1from __future__ import unicode_literals
2
3import json
4import operator
5import re
6
7from .utils import (
8    ExtractorError,
9    remove_quotes,
10)
11
12_OPERATORS = [
13    ('|', operator.or_),
14    ('^', operator.xor),
15    ('&', operator.and_),
16    ('>>', operator.rshift),
17    ('<<', operator.lshift),
18    ('-', operator.sub),
19    ('+', operator.add),
20    ('%', operator.mod),
21    ('/', operator.truediv),
22    ('*', operator.mul),
23]
24_ASSIGN_OPERATORS = [(op + '=', opfunc) for op, opfunc in _OPERATORS]
25_ASSIGN_OPERATORS.append(('=', lambda cur, right: right))
26
27_NAME_RE = r'[a-zA-Z_$][a-zA-Z_$0-9]*'
28
29
30class JSInterpreter(object):
31    def __init__(self, code, objects=None):
32        if objects is None:
33            objects = {}
34        self.code = code
35        self._functions = {}
36        self._objects = objects
37
38    def interpret_statement(self, stmt, local_vars, allow_recursion=100):
39        if allow_recursion < 0:
40            raise ExtractorError('Recursion limit reached')
41
42        should_abort = False
43        stmt = stmt.lstrip()
44        stmt_m = re.match(r'var\s', stmt)
45        if stmt_m:
46            expr = stmt[len(stmt_m.group(0)):]
47        else:
48            return_m = re.match(r'return(?:\s+|$)', stmt)
49            if return_m:
50                expr = stmt[len(return_m.group(0)):]
51                should_abort = True
52            else:
53                # Try interpreting it as an expression
54                expr = stmt
55
56        v = self.interpret_expression(expr, local_vars, allow_recursion)
57        return v, should_abort
58
59    def interpret_expression(self, expr, local_vars, allow_recursion):
60        expr = expr.strip()
61        if expr == '':  # Empty expression
62            return None
63
64        if expr.startswith('('):
65            parens_count = 0
66            for m in re.finditer(r'[()]', expr):
67                if m.group(0) == '(':
68                    parens_count += 1
69                else:
70                    parens_count -= 1
71                    if parens_count == 0:
72                        sub_expr = expr[1:m.start()]
73                        sub_result = self.interpret_expression(
74                            sub_expr, local_vars, allow_recursion)
75                        remaining_expr = expr[m.end():].strip()
76                        if not remaining_expr:
77                            return sub_result
78                        else:
79                            expr = json.dumps(sub_result) + remaining_expr
80                        break
81            else:
82                raise ExtractorError('Premature end of parens in %r' % expr)
83
84        for op, opfunc in _ASSIGN_OPERATORS:
85            m = re.match(r'''(?x)
86                (?P<out>%s)(?:\[(?P<index>[^\]]+?)\])?
87                \s*%s
88                (?P<expr>.*)$''' % (_NAME_RE, re.escape(op)), expr)
89            if not m:
90                continue
91            right_val = self.interpret_expression(
92                m.group('expr'), local_vars, allow_recursion - 1)
93
94            if m.groupdict().get('index'):
95                lvar = local_vars[m.group('out')]
96                idx = self.interpret_expression(
97                    m.group('index'), local_vars, allow_recursion)
98                assert isinstance(idx, int)
99                cur = lvar[idx]
100                val = opfunc(cur, right_val)
101                lvar[idx] = val
102                return val
103            else:
104                cur = local_vars.get(m.group('out'))
105                val = opfunc(cur, right_val)
106                local_vars[m.group('out')] = val
107                return val
108
109        if expr.isdigit():
110            return int(expr)
111
112        var_m = re.match(
113            r'(?!if|return|true|false)(?P<name>%s)$' % _NAME_RE,
114            expr)
115        if var_m:
116            return local_vars[var_m.group('name')]
117
118        try:
119            return json.loads(expr)
120        except ValueError:
121            pass
122
123        m = re.match(
124            r'(?P<in>%s)\[(?P<idx>.+)\]$' % _NAME_RE, expr)
125        if m:
126            val = local_vars[m.group('in')]
127            idx = self.interpret_expression(
128                m.group('idx'), local_vars, allow_recursion - 1)
129            return val[idx]
130
131        m = re.match(
132            r'(?P<var>%s)(?:\.(?P<member>[^(]+)|\[(?P<member2>[^]]+)\])\s*(?:\(+(?P<args>[^()]*)\))?$' % _NAME_RE,
133            expr)
134        if m:
135            variable = m.group('var')
136            member = remove_quotes(m.group('member') or m.group('member2'))
137            arg_str = m.group('args')
138
139            if variable in local_vars:
140                obj = local_vars[variable]
141            else:
142                if variable not in self._objects:
