode

    def traverse(self, condition=None, include_self=True, descend=True,
                 siblings=False, ascend=False):
        """
        Return an iterable containing

        * self (if include_self is true)
        * all descendants in tree traversal order (if descend is true)
        * all siblings (if siblings is true) and their descendants (if
          also descend is true)
        * the siblings of the parent (if ascend is true) and their
          descendants (if also descend is true), and so on

        If `condition` is not None, the iterable contains only nodes
        for which ``condition(node)`` is true.  If `condition` is a
        node class ``cls``, it is equivalent to a function consisting
        of ``return isinstance(node, cls)``.

        If ascend is true, assume siblings to be true as well.

        For example, given the following tree::

            <paragraph>
                <emphasis>      <--- emphasis.traverse() and
                    <strong>    <--- strong.traverse() are called.
                        Foo
                    Bar
                <reference name="Baz" refid="baz">
                    Baz

        Then list(emphasis.traverse()) equals ::

            [<emphasis>, <strong>, <#text: Foo>, <#text: Bar>]

        and list(strong.traverse(ascend=True)) equals ::

            [<strong>, <#text: Foo>, <#text: Bar>, <reference>, <#text: Baz>]
        """
        # Although the documented API only promises an "iterable" as return
        # value, the implementation returned a list up to v. 0.15. Some 3rd
        # party code still relies on this (e.g. Sphinx as of 2019-09-07).
        # Therefore, let's return a list until this is sorted out:
        return _traversal_list(self._traverse(condition, include_self,
                                   descend, siblings, ascend))

    def _traverse(self, condition=None, include_self=True, descend=True,
                  siblings=False, ascend=False):
        """Return iterator over nodes following `self`. See `traverse()`."""
        if ascend:
            siblings=True
        # Check for special argument combinations that allow using an
        # optimized version of traverse()
        if include_self and descend and not siblings:
            if condition is None:
                for subnode in self._all_traverse():
                    yield subnode
                return
            elif isinstance(condition, type):
                for subnode in self._fast_traverse(condition):
                    yield subnode
                return
        # Check if `condition` is a class (check for TypeType for Python
        # implementations that use only new-style classes, like PyPy).
        if isinstance(condition, type):
            node_class = condition
            def condition(node, node_class=node_class):
                return isinstance(node, node_class)


        if include_self and (condition is None or condition(self)):
            yield self
        if descend and len(self.children):
            for child in self:
                for subnode in child._traverse(condition=condition,
                                    include_self=True, descend=True,
                                    siblings=False, ascend=False):
                    yield subnode
        if siblings or ascend:
            node = self
            while node.parent:
                index = node.parent.index(node)
                for sibling in node.parent[index+1:]:
                    for subnode in sibling._traverse(condition=condition,
                                        include_self=True, descend=descend,
                                        siblings=False, ascend=False):
                        yield subnode
                if not ascend:
                    break
                else:
                    node = node.parent

    def next_node(self, condition=None, include_self=False, descend=True,
                  siblings=False, ascend=False):
        """
        Return the first node in the iterable returned by traverse(),
        or None if the iterable is empty.

        Parameter list is the same as of traverse.  Note that
        include_self defaults to False, though.
        """
        node_iterator = self._traverse(condition, include_self,
                                      descend, siblings, ascend)
        try:
            return next(node_iterator)
        except StopIteration:
            return None

if sys.version_info < (3, 0):
    class reprunicode(unicode):
        """
        A unicode sub-class that removes the initial u from unicode's repr.
        """

        def __repr__(self):
            return unicode.__repr__(self)[1:]
else:
    reprunicode = unicode


def ensure_str(s):
    """
    Failsave conversion of `unicode` to `str`.
    """
    if sys.version_info < (3, 0) and isinstance(s, unicode):
        return s.encode('ascii', 'backslashreplace')
    return s

# definition moved here from `utils` to avoid circular import dependency
def unescape(text, restore_backslashes=False, respect_whitespace=False):
    """
    Return a string with nulls removed or restored to backslashes.
    Backslash-escaped spaces are also removed.
    """
    # `respect_whitespace` is ignored (since introduction 2016-12-16)
    if restore_backslashes:
        return text.replace('\x00', '\\')
    else:
        for sep in ['\x00 ', '\x00\n', '\x00']:
            text = ''.join(text.split(sep))
        return text


class Text(Node, reprunicode):

    """
    Instances are terminal nodes (leaves) containing text only; no child
    nodes or attributes.  Initialize by passing a string to the constructor.
    Access the text itself with the `astext` method.
    """

    tagname = '#text'

    children = ()
    """Text nodes have no children, and cannot have children."""

    if sys.version_info > (3, 0):
        def __new__(cls, data, rawsource=None):
            """Prevent the rawsource argument from propagating to str."""
            if isinstance(data, bytes):
                raise TypeError('expecting str data, not bytes')
            return reprunicode.__new__(cls, data)
    else:
        def __new__(cls, data, rawsource=None):
            """Prevent the rawsource argument from propagating to str."""
            return reprunicode.__new__(cls, data)

    def __init__(self, data, rawsource=''):
        self.rawsource = rawsource
        """The raw text from which this element was constructed."""

    def shortrepr(self, maxlen=18):
        data = self
        if len(data) > maxlen:
            data = data[:maxlen-4] + ' ...'
        return '<%s: %r>' % (self.tagname, reprunicode(data))

    def __repr__(self):
        return self.shortrepr(maxlen=68)

    def _dom_node(self, domroot):
        return domroot.createTextNode(unicode(self))

    def astext(self):
        return reprunicode(unescape(self))

    # Note about __unicode__: The implementation of __unicode__ here,
    # and the one raising NotImplemented in the superclass Node had
    # to be removed when changing Text to a subclass of unicode instead
    # of UserString, since there is no way to delegate the __unicode__
    # call to the superclass unicode:
    # unicode itself does not have __unicode__ method to delegate to
    # and calling unicode(self) or unicode.__new__ directly creates
    # an infinite loop

    def copy(self):
        return self.__class__(reprunicode(self), rawsource=self.rawsource)

    def deepcopy(self):
        return self.copy()

    def pformat(self, indent='    ', level=0):
        try:
            if self.document.settings.detailled:
                lines = ['%s%s' % (indent * level, '<#text>')
                        ] + [indent*(level+1) + repr(line)
                             for line in self.splitlines(keepends=True)]
                return '\n'.join(lines) + '\n'
        except AttributeError:
            pass
        indent = indent * level
        lines = [indent+line for line in self.astext().splitlines()]
        if not lines:
            return ''
        return '\n'.join(lines) + '\n'

    # rstrip and lstrip are used by substitution definitions where
    # they are expected to return a Text instance, this was formerly
    # taken care of by UserString.

    def rstrip(self, chars=None):
        return self.__class__(reprunicode.rstrip(self, chars), self.rawsource)

    def lstrip(self, chars=None):
        return self.__class__(reprunicode.lstrip(self, chars), self.rawsource)

class Element(Node):

    """
    `Element` is the superclass to all specific elements.

    Elements contain attributes and child nodes.  Elements emulate
    dictionaries for attributes, indexing by attribute name (a string).  To
    set the attribute 'att' to 'value', do::

        element['att'] = 'value'

    There are two special attributes: 'ids' and 'names'.  Both are
    lists of unique identifiers, and names serve as human interfaces
    to IDs.  Names are case- and whitespace-normalized (see the
    fully_normalize_name() function), and IDs conform to the regular
    expression ``[a-z](-?[a-z0-9]+)*`` (see the make_id() function).

