[youtube] Move JavaScript interpreter into its own module

2 files changed, 118 insertions, 107 deletions

diff --git a/youtube_dl/extractor/youtube.py b/youtube_dl/extractor/youtube.py
index 3a3a5a39e..2d1a19123 100644
--- a/youtube_dl/extractor/youtube.py
+++ b/youtube_dl/extractor/youtube.py
@@ -14,6 +14,7 @@ import zlib
 
 from .common import InfoExtractor, SearchInfoExtractor
 from .subtitles import SubtitlesInfoExtractor
+from ..jsinterp import JSInterpreter
 from ..utils import (
     compat_chr,
     compat_parse_qs,
@@ -438,113 +439,10 @@ class YoutubeIE(YoutubeBaseInfoExtractor, SubtitlesInfoExtractor):
     def _parse_sig_js(self, jscode):
         funcname = self._search_regex(
             r'signature=([a-zA-Z]+)', jscode,
-            u'Initial JS player signature function name')
-
-        functions = {}
-
-        def argidx(varname):
-            return string.lowercase.index(varname)
-
-        def interpret_statement(stmt, local_vars, allow_recursion=20):
-            if allow_recursion < 0:
-                raise ExtractorError(u'Recursion limit reached')
-
-            if stmt.startswith(u'var '):
-                stmt = stmt[len(u'var '):]
-            ass_m = re.match(r'^(?P<out>[a-z]+)(?:\[(?P<index>[^\]]+)\])?' +
-                             r'=(?P<expr>.*)$', stmt)
-            if ass_m:
-                if ass_m.groupdict().get('index'):
-                    def assign(val):
-                        lvar = local_vars[ass_m.group('out')]
-                        idx = interpret_expression(ass_m.group('index'),
-                                                   local_vars, allow_recursion)
-                        assert isinstance(idx, int)
-                        lvar[idx] = val
-                        return val
-                    expr = ass_m.group('expr')
-                else:
-                    def assign(val):
-                        local_vars[ass_m.group('out')] = val
-                        return val
-                    expr = ass_m.group('expr')
-            elif stmt.startswith(u'return '):
-                assign = lambda v: v
-                expr = stmt[len(u'return '):]
-            else:
-                raise ExtractorError(
-                    u'Cannot determine left side of statement in %r' % stmt)
-
-            v = interpret_expression(expr, local_vars, allow_recursion)
-            return assign(v)
-
-        def interpret_expression(expr, local_vars, allow_recursion):
-            if expr.isdigit():
-                return int(expr)
-
-            if expr.isalpha():
-                return local_vars[expr]
-
-            m = re.match(r'^(?P<in>[a-z]+)\.(?P<member>.*)$', expr)
-            if m:
-                member = m.group('member')
-                val = local_vars[m.group('in')]
-                if member == 'split("")':
-                    return list(val)
-                if member == 'join("")':
-                    return u''.join(val)
-                if member == 'length':
-                    return len(val)
-                if member == 'reverse()':
-                    return val[::-1]
-                slice_m = re.match(r'slice\((?P<idx>.*)\)', member)
-                if slice_m:
-                    idx = interpret_expression(
-                        slice_m.group('idx'), local_vars, allow_recursion-1)
-                    return val[idx:]
-
-            m = re.match(
-                r'^(?P<in>[a-z]+)\[(?P<idx>.+)\]$', expr)
-            if m:
-                val = local_vars[m.group('in')]
-                idx = interpret_expression(m.group('idx'), local_vars,
-                                           allow_recursion-1)
-                return val[idx]
-
-            m = re.match(r'^(?P<a>.+?)(?P<op>[%])(?P<b>.+?)$', expr)
-            if m:
-                a = interpret_expression(m.group('a'),
-                                         local_vars, allow_recursion)
-                b = 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')
-                if fname not in functions:
-                    functions[fname] = extract_function(fname)
-                argvals = [int(v) if v.isdigit() else local_vars[v]
-                           for v in m.group('args').split(',')]
-                return functions[fname](argvals)
-            raise ExtractorError(u'Unsupported JS expression %r' % expr)
-
-        def extract_function(funcname):
-            func_m = re.search(
-                r'function ' + re.escape(funcname) +
-                r'\((?P<args>[a-z,]+)\){(?P<code>[^}]+)}',
-                jscode)
-            argnames = func_m.group('args').split(',')
-
-            def resf(args):
-                local_vars = dict(zip(argnames, args))
-                for stmt in func_m.group('code').split(';'):
-                    res = interpret_statement(stmt, local_vars)
-                return res
-            return resf
-
-        initial_function = extract_function(funcname)
+             u'Initial JS player signature function name')
+
+        jsi = JSInterpreter(jscode)
+        initial_function = jsi.extract_function(funcname)
         return lambda s: initial_function([s])
 