143                    self._objects[variable] = self.extract_object(variable)
144                obj = self._objects[variable]
145
146            if arg_str is None:
147                # Member access
148                if member == 'length':
149                    return len(obj)
150                return obj[member]
151
152            assert expr.endswith(')')
153            # Function call
154            if arg_str == '':
155                argvals = tuple()
156            else:
157                argvals = tuple([
158                    self.interpret_expression(v, local_vars, allow_recursion)
159                    for v in arg_str.split(',')])
160
161            if member == 'split':
162                assert argvals == ('',)
163                return list(obj)
164            if member == 'join':
165                assert len(argvals) == 1
166                return argvals[0].join(obj)
167            if member == 'reverse':
168                assert len(argvals) == 0
169                obj.reverse()
170                return obj
171            if member == 'slice':
172                assert len(argvals) == 1
173                return obj[argvals[0]:]
174            if member == 'splice':
175                assert isinstance(obj, list)
176                index, howMany = argvals
177                res = []
178                for i in range(index, min(index + howMany, len(obj))):
179                    res.append(obj.pop(index))
180                return res
181
182            return obj[member](argvals)
183
184        for op, opfunc in _OPERATORS:
185            m = re.match(r'(?P<x>.+?)%s(?P<y>.+)' % re.escape(op), expr)
186            if not m:
187                continue
188            x, abort = self.interpret_statement(
189                m.group('x'), local_vars, allow_recursion - 1)
190            if abort:
191                raise ExtractorError(
192                    'Premature left-side return of %s in %r' % (op, expr))
193            y, abort = self.interpret_statement(
194                m.group('y'), local_vars, allow_recursion - 1)
195            if abort:
196                raise ExtractorError(
197                    'Premature right-side return of %s in %r' % (op, expr))
198            return opfunc(x, y)
199
200        m = re.match(
201            r'^(?P<func>%s)\((?P<args>[a-zA-Z0-9_$,]*)\)$' % _NAME_RE, expr)
202        if m:
203            fname = m.group('func')
204            argvals = tuple([
205                int(v) if v.isdigit() else local_vars[v]
206                for v in m.group('args').split(',')]) if len(m.group('args')) > 0 else tuple()
207            if fname not in self._functions:
208                self._functions[fname] = self.extract_function(fname)
209            return self._functions[fname](argvals)
210
211        raise ExtractorError('Unsupported JS expression %r' % expr)
212
213    def extract_object(self, objname):
214        _FUNC_NAME_RE = r'''(?:[a-zA-Z$0-9]+|"[a-zA-Z$0-9]+"|'[a-zA-Z$0-9]+')'''
215        obj = {}
216        obj_m = re.search(
217            r'''(?x)
218                (?<!this\.)%s\s*=\s*{\s*
219                    (?P<fields>(%s\s*:\s*function\s*\(.*?\)\s*{.*?}(?:,\s*)?)*)
220                }\s*;
221            ''' % (re.escape(objname), _FUNC_NAME_RE),
222            self.code)
223        fields = obj_m.group('fields')
224        # Currently, it only supports function definitions
225        fields_m = re.finditer(
226            r'''(?x)
227                (?P<key>%s)\s*:\s*function\s*\((?P<args>[a-z,]+)\){(?P<code>[^}]+)}
228            ''' % _FUNC_NAME_RE,
229            fields)
230        for f in fields_m:
231            argnames = f.group('args').split(',')
232            obj[remove_quotes(f.group('key'))] = self.build_function(argnames, f.group('code'))
233
234        return obj
235
236    def extract_function(self, funcname):
237        func_m = re.search(
238            r'''(?x)
239                (?:function\s+%s|[{;,]\s*%s\s*=\s*function|var\s+%s\s*=\s*function)\s*
240                \((?P<args>[^)]*)\)\s*
241                \{(?P<code>[^}]+)\}''' % (
242                re.escape(funcname), re.escape(funcname), re.escape(funcname)),
243            self.code)
244        if func_m is None:
245            raise ExtractorError('Could not find JS function %r' % funcname)
246        argnames = func_m.group('args').split(',')
247
248        return self.build_function(argnames, func_m.group('code'))
249
250    def call_function(self, funcname, *args):
251        f = self.extract_function(funcname)
252        return f(args)
253
254    def build_function(self, argnames, code):
255        def resf(args):
256            local_vars = dict(zip(argnames, args))
257            for stmt in code.split(';'):
258                res, abort = self.interpret_statement(stmt, local_vars)
259                if abort:
260                    break
261            return res
262        return resf
263