"""
Python-Markdown Markdown in HTML Extension
===============================

An implementation of [PHP Markdown Extra](http://michelf.com/projects/php-markdown/extra/)'s
parsing of Markdown syntax in raw HTML.

See <https://Python-Markdown.github.io/extensions/raw_html>
for documentation.

Copyright The Python Markdown Project

License: [BSD](https://opensource.org/licenses/bsd-license.php)

"""

from . import Extension
from ..blockprocessors import BlockProcessor
from ..preprocessors import Preprocessor
from ..postprocessors import RawHtmlPostprocessor
from .. import util
from ..htmlparser import HTMLExtractor, blank_line_re
import xml.etree.ElementTree as etree


class HTMLExtractorExtra(HTMLExtractor):
    """
    Override `HTMLExtractor` and create `etree` `Elements` for any elements which should have content parsed as
    Markdown.
    """

    def __init__(self, md, *args, **kwargs):
        # All block-level tags.
        self.block_level_tags = set(md.block_level_elements.copy())
        # Block-level tags in which the content only gets span level parsing
        self.span_tags = set(
            ['address', 'dd', 'dt', 'h1', 'h2', 'h3', 'h4', 'h5', 'h6', 'legend', 'li', 'p', 'summary', 'td', 'th']
        )
        # Block-level tags which never get their content parsed.
        self.raw_tags = set(['canvas', 'math', 'option', 'pre', 'script', 'style', 'textarea'])

        super().__init__(md, *args, **kwargs)

        # Block-level tags in which the content gets parsed as blocks
        self.block_tags = set(self.block_level_tags) - (self.span_tags | self.raw_tags | self.empty_tags)
        self.span_and_blocks_tags = self.block_tags | self.span_tags

    def reset(self):
        """Reset this instance.  Loses all unprocessed data."""
        self.mdstack = []  # When markdown=1, stack contains a list of tags
        self.treebuilder = etree.TreeBuilder()
        self.mdstate = []  # one of 'block', 'span', 'off', or None
        super().reset()

    def close(self):
        """Handle any buffered data."""
        super().close()
        # Handle any unclosed tags.
        if self.mdstack:
            # Close the outermost parent. `handle_endtag` will close all unclosed children.
            self.handle_endtag(self.mdstack[0])

    def get_element(self):
        """ Return element from `treebuilder` and reset `treebuilder` for later use. """
        element = self.treebuilder.close()
        self.treebuilder = etree.TreeBuilder()
        return element

    def get_state(self, tag, attrs):
        """ Return state from tag and `markdown` attribute. One of 'block', 'span', or 'off'. """
        md_attr = attrs.get('markdown', '0')
        if md_attr == 'markdown':
            # `<tag markdown>` is the same as `<tag markdown='1'>`.
            md_attr = '1'
        parent_state = self.mdstate[-1] if self.mdstate else None
        if parent_state == 'off' or (parent_state == 'span' and md_attr != '0'):
            # Only use the parent state if it is more restrictive than the markdown attribute.
            md_attr = parent_state
        if ((md_attr == '1' and tag in self.block_tags) or
                (md_attr == 'block' and tag in self.span_and_blocks_tags)):
            return 'block'
        elif ((md_attr == '1' and tag in self.span_tags) or
              (md_attr == 'span' and tag in self.span_and_blocks_tags)):
            return 'span'
        elif tag in self.block_level_tags:
            return 'off'
        else:  # pragma: no cover
            return None

    def handle_starttag(self, tag, attrs):
        # Handle tags that should always be empty and do not specify a closing tag
        if tag in self.empty_tags and (self.at_line_start() or self.intail):
            attrs = {key: value if value is not None else key for key, value in attrs}
            if "markdown" in attrs:
                attrs.pop('markdown')
                element = etree.Element(tag, attrs)
                data = etree.tostring(element, encoding='unicode', method='html')
            else:
                data = self.get_starttag_text()
            self.handle_empty_tag(data, True)
            return

