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

third_party/Python-Markdown/markdown/preprocessors.py

Index: third_party/Python-Markdown/markdown/preprocessors.py
diff --git a/third_party/Python-Markdown/markdown/preprocessors.py b/third_party/Python-Markdown/markdown/preprocessors.py
new file mode 100644
index 0000000000000000000000000000000000000000..7fd38d331fb5685a4c06f23e646c9d4d40e69b8b
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+"""
+PRE-PROCESSORS
+=============================================================================
+
+Preprocessors work on source text before we start doing anything too
+complicated.
+"""
+
+from __future__ import absolute_import
+from __future__ import unicode_literals
+from . import util
+from . import odict
+import re
+
+
+def build_preprocessors(md_instance, **kwargs):
+    """ Build the default set of preprocessors used by Markdown. """
+    preprocessors = odict.OrderedDict()
+    preprocessors['normalize_whitespace'] = NormalizeWhitespace(md_instance)
+    if md_instance.safeMode != 'escape':
+        preprocessors["html_block"] = HtmlBlockPreprocessor(md_instance)
+    preprocessors["reference"] = ReferencePreprocessor(md_instance)
+    return preprocessors
+
+
+class Preprocessor(util.Processor):
+    """
+    Preprocessors are run after the text is broken into lines.
+
+    Each preprocessor implements a "run" method that takes a pointer to a
+    list of lines of the document, modifies it as necessary and returns
+    either the same pointer or a pointer to a new list.
+
+    Preprocessors must extend markdown.Preprocessor.
+
+    """
+    def run(self, lines):
+        """
+        Each subclass of Preprocessor should override the `run` method, which
+        takes the document as a list of strings split by newlines and returns
+        the (possibly modified) list of lines.
+
+        """
+        pass  # pragma: no cover
+
+
+class NormalizeWhitespace(Preprocessor):
+    """ Normalize whitespace for consistant parsing. """
+
+    def run(self, lines):
+        source = '\n'.join(lines)
+        source = source.replace(util.STX, "").replace(util.ETX, "")
+        source = source.replace("\r\n", "\n").replace("\r", "\n") + "\n\n"
+        source = source.expandtabs(self.markdown.tab_length)
+        source = re.sub(r'(?<=\n) +\n', '\n', source)
+        return source.split('\n')
+
+
+class HtmlBlockPreprocessor(Preprocessor):
+    """Remove html blocks from the text and store them for later retrieval."""
+
+    right_tag_patterns = ["</%s>", "%s>"]
+    attrs_pattern = r"""
+        \s+(?P<attr>[^>"'/= ]+)=(?P<q>['"])(?P<value>.*?)(?P=q) # attr="value"
+        |                                                       # OR
+        \s+(?P<attr1>[^>"'/= ]+)=(?P<value1>[^> ]+)             # attr=value
+        |                                                       # OR
+        \s+(?P<attr2>[^>"'/= ]+)                                # attr
+        """
+    left_tag_pattern = r'^\<(?P<tag>[^> ]+)(?P<attrs>(%s)*)\s*\/?\>?' % \
+                       attrs_pattern
+    attrs_re = re.compile(attrs_pattern, re.VERBOSE)
+    left_tag_re = re.compile(left_tag_pattern, re.VERBOSE)
+    markdown_in_raw = False
+
+    def _get_left_tag(self, block):
+        m = self.left_tag_re.match(block)
+        if m:
+            tag = m.group('tag')
+            raw_attrs = m.group('attrs')
+            attrs = {}
+            if raw_attrs:
+                for ma in self.attrs_re.finditer(raw_attrs):
+                    if ma.group('attr'):
+                        if ma.group('value'):
+                            attrs[ma.group('attr').strip()] = ma.group('value')
+                        else:
+                            attrs[ma.group('attr').strip()] = ""
+                    elif ma.group('attr1'):
+                        if ma.group('value1'):
+                            attrs[ma.group('attr1').strip()] = ma.group(
+                                'value1'
+                            )
+                        else:
+                            attrs[ma.group('attr1').strip()] = ""
+                    elif ma.group('attr2'):
+                        attrs[ma.group('attr2').strip()] = ""
+            return tag, len(m.group(0)), attrs
+        else:
+            tag = block[1:].split(">", 1)[0].lower()
+            return tag, len(tag)+2, {}
+
+    def _recursive_tagfind(self, ltag, rtag, start_index, block):
+        while 1:
+            i = block.find(rtag, start_index)
+            if i == -1:
+                return -1
+            j = block.find(ltag, start_index)
+            # if no ltag, or rtag found before another ltag, return index
+            if (j > i or j == -1):
+                return i + len(rtag)
+            # another ltag found before rtag, use end of ltag as starting
+            # point and search again
+            j = block.find('>', j)
+            start_index = self._recursive_tagfind(ltag, rtag, j + 1, block)
+            if start_index == -1:
+                # HTML potentially malformed- ltag has no corresponding
+                # rtag
+                return -1
+
+    def _get_right_tag(self, left_tag, left_index, block):
+        for p in self.right_tag_patterns:
+            tag = p % left_tag
+            i = self._recursive_tagfind(
+                "<%s" % left_tag, tag, left_index, block
+            )
+            if i > 2:
+                return tag.lstrip("<").rstrip(">"), i
+        return block.rstrip()[-left_index:-1].lower(), len(block)
+
+    def _equal_tags(self, left_tag, right_tag):
+        if left_tag[0] in ['?', '@', '%']:  # handle PHP, etc.