    Elements also emulate lists for child nodes (element nodes and/or text
    nodes), indexing by integer.  To get the first child node, use::

        element[0]

    Elements may be constructed using the ``+=`` operator.  To add one new
    child node to element, do::

        element += node

    This is equivalent to ``element.append(node)``.

    To add a list of multiple child nodes at once, use the same ``+=``
    operator::

        element += [node1, node2]

    This is equivalent to ``element.extend([node1, node2])``.
    """

    basic_attributes = ('ids', 'classes', 'names', 'dupnames')
    """List attributes which are defined for every Element-derived class
    instance and can be safely transferred to a different node."""

    local_attributes = ('backrefs',)
    """A list of class-specific attributes that should not be copied with the
    standard attributes when replacing a node.

    NOTE: Derived classes should override this value to prevent any of its
    attributes being copied by adding to the value in its parent class."""

    list_attributes = basic_attributes + local_attributes
    """List attributes, automatically initialized to empty lists for
    all nodes."""

    known_attributes = list_attributes + ('source', 'rawsource')
    """List attributes that are known to the Element base class."""

    tagname = None
    """The element generic identifier. If None, it is set as an instance
    attribute to the name of the class."""

    child_text_separator = '\n\n'
    """Separator for child nodes, used by `astext()` method."""

    def __init__(self, rawsource='', *children, **attributes):
        self.rawsource = rawsource
        """The raw text from which this element was constructed.

        NOTE: some elements do not set this value (default '').
        """

        self.children = []
        """List of child nodes (elements and/or `Text`)."""

        self.extend(children)           # maintain parent info

        self.attributes = {}
        """Dictionary of attribute {name: value}."""

        # Initialize list attributes.
        for att in self.list_attributes:
            self.attributes[att] = []

        for att, value in attributes.items():
            att = att.lower()
            if att in self.list_attributes:
                # mutable list; make a copy for this node
                self.attributes[att] = value[:]
            else:
                self.attributes[att] = value

        if self.tagname is None:
            self.tagname = self.__class__.__name__

    def _dom_node(self, domroot):
        element = domroot.createElement(self.tagname)
        for attribute, value in self.attlist():
            if isinstance(value, list):
                value = ' '.join([serial_escape('%s' % (v,)) for v in value])
            element.setAttribute(attribute, '%s' % value)
        for child in self.children:
            element.appendChild(child._dom_node(domroot))
        return element

    def __repr__(self):
        data = ''
        for c in self.children:
            data += c.shortrepr()
            if len(data) > 60:
                data = data[:56] + ' ...'
                break
        if self['names']:
            return '<%s "%s": %s>' % (self.__class__.__name__,
                '; '.join([ensure_str(n) for n in self['names']]), data)
        else:
            return '<%s: %s>' % (self.__class__.__name__, data)

    def shortrepr(self):
        if self['names']:
            return '<%s "%s"...>' % (self.__class__.__name__,
                '; '.join([ensure_str(n) for n in self['names']]))
        else:
            return '<%s...>' % self.tagname

    def __unicode__(self):
        if self.children:
            return u'%s%s%s' % (self.starttag(),
                                ''.join([unicode(c) for c in self.children]),
                                self.endtag())
        else:
            return self.emptytag()

    if sys.version_info >= (3, 0):
        __str__ = __unicode__

    def starttag(self, quoteattr=None):
        # the optional arg is used by the docutils_xml writer
        if quoteattr is None:
            quoteattr = pseudo_quoteattr
        parts = [self.tagname]
        for name, value in self.attlist():
            if value is None:           # boolean attribute
                parts.append('%s="True"' % name)
                continue
            if isinstance(value, list):
                values = [serial_escape('%s' % (v,)) for v in value]
                value = ' '.join(values)
            else:
                value = unicode(value)
            value = quoteattr(value)
            parts.append(u'%s=%s' % (name, value))
        return u'<%s>' % u' '.join(parts)

    def endtag(self):
        return '</%s>' % self.tagname

    def emptytag(self):
        return u'<%s/>' % u' '.join([self.tagname] +
                                    ['%s="%s"' % (n, v)
                                     for n, v in self.attlist()])

    def __len__(self):
        return len(self.children)

    def __contains__(self, key):
        # Test for both, children and attributes with operator ``in``.
        if isinstance(key, basestring):
            return key in self.attributes
        return key in self.children

    def __getitem__(self, key):
        if isinstance(key, basestring):
            return self.attributes[key]
        elif isinstance(key, int):
            return self.children[key]
        elif isinstance(key, slice):
            assert key.step in (None, 1), 'cannot handle slice with stride'
            return self.children[key.start:key.stop]
        else:
            raise TypeError('element index must be an integer, a slice, or '
                            'an attribute name string')

    def __setitem__(self, key, item):
        if isinstance(key, basestring):
            self.attributes[str(key)] = item
        elif isinstance(key, int):
            self.setup_child(item)
            self.children[key] = item
        elif isinstance(key, slice):
            assert key.step in (None, 1), 'cannot handle slice with stride'
            for node in item:
                self.setup_child(node)
            self.children[key.start:key.stop] = item
        else:
            raise TypeError('element index must be an integer, a slice, or '
                            'an attribute name string')

    def __delitem__(self, key):
        if isinstance(key, basestring):
            del self.attributes[key]
        elif isinstance(key, int):
            del self.children[key]
        elif isinstance(key, slice):
            assert key.step in (None, 1), 'cannot handle slice with stride'
            del self.children[key.start:key.stop]
        else:
            raise TypeError('element index must be an integer, a simple '
                            'slice, or an attribute name string')

    def __add__(self, other):
        return self.children + other

    def __radd__(self, other):
        return other + self.children

    def __iadd__(self, other):
        """Append a node or a list of nodes to `self.children`."""
        if isinstance(other, Node):
            self.append(other)
        elif other is not None:
            self.extend(other)
        return self

    def astext(self):
        return self.child_text_separator.join(
              [child.astext() for child in self.children])

    def non_default_attributes(self):
        atts = {}
        for key, value in self.attributes.items():
            if self.is_not_default(key):
                atts[key] = value
        return atts

    def attlist(self):
        attlist = sorted(self.non_default_attributes().items())
        return attlist

    def get(self, key, failobj=None):
        return self.attributes.get(key, failobj)

    def hasattr(self, attr):
        return attr in self.attributes

    def delattr(self, attr):
        if attr in self.attributes:
            del self.attributes[attr]

    def setdefault(self, key, failobj=None):
        return self.attributes.setdefault(key, failobj)

    has_key = hasattr

    def get_language_code(self, fallback=''):
        """Return node's language tag.

        Look iteratively in self and parents for a class argument
        starting with ``language-`` and return the remainder of it
        (which should be a `BCP49` language tag) or the `fallback`.
        """
        for cls in self.get('classes', []):
            if cls.startswith('language-'):
                return cls[9:]
        try:
            return self.parent.get_language(fallback)
        except AttributeError:
            return fallback

    def append(self, item):
        self.setup_child(item)
        self.children.append(item)

    def extend(self, item):
        for node in item:
            self.append(node)

    def insert(self, index, item):
        if isinstance(item, Node):
            self.setup_child(item)
            self.children.insert(index, item)
        elif item is not None:
            self[index:index] = item

    def pop(self, i=-1):
        return self.children.pop(i)

    def remove(self, item):
        self.children.remove(item)

    def index(self, item):
        return self.children.index(item)

    def is_not_default(self, key):
        if self[key] == [] and key in self.list_attributes:
            return 0
        else:
            return 1

    def update_basic_atts(self, dict_):
        """
        Update basic attributes ('ids', 'names', 'classes',
        'dupnames', but not 'source') from node or dictionary `dict_`.
        """
        if isinstance(dict_, Node):
            dict_ = dict_.attributes
        for att in self.basic_attributes:
            self.append_attr_list(att, dict_.get(att, []))

    def append_attr_list(self, attr, values):
        """
        For each element in values, if it does not exist in self[attr], append
        it.