        if tag in self.block_level_tags and (self.at_line_start() or self.intail):
            # Valueless attribute (ex: `<tag checked>`) results in `[('checked', None)]`.
            # Convert to `{'checked': 'checked'}`.
            attrs = {key: value if value is not None else key for key, value in attrs}
            state = self.get_state(tag, attrs)
            if self.inraw or (state in [None, 'off'] and not self.mdstack):
                # fall back to default behavior
                attrs.pop('markdown', None)
                super().handle_starttag(tag, attrs)
            else:
                if 'p' in self.mdstack and tag in self.block_level_tags:
                    # Close unclosed 'p' tag
                    self.handle_endtag('p')
                self.mdstate.append(state)
                self.mdstack.append(tag)
                attrs['markdown'] = state
                self.treebuilder.start(tag, attrs)
        else:
            # Span level tag
            if self.inraw:
                super().handle_starttag(tag, attrs)
            else:
                text = self.get_starttag_text()
                if self.mdstate and self.mdstate[-1] == "off":
                    self.handle_data(self.md.htmlStash.store(text))
                else:
                    self.handle_data(text)
                if tag in self.CDATA_CONTENT_ELEMENTS:
                    # This is presumably a standalone tag in a code span (see #1036).
                    self.clear_cdata_mode()

    def handle_endtag(self, tag):
        if tag in self.block_level_tags:
            if self.inraw:
                super().handle_endtag(tag)
            elif tag in self.mdstack:
                # Close element and any unclosed children
                while self.mdstack:
                    item = self.mdstack.pop()
                    self.mdstate.pop()
                    self.treebuilder.end(item)
                    if item == tag:
                        break
                if not self.mdstack:
                    # Last item in stack is closed. Stash it
                    element = self.get_element()
                    # Get last entry to see if it ends in newlines
                    # If it is an element, assume there is no newlines
                    item = self.cleandoc[-1] if self.cleandoc else ''
                    # If we only have one newline before block element, add another
                    if not item.endswith('\n\n') and item.endswith('\n'):
                        self.cleandoc.append('\n')
                    self.cleandoc.append(self.md.htmlStash.store(element))
                    self.cleandoc.append('\n\n')
                    self.state = []
                    # Check if element has a tail
                    if not blank_line_re.match(
                            self.rawdata[self.line_offset + self.offset + len(self.get_endtag_text(tag)):]):
                        # More content exists after `endtag`.
                        self.intail = True
            else:
                # Treat orphan closing tag as a span level tag.
                text = self.get_endtag_text(tag)
                if self.mdstate and self.mdstate[-1] == "off":
                    self.handle_data(self.md.htmlStash.store(text))
                else:
                    self.handle_data(text)
        else:
            # Span level tag
            if self.inraw:
                super().handle_endtag(tag)
            else:
                text = self.get_endtag_text(tag)
                if self.mdstate and self.mdstate[-1] == "off":
                    self.handle_data(self.md.htmlStash.store(text))
                else:
                    self.handle_data(text)

    def handle_startendtag(self, tag, attrs):
        if tag in self.empty_tags:
            attrs = {key: value if value is not None else key for key, value in attrs}
            if "markdown" in attrs:
                attrs.pop('markdown')
                element = etree.Element(tag, attrs)
                data = etree.tostring(element, encoding='unicode', method='html')
            else:
                data = self.get_starttag_text()
        else:
            data = self.get_starttag_text()
        self.handle_empty_tag(data, is_block=self.md.is_block_level(tag))

    def handle_data(self, data):
        if self.intail and '\n' in data:
            self.intail = False
        if self.inraw or not self.mdstack:
            super().handle_data(data)
        else:
            self.treebuilder.data(data)

    def handle_empty_tag(self, data, is_block):
        if self.inraw or not self.mdstack:
            super().handle_empty_tag(data, is_block)
        else:
            if self.at_line_start() and is_block:
                self.handle_data('\n' + self.md.htmlStash.store(data) + '\n\n')
            else:
                self.handle_data(self.md.htmlStash.store(data))

    def parse_pi(self, i):
        if self.at_line_start() or self.intail or self.mdstack:
            # The same override exists in `HTMLExtractor` without the check
            # for `mdstack`. Therefore, use parent of `HTMLExtractor` instead.
            return super(HTMLExtractor, self).parse_pi(i)
        # This is not the beginning of a raw block so treat as plain data
        # and avoid consuming any tags which may follow (see #1066).
        self.handle_data('<?')
        return i + 2

    def parse_html_declaration(self, i):
        if self.at_line_start() or self.intail or self.mdstack:
            # The same override exists in `HTMLExtractor` without the check
            # for `mdstack`. Therefore, use parent of `HTMLExtractor` instead.
            return super(HTMLExtractor, self).parse_html_declaration(i)
        # This is not the beginning of a raw block so treat as plain data
        # and avoid consuming any tags which may follow (see #1066).
        self.handle_data('<!')
        return i + 2


class HtmlBlockPreprocessor(Preprocessor):
    """Remove html blocks from the text and store them for later retrieval."""

    def run(self, lines):
        source = '\n'.join(lines)
        parser = HTMLExtractorExtra(self.md)
        parser.feed(source)
        parser.close()
        return ''.join(parser.cleandoc).split('\n')


class MarkdownInHtmlProcessor(BlockProcessor):
    """Process Markdown Inside HTML Blocks which have been stored in the `HtmlStash`."""

    def test(self, parent, block):
        # Always return True. `run` will return `False` it not a valid match.
        return True

    def parse_element_content(self, element):
        """
        Recursively parse the text content of an `etree` Element as Markdown.

