"""
# YAML Meta Data Extension for [Python-Markdown](https://github.com/waylan/Python-Markdown)

This extension adds YAML meta data handling to markdown.

As in the original, meta data is parsed but not used in processing.

(YAML meta data is used e.g. by [pandoc](http://johnmacfarlane.net/pandoc/))

Dependencies: [PyYAML](http://pyyaml.org/)


Basic Usage:

	>>> import markdown
	>>> text = '''---
	... Title: Test Doc.
	... Author: Waylan Limberg
	... Blank_Data:
	... ...
	...
	... The body. This is paragraph one.
	... '''
	>>> md = markdown.Markdown(['meta_yaml'])
	>>> print(md.convert(text))
	<p>The body. This is paragraph one.</p>
	>>> print(md.Meta) # doctest: +SKIP
	{'blank_data': [''], 'author': ['Waylan Limberg'], 'title': ['Test Doc.']}

Make sure text without Meta Data still works (markdown < 1.6b returns a <p>).

	>>> text = '	Some Code - not extra lines of meta data.'
	>>> md = markdown.Markdown(['meta_yaml'])
	>>> print(md.convert(text))
	<pre><code>Some Code - not extra lines of meta data.
	</code></pre>
	>>> md.Meta
	{}


Copyright 2014 Bernhard Fisseni

Based on the meta data extension included with Python-Markdown,
Copyright 2007-2008 [Waylan Limberg](http://achinghead.com).

License: BSD (see LICENSE.md for details)

"""

from __future__ import absolute_import
from __future__ import unicode_literals
from markdown import Extension
from markdown.preprocessors import Preprocessor
import yaml
# from yaml.scanner import ScannerError


class MetaYamlExtension (Extension):
	"""Extension for parsing YAML-Metadata with Python-Markdown."""

	def extendMarkdown(self, md, md_globals):
		"""Add MetaYamlPreprocessor to Markdown instance."""

		md.preprocessors.add('meta_yaml', MetaYamlPreprocessor(md), "_begin")


class MetaYamlPreprocessor(Preprocessor):
	"""
	Get Meta-Data.

	A YAML block is delimited by
	- a line '---' at the start
	- and a '...' or '---' line
	at the end.
	"""

	def run(self, lines):
		""" Parse Meta-Data and store in Markdown.Meta. """

		in_yaml = False
		yaml_block = []
		line = lines.pop(0)

		if line == '---':
			in_yaml = True
		else:
			lines.insert(0, line)

		while in_yaml and lines:
			line = lines.pop(0)
			if line == '---' or line == '...':
				break
			yaml_block.append(line)

		if yaml_block:
			yaml_block = "\n".join(yaml_block)
			meta = yaml.load(yaml_block)
			self.markdown.Meta = meta

		return lines