from __future__ import unicode_literals import json import re from .utils import ( ExtractorError, ) class JSInterpreter(object): def __init__(self, code): self.code = code self._functions = {} self._objects = {} def interpret_statement(self, stmt, local_vars, allow_recursion=20): if allow_recursion < 0: raise ExtractorError('Recursion limit reached') if stmt.startswith('var '): stmt = stmt[len('var '):] ass_m = re.match(r'^(?P<out>[a-z]+)(?:\[(?P<index>[^\]]+)\])?' + r'=(?P<expr>.*)$', stmt) if ass_m: if ass_m.groupdict().get('index'): def assign(val): lvar = local_vars[ass_m.group('out')] idx = self.interpret_expression( ass_m.group('index'), local_vars, allow_recursion) assert isinstance(idx, int) lvar[idx] = val return val expr = ass_m.group('expr') else: def assign(val): local_vars[ass_m.group('out')] = val return val expr = ass_m.group('expr') elif stmt.startswith('return '): assign = lambda v: v expr = stmt[len('return '):] else: # Try interpreting it as an expression expr = stmt assign = lambda v: v v = self.interpret_expression(expr, local_vars, allow_recursion) return assign(v) def interpret_expression(self, expr, local_vars, allow_recursion): if expr.isdigit(): return int(expr) if expr.isalpha(): return local_vars[expr] try: return json.loads(expr) except ValueError: pass m = re.match( r'^(?P<var>[$a-zA-Z0-9_]+)\.(?P<member>[^(]+)(?:\(+(?P<args>[^()]*)\))?$', expr) if m: variable = m.group('var') member = m.group('member') arg_str = m.group('args') if variable in local_vars: obj = local_vars[variable] else: if variable not in self._objects: self._objects[variable] = self.extract_object(variable) obj = self._objects[variable] if arg_str is None: # Member access if member == 'length': return len(obj) return obj[member] assert expr.endswith(')') # Function call if arg_str == '': argvals = tuple() else: argvals = tuple([ self.interpret_expression(v, local_vars, allow_recursion) for v in arg_str.split(',')]) if member == 'split': assert argvals == ('',) return list(obj) if member == 'join': assert len(argvals) == 1 return argvals[0].join(obj) if member == 'reverse': assert len(argvals) == 0 obj.reverse() return obj if member == 'slice': assert len(argvals) == 1 return obj[argvals[0]:] if member == 'splice': assert isinstance(obj, list) index, howMany = argvals res = [] for i in range(index, min(index + howMany, len(obj))): res.append(obj.pop(index)) return res return obj[member](argvals) m = re.match( r'^(?P<in>[a-z]+)\[(?P<idx>.+)\]$', expr) if m: val = local_vars[m.group('in')] idx = self.interpret_expression( m.group('idx'), local_vars, allow_recursion - 1) return val[idx] m = re.match(r'^(?P<a>.+?)(?P<op>[%])(?P<b>.+?)$', expr) if m: a = self.interpret_expression( m.group('a'), local_vars, allow_recursion) b = self.interpret_expression( m.group('b'), local_vars, allow_recursion) return a % b m = re.match( r'^(?P<func>[a-zA-Z$]+)\((?P<args>[a-z0-9,]+)\)$', expr) if m: fname = m.group('func') argvals = tuple([ int(v) if v.isdigit() else local_vars[v] for v in m.group('args').split(',')]) if fname not in self._functions: self._functions[fname] = self.extract_function(fname) return self._functions[fname](argvals) raise ExtractorError('Unsupported JS expression %r' % expr) def extract_object(self, objname): obj = {} obj_m = re.search( (r'(?:var\s+)?%s\s*=\s*\{' % re.escape(objname)) + r'\s*(?P<fields>([a-zA-Z$0-9]+\s*:\s*function\(.*?\)\s*\{.*?\})*)' + r'\}\s*;', self.code) fields = obj_m.group('fields') # Currently, it only supports function definitions fields_m = re.finditer( r'(?P<key>[a-zA-Z$0-9]+)\s*:\s*function' r'\((?P<args>[a-z,]+)\){(?P<code>[^}]+)}', fields) for f in fields_m: argnames = f.group('args').split(',') obj[f.group('key')] = self.build_function(argnames, f.group('code')) return obj def extract_function(self, funcname): func_m = re.search( (r'(?:function %s|[{;]%s\s*=\s*function)' % ( re.escape(funcname), re.escape(funcname))) + r'\((?P<args>[a-z,]+)\){(?P<code>[^}]+)}', self.code) if func_m is None: raise ExtractorError('Could not find JS function %r' % funcname) argnames = func_m.group('args').split(',') return self.build_function(argnames, func_m.group('code')) def build_function(self, argnames, code): def resf(args): local_vars = dict(zip(argnames, args)) for stmt in code.split(';'): res = self.interpret_statement(stmt, local_vars) return res return resf