Initial import

ebook_converter/tinycss/parsing.py

@@ -0,0 +1,165 @@
+# coding: utf8
+"""
+    tinycss.parsing
+    ---------------
+
+    Utilities for parsing lists of tokens.
+
+    :copyright: (c) 2012 by Simon Sapin.
+    :license: BSD, see LICENSE for more details.
+"""
+
+from __future__ import unicode_literals
+
+
+# TODO: unit tests
+
+def split_on_comma(tokens):
+    """Split a list of tokens on commas, ie ``,`` DELIM tokens.
+
+    Only "top-level" comma tokens are splitting points, not commas inside a
+    function or other :class:`ContainerToken`.
+
+    :param tokens:
+        An iterable of :class:`~.token_data.Token` or
+        :class:`~.token_data.ContainerToken`.
+    :returns:
+        A list of lists of tokens
+
+    """
+    parts = []
+    this_part = []
+    for token in tokens:
+        if token.type == 'DELIM' and token.value == ',':
+            parts.append(this_part)
+            this_part = []
+        else:
+            this_part.append(token)
+    parts.append(this_part)
+    return parts
+
+
+def strip_whitespace(tokens):
+    """Remove whitespace at the beggining and end of a token list.
+
+    Whitespace tokens in-between other tokens in the list are preserved.
+
+    :param tokens:
+        A list of :class:`~.token_data.Token` or
+        :class:`~.token_data.ContainerToken`.
+    :return:
+        A new sub-sequence of the list.
+
+    """
+    for i, token in enumerate(tokens):
+        if token.type != 'S':
+            break
+    else:
+        return []  # only whitespace
+    tokens = tokens[i:]
+    while tokens and tokens[-1].type == 'S':
+        tokens.pop()
+    return tokens
+
+
+def remove_whitespace(tokens):
+    """Remove any top-level whitespace in a token list.
+
+    Whitespace tokens inside recursive :class:`~.token_data.ContainerToken`
+    are preserved.
+
+    :param tokens:
+        A list of :class:`~.token_data.Token` or
+        :class:`~.token_data.ContainerToken`.
+    :return:
+        A new sub-sequence of the list.
+
+    """
+    return [token for token in tokens if token.type != 'S']
+
+
+def validate_value(tokens):
+    """Validate a property value.
+
+    :param tokens:
+        an iterable of tokens
+    :raises:
+        :class:`ParseError` if there is any invalid token for the 'value'
+        production of the core grammar.
+
+    """
+    for token in tokens:
+        type_ = token.type
+        if type_ == '{':
+            validate_block(token.content, 'property value')
+        else:
+            validate_any(token, 'property value')
+
+def validate_block(tokens, context):
+    """
+    :raises:
+        :class:`ParseError` if there is any invalid token for the 'block'
+        production of the core grammar.
+    :param tokens: an iterable of tokens
+    :param context: a string for the 'unexpected in ...' message
+
+    """
+    for token in tokens:
+        type_ = token.type
+        if type_ == '{':
+            validate_block(token.content, context)
+        elif type_ not in (';', 'ATKEYWORD'):
+            validate_any(token, context)
+
+
+def validate_any(token, context):
+    """
+    :raises:
+        :class:`ParseError` if this is an invalid token for the
+        'any' production of the core grammar.
+    :param token: a single token
+    :param context: a string for the 'unexpected in ...' message
+
+    """
+    type_ = token.type
+    if type_ in ('FUNCTION', '(', '['):
+        for token in token.content:
+            validate_any(token, type_)
+    elif type_ not in ('S', 'IDENT', 'DIMENSION', 'PERCENTAGE', 'NUMBER',
+                       'INTEGER', 'URI', 'DELIM', 'STRING', 'HASH', ':',
+                       'UNICODE-RANGE'):
+        if type_ in ('}', ')', ']'):
+            adjective = 'unmatched'
+        else:
+            adjective = 'unexpected'
+        raise ParseError(token,
+            '{0} {1} token in {2}'.format(adjective, type_, context))
+
+
+class ParseError(ValueError):
+    """Details about a CSS syntax error. Usually indicates that something
+    (a rule or a declaration) was ignored and will not appear as a parsed
+    object.
+
+    This exception is typically logged in a list rather than being propagated
+    to the user API.
+
+    .. attribute:: line
+
+        Source line where the error occured.
+
+    .. attribute:: column
+
+        Column in the source line where the error occured.
+
+    .. attribute:: reason
+
+        What happend (a string).
+
+    """
+    def __init__(self, subject, reason):
+        self.line = subject.line
+        self.column = subject.column
+        self.reason = reason
+        super(ParseError, self).__init__(
+            'Parse error at {0.line}:{0.column}, {0.reason}'.format(self))