Re-land "Check in a simple pure-python based Markdown previewer."

third_party/Python-Markdown/markdown/util.py

Index: third_party/Python-Markdown/markdown/util.py
diff --git a/third_party/Python-Markdown/markdown/util.py b/third_party/Python-Markdown/markdown/util.py
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+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+import re
+import sys
+
+
+"""
+Python 3 Stuff
+=============================================================================
+"""
+PY3 = sys.version_info[0] == 3
+
+if PY3:  # pragma: no cover
+    string_type = str
+    text_type = str
+    int2str = chr
+else:  # pragma: no cover
+    string_type = basestring   # noqa
+    text_type = unicode        # noqa
+    int2str = unichr           # noqa
+
+
+"""
+Constants you might want to modify
+-----------------------------------------------------------------------------
+"""
+
+
+BLOCK_LEVEL_ELEMENTS = re.compile(
+    "^(p|div|h[1-6]|blockquote|pre|table|dl|ol|ul"
+    "|script|noscript|form|fieldset|iframe|math"
+    "|hr|hr/|style|li|dt|dd|thead|tbody"
+    "|tr|th|td|section|footer|header|group|figure"
+    "|figcaption|aside|article|canvas|output"
+    "|progress|video|nav)$",
+    re.IGNORECASE
+)
+# Placeholders
+STX = '\u0002'  # Use STX ("Start of text") for start-of-placeholder
+ETX = '\u0003'  # Use ETX ("End of text") for end-of-placeholder
+INLINE_PLACEHOLDER_PREFIX = STX+"klzzwxh:"
+INLINE_PLACEHOLDER = INLINE_PLACEHOLDER_PREFIX + "%s" + ETX
+INLINE_PLACEHOLDER_RE = re.compile(INLINE_PLACEHOLDER % r'([0-9]+)')
+AMP_SUBSTITUTE = STX+"amp"+ETX
+HTML_PLACEHOLDER = STX + "wzxhzdk:%s" + ETX
+HTML_PLACEHOLDER_RE = re.compile(HTML_PLACEHOLDER % r'([0-9]+)')
+TAG_PLACEHOLDER = STX + "hzzhzkh:%s" + ETX
+
+
+"""
+Constants you probably do not need to change
+-----------------------------------------------------------------------------
+"""
+
+RTL_BIDI_RANGES = (
+    ('\u0590', '\u07FF'),
+    # Hebrew (0590-05FF), Arabic (0600-06FF),
+    # Syriac (0700-074F), Arabic supplement (0750-077F),
+    # Thaana (0780-07BF), Nko (07C0-07FF).
+    ('\u2D30', '\u2D7F')  # Tifinagh
+)
+
+# Extensions should use "markdown.util.etree" instead of "etree" (or do `from
+# markdown.util import etree`).  Do not import it by yourself.
+
+try:  # pragma: no cover
+    # Is the C implementation of ElementTree available?
+    import xml.etree.cElementTree as etree
+    from xml.etree.ElementTree import Comment
+    # Serializers (including ours) test with non-c Comment
+    etree.test_comment = Comment
+    if etree.VERSION < "1.0.5":
+        raise RuntimeError("cElementTree version 1.0.5 or higher is required.")
+except (ImportError, RuntimeError):  # pragma: no cover
+    # Use the Python implementation of ElementTree?
+    import xml.etree.ElementTree as etree
+    if etree.VERSION < "1.1":
+        raise RuntimeError("ElementTree version 1.1 or higher is required")
+
+
+"""
+AUXILIARY GLOBAL FUNCTIONS
+=============================================================================
+"""
+
+
+def isBlockLevel(tag):
+    """Check if the tag is a block level HTML tag."""
+    if isinstance(tag, string_type):
+        return BLOCK_LEVEL_ELEMENTS.match(tag)
+    # Some ElementTree tags are not strings, so return False.
+    return False
+
+
+def parseBoolValue(value, fail_on_errors=True, preserve_none=False):
+    """Parses a string representing bool value. If parsing was successful,
+       returns True or False. If preserve_none=True, returns True, False,
+       or None. If parsing was not successful, raises  ValueError, or, if
+       fail_on_errors=False, returns None."""
+    if not isinstance(value, string_type):
+        if preserve_none and value is None:
+            return value
+        return bool(value)
+    elif preserve_none and value.lower() == 'none':
+        return None
+    elif value.lower() in ('true', 'yes', 'y', 'on', '1'):
+        return True
+    elif value.lower() in ('false', 'no', 'n', 'off', '0', 'none'):
+        return False
+    elif fail_on_errors:
+        raise ValueError('Cannot parse bool value: %r' % value)
+
+
+"""
+MISC AUXILIARY CLASSES
+=============================================================================
+"""
+
+
+class AtomicString(text_type):
+    """A string which should not be further processed."""
+    pass
+
+
+class Processor(object):
+    def __init__(self, markdown_instance=None):
+        if markdown_instance:
+            self.markdown = markdown_instance
+
+
+class HtmlStash(object):
+    """
+    This class is used for stashing HTML objects that we extract
+    in the beginning and replace with place-holders.
+    """
+
+    def __init__(self):
+        """ Create a HtmlStash. """
+        self.html_counter = 0  # for counting inline html segments
+        self.rawHtmlBlocks = []
+        self.tag_counter = 0
+        self.tag_data = []  # list of dictionaries in the order tags appear
+
+    def store(self, html, safe=False):
+        """
+        Saves an HTML segment for later reinsertion.  Returns a
+        placeholder string that needs to be inserted into the
+        document.
+
+        Keyword arguments:
+
+        * html: an html segment
+        * safe: label an html segment as safe for safemode
+
+        Returns : a placeholder string
+
+        """
+        self.rawHtmlBlocks.append((html, safe))
+        placeholder = self.get_placeholder(self.html_counter)
+        self.html_counter += 1
+        return placeholder
+
+    def reset(self):
+        self.html_counter = 0
+        self.rawHtmlBlocks = []
+
+    def get_placeholder(self, key):
+        return HTML_PLACEHOLDER % key
+
+    def store_tag(self, tag, attrs, left_index, right_index):
+        """Store tag data and return a placeholder."""
+        self.tag_data.append({'tag': tag, 'attrs': attrs,
+                              'left_index': left_index,
+                              'right_index': right_index})
+        placeholder = TAG_PLACEHOLDER % str(self.tag_counter)
+        self.tag_counter += 1  # equal to the tag's index in self.tag_data
+        return placeholder