        NOTE: Requires self[attr] and values to be sequence type and the
        former should specifically be a list.
        """
        # List Concatenation
        for value in values:
            if not value in self[attr]:
                self[attr].append(value)

    def coerce_append_attr_list(self, attr, value):
        """
        First, convert both self[attr] and value to a non-string sequence
        type; if either is not already a sequence, convert it to a list of one
        element.  Then call append_attr_list.

        NOTE: self[attr] and value both must not be None.
        """
        # List Concatenation
        if not isinstance(self.get(attr), list):
            self[attr] = [self[attr]]
        if not isinstance(value, list):
            value = [value]
        self.append_attr_list(attr, value)

    def replace_attr(self, attr, value, force = True):
        """
        If self[attr] does not exist or force is True or omitted, set
        self[attr] to value, otherwise do nothing.
        """
        # One or the other
        if force or self.get(attr) is None:
            self[attr] = value

    def copy_attr_convert(self, attr, value, replace = True):
        """
        If attr is an attribute of self, set self[attr] to
        [self[attr], value], otherwise set self[attr] to value.

        NOTE: replace is not used by this function and is kept only for
              compatibility with the other copy functions.
        """
        if self.get(attr) is not value:
            self.coerce_append_attr_list(attr, value)

    def copy_attr_coerce(self, attr, value, replace):
        """
        If attr is an attribute of self and either self[attr] or value is a
        list, convert all non-sequence values to a sequence of 1 element and
        then concatenate the two sequence, setting the result to self[attr].
        If both self[attr] and value are non-sequences and replace is True or
        self[attr] is None, replace self[attr] with value. Otherwise, do
        nothing.
        """
        if self.get(attr) is not value:
            if isinstance(self.get(attr), list) or \
               isinstance(value, list):
                self.coerce_append_attr_list(attr, value)
            else:
                self.replace_attr(attr, value, replace)

    def copy_attr_concatenate(self, attr, value, replace):
        """
        If attr is an attribute of self and both self[attr] and value are
        lists, concatenate the two sequences, setting the result to
        self[attr].  If either self[attr] or value are non-sequences and
        replace is True or self[attr] is None, replace self[attr] with value.
        Otherwise, do nothing.
        """
        if self.get(attr) is not value:
            if isinstance(self.get(attr), list) and \
               isinstance(value, list):
                self.append_attr_list(attr, value)
            else:
                self.replace_attr(attr, value, replace)

    def copy_attr_consistent(self, attr, value, replace):
        """
        If replace is True or self[attr] is None, replace self[attr] with
        value.  Otherwise, do nothing.
        """
        if self.get(attr) is not value:
            self.replace_attr(attr, value, replace)

    def update_all_atts(self, dict_, update_fun = copy_attr_consistent,
                        replace = True, and_source = False):
        """
        Updates all attributes from node or dictionary `dict_`.

        Appends the basic attributes ('ids', 'names', 'classes',
        'dupnames', but not 'source') and then, for all other attributes in
        dict_, updates the same attribute in self.  When attributes with the
        same identifier appear in both self and dict_, the two values are
        merged based on the value of update_fun.  Generally, when replace is
        True, the values in self are replaced or merged with the values in
        dict_; otherwise, the values in self may be preserved or merged.  When
        and_source is True, the 'source' attribute is included in the copy.

        NOTE: When replace is False, and self contains a 'source' attribute,
              'source' is not replaced even when dict_ has a 'source'
              attribute, though it may still be merged into a list depending
              on the value of update_fun.
        NOTE: It is easier to call the update-specific methods then to pass
              the update_fun method to this function.
        """
        if isinstance(dict_, Node):
            dict_ = dict_.attributes

        # Include the source attribute when copying?
        if and_source:
            filter_fun = self.is_not_list_attribute
        else:
            filter_fun = self.is_not_known_attribute

        # Copy the basic attributes
        self.update_basic_atts(dict_)

        # Grab other attributes in dict_ not in self except the
        # (All basic attributes should be copied already)
        for att in filter(filter_fun, dict_):
            update_fun(self, att, dict_[att], replace)

    def update_all_atts_consistantly(self, dict_, replace = True,
                                     and_source = False):
        """
        Updates all attributes from node or dictionary `dict_`.

        Appends the basic attributes ('ids', 'names', 'classes',
        'dupnames', but not 'source') and then, for all other attributes in
        dict_, updates the same attribute in self.  When attributes with the
        same identifier appear in both self and dict_ and replace is True, the
        values in self are replaced with the values in dict_; otherwise, the
        values in self are preserved.  When and_source is True, the 'source'
        attribute is included in the copy.

        NOTE: When replace is False, and self contains a 'source' attribute,
              'source' is not replaced even when dict_ has a 'source'
              attribute, though it may still be merged into a list depending
              on the value of update_fun.
        """
        self.update_all_atts(dict_, Element.copy_attr_consistent, replace,
                             and_source)

    def update_all_atts_concatenating(self, dict_, replace = True,
                                      and_source = False):
        """
        Updates all attributes from node or dictionary `dict_`.

        Appends the basic attributes ('ids', 'names', 'classes',
        'dupnames', but not 'source') and then, for all other attributes in
        dict_, updates the same attribute in self.  When attributes with the
        same identifier appear in both self and dict_ whose values aren't each
        lists and replace is True, the values in self are replaced with the
        values in dict_; if the values from self and dict_ for the given
        identifier are both of list type, then the two lists are concatenated
        and the result stored in self; otherwise, the values in self are
        preserved.  When and_source is True, the 'source' attribute is
        included in the copy.

        NOTE: When replace is False, and self contains a 'source' attribute,
              'source' is not replaced even when dict_ has a 'source'
              attribute, though it may still be merged into a list depending
              on the value of update_fun.
        """
        self.update_all_atts(dict_, Element.copy_attr_concatenate, replace,
                             and_source)

    def update_all_atts_coercion(self, dict_, replace = True,
                                 and_source = False):
        """
        Updates all attributes from node or dictionary `dict_`.

        Appends the basic attributes ('ids', 'names', 'classes',
        'dupnames', but not 'source') and then, for all other attributes in
        dict_, updates the same attribute in self.  When attributes with the
        same identifier appear in both self and dict_ whose values are both
        not lists and replace is True, the values in self are replaced with
        the values in dict_; if either of the values from self and dict_ for
        the given identifier are of list type, then first any non-lists are
        converted to 1-element lists and then the two lists are concatenated
        and the result stored in self; otherwise, the values in self are
        preserved.  When and_source is True, the 'source' attribute is
        included in the copy.

        NOTE: When replace is False, and self contains a 'source' attribute,
              'source' is not replaced even when dict_ has a 'source'
              attribute, though it may still be merged into a list depending
              on the value of update_fun.
        """
        self.update_all_atts(dict_, Element.copy_attr_coerce, replace,
                             and_source)

    def update_all_atts_convert(self, dict_, and_source = False):
        """
        Updates all attributes from node or dictionary `dict_`.

        Appends the basic attributes ('ids', 'names', 'classes',
        'dupnames', but not 'source') and then, for all other attributes in
        dict_, updates the same attribute in self.  When attributes with the
        same identifier appear in both self and dict_ then first any non-lists
        are converted to 1-element lists and then the two lists are
        concatenated and the result stored in self; otherwise, the values in
        self are preserved.  When and_source is True, the 'source' attribute
        is included in the copy.

