# encoding: utf-8
"""Use the HTMLParser library to parse HTML files that aren't too bad."""

# Use of this source code is governed by the MIT license.
__license__ = "MIT"

__all__ = [
    'HTMLParserTreeBuilder',
    ]

from html.parser import HTMLParser

try:
    from html.parser import HTMLParseError
except ImportError as e:
    # HTMLParseError is removed in Python 3.5. Since it can never be
    # thrown in 3.5, we can just define our own class as a placeholder.
    class HTMLParseError(Exception):
        pass

import sys
import warnings

# Starting in Python 3.2, the HTMLParser constructor takes a 'strict'
# argument, which we'd like to set to False. Unfortunately,
# http://bugs.python.org/issue13273 makes strict=True a better bet
# before Python 3.2.3.
#
# At the end of this file, we monkeypatch HTMLParser so that
# strict=True works well on Python 3.2.2.
major, minor, release = sys.version_info[:3]
CONSTRUCTOR_TAKES_STRICT = major == 3 and minor == 2 and release >= 3
CONSTRUCTOR_STRICT_IS_DEPRECATED = major == 3 and minor == 3
CONSTRUCTOR_TAKES_CONVERT_CHARREFS = major == 3 and minor >= 4


from bs4.element import (
    CData,
    Comment,
    Declaration,
    Doctype,
    ProcessingInstruction,
    )
from bs4.dammit import EntitySubstitution, UnicodeDammit

from bs4.builder import (
    HTML,
    HTMLTreeBuilder,
    STRICT,
    )


HTMLPARSER = 'html.parser'

class BeautifulSoupHTMLParser(HTMLParser):

    def __init__(self, *args, **kwargs):
        HTMLParser.__init__(self, *args, **kwargs)

        # Keep a list of empty-element tags that were encountered
        # without an explicit closing tag. If we encounter a closing tag
        # of this type, we'll associate it with one of those entries.
        #
        # This isn't a stack because we don't care about the
        # order. It's a list of closing tags we've already handled and
        # will ignore, assuming they ever show up.
        self.already_closed_empty_element = []

    def error(self, msg):
        """In Python 3, HTMLParser subclasses must implement error(), although this
        requirement doesn't appear to be documented.

        In Python 2, HTMLParser implements error() as raising an exception.

        In any event, this method is called only on very strange markup and our best strategy
        is to pretend it didn't happen and keep going.
        """
        warnings.warn(msg)
        
    def handle_startendtag(self, name, attrs):
        # This is only called when the markup looks like
        # <tag/>.

        # is_startend() tells handle_starttag not to close the tag
        # just because its name matches a known empty-element tag. We
        # know that this is an empty-element tag and we want to call
        # handle_endtag ourselves.
        tag = self.handle_starttag(name, attrs, handle_empty_element=False)
        self.handle_endtag(name)
        
    def handle_starttag(self, name, attrs, handle_empty_element=True):
        # XXX namespace
        attr_dict = {}
        for key, value in attrs:
            # Change None attribute values to the empty string
            # for consistency with the other tree builders.
            if value is None:
                value = ''
            attr_dict[key] = value
            attrvalue = '""'
        #print "START", name
        sourceline, sourcepos = self.getpos()
        tag = self.soup.handle_starttag(
            name, None, None, attr_dict, sourceline=sourceline,
            sourcepos=sourcepos
        )
        if tag and tag.is_empty_element and handle_empty_element:
            # Unlike other parsers, html.parser doesn't send separate end tag
            # events for empty-element tags. (It's handled in
            # handle_startendtag, but only if the original markup looked like
            # <tag/>.)
            #
            # So we need to call handle_endtag() ourselves. Since we
            # know the start event is identical to the end event, we
            # don't want handle_endtag() to cross off any previous end
            # events for tags of this name.
            self.handle_endtag(name, check_already_closed=False)