        Any block level elements generated from the Markdown will be inserted as children of the element in place
        of the text content. All `markdown` attributes are removed. For any elements in which Markdown parsing has
        been disabled, the text content of it and its children are wrapped in an `AtomicString`.
        """

        md_attr = element.attrib.pop('markdown', 'off')

        if md_attr == 'block':
            # Parse content as block level
            # The order in which the different parts are parsed (text, children, tails) is important here as the
            # order of elements needs to be preserved. We can't be inserting items at a later point in the current
            # iteration as we don't want to do raw processing on elements created from parsing Markdown text (for
            # example). Therefore, the order of operations is children, tails, text.

            # Recursively parse existing children from raw HTML
            for child in list(element):
                self.parse_element_content(child)

            # Parse Markdown text in tail of children. Do this separate to avoid raw HTML parsing.
            # Save the position of each item to be inserted later in reverse.
            tails = []
            for pos, child in enumerate(element):
                if child.tail:
                    block = child.tail.rstrip('\n')
                    child.tail = ''
                    # Use a dummy placeholder element.
                    dummy = etree.Element('div')
                    self.parser.parseBlocks(dummy, block.split('\n\n'))
                    children = list(dummy)
                    children.reverse()
                    tails.append((pos + 1, children))

            # Insert the elements created from the tails in reverse.
            tails.reverse()
            for pos, tail in tails:
                for item in tail:
                    element.insert(pos, item)

            # Parse Markdown text content. Do this last to avoid raw HTML parsing.
            if element.text:
                block = element.text.rstrip('\n')
                element.text = ''
                # Use a dummy placeholder element as the content needs to get inserted before existing children.
                dummy = etree.Element('div')
                self.parser.parseBlocks(dummy, block.split('\n\n'))
                children = list(dummy)
                children.reverse()
                for child in children:
                    element.insert(0, child)

        elif md_attr == 'span':
            # Span level parsing will be handled by inline processors.
            # Walk children here to remove any `markdown` attributes.
            for child in list(element):
                self.parse_element_content(child)

        else:
            # Disable inline parsing for everything else
            if element.text is None:
                element.text = ''
            element.text = util.AtomicString(element.text)
            for child in list(element):
                self.parse_element_content(child)
                if child.tail:
                    child.tail = util.AtomicString(child.tail)

    def run(self, parent, blocks):
        m = util.HTML_PLACEHOLDER_RE.match(blocks[0])
        if m:
            index = int(m.group(1))
            element = self.parser.md.htmlStash.rawHtmlBlocks[index]
            if isinstance(element, etree.Element):
                # We have a matched element. Process it.
                blocks.pop(0)
                self.parse_element_content(element)
                parent.append(element)
                # Cleanup stash. Replace element with empty string to avoid confusing postprocessor.
                self.parser.md.htmlStash.rawHtmlBlocks.pop(index)
                self.parser.md.htmlStash.rawHtmlBlocks.insert(index, '')
                # Confirm the match to the `blockparser`.
                return True
        # No match found.
        return False


class MarkdownInHTMLPostprocessor(RawHtmlPostprocessor):
    def stash_to_string(self, text):
        """ Override default to handle any `etree` elements still in the stash. """
        if isinstance(text, etree.Element):
            return self.md.serializer(text)
        else:
            return str(text)


class MarkdownInHtmlExtension(Extension):
    """Add Markdown parsing in HTML to Markdown class."""

    def extendMarkdown(self, md):
        """ Register extension instances. """

        # Replace raw HTML preprocessor
        md.preprocessors.register(HtmlBlockPreprocessor(md), 'html_block', 20)
        # Add `blockprocessor` which handles the placeholders for `etree` elements
        md.parser.blockprocessors.register(
            MarkdownInHtmlProcessor(md.parser), 'markdown_block', 105
        )
        # Replace raw HTML postprocessor
        md.postprocessors.register(MarkdownInHTMLPostprocessor(md), 'raw_html', 30)


def makeExtension(**kwargs):  # pragma: no cover
    return MarkdownInHtmlExtension(**kwargs)