+            return True
+        if ("/" + left_tag) == right_tag:
+            return True
+        if (right_tag == "--" and left_tag == "--"):
+            return True
+        elif left_tag == right_tag[1:] and right_tag[0] == "/":
+            return True
+        else:
+            return False
+
+    def _is_oneliner(self, tag):
+        return (tag in ['hr', 'hr/'])
+
+    def _stringindex_to_listindex(self, stringindex, items):
+        """
+        Same effect as concatenating the strings in items,
+        finding the character to which stringindex refers in that string,
+        and returning the index of the item in which that character resides.
+        """
+        items.append('dummy')
+        i, count = 0, 0
+        while count <= stringindex:
+            count += len(items[i])
+            i += 1
+        return i - 1
+
+    def _nested_markdown_in_html(self, items):
+        """Find and process html child elements of the given element block."""
+        for i, item in enumerate(items):
+            if self.left_tag_re.match(item):
+                left_tag, left_index, attrs = \
+                    self._get_left_tag(''.join(items[i:]))
+                right_tag, data_index = self._get_right_tag(
+                    left_tag, left_index, ''.join(items[i:]))
+                right_listindex = \
+                    self._stringindex_to_listindex(data_index, items[i:]) + i
+                if 'markdown' in attrs.keys():
+                    items[i] = items[i][left_index:]  # remove opening tag
+                    placeholder = self.markdown.htmlStash.store_tag(
+                        left_tag, attrs, i + 1, right_listindex + 1)
+                    items.insert(i, placeholder)
+                    if len(items) - right_listindex <= 1:  # last nest, no tail
+                        right_listindex -= 1
+                    items[right_listindex] = items[right_listindex][
+                        :-len(right_tag) - 2]  # remove closing tag
+                else:  # raw html
+                    if len(items) - right_listindex <= 1:  # last element
+                        right_listindex -= 1
+                    offset = 1 if i == right_listindex else 0
+                    placeholder = self.markdown.htmlStash.store('\n\n'.join(
+                        items[i:right_listindex + offset]))
+                    del items[i:right_listindex + offset]
+                    items.insert(i, placeholder)
+        return items
+
+    def run(self, lines):
+        text = "\n".join(lines)
+        new_blocks = []
+        text = text.rsplit("\n\n")
+        items = []
+        left_tag = ''
+        right_tag = ''
+        in_tag = False  # flag
+
+        while text:
+            block = text[0]
+            if block.startswith("\n"):
+                block = block[1:]
+            text = text[1:]
+
+            if block.startswith("\n"):
+                block = block[1:]
+
+            if not in_tag:
+                if block.startswith("<") and len(block.strip()) > 1:
+
+                    if block[1:4] == "!--":
+                        # is a comment block
+                        left_tag, left_index, attrs = "--", 2, {}
+                    else:
+                        left_tag, left_index, attrs = self._get_left_tag(block)
+                    right_tag, data_index = self._get_right_tag(left_tag,
+                                                                left_index,
+                                                                block)
+                    # keep checking conditions below and maybe just append
+
+                    if data_index < len(block) and (util.isBlockLevel(left_tag) or left_tag == '--'):
+                        text.insert(0, block[data_index:])
+                        block = block[:data_index]
+
+                    if not (util.isBlockLevel(left_tag) or block[1] in ["!", "?", "@", "%"]):
+                        new_blocks.append(block)
+                        continue
+
+                    if self._is_oneliner(left_tag):
+                        new_blocks.append(block.strip())
+                        continue
+
+                    if block.rstrip().endswith(">") \
+                            and self._equal_tags(left_tag, right_tag):
+                        if self.markdown_in_raw and 'markdown' in attrs.keys():
+                            block = block[left_index:-len(right_tag) - 2]
+                            new_blocks.append(self.markdown.htmlStash.