        NOTE: When replace is False, and self contains a 'source' attribute,
              'source' is not replaced even when dict_ has a 'source'
              attribute, though it may still be merged into a list depending
              on the value of update_fun.
        """
        self.update_all_atts(dict_, Element.copy_attr_convert,
                             and_source = and_source)

    def clear(self):
        self.children = []

    def replace(self, old, new):
        """Replace one child `Node` with another child or children."""
        index = self.index(old)
        if isinstance(new, Node):
            self.setup_child(new)
            self[index] = new
        elif new is not None:
            self[index:index+1] = new

    def replace_self(self, new):
        """
        Replace `self` node with `new`, where `new` is a node or a
        list of nodes.
        """
        update = new
        if not isinstance(new, Node):
            # `new` is a list; update first child.
            try:
                update = new[0]
            except IndexError:
                update = None
        if isinstance(update, Element):
            update.update_basic_atts(self)
        else:
            # `update` is a Text node or `new` is an empty list.
            # Assert that we aren't losing any attributes.
            for att in self.basic_attributes:
                assert not self[att], \
                       'Losing "%s" attribute: %s' % (att, self[att])
        self.parent.replace(self, new)

    def first_child_matching_class(self, childclass, start=0, end=sys.maxsize):
        """
        Return the index of the first child whose class exactly matches.

        Parameters:

        - `childclass`: A `Node` subclass to search for, or a tuple of `Node`
          classes. If a tuple, any of the classes may match.
        - `start`: Initial index to check.
        - `end`: Initial index to *not* check.
        """
        if not isinstance(childclass, tuple):
            childclass = (childclass,)
        for index in range(start, min(len(self), end)):
            for c in childclass:
                if isinstance(self[index], c):
                    return index
        return None

    def first_child_not_matching_class(self, childclass, start=0,
                                       end=sys.maxsize):
        """
        Return the index of the first child whose class does *not* match.

        Parameters:

        - `childclass`: A `Node` subclass to skip, or a tuple of `Node`
          classes. If a tuple, none of the classes may match.
        - `start`: Initial index to check.
        - `end`: Initial index to *not* check.
        """
        if not isinstance(childclass, tuple):
            childclass = (childclass,)
        for index in range(start, min(len(self), end)):
            for c in childclass:
                if isinstance(self.children[index], c):
                    break
            else:
                return index
        return None

    def pformat(self, indent='    ', level=0):
        return ''.join(['%s%s\n' % (indent * level, self.starttag())] +
                       [child.pformat(indent, level+1)
                        for child in self.children])

    def copy(self):
        obj = self.__class__(rawsource=self.rawsource, **self.attributes)
        obj._document = self._document
        obj.source = self.source
        obj.line = self.line
        return obj

    def deepcopy(self):
        copy = self.copy()
        copy.extend([child.deepcopy() for child in self.children])
        return copy

    def set_class(self, name):
        """Add a new class to the "classes" attribute."""
        warnings.warn('docutils.nodes.Element.set_class deprecated; '
                      "append to Element['classes'] list attribute directly",
                      DeprecationWarning, stacklevel=2)
        assert ' ' not in name
        self['classes'].append(name.lower())

    def note_referenced_by(self, name=None, id=None):
        """Note that this Element has been referenced by its name
        `name` or id `id`."""
        self.referenced = 1
        # Element.expect_referenced_by_* dictionaries map names or ids
        # to nodes whose ``referenced`` attribute is set to true as
        # soon as this node is referenced by the given name or id.
        # Needed for target propagation.
        by_name = getattr(self, 'expect_referenced_by_name', {}).get(name)
        by_id = getattr(self, 'expect_referenced_by_id', {}).get(id)
        if by_name:
            assert name is not None
            by_name.referenced = 1
        if by_id:
            assert id is not None
            by_id.referenced = 1

    @classmethod
    def is_not_list_attribute(cls, attr):
        """
        Returns True if and only if the given attribute is NOT one of the
        basic list attributes defined for all Elements.
        """
        return attr not in cls.list_attributes

    @classmethod
    def is_not_known_attribute(cls, attr):
        """
        Returns True if and only if the given attribute is NOT recognized by
        this class.
        """
        return attr not in cls.known_attributes


class TextElement(Element):

    """
    An element which directly contains text.

    Its children are all `Text` or `Inline` subclass nodes.  You can
    check whether an element's context is inline simply by checking whether
    its immediate parent is a `TextElement` instance (including subclasses).
    This is handy for nodes like `image` that can appear both inline and as
    standalone body elements.

    If passing children to `__init__()`, make sure to set `text` to
    ``''`` or some other suitable value.
    """

    child_text_separator = ''
    """Separator for child nodes, used by `astext()` method."""

    def __init__(self, rawsource='', text='', *children, **attributes):
        if text != '':
            textnode = Text(text)
            Element.__init__(self, rawsource, textnode, *children,
                              **attributes)
        else:
            Element.__init__(self, rawsource, *children, **attributes)


class FixedTextElement(TextElement):

    """An element which directly contains preformatted text."""

    def __init__(self, rawsource='', text='', *children, **attributes):
        TextElement.__init__(self, rawsource, text, *children, **attributes)
        self.attributes['xml:space'] = 'preserve'


# ========
#  Mixins
# ========

class Resolvable(object):

    resolved = 0


class BackLinkable(object):

    def add_backref(self, refid):
        self['backrefs'].append(refid)


# ====================
#  Element Categories
# ====================

class Root(object):
    pass


class Titular(object):
    pass


class PreBibliographic(object):
    """Category of Node which may occur before Bibliographic Nodes."""


class Bibliographic(object):
    pass


class Decorative(PreBibliographic):
    pass


class Structural(object):
    pass


class Body(object):
    pass


class General(Body):
    pass


class Sequential(Body):
    """List-like elements."""


class Admonition(Body): pass


class Special(Body):
    """Special internal body elements."""


class Invisible(PreBibliographic):
    """Internal elements that don't appear in output."""


class Part(object):
    pass


class Inline(object):
    pass


class Referential(Resolvable):
    pass


class Targetable(Resolvable):

    referenced = 0

    indirect_reference_name = None
    """Holds the whitespace_normalized_name (contains mixed case) of a target.
    Required for MoinMoin/reST compatibility."""


class Labeled(object):
    """Contains a `label` as its first element."""


# ==============
#  Root Element
# ==============

class document(Root, Structural, Element):

    """
    The document root element.

    Do not instantiate this class directly; use
    `docutils.utils.new_document()` instead.
    """

    def __init__(self, settings, reporter, *args, **kwargs):
        Element.__init__(self, *args, **kwargs)

        self.current_source = None
        """Path to or description of the input source being processed."""

        self.current_line = None
        """Line number (1-based) of `current_source`."""

        self.settings = settings
        """Runtime settings data record."""

        self.reporter = reporter
        """System message generator."""

        self.indirect_targets = []
        """List of indirect target nodes."""

        self.substitution_defs = {}
        """Mapping of substitution names to substitution_definition nodes."""

        self.substitution_names = {}
        """Mapping of case-normalized substitution names to case-sensitive
        names."""

        self.refnames = {}
        """Mapping of names to lists of referencing nodes."""

        self.refids = {}
        """Mapping of ids to lists of referencing nodes."""

        self.nameids = {}
        """Mapping of names to unique id's."""

        self.nametypes = {}
        """Mapping of names to hyperlink type (boolean: True => explicit,
        False => implicit."""

        self.ids = {}
        """Mapping of ids to nodes."""

        self.footnote_refs = {}
        """Mapping of footnote labels to lists of footnote_reference nodes."""

        self.citation_refs = {}
        """Mapping of citation labels to lists of citation_reference nodes."""