            # But we might encounter an explicit closing tag for this tag
            # later on. If so, we want to ignore it.
            self.already_closed_empty_element.append(name)
            
    def handle_endtag(self, name, check_already_closed=True):
        #print "END", name
        if check_already_closed and name in self.already_closed_empty_element:
            # This is a redundant end tag for an empty-element tag.
            # We've already called handle_endtag() for it, so just
            # check it off the list.
            # print "ALREADY CLOSED", name
            self.already_closed_empty_element.remove(name)
        else:
            self.soup.handle_endtag(name)

    def handle_data(self, data):
        self.soup.handle_data(data)

    def handle_charref(self, name):
        # XXX workaround for a bug in HTMLParser. Remove this once
        # it's fixed in all supported versions.
        # http://bugs.python.org/issue13633
        if name.startswith('x'):
            real_name = int(name.lstrip('x'), 16)
        elif name.startswith('X'):
            real_name = int(name.lstrip('X'), 16)
        else:
            real_name = int(name)

        data = None
        if real_name < 256:
            # HTML numeric entities are supposed to reference Unicode
            # code points, but sometimes they reference code points in
            # some other encoding (ahem, Windows-1252). E.g. &#147;
            # instead of &#201; for LEFT DOUBLE QUOTATION MARK. This
            # code tries to detect this situation and compensate.
            for encoding in (self.soup.original_encoding, 'windows-1252'):
                if not encoding:
                    continue
                try:
                    data = bytearray([real_name]).decode(encoding)
                except UnicodeDecodeError as e:
                    pass
        if not data:
            try:
                data = chr(real_name)
            except (ValueError, OverflowError) as e:
                pass
        data = data or "\N{REPLACEMENT CHARACTER}"
        self.handle_data(data)

    def handle_entityref(self, name):
        character = EntitySubstitution.HTML_ENTITY_TO_CHARACTER.get(name)
        if character is not None:
            data = character
        else:
            # If this were XML, it would be ambiguous whether "&foo"
            # was an character entity reference with a missing
            # semicolon or the literal string "&foo". Since this is
            # HTML, we have a complete list of all character entity references,
            # and this one wasn't found, so assume it's the literal string "&foo".
            data = "&%s" % name
        self.handle_data(data)

    def handle_comment(self, data):
        self.soup.endData()
        self.soup.handle_data(data)
        self.soup.endData(Comment)

    def handle_decl(self, data):
        self.soup.endData()
        if data.startswith("DOCTYPE "):
            data = data[len("DOCTYPE "):]
        elif data == 'DOCTYPE':
            # i.e. "<!DOCTYPE>"
            data = ''
        self.soup.handle_data(data)
        self.soup.endData(Doctype)

    def unknown_decl(self, data):
        if data.upper().startswith('CDATA['):
            cls = CData
            data = data[len('CDATA['):]
        else:
            cls = Declaration
        self.soup.endData()
        self.soup.handle_data(data)
        self.soup.endData(cls)

    def handle_pi(self, data):
        self.soup.endData()
        self.soup.handle_data(data)
        self.soup.endData(ProcessingInstruction)


class HTMLParserTreeBuilder(HTMLTreeBuilder):

    is_xml = False
    picklable = True
    NAME = HTMLPARSER
    features = [NAME, HTML, STRICT]

    # The html.parser knows which line number and position in the
    # original file is the source of an element.
    TRACKS_LINE_NUMBERS = True
    
    def __init__(self, parser_args=None, parser_kwargs=None, **kwargs):
        super(HTMLParserTreeBuilder, self).__init__(**kwargs)
        parser_args = parser_args or []
        parser_kwargs = parser_kwargs or {}
        if CONSTRUCTOR_TAKES_STRICT and not CONSTRUCTOR_STRICT_IS_DEPRECATED:
            parser_kwargs['strict'] = False
        if CONSTRUCTOR_TAKES_CONVERT_CHARREFS:
            parser_kwargs['convert_charrefs'] = False
        self.parser_args = (parser_args, parser_kwargs)

    def prepare_markup(self, markup, user_specified_encoding=None,
                       document_declared_encoding=None, exclude_encodings=None):
        """
        :return: A 4-tuple (markup, original encoding, encoding
        declared within markup, whether any characters had to be
        replaced with REPLACEMENT CHARACTER).
        """
        if isinstance(markup, str):
            yield (markup, None, None, False)
            return

        try_encodings = [user_specified_encoding, document_declared_encoding]
        dammit = UnicodeDammit(markup, try_encodings, is_html=True,
                               exclude_encodings=exclude_encodings)
        yield (dammit.markup, dammit.original_encoding,
               dammit.declared_html_encoding,
               dammit.contains_replacement_characters)

    def feed(self, markup):
        args, kwargs = self.parser_args
        parser = BeautifulSoupHTMLParser(*args, **kwargs)
        parser.soup = self.soup
        try:
            parser.feed(markup)
            parser.close()
        except HTMLParseError as e:
            warnings.warn(RuntimeWarning(
                "Python's built-in HTMLParser cannot parse the given document. This is not a bug in Beautiful Soup. The best solution is to install an external parser (lxml or html5lib), and use Beautiful Soup with that parser. See http://www.crummy.com/software/BeautifulSoup/bs4/doc/#installing-a-parser for help."))
            raise e
        parser.already_closed_empty_element = []