+                                              store_tag(left_tag, attrs, 0, 2))
+                            new_blocks.extend([block])
+                        else:
+                            new_blocks.append(
+                                self.markdown.htmlStash.store(block.strip()))
+                        continue
+                    else:
+                        # if is block level tag and is not complete
+                        if (not self._equal_tags(left_tag, right_tag)) and \
+                           (util.isBlockLevel(left_tag) or left_tag == "--"):
+                            items.append(block.strip())
+                            in_tag = True
+                        else:
+                            new_blocks.append(
+                                self.markdown.htmlStash.store(block.strip())
+                            )
+                        continue
+
+                else:
+                    new_blocks.append(block)
+
+            else:
+                items.append(block)
+
+                right_tag, data_index = self._get_right_tag(left_tag, 0, block)
+
+                if self._equal_tags(left_tag, right_tag):
+                    # if find closing tag
+
+                    if data_index < len(block):
+                        # we have more text after right_tag
+                        items[-1] = block[:data_index]
+                        text.insert(0, block[data_index:])
+
+                    in_tag = False
+                    if self.markdown_in_raw and 'markdown' in attrs.keys():
+                        items[0] = items[0][left_index:]
+                        items[-1] = items[-1][:-len(right_tag) - 2]
+                        if items[len(items) - 1]:  # not a newline/empty string
+                            right_index = len(items) + 3
+                        else:
+                            right_index = len(items) + 2
+                        new_blocks.append(self.markdown.htmlStash.store_tag(
+                            left_tag, attrs, 0, right_index))
+                        placeholderslen = len(self.markdown.htmlStash.tag_data)
+                        new_blocks.extend(
+                            self._nested_markdown_in_html(items))
+                        nests = len(self.markdown.htmlStash.tag_data) - \
+                            placeholderslen
+                        self.markdown.htmlStash.tag_data[-1 - nests][
+                            'right_index'] += nests - 2
+                    else:
+                        new_blocks.append(
+                            self.markdown.htmlStash.store('\n\n'.join(items)))
+                    items = []
+
+        if items:
+            if self.markdown_in_raw and 'markdown' in attrs.keys():
+                items[0] = items[0][left_index:]
+                items[-1] = items[-1][:-len(right_tag) - 2]
+                if items[len(items) - 1]:  # not a newline/empty string
+                    right_index = len(items) + 3
+                else:
+                    right_index = len(items) + 2
+                new_blocks.append(
+                    self.markdown.htmlStash.store_tag(
+                        left_tag, attrs, 0, right_index))
+                placeholderslen = len(self.markdown.htmlStash.tag_data)
+                new_blocks.extend(self._nested_markdown_in_html(items))
+                nests = len(self.markdown.htmlStash.tag_data) - placeholderslen
+                self.markdown.htmlStash.tag_data[-1 - nests][
+                    'right_index'] += nests - 2
+            else:
+                new_blocks.append(
+                    self.markdown.htmlStash.store('\n\n'.join(items)))
+            new_blocks.append('\n')
+
+        new_text = "\n\n".join(new_blocks)
+        return new_text.split("\n")
+
+
+class ReferencePreprocessor(Preprocessor):
+    """ Remove reference definitions from text and store for later use. """
+
+    TITLE = r'[ ]*(\"(.*)\"|\'(.*)\'|\((.*)\))[ ]*'
+    RE = re.compile(
+        r'^[ ]{0,3}\[([^\]]*)\]:\s*([^ ]*)[ ]*(%s)?$' % TITLE, re.DOTALL
+    )
+    TITLE_RE = re.compile(r'^%s$' % TITLE)
+
+    def run(self, lines):
+        new_text = []
+        while lines:
+            line = lines.pop(0)
+            m = self.RE.match(line)
+            if m:
+                id = m.group(1).strip().lower()
+                link = m.group(2).lstrip('<').rstrip('>')
+                t = m.group(5) or m.group(6) or m.group(7)
+                if not t:
+                    # Check next line for title
+                    tm = self.TITLE_RE.match(lines[0])
+                    if tm:
+                        lines.pop(0)
+                        t = tm.group(2) or tm.group(3) or tm.group(4)
+                self.markdown.references[id] = (link, t)
+            else:
+                new_text.append(line)
+
+        return new_text  # + "\n"