1 files changed, 137 insertions, 0 deletions
diff --git a/src/mistune/helpers.py b/src/mistune/helpers.py
new file mode 100644
index 0000000..04c1df1
--- /dev/null
+++ b/src/mistune/helpers.py
@@ -0,0 +1,137 @@
+import re
+import string
+from .util import escape_url
+
+PREVENT_BACKSLASH = r'(?<!\\)(?:\\\\)*'
+PUNCTUATION = r'[' + re.escape(string.punctuation) + r']'
+
+LINK_LABEL = r'(?:[^\\\[\]]|\\.){0,500}'
+
+LINK_BRACKET_START = re.compile(r'[ \t]*\n?[ \t]*<')
+LINK_BRACKET_RE = re.compile(r'<([^<>\n\\\x00]*)>')
+LINK_HREF_BLOCK_RE = re.compile(r'[ \t]*\n?[ \t]*([^\s]+)(?:\s|$)')
+LINK_HREF_INLINE_RE = re.compile(
+    r'[ \t]*\n?[ \t]*([^ \t\n]*?)(?:[ \t\n]|'
+    r'(?:' + PREVENT_BACKSLASH + r'\)))'
+)
+
+LINK_TITLE_RE = re.compile(
+    r'[ \t\n]+('
+    r'"(?:\\' + PUNCTUATION + r'|[^"\x00])*"|'  # "title"
+    r"'(?:\\" + PUNCTUATION + r"|[^'\x00])*'"  # 'title'
+    r')'
+)
+PAREN_END_RE = re.compile(r'\s*\)')
+
+HTML_TAGNAME = r'[A-Za-z][A-Za-z0-9-]*'
+HTML_ATTRIBUTES = (
+    r'(?:\s+[A-Za-z_:][A-Za-z0-9_.:-]*'
+    r'(?:\s*=\s*(?:[^ !"\'=<>`]+|\'[^\']*?\'|"[^\"]*?"))?)*'
+)
+
+BLOCK_TAGS = (
+    'address', 'article', 'aside', 'base', 'basefont', 'blockquote',
+    'body', 'caption', 'center', 'col', 'colgroup', 'dd', 'details',
+    'dialog', 'dir', 'div', 'dl', 'dt', 'fieldset', 'figcaption',
+    'figure', 'footer', 'form', 'frame', 'frameset', 'h1', 'h2', 'h3',
+    'h4', 'h5', 'h6', 'head', 'header', 'hr', 'html', 'iframe',
+    'legend', 'li', 'link', 'main', 'menu', 'menuitem', 'meta', 'nav',
+    'noframes', 'ol', 'optgroup', 'option', 'p', 'param', 'section',
+    'source', 'summary', 'table', 'tbody', 'td', 'tfoot', 'th', 'thead',
+    'title', 'tr', 'track', 'ul'
+)
+PRE_TAGS = ('pre', 'script', 'style', 'textarea')
+
+_INLINE_LINK_LABEL_RE = re.compile(LINK_LABEL + r'\]')
+_INLINE_SQUARE_BRACKET_RE = re.compile(PREVENT_BACKSLASH + r'[\[\]]')
+_ESCAPE_CHAR_RE = re.compile(r'\\(' + PUNCTUATION + r')')
+
+
+def unescape_char(text):
+    return _ESCAPE_CHAR_RE.sub(r'\1', text)
+
+
+def parse_link_text(src, pos):
+    level = 1
+    found = False
+    start_pos = pos
+
+    while pos < len(src):
+        m = _INLINE_SQUARE_BRACKET_RE.search(src, pos)
+        if not m:
+            break
+
+        pos = m.end()
+        marker = m.group(0)
+        if marker == ']':
+            level -= 1
+            if level == 0:
+                found = True
+                break
+        else:
+            level += 1
+
+    if found:
+        text = src[start_pos:pos-1]
+        return text, pos
+    return None, None
+
+
+def parse_link_label(src, start_pos):
+    m = _INLINE_LINK_LABEL_RE.match(src, start_pos)
+    if m:
+        label = m.group(0)[:-1]
+        return label, m.end()
+    return None, None
+
+
+def parse_link_href(src, start_pos, block=False):
+    m = LINK_BRACKET_START.match(src, start_pos)
+    if m:
+        start_pos = m.end() - 1
+        m = LINK_BRACKET_RE.match(src, start_pos)
+        if m:
+            return m.group(1), m.end()
+        return None, None
+
+    if block:
+        m = LINK_HREF_BLOCK_RE.match(src, start_pos)
+    else:
+        m = LINK_HREF_INLINE_RE.match(src, start_pos)
+
+    if not m:
+        return None, None
+
+    end_pos = m.end()
+    href = m.group(1)
+
+    if block and src[end_pos - 1] == href[-1]:
+        return href, end_pos
+    return href, end_pos - 1
+
+
+def parse_link_title(src, start_pos, max_pos):
+    m = LINK_TITLE_RE.match(src, start_pos, max_pos)
+    if m:
+        title = m.group(1)[1:-1]
+        title = unescape_char(title)
+        return title, m.end()
+    return None, None
+
+
+def parse_link(src, pos):
+    href, href_pos = parse_link_href(src, pos)
+    if href is None:
+        return None, None
+
+    title, title_pos = parse_link_title(src, href_pos, len(src))
+    next_pos = title_pos or href_pos
+    m = PAREN_END_RE.match(src, next_pos)
+    if not m:
+        return None, None
+
+    href = unescape_char(href)
+    attrs = {'url': escape_url(href)}
+    if title:
+        attrs['title'] = title
+    return attrs, m.end()