        self.autofootnotes = []
        """List of auto-numbered footnote nodes."""

        self.autofootnote_refs = []
        """List of auto-numbered footnote_reference nodes."""

        self.symbol_footnotes = []
        """List of symbol footnote nodes."""

        self.symbol_footnote_refs = []
        """List of symbol footnote_reference nodes."""

        self.footnotes = []
        """List of manually-numbered footnote nodes."""

        self.citations = []
        """List of citation nodes."""

        self.autofootnote_start = 1
        """Initial auto-numbered footnote number."""

        self.symbol_footnote_start = 0
        """Initial symbol footnote symbol index."""

        self.id_counter = Counter()
        """Numbers added to otherwise identical IDs."""

        self.parse_messages = []
        """System messages generated while parsing."""

        self.transform_messages = []
        """System messages generated while applying transforms."""

        import docutils.transforms
        self.transformer = docutils.transforms.Transformer(self)
        """Storage for transforms to be applied to this document."""

        self.include_log = []
        """The current source's parents (to detect inclusion loops)."""

        self.decoration = None
        """Document's `decoration` node."""

        self._document = self

    def __getstate__(self):
        """
        Return dict with unpicklable references removed.
        """
        state = self.__dict__.copy()
        state['reporter'] = None
        state['transformer'] = None
        return state

    def asdom(self, dom=None):
        """Return a DOM representation of this document."""
        if dom is None:
            import xml.dom.minidom as dom
        domroot = dom.Document()
        domroot.appendChild(self._dom_node(domroot))
        return domroot

    def set_id(self, node, msgnode=None, suggested_prefix=''):
        if node['ids']:
            # register and check for duplicates
            for id in node['ids']:
                self.ids.setdefault(id, node)
                if self.ids[id] is not node:
                    msg = self.reporter.severe('Duplicate ID: "%s".' % id)
                    if msgnode != None:
                        msgnode += msg
            return id
        # generate and set id
        id_prefix = self.settings.id_prefix
        auto_id_prefix = self.settings.auto_id_prefix
        base_id = ''
        id = ''
        for name in node['names']:
            base_id = make_id(name)
            id = id_prefix + base_id
            # TODO: allow names starting with numbers if `id_prefix`
            # is non-empty:  id = make_id(id_prefix + name)
            if base_id and id not in self.ids:
                break
        else:
            if base_id and auto_id_prefix.endswith('%'):
                # disambiguate name-derived ID
                # TODO: remove second condition after announcing change
                prefix = id + '-'
            else:
                prefix = id_prefix + auto_id_prefix
                if  prefix.endswith('%'):
                    prefix = '%s%s-' % (prefix[:-1], suggested_prefix
                                                or make_id(node.tagname))
            while True:
                self.id_counter[prefix] += 1
                id = '%s%d' % (prefix, self.id_counter[prefix])
                if id not in self.ids:
                    break
        node['ids'].append(id)
        self.ids[id] = node
        return id

    def set_name_id_map(self, node, id, msgnode=None, explicit=None):
        """
        `self.nameids` maps names to IDs, while `self.nametypes` maps names to
        booleans representing hyperlink type (True==explicit,
        False==implicit).  This method updates the mappings.

        The following state transition table shows how `self.nameids` ("ids")
        and `self.nametypes` ("types") change with new input (a call to this
        method), and what actions are performed ("implicit"-type system
        messages are INFO/1, and "explicit"-type system messages are ERROR/3):

        ====  =====  ========  ========  =======  ====  =====  =====
         Old State    Input          Action        New State   Notes
        -----------  --------  -----------------  -----------  -----
        ids   types  new type  sys.msg.  dupname  ids   types
        ====  =====  ========  ========  =======  ====  =====  =====
        -     -      explicit  -         -        new   True
        -     -      implicit  -         -        new   False
        None  False  explicit  -         -        new   True
        old   False  explicit  implicit  old      new   True
        None  True   explicit  explicit  new      None  True
        old   True   explicit  explicit  new,old  None  True   [#]_
        None  False  implicit  implicit  new      None  False
        old   False  implicit  implicit  new,old  None  False
        None  True   implicit  implicit  new      None  True
        old   True   implicit  implicit  new      old   True
        ====  =====  ========  ========  =======  ====  =====  =====

        .. [#] Do not clear the name-to-id map or invalidate the old target if
           both old and new targets are external and refer to identical URIs.
           The new target is invalidated regardless.
        """
        for name in node['names']:
            if name in self.nameids:
                self.set_duplicate_name_id(node, id, name, msgnode, explicit)
            else:
                self.nameids[name] = id
                self.nametypes[name] = explicit

    def set_duplicate_name_id(self, node, id, name, msgnode, explicit):
        old_id = self.nameids[name]
        old_explicit = self.nametypes[name]
        self.nametypes[name] = old_explicit or explicit
        if explicit:
            if old_explicit:
                level = 2
                if old_id is not None:
                    old_node = self.ids[old_id]
                    if 'refuri' in node:
                        refuri = node['refuri']
                        if old_node['names'] \
                               and 'refuri' in old_node \
                               and old_node['refuri'] == refuri:
                            level = 1   # just inform if refuri's identical
                    if level > 1:
                        dupname(old_node, name)
                        self.nameids[name] = None
                msg = self.reporter.system_message(
                    level, 'Duplicate explicit target name: "%s".' % name,
                    backrefs=[id], base_node=node)
                if msgnode != None:
                    msgnode += msg
                dupname(node, name)
            else:
                self.nameids[name] = id
                if old_id is not None:
                    old_node = self.ids[old_id]
                    dupname(old_node, name)
        else:
            if old_id is not None and not old_explicit:
                self.nameids[name] = None
                old_node = self.ids[old_id]
                dupname(old_node, name)
            dupname(node, name)
        if not explicit or (not old_explicit and old_id is not None):
            msg = self.reporter.info(
                'Duplicate implicit target name: "%s".' % name,
                backrefs=[id], base_node=node)
            if msgnode != None:
                msgnode += msg

    def has_name(self, name):
        return name in self.nameids

    # "note" here is an imperative verb: "take note of".
    def note_implicit_target(self, target, msgnode=None):
        id = self.set_id(target, msgnode)
        self.set_name_id_map(target, id, msgnode, explicit=None)

    def note_explicit_target(self, target, msgnode=None):
        id = self.set_id(target, msgnode)
        self.set_name_id_map(target, id, msgnode, explicit=True)

    def note_refname(self, node):
        self.refnames.setdefault(node['refname'], []).append(node)

    def note_refid(self, node):
        self.refids.setdefault(node['refid'], []).append(node)

    def note_indirect_target(self, target):
        self.indirect_targets.append(target)
        if target['names']:
            self.note_refname(target)

    def note_anonymous_target(self, target):
        self.set_id(target)

    def note_autofootnote(self, footnote):
        self.set_id(footnote)
        self.autofootnotes.append(footnote)

    def note_autofootnote_ref(self, ref):
        self.set_id(ref)
        self.autofootnote_refs.append(ref)

    def note_symbol_footnote(self, footnote):
        self.set_id(footnote)
        self.symbol_footnotes.append(footnote)

    def note_symbol_footnote_ref(self, ref):
        self.set_id(ref)
        self.symbol_footnote_refs.append(ref)

    def note_footnote(self, footnote):
        self.set_id(footnote)
        self.footnotes.append(footnote)

    def note_footnote_ref(self, ref):
        self.set_id(ref)
        self.footnote_refs.setdefault(ref['refname'], []).append(ref)
        self.note_refname(ref)

    def note_citation(self, citation):
        self.citations.append(citation)

    def note_citation_ref(self, ref):
        self.set_id(ref)
        self.citation_refs.setdefault(ref['refname'], []).append(ref)
        self.note_refname(ref)

