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1 # -*- coding: utf-8 -*-
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2 #
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3 # Copyright (C) 2006 Edgewall Software
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4 # All rights reserved.
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5 #
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6 # This software is licensed as described in the file COPYING, which
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7 # you should have received as part of this distribution. The terms
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8 # are also available at http://trac.edgewall.com/license.html.
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9 #
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10 # This software consists of voluntary contributions made by many
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11 # individuals. For the exact contribution history, see the revision
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12 # history and logs, available at http://projects.edgewall.com/trac/.
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13
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14 """Basic support for evaluating XPath expressions against streams."""
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15
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16 import re
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17
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18 from markup.core import QName, Stream
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19
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20 __all__ = ['Path']
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21
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22 _QUOTES = (("'", "'"), ('"', '"'))
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23
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24 class Path(object):
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25 """Basic XPath support on markup event streams.
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26
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27 >>> from markup.input import XML
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28
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29 Selecting specific tags:
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30
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31 >>> Path('root').select(XML('<root/>')).render()
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32 '<root/>'
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33 >>> Path('//root').select(XML('<root/>')).render()
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34 '<root/>'
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35
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36 Using wildcards for tag names:
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37
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38 >>> Path('*').select(XML('<root/>')).render()
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39 '<root/>'
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40 >>> Path('//*').select(XML('<root/>')).render()
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41 '<root/>'
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42
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43 Selecting attribute values:
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44
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45 >>> Path('@foo').select(XML('<root/>')).render()
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46 ''
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47 >>> Path('@foo').select(XML('<root foo="bar"/>')).render()
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48 'bar'
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49
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50 Selecting descendants:
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51
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52 >>> Path("root/*").select(XML('<root><foo/><bar/></root>')).render()
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53 '<foo/><bar/>'
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54 >>> Path("root/bar").select(XML('<root><foo/><bar/></root>')).render()
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55 '<bar/>'
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56 >>> Path("root/baz").select(XML('<root><foo/><bar/></root>')).render()
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57 ''
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24
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58 >>> Path("root/foo/*").select(
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59 ... XML('<root><foo><bar/></foo></root>')).render()
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1
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60 '<bar/>'
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61
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62 Selecting text nodes:
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24
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63 >>> Path("item/text()").select(
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64 ... XML('<root><item>Foo</item></root>')).render()
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65 'Foo'
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24
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66 >>> Path("item/text()").select(
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67 ... XML('<root><item>Foo</item><item>Bar</item></root>')).render()
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68 'FooBar'
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69
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70 Skipping ancestors:
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71
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24
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72 >>> Path("foo/bar").select(
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73 ... XML('<root><foo><bar/></foo></root>')).render()
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74 '<bar/>'
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24
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75 >>> Path("foo/*").select(
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76 ... XML('<root><foo><bar/></foo></root>')).render()
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77 '<bar/>'
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24
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78 >>> Path("root/bar").select(
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79 ... XML('<root><foo><bar/></foo></root>')).render()
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80 ''
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24
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81 >>> Path("root/bar").select(
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82 ... XML('<root><foo><bar id="1"/></foo><bar id="2"/></root>')).render()
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83 '<bar id="2"/>'
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24
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84 >>> Path("root/*/bar").select(
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85 ... XML('<root><foo><bar/></foo></root>')).render()
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86 '<bar/>'
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24
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87 >>> Path("root//bar").select(
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88 ... XML('<root><foo><bar id="1"/></foo><bar id="2"/></root>')).render()
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89 '<bar id="1"/><bar id="2"/>'
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24
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90 >>> Path("root//bar").select(
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91 ... XML('<root><foo><bar id="1"/></foo><bar id="2"/></root>')).render()
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92 '<bar id="1"/><bar id="2"/>'
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93
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94 Using simple attribute predicates:
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24
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95 >>> Path("root/item[@important]").select(
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96 ... XML('<root><item/><item important="very"/></root>')).render()
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97 '<item important="very"/>'
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24
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98 >>> Path('root/item[@important="very"]').select(
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99 ... XML('<root><item/><item important="very"/></root>')).render()
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100 '<item important="very"/>'
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24
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101 >>> Path("root/item[@important='very']").select(
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102 ... XML('<root><item/><item important="notso"/></root>')).render()
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103 ''
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104 >>> Path("root/item[@important!='very']").select(
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105 ... XML('<root><item/><item important="notso"/></root>')).render()
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106 '<item/><item important="notso"/>'
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107 """
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108
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109 _TOKEN_RE = re.compile('(::|\.\.|\(\)|[/.:\[\]\(\)@=!])|'
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110 '([^/:\[\]\(\)@=!\s]+)|'
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111 '\s+')
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112
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113 def __init__(self, text):
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114 self.source = text
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115
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116 steps = []
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117 cur_op = ''
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118 cur_tag = ''
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119 in_predicate = False
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120 for op, tag in self._TOKEN_RE.findall(text):
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121 if op:
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122 if op == '[':
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123 in_predicate = True
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124 elif op == ']':
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125 in_predicate = False
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126 elif op.startswith('('):
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127 if cur_tag == 'text':
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128 steps[-1] = (False, self.fn_text(), [])
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129 else:
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130 raise NotImplementedError('XPath function "%s" not '
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131 'supported' % cur_tag)
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132 else:
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133 cur_op += op
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134 cur_tag = ''
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135 else:
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136 closure = cur_op in ('', '//')
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137 if cur_op == '@':
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138 if tag == '*':
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139 node_test = self.any_attribute()
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140 else:
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141 node_test = self.attribute_by_name(tag)
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142 else:
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143 if tag == '*':
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144 node_test = self.any_element()
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145 elif in_predicate:
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146 if len(tag) > 1 and (tag[0], tag[-1]) in _QUOTES:
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147 node_test = self.literal_string(tag[1:-1])
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148 if cur_op == '=':
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149 node_test = self.op_eq(steps[-1][2][-1], node_test)
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150 steps[-1][2].pop()
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151 elif cur_op == '!=':
