1 files changed, 132 insertions, 0 deletions
diff --git a/youtube/template.py b/youtube/template.py
new file mode 100644
index 0000000..7f13415
--- /dev/null
+++ b/youtube/template.py
@@ -0,0 +1,132 @@
+
+import re as _re
+from collections import ChainMap as _ChainMap
+
+class _TemplateMetaclass(type):
+    pattern = r"""
+    %(delim)s(?:
+      (?P<escaped>%(delim)s) |   # Escape sequence of two delimiters
+      (?P<named>%(id)s)      |   # delimiter and a Python identifier
+      {(?P<braced>%(id)s)}   |   # delimiter and a braced identifier
+      (?P<invalid>)              # Other ill-formed delimiter exprs
+    )
+    """
+
+    def __init__(cls, name, bases, dct):
+        super(_TemplateMetaclass, cls).__init__(name, bases, dct)
+        if 'pattern' in dct:
+            pattern = cls.pattern
+        else:
+            pattern = _TemplateMetaclass.pattern % {
+                'delim' : _re.escape(cls.delimiter),
+                'id'    : cls.idpattern,
+                }
+        cls.pattern = _re.compile(pattern, cls.flags | _re.VERBOSE)
+
+
+class Template(metaclass=_TemplateMetaclass):
+    """A string class for supporting $-substitutions."""
+
+    delimiter = '$'
+    idpattern = r'[_a-z][_a-z0-9]*'
+    flags = _re.IGNORECASE
+
+    def __init__(self, template):
+        self.template = template
+
+    # Search for $$, $identifier, ${identifier}, and any bare $'s
+
+    def _invalid(self, mo):
+        i = mo.start('invalid')
+        lines = self.template[:i].splitlines(keepends=True)
+        if not lines:
+            colno = 1
+            lineno = 1
+        else:
+            colno = i - len(''.join(lines[:-1]))
+            lineno = len(lines)
+        raise ValueError('Invalid placeholder in string: line %d, col %d' %
+                         (lineno, colno))
+
+    def substitute(*args, **kws):
+        if not args:
+            raise TypeError("descriptor 'substitute' of 'Template' object "
+                            "needs an argument")
+        self, *args = args  # allow the "self" keyword be passed
+        if len(args) > 1:
+            raise TypeError('Too many positional arguments')
+        if not args:
+            mapping = kws
+        elif kws:
+            mapping = _ChainMap(kws, args[0])
+        else:
+            mapping = args[0]
+        # Helper function for .sub()
+        def convert(mo):
+            # Check the most common path first.
+            named = mo.group('named') or mo.group('braced')
+            if named is not None:
+                return str(mapping.get(named,''))
+            if mo.group('escaped') is not None:
+                return self.delimiter
+            if mo.group('invalid') is not None:
+                self._invalid(mo)
+            raise ValueError('Unrecognized named group in pattern',
+                             self.pattern)
+        return self.pattern.sub(convert, self.template)
+    
+    def strict_substitute(*args, **kws):
+        if not args:
+            raise TypeError("descriptor 'substitute' of 'Template' object "
+                            "needs an argument")
+        self, *args = args  # allow the "self" keyword be passed
+        if len(args) > 1:
+            raise TypeError('Too many positional arguments')
+        if not args:
+            mapping = kws
+        elif kws:
+            mapping = _ChainMap(kws, args[0])
+        else:
+            mapping = args[0]
+        # Helper function for .sub()
+        def convert(mo):
+            # Check the most common path first.
+            named = mo.group('named') or mo.group('braced')
+            if named is not None:
+                return str(mapping[named])
+            if mo.group('escaped') is not None:
+                return self.delimiter
+            if mo.group('invalid') is not None:
+                self._invalid(mo)
+            raise ValueError('Unrecognized named group in pattern',
+                             self.pattern)
+        return self.pattern.sub(convert, self.template)
+
+    def safe_substitute(*args, **kws):
+        if not args:
+            raise TypeError("descriptor 'safe_substitute' of 'Template' object "
+                            "needs an argument")
+        self, *args = args  # allow the "self" keyword be passed
+        if len(args) > 1:
+            raise TypeError('Too many positional arguments')
+        if not args:
+            mapping = kws
+        elif kws:
+            mapping = _ChainMap(kws, args[0])
+        else:
+            mapping = args[0]
+        # Helper function for .sub()
+        def convert(mo):
+            named = mo.group('named') or mo.group('braced')
+            if named is not None:
+                try:
+                    return str(mapping[named])
+                except KeyError:
+                    return mo.group()
+            if mo.group('escaped') is not None:
+                return self.delimiter
+            if mo.group('invalid') is not None:
+                return mo.group()
+            raise ValueError('Unrecognized named group in pattern',
+                             self.pattern)
+        return self.pattern.sub(convert, self.template)
+\ No newline at end of file