    def note_substitution_def(self, subdef, def_name, msgnode=None):
        name = whitespace_normalize_name(def_name)
        if name in self.substitution_defs:
            msg = self.reporter.error(
                  'Duplicate substitution definition name: "%s".' % name,
                  base_node=subdef)
            if msgnode != None:
                msgnode += msg
            oldnode = self.substitution_defs[name]
            dupname(oldnode, name)
        # keep only the last definition:
        self.substitution_defs[name] = subdef
        # case-insensitive mapping:
        self.substitution_names[fully_normalize_name(name)] = name

    def note_substitution_ref(self, subref, refname):
        subref['refname'] = whitespace_normalize_name(refname)

    def note_pending(self, pending, priority=None):
        self.transformer.add_pending(pending, priority)

    def note_parse_message(self, message):
        self.parse_messages.append(message)

    def note_transform_message(self, message):
        self.transform_messages.append(message)

    def note_source(self, source, offset):
        self.current_source = source
        if offset is None:
            self.current_line = offset
        else:
            self.current_line = offset + 1

    def copy(self):
        obj = self.__class__(self.settings, self.reporter,
                              **self.attributes)
        obj.source = self.source
        obj.line = self.line
        return obj

    def get_decoration(self):
        if not self.decoration:
            self.decoration = decoration()
            index = self.first_child_not_matching_class(Titular)
            if index is None:
                self.append(self.decoration)
            else:
                self.insert(index, self.decoration)
        return self.decoration


# ================
#  Title Elements
# ================

class title(Titular, PreBibliographic, TextElement): pass
class subtitle(Titular, PreBibliographic, TextElement): pass
class rubric(Titular, TextElement): pass


# ========================
#  Bibliographic Elements
# ========================

class docinfo(Bibliographic, Element): pass
class author(Bibliographic, TextElement): pass
class authors(Bibliographic, Element): pass
class organization(Bibliographic, TextElement): pass
class address(Bibliographic, FixedTextElement): pass
class contact(Bibliographic, TextElement): pass
class version(Bibliographic, TextElement): pass
class revision(Bibliographic, TextElement): pass
class status(Bibliographic, TextElement): pass
class date(Bibliographic, TextElement): pass
class copyright(Bibliographic, TextElement): pass


# =====================
#  Decorative Elements
# =====================

class decoration(Decorative, Element):

    def get_header(self):
        if not len(self.children) or not isinstance(self.children[0], header):
            self.insert(0, header())
        return self.children[0]

    def get_footer(self):
        if not len(self.children) or not isinstance(self.children[-1], footer):
            self.append(footer())
        return self.children[-1]


class header(Decorative, Element): pass
class footer(Decorative, Element): pass


# =====================
#  Structural Elements
# =====================

class section(Structural, Element): pass


class topic(Structural, Element):

    """
    Topics are terminal, "leaf" mini-sections, like block quotes with titles,
    or textual figures.  A topic is just like a section, except that it has no
    subsections, and it doesn't have to conform to section placement rules.

    Topics are allowed wherever body elements (list, table, etc.) are allowed,
    but only at the top level of a section or document.  Topics cannot nest
    inside topics, sidebars, or body elements; you can't have a topic inside a
    table, list, block quote, etc.
    """


class sidebar(Structural, Element):

    """
    Sidebars are like miniature, parallel documents that occur inside other
    documents, providing related or reference material.  A sidebar is
    typically offset by a border and "floats" to the side of the page; the
    document's main text may flow around it.  Sidebars can also be likened to
    super-footnotes; their content is outside of the flow of the document's
    main text.

    Sidebars are allowed wherever body elements (list, table, etc.) are
    allowed, but only at the top level of a section or document.  Sidebars
    cannot nest inside sidebars, topics, or body elements; you can't have a
    sidebar inside a table, list, block quote, etc.
    """


class transition(Structural, Element): pass


# ===============
#  Body Elements
# ===============

class paragraph(General, TextElement): pass
class compound(General, Element): pass
class container(General, Element): pass
class bullet_list(Sequential, Element): pass
class enumerated_list(Sequential, Element): pass
class list_item(Part, Element): pass
class definition_list(Sequential, Element): pass
class definition_list_item(Part, Element): pass
class term(Part, TextElement): pass
class classifier(Part, TextElement): pass
class definition(Part, Element): pass
class field_list(Sequential, Element): pass
class field(Part, Element): pass
class field_name(Part, TextElement): pass
class field_body(Part, Element): pass


class option(Part, Element):

    child_text_separator = ''


class option_argument(Part, TextElement):

    def astext(self):
        return self.get('delimiter', ' ') + TextElement.astext(self)


class option_group(Part, Element):

    child_text_separator = ', '


class option_list(Sequential, Element): pass


class option_list_item(Part, Element):

    child_text_separator = '  '


class option_string(Part, TextElement): pass
class description(Part, Element): pass
class literal_block(General, FixedTextElement): pass
class doctest_block(General, FixedTextElement): pass
class math_block(General, FixedTextElement): pass
class line_block(General, Element): pass


class line(Part, TextElement):

    indent = None


class block_quote(General, Element): pass
class attribution(Part, TextElement): pass
class attention(Admonition, Element): pass
class caution(Admonition, Element): pass
class danger(Admonition, Element): pass
class error(Admonition, Element): pass
class important(Admonition, Element): pass
class note(Admonition, Element): pass
class tip(Admonition, Element): pass
class hint(Admonition, Element): pass
class warning(Admonition, Element): pass
class admonition(Admonition, Element): pass
class comment(Special, Invisible, FixedTextElement): pass
class substitution_definition(Special, Invisible, TextElement): pass
class target(Special, Invisible, Inline, TextElement, Targetable): pass
class footnote(General, BackLinkable, Element, Labeled, Targetable): pass
class citation(General, BackLinkable, Element, Labeled, Targetable): pass
class label(Part, TextElement): pass
class figure(General, Element): pass
class caption(Part, TextElement): pass
class legend(Part, Element): pass
class table(General, Element): pass
class tgroup(Part, Element): pass
class colspec(Part, Element): pass
class thead(Part, Element): pass
class tbody(Part, Element): pass
class row(Part, Element): pass
class entry(Part, Element): pass


class system_message(Special, BackLinkable, PreBibliographic, Element):

    """
    System message element.

    Do not instantiate this class directly; use
    ``document.reporter.info/warning/error/severe()`` instead.
    """

    def __init__(self, message=None, *children, **attributes):
        rawsource = attributes.pop('rawsource', '')
        if message:
            p = paragraph('', message)
            children = (p,) + children
        try:
            Element.__init__(self, rawsource, *children, **attributes)
        except:
            print('system_message: children=%r' % (children,))
            raise

    def astext(self):
        line = self.get('line', '')
        return u'%s:%s: (%s/%s) %s' % (self['source'], line, self['type'],
                                       self['level'], Element.astext(self))


class pending(Special, Invisible, Element):

    """
    The "pending" element is used to encapsulate a pending operation: the
    operation (transform), the point at which to apply it, and any data it
    requires.  Only the pending operation's location within the document is
    stored in the public document tree (by the "pending" object itself); the
    operation and its data are stored in the "pending" object's internal
    instance attributes.

