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1 from __future__ import unicode_literals
2
3 import json
4 import re
5
6 from .utils import (
7     ExtractorError,
8 )
9
10
11 class JSInterpreter(object):
12     def __init__(self, code):
13         self.code = code
14         self._functions = {}
15         self._objects = {}
16
17     def interpret_statement(self, stmt, local_vars, allow_recursion=20):
18         if allow_recursion < 0:
19             raise ExtractorError('Recursion limit reached')
20
21         if stmt.startswith('var '):
22             stmt = stmt[len('var '):]
23         ass_m = re.match(r'^(?P<out>[a-z]+)(?:\[(?P<index>[^\]]+)\])?' +
24                          r'=(?P<expr>.*)$', stmt)
25         if ass_m:
26             if ass_m.groupdict().get('index'):
27                 def assign(val):
28                     lvar = local_vars[ass_m.group('out')]
29                     idx = self.interpret_expression(
30                         ass_m.group('index'), local_vars, allow_recursion)
31                     assert isinstance(idx, int)
32                     lvar[idx] = val
33                     return val
34                 expr = ass_m.group('expr')
35             else:
36                 def assign(val):
37                     local_vars[ass_m.group('out')] = val
38                     return val
39                 expr = ass_m.group('expr')
40         elif stmt.startswith('return '):
41             assign = lambda v: v
42             expr = stmt[len('return '):]
43         else:
44             # Try interpreting it as an expression
45             expr = stmt
46             assign = lambda v: v
47
48         v = self.interpret_expression(expr, local_vars, allow_recursion)
49         return assign(v)
50
51     def interpret_expression(self, expr, local_vars, allow_recursion):
52         if expr.isdigit():
53             return int(expr)
54
55         if expr.isalpha():
56             return local_vars[expr]
57
58         try:
59             return json.loads(expr)
60         except ValueError:
61             pass
62
63         m = re.match(
64             r'^(?P<var>[$a-zA-Z0-9_]+)\.(?P<member>[^(]+)(?:\(+(?P<args>[^()]*)\))?$',
65             expr)
66         if m:
67             variable = m.group('var')
68             member = m.group('member')
69             arg_str = m.group('args')
70
71             if variable in local_vars:
72                 obj = local_vars[variable]
73             else:
74                 if variable not in self._objects:
75                     self._objects[variable] = self.extract_object(variable)
76                 obj = self._objects[variable]
77
78             if arg_str is None:
79                 # Member access
80                 if member == 'length':
81                     return len(obj)
82                 return obj[member]
83
84             assert expr.endswith(')')
85             # Function call
86             if arg_str == '':
87                 argvals = tuple()
88             else:
89                 argvals = tuple([
90                     self.interpret_expression(v, local_vars, allow_recursion)
91                     for v in arg_str.split(',')])
92
93             if member == 'split':
94                 assert argvals == ('',)
95                 return list(obj)
96             if member == 'join':
97                 assert len(argvals) == 1
98                 return argvals[0].join(obj)
99             if member == 'reverse':
100                 assert len(argvals) == 0
101                 obj.reverse()
102                 return obj
103             if member == 'slice':
104                 assert len(argvals) == 1
105                 return obj[argvals[0]:]
106             if member == 'splice':
107                 assert isinstance(obj, list)
108                 index, howMany = argvals
109                 res = []
110                 for i in range(index, min(index + howMany, len(obj))):
111                     res.append(obj.pop(index))
112                 return res
113
114             return obj[member](argvals)
115
116         m = re.match(
117             r'^(?P<in>[a-z]+)\[(?P<idx>.+)\]$', expr)
118         if m:
119             val = local_vars[m.group('in')]
120             idx = self.interpret_expression(
121                 m.group('idx'), local_vars, allow_recursion - 1)
122             return val[idx]
123
124         m = re.match(r'^(?P<a>.+?)(?P<op>[%])(?P<b>.+?)$', expr)
125         if m:
126             a = self.interpret_expression(
127                 m.group('a'), local_vars, allow_recursion)
128             b = self.interpret_expression(
129                 m.group('b'), local_vars, allow_recursion)
130             return a % b
131
132         m = re.match(
133             r'^(?P<func>[a-zA-Z$]+)\((?P<args>[a-z0-9,]+)\)$', expr)
134         if m:
135             fname = m.group('func')
136             argvals = tuple([
137                 int(v) if v.isdigit() else local_vars[v]
138                 for v in m.group('args').split(',')])
139             if fname not in self._functions:
140                 self._functions[fname] = self.extract_function(fname)
141             return self._functions[fname](argvals)
142         raise ExtractorError('Unsupported JS expression %r' % expr)
143
144     def extract_object(self, objname):
145         obj = {}
146         obj_m = re.search(
147             (r'(?:var\s+)?%s\s*=\s*\{' % re.escape(objname)) +
148             r'\s*(?P<fields>([a-zA-Z$0-9]+\s*:\s*function\(.*?\)\s*\{.*?\})*)' +
149             r'\}\s*;',
150             self.code)
151         fields = obj_m.group('fields')
152         # Currently, it only supports function definitions
153         fields_m = re.finditer(
154             r'(?P<key>[a-zA-Z$0-9]+)\s*:\s*function'
155             r'\((?P<args>[a-z,]+)\){(?P<code>[^}]+)}',
156             fields)
157         for f in fields_m:
158             argnames = f.group('args').split(',')
159             obj[f.group('key')] = self.build_function(argnames, f.group('code'))
160
161         return obj
162
163     def extract_function(self, funcname):
164         func_m = re.search(
165             (r'(?:function %s|[{;]%s\s*=\s*function)' % (
166                 re.escape(funcname), re.escape(funcname))) +
167             r'\((?P<args>[a-z,]+)\){(?P<code>[^}]+)}',
168             self.code)
169         if func_m is None:
170             raise ExtractorError('Could not find JS function %r' % funcname)
171         argnames = func_m.group('args').split(',')
172
173         return self.build_function(argnames, func_m.group('code'))
174
175     def build_function(self, argnames, code):
176         def resf(args):
177             local_vars = dict(zip(argnames, args))
178             for stmt in code.split(';'):
179                 res = self.interpret_statement(stmt, local_vars)
180             return res
181         return resf