     def _parse_sig_swf(self, file_contents):
diff --git a/youtube_dl/jsinterp.py b/youtube_dl/jsinterp.py
new file mode 100644
index 000000000..129a4027b
--- /dev/null
+++ b/youtube_dl/jsinterp.py
@@ -0,0 +1,113 @@
+from __future__ import unicode_literals
+
+import re
+
+from .utils import (
+    ExtractorError,
+)
+
+
+class JSInterpreter(object):
+    def __init__(self, code):
+        self.code = code
+        self._functions = {}
+
+    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>.*)$', stmt)
+        if ass_m:
+            if ass_m.groupdict().get('index'):
+                def assign(val):
+                    lvar = local_vars[ass_m.group('out')]
+                    idx = self.interpret_expression(
+                        ass_m.group('index'), local_vars, allow_recursion)
+                    assert isinstance(idx, int)
+                    lvar[idx] = val
+                    return val
+                expr = ass_m.group('expr')
+            else:
+                def assign(val):
+                    local_vars[ass_m.group('out')] = val
+                    return val
+                expr = ass_m.group('expr')
+        elif stmt.startswith('return '):
+            assign = lambda v: v
+            expr = stmt[len('return '):]
+        else:
+            raise ExtractorError(
+                'Cannot determine left side of statement in %r' % stmt)
+
+        v = self.interpret_expression(expr, local_vars, allow_recursion)
+        return assign(v)
+
+    def interpret_expression(self, expr, local_vars, allow_recursion):
+        if expr.isdigit():
+            return int(expr)
+
+        if expr.isalpha():
+            return local_vars[expr]
+
+        m = re.match(r'^(?P<in>[a-z]+)\.(?P<member>.*)$', expr)
+        if m:
+            member = m.group('member')
+            val = local_vars[m.group('in')]
+            if member == 'split("")':
+                return list(val)
+            if member == 'join("")':
+                return u''.join(val)
+            if member == 'length':
+                return len(val)
+            if member == 'reverse()':
+                return val[::-1]
+            slice_m = re.match(r'slice\((?P<idx>.*)\)', member)
+            if slice_m:
+                idx = self.interpret_expression(
+                    slice_m.group('idx'), local_vars, allow_recursion - 1)
+                return val[idx:]
+
+        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')
+            if fname not in self._functions:
+                self._functions[fname] = self.extract_function(fname)
+            argvals = [int(v) if v.isdigit() else local_vars[v]
+                       for v in m.group('args').split(',')]
+            return self._functions[fname](argvals)
+        raise ExtractorError('Unsupported JS expression %r' % expr)
+
+    def extract_function(self, funcname):
+        func_m = re.search(
+            r'function ' + re.escape(funcname) +
+            r'\((?P<args>[a-z,]+)\){(?P<code>[^}]+)}',
+            self.code)
+        argnames = func_m.group('args').split(',')
+
+        def resf(args):
+            local_vars = dict(zip(argnames, args))
+            for stmt in func_m.group('code').split(';'):
+                res = self.interpret_statement(stmt, local_vars)
+            return res
+        return resf
+