    For example, say you want a table of contents in your reStructuredText
    document.  The easiest way to specify where to put it is from within the
    document, with a directive::

        .. contents::

    But the "contents" directive can't do its work until the entire document
    has been parsed and possibly transformed to some extent.  So the directive
    code leaves a placeholder behind that will trigger the second phase of its
    processing, something like this::

        <pending ...public attributes...> + internal attributes

    Use `document.note_pending()` so that the
    `docutils.transforms.Transformer` stage of processing can run all pending
    transforms.
    """

    def __init__(self, transform, details=None,
                 rawsource='', *children, **attributes):
        Element.__init__(self, rawsource, *children, **attributes)

        self.transform = transform
        """The `docutils.transforms.Transform` class implementing the pending
        operation."""

        self.details = details or {}
        """Detail data (dictionary) required by the pending operation."""

    def pformat(self, indent='    ', level=0):
        internals = [
              '.. internal attributes:',
              '     .transform: %s.%s' % (self.transform.__module__,
                                          self.transform.__name__),
              '     .details:']
        details = sorted(self.details.items())
        for key, value in details:
            if isinstance(value, Node):
                internals.append('%7s%s:' % ('', key))
                internals.extend(['%9s%s' % ('', line)
                                  for line in value.pformat().splitlines()])
            elif value and isinstance(value, list) \
                  and isinstance(value[0], Node):
                internals.append('%7s%s:' % ('', key))
                for v in value:
                    internals.extend(['%9s%s' % ('', line)
                                      for line in v.pformat().splitlines()])
            else:
                internals.append('%7s%s: %r' % ('', key, value))
        return (Element.pformat(self, indent, level)
                + ''.join([('    %s%s\n' % (indent * level, line))
                           for line in internals]))

    def copy(self):
        obj = self.__class__(self.transform, self.details, self.rawsource,
                              **self.attributes)
        obj._document = self._document
        obj.source = self.source
        obj.line = self.line
        return obj


class raw(Special, Inline, PreBibliographic, FixedTextElement):

    """
    Raw data that is to be passed untouched to the Writer.
    """

    pass


# =================
#  Inline Elements
# =================

class emphasis(Inline, TextElement): pass
class strong(Inline, TextElement): pass
class literal(Inline, TextElement): pass
class reference(General, Inline, Referential, TextElement): pass
class footnote_reference(Inline, Referential, TextElement): pass
class citation_reference(Inline, Referential, TextElement): pass
class substitution_reference(Inline, TextElement): pass
class title_reference(Inline, TextElement): pass
class abbreviation(Inline, TextElement): pass
class acronym(Inline, TextElement): pass
class superscript(Inline, TextElement): pass
class subscript(Inline, TextElement): pass
class math(Inline, TextElement): pass


class image(General, Inline, Element):

    def astext(self):
        return self.get('alt', '')


class inline(Inline, TextElement): pass
class problematic(Inline, TextElement): pass
class generated(Inline, TextElement): pass


# ========================================
#  Auxiliary Classes, Functions, and Data
# ========================================

node_class_names = """
    Text
    abbreviation acronym address admonition attention attribution author
        authors
    block_quote bullet_list
    caption caution citation citation_reference classifier colspec comment
        compound contact container copyright
    danger date decoration definition definition_list definition_list_item
        description docinfo doctest_block document
    emphasis entry enumerated_list error
    field field_body field_list field_name figure footer
        footnote footnote_reference
    generated
    header hint
    image important inline
    label legend line line_block list_item literal literal_block
    math math_block
    note
    option option_argument option_group option_list option_list_item
        option_string organization
    paragraph pending problematic
    raw reference revision row rubric
    section sidebar status strong subscript substitution_definition
        substitution_reference subtitle superscript system_message
    table target tbody term tgroup thead tip title title_reference topic
        transition
    version
    warning""".split()
"""A list of names of all concrete Node subclasses."""


class NodeVisitor(object):

    """
    "Visitor" pattern [GoF95]_ abstract superclass implementation for
    document tree traversals.

    Each node class has corresponding methods, doing nothing by
    default; override individual methods for specific and useful
    behaviour.  The `dispatch_visit()` method is called by
    `Node.walk()` upon entering a node.  `Node.walkabout()` also calls
    the `dispatch_departure()` method before exiting a node.

    The dispatch methods call "``visit_`` + node class name" or
    "``depart_`` + node class name", resp.

    This is a base class for visitors whose ``visit_...`` & ``depart_...``
    methods should be implemented for *all* node types encountered (such as
    for `docutils.writers.Writer` subclasses).  Unimplemented methods will
    raise exceptions.

    For sparse traversals, where only certain node types are of interest, use
    subclass `SparseNodeVisitor` instead.  When (mostly or entirely) uniform
    processing is desired, subclass `GenericNodeVisitor`.

    .. [GoF95] Gamma, Helm, Johnson, Vlissides. *Design Patterns: Elements of
       Reusable Object-Oriented Software*. Addison-Wesley, Reading, MA, USA,
       1995.
    """

    optional = ()
    """
    Tuple containing node class names (as strings).

    No exception will be raised if writers do not implement visit
    or departure functions for these node classes.

    Used to ensure transitional compatibility with existing 3rd-party writers.
    """

    def __init__(self, document):
        self.document = document

    def dispatch_visit(self, node):
        """
        Call self."``visit_`` + node class name" with `node` as
        parameter.  If the ``visit_...`` method does not exist, call
        self.unknown_visit.
        """
        node_name = node.__class__.__name__
        method = getattr(self, 'visit_' + node_name, self.unknown_visit)
        self.document.reporter.debug(
            'docutils.nodes.NodeVisitor.dispatch_visit calling %s for %s'
            % (method.__name__, node_name))
        return method(node)

    def dispatch_departure(self, node):
        """
        Call self."``depart_`` + node class name" with `node` as
        parameter.  If the ``depart_...`` method does not exist, call
        self.unknown_departure.
        """
        node_name = node.__class__.__name__
        method = getattr(self, 'depart_' + node_name, self.unknown_departure)
        self.document.reporter.debug(
            'docutils.nodes.NodeVisitor.dispatch_departure calling %s for %s'
            % (method.__name__, node_name))
        return method(node)

    def unknown_visit(self, node):
        """
        Called when entering unknown `Node` types.

        Raise an exception unless overridden.
        """
        if  (self.document.settings.strict_visitor
             or node.__class__.__name__ not in self.optional):
            raise NotImplementedError(
                '%s visiting unknown node type: %s'
                % (self.__class__, node.__class__.__name__))

    def unknown_departure(self, node):
        """
        Called before exiting unknown `Node` types.

        Raise exception unless overridden.
        """
        if  (self.document.settings.strict_visitor
             or node.__class__.__name__ not in self.optional):
            raise NotImplementedError(
                '%s departing unknown node type: %s'
                % (self.__class__, node.__class__.__name__))


class SparseNodeVisitor(NodeVisitor):

    """
    Base class for sparse traversals, where only certain node types are of
    interest.  When ``visit_...`` & ``depart_...`` methods should be
    implemented for *all* node types (such as for `docutils.writers.Writer`
    subclasses), subclass `NodeVisitor` instead.
    """


class GenericNodeVisitor(NodeVisitor):

    """
    Generic "Visitor" abstract superclass, for simple traversals.

    Unless overridden, each ``visit_...`` method calls `default_visit()`, and
    each ``depart_...`` method (when using `Node.walkabout()`) calls
    `default_departure()`. `default_visit()` (and `default_departure()`) must
    be overridden in subclasses.

    Define fully generic visitors by overriding `default_visit()` (and
    `default_departure()`) only. Define semi-generic visitors by overriding
    individual ``visit_...()`` (and ``depart_...()``) methods also.