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152 node_test = self.op_neq(steps[-1][2][-1], node_test)
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153 steps[-1][2].pop()
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154 else:
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155 node_test = self.element_by_name(tag)
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156 if in_predicate:
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157 steps[-1][2].append(node_test)
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158 else:
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159 steps.append([closure, node_test, []])
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160 cur_op = ''
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161 cur_tag = tag
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162 self.steps = steps
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163
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164 def __repr__(self):
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165 return '<%s "%s">' % (self.__class__.__name__, self.source)
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166
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167 def select(self, stream):
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168 stream = iter(stream)
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169 def _generate(tests):
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170 test = self.test()
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171 for kind, data, pos in stream:
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172 result = test(kind, data, pos)
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173 if result is True:
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174 yield kind, data, pos
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175 depth = 1
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176 while depth > 0:
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177 ev = stream.next()
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178 if ev[0] is Stream.START:
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179 depth += 1
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180 elif ev[0] is Stream.END:
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181 depth -= 1
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182 yield ev
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183 test(*ev)
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184 elif result:
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185 yield result
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186 return Stream(_generate(self.steps))
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187
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188 def test(self):
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189 stack = [0] # stack of cursors into the location path
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190
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191 def _test(kind, data, pos):
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192 if not stack:
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193 return False
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194
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195 if kind is Stream.END:
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196 stack.pop()
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197 return None
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198
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199 if kind is Stream.START:
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200 stack.append(stack[-1])
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201
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202 matched = False
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203 closure, node_test, predicates = self.steps[stack[-1]]
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204
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205 matched = node_test(kind, data, pos)
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206 if matched and predicates:
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207 for predicate in predicates:
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208 if not predicate(kind, data, pos):
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209 matched = None
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210 break
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211
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212 if matched:
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213 if stack[-1] == len(self.steps) - 1:
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214 return matched
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215
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216 stack[-1] += 1
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217
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218 elif kind is Stream.START and not closure:
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24
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219 # If this step is not a closure, it cannot be matched until the
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220 # current element is closed... so we need to move the cursor
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221 # back to the last closure and retest that against the current
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222 # element
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223 closures = [step for step in self.steps[:stack[-1]] if step[0]]
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24
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224 closures.reverse()
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225 for closure, node_test, predicates in closures:
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226 stack[-1] -= 1
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227 if closure:
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228 matched = node_test(kind, data, pos)
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229 if matched:
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230 stack[-1] += 1
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231 break
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232
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233 return None
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234
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235 return _test
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236
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237 class any_element(object):
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238 def __call__(self, kind, data, pos):
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239 if kind is Stream.START:
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240 return True
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241 return None
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242 def __repr__(self):
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243 return '<%s>' % self.__class__.__name__
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244
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245 class element_by_name(object):
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246 def __init__(self, name):
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247 self.name = QName(name)
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248 def __call__(self, kind, data, pos):
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249 if kind is Stream.START:
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250 return data[0].localname == self.name
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251 return None
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252 def __repr__(self):
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253 return '<%s "%s">' % (self.__class__.__name__, self.name)
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254
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255 class any_attribute(object):
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256 def __call__(self, kind, data, pos):
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257 if kind is Stream.START:
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258 text = ''.join([val for name, val in data[1]])
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259 if text:
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260 return Stream.TEXT, text, pos
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261 return None
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262 return None
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263 def __repr__(self):
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264 return '<%s>' % (self.__class__.__name__)
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265
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266 class attribute_by_name(object):
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267 def __init__(self, name):
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268 self.name = QName(name)
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269 def __call__(self, kind, data, pos):
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270 if kind is Stream.START:
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271 if self.name in data[1]:
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272 return Stream.TEXT, data[1].get(self.name), pos
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273 return None
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274 return None
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275 def __repr__(self):
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276 return '<%s "%s">' % (self.__class__.__name__, self.name)
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277
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278 class fn_text(object):
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279 def __call__(self, kind, data, pos):
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280 if kind is Stream.TEXT:
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281 return kind, data, pos
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282 return None
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283 def __repr__(self):
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284 return '<%s>' % (self.__class__.__name__)
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285
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286 class literal_string(object):
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287 def __init__(self, value):
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288 self.value = value
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289 def __call__(self, kind, data, pos):
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290 return Stream.TEXT, self.value, (-1, -1)
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291 def __repr__(self):
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292 return '<%s>' % (self.__class__.__name__)
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293
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294 class op_eq(object):
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295 def __init__(self, lval, rval):
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296 self.lval = lval
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297 self.rval = rval
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298 def __call__(self, kind, data, pos):
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299 lval = self.lval(kind, data, pos)
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300 rval = self.rval(kind, data, pos)
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301 return (lval and lval[1]) == (rval and rval[1])
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302 def __repr__(self):
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303 return '<%s %r = %r>' % (self.__class__.__name__, self.lval,
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304 self.rval)
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305
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306 class op_neq(object):
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307 def __init__(self, lval, rval):
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308 self.lval = lval
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309 self.rval = rval
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310 def __call__(self, kind, data, pos):
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311 lval = self.lval(kind, data, pos)
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312 rval = self.rval(kind, data, pos)
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313 return (lval and lval[1]) != (rval and rval[1])
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314 def __repr__(self):
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315 return '<%s %r != %r>' % (self.__class__.__name__, self.lval,
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316 self.rval)
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