# Patch 3.2 versions of HTMLParser earlier than 3.2.3 to use some
# 3.2.3 code. This ensures they don't treat markup like <p></p> as a
# string.
#
# XXX This code can be removed once most Python 3 users are on 3.2.3.
if major == 3 and minor == 2 and not CONSTRUCTOR_TAKES_STRICT:
    import re
    attrfind_tolerant = re.compile(
        r'\s*((?<=[\'"\s])[^\s/>][^\s/=>]*)(\s*=+\s*'
        r'(\'[^\']*\'|"[^"]*"|(?![\'"])[^>\s]*))?')
    HTMLParserTreeBuilder.attrfind_tolerant = attrfind_tolerant

    locatestarttagend = re.compile(r"""
  <[a-zA-Z][-.a-zA-Z0-9:_]*          # tag name
  (?:\s+                             # whitespace before attribute name
    (?:[a-zA-Z_][-.:a-zA-Z0-9_]*     # attribute name
      (?:\s*=\s*                     # value indicator
        (?:'[^']*'                   # LITA-enclosed value
          |\"[^\"]*\"                # LIT-enclosed value
          |[^'\">\s]+                # bare value
         )
       )?
     )
   )*
  \s*                                # trailing whitespace
""", re.VERBOSE)
    BeautifulSoupHTMLParser.locatestarttagend = locatestarttagend

    from html.parser import tagfind, attrfind

    def parse_starttag(self, i):
        self.__starttag_text = None
        endpos = self.check_for_whole_start_tag(i)
        if endpos < 0:
            return endpos
        rawdata = self.rawdata
        self.__starttag_text = rawdata[i:endpos]

        # Now parse the data between i+1 and j into a tag and attrs
        attrs = []
        match = tagfind.match(rawdata, i+1)
        assert match, 'unexpected call to parse_starttag()'
        k = match.end()
        self.lasttag = tag = rawdata[i+1:k].lower()
        while k < endpos:
            if self.strict:
                m = attrfind.match(rawdata, k)
            else:
                m = attrfind_tolerant.match(rawdata, k)
            if not m:
                break
            attrname, rest, attrvalue = m.group(1, 2, 3)
            if not rest:
                attrvalue = None
            elif attrvalue[:1] == '\'' == attrvalue[-1:] or \
                 attrvalue[:1] == '"' == attrvalue[-1:]:
                attrvalue = attrvalue[1:-1]
            if attrvalue:
                attrvalue = self.unescape(attrvalue)
            attrs.append((attrname.lower(), attrvalue))
            k = m.end()

        end = rawdata[k:endpos].strip()
        if end not in (">", "/>"):
            lineno, offset = self.getpos()
            if "\n" in self.__starttag_text:
                lineno = lineno + self.__starttag_text.count("\n")
                offset = len(self.__starttag_text) \
                         - self.__starttag_text.rfind("\n")
            else:
                offset = offset + len(self.__starttag_text)
            if self.strict:
                self.error("junk characters in start tag: %r"
                           % (rawdata[k:endpos][:20],))
            self.handle_data(rawdata[i:endpos])
            return endpos
        if end.endswith('/>'):
            # XHTML-style empty tag: <span attr="value" />
            self.handle_startendtag(tag, attrs)
        else:
            self.handle_starttag(tag, attrs)
            if tag in self.CDATA_CONTENT_ELEMENTS:
                self.set_cdata_mode(tag)
        return endpos

    def set_cdata_mode(self, elem):
        self.cdata_elem = elem.lower()
        self.interesting = re.compile(r'</\s*%s\s*>' % self.cdata_elem, re.I)

    BeautifulSoupHTMLParser.parse_starttag = parse_starttag
    BeautifulSoupHTMLParser.set_cdata_mode = set_cdata_mode

    CONSTRUCTOR_TAKES_STRICT = True