    `NodeVisitor.unknown_visit()` (`NodeVisitor.unknown_departure()`) should
    be overridden for default behavior.
    """

    def default_visit(self, node):
        """Override for generic, uniform traversals."""
        raise NotImplementedError

    def default_departure(self, node):
        """Override for generic, uniform traversals."""
        raise NotImplementedError

def _call_default_visit(self, node):
    self.default_visit(node)

def _call_default_departure(self, node):
    self.default_departure(node)

def _nop(self, node):
    pass

def _add_node_class_names(names):
    """Save typing with dynamic assignments:"""
    for _name in names:
        setattr(GenericNodeVisitor, "visit_" + _name, _call_default_visit)
        setattr(GenericNodeVisitor, "depart_" + _name, _call_default_departure)
        setattr(SparseNodeVisitor, 'visit_' + _name, _nop)
        setattr(SparseNodeVisitor, 'depart_' + _name, _nop)

_add_node_class_names(node_class_names)


class TreeCopyVisitor(GenericNodeVisitor):

    """
    Make a complete copy of a tree or branch, including element attributes.
    """

    def __init__(self, document):
        GenericNodeVisitor.__init__(self, document)
        self.parent_stack = []
        self.parent = []

    def get_tree_copy(self):
        return self.parent[0]

    def default_visit(self, node):
        """Copy the current node, and make it the new acting parent."""
        newnode = node.copy()
        self.parent.append(newnode)
        self.parent_stack.append(self.parent)
        self.parent = newnode

    def default_departure(self, node):
        """Restore the previous acting parent."""
        self.parent = self.parent_stack.pop()


class TreePruningException(Exception):

    """
    Base class for `NodeVisitor`-related tree pruning exceptions.

    Raise subclasses from within ``visit_...`` or ``depart_...`` methods
    called from `Node.walk()` and `Node.walkabout()` tree traversals to prune
    the tree traversed.
    """

    pass


class SkipChildren(TreePruningException):

    """
    Do not visit any children of the current node.  The current node's
    siblings and ``depart_...`` method are not affected.
    """

    pass


class SkipSiblings(TreePruningException):

    """
    Do not visit any more siblings (to the right) of the current node.  The
    current node's children and its ``depart_...`` method are not affected.
    """

    pass


class SkipNode(TreePruningException):

    """
    Do not visit the current node's children, and do not call the current
    node's ``depart_...`` method.
    """

    pass


class SkipDeparture(TreePruningException):

    """
    Do not call the current node's ``depart_...`` method.  The current node's
    children and siblings are not affected.
    """

    pass


class NodeFound(TreePruningException):

    """
    Raise to indicate that the target of a search has been found.  This
    exception must be caught by the client; it is not caught by the traversal
    code.
    """

    pass


class StopTraversal(TreePruningException):

    """
    Stop the traversal alltogether.  The current node's ``depart_...`` method
    is not affected.  The parent nodes ``depart_...`` methods are also called
    as usual.  No other nodes are visited.  This is an alternative to
    NodeFound that does not cause exception handling to trickle up to the
    caller.
    """

    pass


def make_id(string):
    """
    Convert `string` into an identifier and return it.

    Docutils identifiers will conform to the regular expression
    ``[a-z](-?[a-z0-9]+)*``.  For CSS compatibility, identifiers (the "class"
    and "id" attributes) should have no underscores, colons, or periods.
    Hyphens may be used.

    - The `HTML 4.01 spec`_ defines identifiers based on SGML tokens:

          ID and NAME tokens must begin with a letter ([A-Za-z]) and may be
          followed by any number of letters, digits ([0-9]), hyphens ("-"),
          underscores ("_"), colons (":"), and periods (".").

    - However the `CSS1 spec`_ defines identifiers based on the "name" token,
      a tighter interpretation ("flex" tokenizer notation; "latin1" and
      "escape" 8-bit characters have been replaced with entities)::

          unicode     \\[0-9a-f]{1,4}
          latin1      [&iexcl;-&yuml;]
          escape      {unicode}|\\[ -~&iexcl;-&yuml;]
          nmchar      [-a-z0-9]|{latin1}|{escape}
          name        {nmchar}+

    The CSS1 "nmchar" rule does not include underscores ("_"), colons (":"),
    or periods ("."), therefore "class" and "id" attributes should not contain
    these characters. They should be replaced with hyphens ("-"). Combined
    with HTML's requirements (the first character must be a letter; no
    "unicode", "latin1", or "escape" characters), this results in the
    ``[a-z](-?[a-z0-9]+)*`` pattern.

    .. _HTML 4.01 spec: http://www.w3.org/TR/html401
    .. _CSS1 spec: http://www.w3.org/TR/REC-CSS1
    """
    id = string.lower()
    if not isinstance(id, unicode):
        id = id.decode()
    id = id.translate(_non_id_translate_digraphs)
    id = id.translate(_non_id_translate)
    # get rid of non-ascii characters.
    # 'ascii' lowercase to prevent problems with turkish locale.
    id = unicodedata.normalize('NFKD', id).\
         encode('ascii', 'ignore').decode('ascii')
    # shrink runs of whitespace and replace by hyphen
    id = _non_id_chars.sub('-', ' '.join(id.split()))
    id = _non_id_at_ends.sub('', id)
    return str(id)

_non_id_chars = re.compile('[^a-z0-9]+')
_non_id_at_ends = re.compile('^[-0-9]+|-+$')
_non_id_translate = {
    0x00f8: u'o',       # o with stroke
    0x0111: u'd',       # d with stroke
    0x0127: u'h',       # h with stroke
    0x0131: u'i',       # dotless i
    0x0142: u'l',       # l with stroke
    0x0167: u't',       # t with stroke
    0x0180: u'b',       # b with stroke
    0x0183: u'b',       # b with topbar
    0x0188: u'c',       # c with hook
    0x018c: u'd',       # d with topbar
    0x0192: u'f',       # f with hook
    0x0199: u'k',       # k with hook
    0x019a: u'l',       # l with bar
    0x019e: u'n',       # n with long right leg
    0x01a5: u'p',       # p with hook
    0x01ab: u't',       # t with palatal hook
    0x01ad: u't',       # t with hook
    0x01b4: u'y',       # y with hook
    0x01b6: u'z',       # z with stroke
    0x01e5: u'g',       # g with stroke
    0x0225: u'z',       # z with hook
    0x0234: u'l',       # l with curl
    0x0235: u'n',       # n with curl
    0x0236: u't',       # t with curl
    0x0237: u'j',       # dotless j
    0x023c: u'c',       # c with stroke
    0x023f: u's',       # s with swash tail
    0x0240: u'z',       # z with swash tail
    0x0247: u'e',       # e with stroke
    0x0249: u'j',       # j with stroke
    0x024b: u'q',       # q with hook tail
    0x024d: u'r',       # r with stroke
    0x024f: u'y',       # y with stroke
}
_non_id_translate_digraphs = {
    0x00df: u'sz',      # ligature sz
    0x00e6: u'ae',      # ae
    0x0153: u'oe',      # ligature oe
    0x0238: u'db',      # db digraph
    0x0239: u'qp',      # qp digraph
}

def dupname(node, name):
    node['dupnames'].append(name)
    node['names'].remove(name)
    # Assume that this method is referenced, even though it isn't; we
    # don't want to throw unnecessary system_messages.
    node.referenced = 1

def fully_normalize_name(name):
    """Return a case- and whitespace-normalized name."""
    return ' '.join(name.lower().split())

def whitespace_normalize_name(name):
    """Return a whitespace-normalized name."""
    return ' '.join(name.split())

def serial_escape(value):
    """Escape string values that are elements of a list, for serialization."""
    return value.replace('\\', r'\\').replace(' ', r'\ ')

def pseudo_quoteattr(value):
    """Quote attributes for pseudo-xml"""
    return '"%s"' % value

# 
#
# Local Variables:
# indent-tabs-mode: nil
# sentence-end-double-space: t
# fill-column: 78
# End: