1 files changed, 146 insertions, 0 deletions
diff --git a/src/mistune/renderers/markdown.py b/src/mistune/renderers/markdown.py
new file mode 100644
index 0000000..78334bc
--- /dev/null
+++ b/src/mistune/renderers/markdown.py
@@ -0,0 +1,146 @@
+import re
+from typing import Dict, Any
+from textwrap import indent
+from ._list import render_list
+from ..core import BaseRenderer, BlockState
+from ..util import strip_end
+
+fenced_re = re.compile(r'^(?:`|~)+', re.M)
+
+
+class MarkdownRenderer(BaseRenderer):
+    """A renderer to re-format Markdown text."""
+    NAME = 'markdown'
+
+    def __call__(self, tokens, state: BlockState):
+        out = self.render_tokens(tokens, state)
+        # special handle for line breaks
+        out += '\n\n'.join(self.render_referrences(state)) + '\n'
+        return strip_end(out)
+
+    def render_referrences(self, state: BlockState):
+        ref_links = state.env['ref_links']
+        for key in ref_links:
+            attrs = ref_links[key]
+            text = '[' + attrs['label'] + ']: ' + attrs['url']
+            title = attrs.get('title')
+            if title:
+                text += ' "' + title + '"'
+            yield text
+
+    def render_children(self, token, state: BlockState):
+        children = token['children']
+        return self.render_tokens(children, state)
+
+    def text(self, token: Dict[str, Any], state: BlockState) -> str:
+        return token['raw']
+
+    def emphasis(self, token: Dict[str, Any], state: BlockState) -> str:
+        return '*' + self.render_children(token, state) + '*'
+
+    def strong(self, token: Dict[str, Any], state: BlockState) -> str:
+        return '**' + self.render_children(token, state) + '**'
+
+    def link(self, token: Dict[str, Any], state: BlockState) -> str:
+        label = token.get('label')
+        text = self.render_children(token, state)
+        out = '[' + text + ']'
+        if label:
+            return out + '[' + label + ']'
+
+        attrs = token['attrs']
+        url = attrs['url']
+        title = attrs.get('title')
+        if text == url and not title:
+            return '<' + text + '>'
+        elif 'mailto:' + text == url and not title:
+            return '<' + text + '>'
+
+        out += '('
+        if '(' in url or ')' in url:
+            out += '<' + url + '>'
+        else:
+            out += url
+        if title:
+            out += ' "' + title + '"'
+        return out + ')'
+
+    def image(self, token: Dict[str, Any], state: BlockState) -> str:
+        return '!' + self.link(token, state)
+
+    def codespan(self, token: Dict[str, Any], state: BlockState) -> str:
+        return '`' + token['raw'] + '`'
+
+    def linebreak(self, token: Dict[str, Any], state: BlockState) -> str:
+        return '  \n'
+
+    def softbreak(self, token: Dict[str, Any], state: BlockState) -> str:
+        return '\n'
+
+    def blank_line(self, token: Dict[str, Any], state: BlockState) -> str:
+        return ''
+
+    def inline_html(self, token: Dict[str, Any], state: BlockState) -> str:
+        return token['raw']
+
+    def paragraph(self, token: Dict[str, Any], state: BlockState) -> str:
+        text = self.render_children(token, state)
+        return text + '\n\n'
+
+    def heading(self, token: Dict[str, Any], state: BlockState) -> str:
+        level = token['attrs']['level']
+        marker = '#' * level
+        text = self.render_children(token, state)
+        return marker + ' ' + text + '\n\n'
+
+    def thematic_break(self, token: Dict[str, Any], state: BlockState) -> str:
+        return '***\n\n'
+
+    def block_text(self, token: Dict[str, Any], state: BlockState) -> str:
+        return self.render_children(token, state) + '\n'
+
+    def block_code(self, token: Dict[str, Any], state: BlockState) -> str:
+        attrs = token.get('attrs', {})
+        info = attrs.get('info', '')
+        code = token['raw']
+        if code and code[-1] != '\n':
+            code += '\n'
+
+        marker = token.get('marker')
+        if not marker:
+            marker = _get_fenced_marker(code)
+        return marker + info + '\n' + code + marker + '\n\n'
+
+    def block_quote(self, token: Dict[str, Any], state: BlockState) -> str:
+        text = indent(self.render_children(token, state), '> ')
+        return text + '\n\n'
+
+    def block_html(self, token: Dict[str, Any], state: BlockState) -> str:
+        return token['raw'] + '\n\n'
+
+    def block_error(self, token: Dict[str, Any], state: BlockState) -> str:
+        return ''
+
+    def list(self, token: Dict[str, Any], state: BlockState) -> str:
+        return render_list(self, token, state)
+
+
+def _get_fenced_marker(code):
+    found = fenced_re.findall(code)
+    if not found:
+        return '```'
+
+    ticks = []  # `
+    waves = []  # ~
+    for s in found:
+        if s[0] == '`':
+            ticks.append(len(s))
+        else:
+            waves.append(len(s))
+
+    if not ticks:
+        return '```'
+
+    if not waves:
+        return '~~~'
+    return '`' * (max(ticks) + 1)