#!/usr/bin/python
# -*- coding: utf-8 -*-

# SAT plugin for managing various text syntaxes
# Copyright (C) 2009, 2010, 2011, 2012, 2013, 2014 Jérôme Poisson (goffi@goffi.org)

# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.

# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU Affero General Public License for more details.

# You should have received a copy of the GNU Affero General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

from sat.core.i18n import _, D_
from sat.core.log import getLogger
log = getLogger(__name__)

from twisted.internet import defer
from twisted.internet.threads import deferToThread
from sat.core import exceptions
from lxml import html
from lxml.html import clean
from cgi import escape
import re


CATEGORY = D_("Composition")
NAME = "Syntax"
_SYNTAX_XHTML = "XHTML"
_SYNTAX_CURRENT = "@CURRENT@"

# TODO: check/adapt following list
STYLES_WHITELIST = ["azimuth", "background-color", "border-bottom-color", "border-collapse", "border-color", "border-left-color", "border-right-color", "border-top-color", "clear", "color", "cursor", "direction", "display", "elevation", "float", "font", "font-family", "font-size", "font-style", "font-variant", "font-weight", "height", "letter-spacing", "line-height", "overflow", "pause", "pause-after", "pause-before", "pitch", "pitch-range", "richness", "speak", "speak-header", "speak-numeral", "speak-punctuation", "speech-rate", "stress", "text-align", "text-decoration", "text-indent", "unicode-bidi", "vertical-align", "voice-family", "volume", "white-space", "width"] # based on feedparser list (http://pythonhosted.org/feedparser/html-sanitization.html)

SAFE_ATTRS = html.defs.safe_attrs.union(('style',))
STYLES_VALUES_REGEX = r'^(' + '|'.join(['([a-z-]+)', # alphabetical names
                                       '(#[0-9a-f]+)', # hex value
                                       '(\d+(.\d+)? *(|%|em|ex|px|in|cm|mm|pt|pc))', # values with units (or not)
                                       'rgb\( *((\d+(.\d+)?), *){2}(\d+(.\d+)?) *\)', # rgb function
                                       'rgba\( *((\d+(.\d+)?), *){3}(\d+(.\d+)?) *\)', # rgba function
                                      ]) + ') *(!important)?$' # we accept "!important" at the end
STYLES_ACCEPTED_VALUE = re.compile(STYLES_VALUES_REGEX)

PLUGIN_INFO = {
    "name": "Text syntaxes",
    "import_name": "TEXT-SYNTAXES",
    "type": "MISC",
    "protocols": [],
    "dependencies": [],
    "main": "TextSyntaxes",
    "handler": "no",
    "description": _("""Management of various text syntaxes (XHTML-IM, Markdown, etc)""")
}

class UnknownSyntax(Exception):
    pass

class TextSyntaxes(object):
    """ Text conversion class
    XHTML utf-8 is used as intermediate language for conversions
    """

    OPT_DEFAULT = "DEFAULT"
    OPT_HIDDEN = "HIDDEN"
    OPT_NO_THREAD = "NO_THREAD"
    SYNTAX_XHTML = _SYNTAX_XHTML
    SYNTAX_MARKDOWN = "markdown"
    SYNTAX_TEXT = "text"

    params = """
    <params>
    <individual>
    <category name="%(category_name)s" label="%(category_label)s">
        <param name="%(name)s" label="%(label)s" type="list" security="0">
            %(options)s
        </param>
    </category>
    </individual>
    </params>
    """

    params_data = {
        'category_name': CATEGORY,
        'category_label': _(CATEGORY),
        'name': NAME,
        'label': _(NAME),
        'syntaxes': {},
        }

    def __init__(self, host):
        log.info(_("Text syntaxes plugin initialization"))
        self.host = host
        self.syntaxes = {}
        self.addSyntax(self.SYNTAX_XHTML, lambda xhtml: defer.succeed(xhtml), lambda xhtml: defer.succeed(xhtml),
                       TextSyntaxes.OPT_NO_THREAD)
        self.addSyntax(self.SYNTAX_TEXT, lambda text: escape(text), lambda xhtml: self._removeMarkups(xhtml), [TextSyntaxes.OPT_HIDDEN])
        try:
            import markdown, html2text

            def _html2text(html, baseurl=''):
                h = html2text.HTML2Text(baseurl=baseurl)
                h.body_width = 0  # do not truncate the lines, it breaks the long URLs
                return h.handle(html)
            self.addSyntax(self.SYNTAX_MARKDOWN, markdown.markdown, _html2text, [TextSyntaxes.OPT_DEFAULT])
        except ImportError:
            log.warning("markdown or html2text not found, can't use Markdown syntax")
        host.bridge.addMethod("syntaxConvert", ".plugin", in_sign='sssbs', out_sign='s',
                              async=True, method=self.convert)

    def _updateParamOptions(self):
        data_synt = TextSyntaxes.params_data['syntaxes']
        syntaxes = []

        for syntax in data_synt.keys():
            flags = data_synt[syntax]["flags"]
            if TextSyntaxes.OPT_HIDDEN not in flags:
                syntaxes.append(syntax)

        syntaxes.sort(key=unicode.lower)
        options = []

        for syntax in syntaxes:
            selected = 'selected="true"' if syntax == _SYNTAX_XHTML else ''
            options.append(u'<option value="%s" %s/>' % (syntax, selected))

        TextSyntaxes.params_data["options"] = u'\n'.join(options)
        self.host.memory.updateParams(TextSyntaxes.params % TextSyntaxes.params_data)

    def getCurrentSyntax(self, profile):
        """ Return the selected syntax for the given profile

        @param profile: %(doc_profile)s
        @return: profile selected syntax
        """
        return self.host.memory.getParamA(NAME, CATEGORY , profile_key=profile)

    def clean_xhtml(self, xhtml):
        """ Clean XHTML text by removing potentially dangerous/malicious parts
        @param xhtml: raw xhtml text to clean (or lxml's HtmlElement)
        """
        def blocking_cleaning(xhtml):
            """ Clean XHTML and style attributes """

            def clean_style(styles_raw):
                """" Remove styles not in the whitelist,
                or where the value doesn't match the regex """
                styles = styles_raw.split(";")
                cleaned_styles = []
                for style in styles:
                    try:
                        key, value = style.split(':')
                    except ValueError:
                        continue
                    key = key.lower().strip()
                    if key not in STYLES_WHITELIST:
                        continue
                    value = value.lower().strip()
                    if not STYLES_ACCEPTED_VALUE.match(value):
                        continue
                    if value == "none":
                        continue
                    cleaned_styles.append((key, value))
                return "; ".join(["%s: %s" % (key, value) for key, value in cleaned_styles])

            if isinstance(xhtml, basestring):
                xhtml_elt = html.fromstring(xhtml)
            elif isinstance(xhtml, html.HtmlElement):
                xhtml_elt = xhtml
            else:
                log.error("Only strings and HtmlElements can be cleaned")
                raise exceptions.DataError
            cleaner = clean.Cleaner(style=False,
                                    add_nofollow=False,
                                    safe_attrs=SAFE_ATTRS)
            xhtml_elt = cleaner.clean_html(xhtml_elt)
            for elt in xhtml_elt.xpath("//*[@style]"):
                elt.set("style", clean_style(elt.get('style')))
            return html.tostring(xhtml_elt, encoding=unicode, method='xml')

        return deferToThread(blocking_cleaning, xhtml)

    def convert(self, text, syntax_from, syntax_to=_SYNTAX_XHTML, safe=True, profile=None):
        """ Convert a text between two syntaxes
        @param text: text to convert
        @param syntax_from: source syntax (e.g. "markdown")
        @param syntax_to: dest syntax (e.g.: "XHTML")
        @param safe: clean resulting XHTML to avoid malicious code if True
        @param profile: needed only when syntax_from or syntax_to is set to _SYNTAX_CURRENT
        @return: converted text """

        if syntax_from == _SYNTAX_CURRENT:
            syntax_from = self.getCurrentSyntax(profile)
        if syntax_to == _SYNTAX_CURRENT:
            syntax_to = self.getCurrentSyntax(profile)
        syntaxes = TextSyntaxes.params_data['syntaxes']
        if syntax_from not in syntaxes:
            raise UnknownSyntax(syntax_from)
        if syntax_to not in syntaxes:
            raise UnknownSyntax(syntax_to)
        d = None

        if TextSyntaxes.OPT_NO_THREAD in syntaxes[syntax_from]["flags"]:
            d = syntaxes[syntax_from]["to"](text)
        else:
            d = deferToThread(syntaxes[syntax_from]["to"], text)

        #TODO: keep only body element and change it to a div here ?

        if safe:
            d.addCallback(self.clean_xhtml)

        if TextSyntaxes.OPT_NO_THREAD in syntaxes[syntax_to]["flags"]:
            d.addCallback(syntaxes[syntax_to]["from"])
        else:
            d.addCallback(lambda xhtml: deferToThread(syntaxes[syntax_to]["from"], xhtml))

        # converters can add new lines that disturb the microblog change detection
        d.addCallback(lambda text: text.rstrip())
        return d

    def addSyntax(self, name, to_xhtml_cb, from_xhtml_cb, flags = None):
        """ Add a new syntax to the manager
        @param name: unique name of the syntax
        @param to_xhtml_cb: callback to convert from syntax to XHTML
        @param from_xhtml_cb: callback to convert from XHTML to syntax
        @param flags: set of optional flags, can be:
            TextSyntaxes.OPT_DEFAULT: use as the default syntax (replace former one)
            TextSyntaxes.OPT_HIDDEN: do not show in parameters
            TextSyntaxes.OPT_NO_THREAD: do not defer to thread when converting (the callback must then return a deferred)

        """
        name = unicode(name)
        flags = flags or []
        if TextSyntaxes.OPT_HIDDEN in flags and TextSyntaxes.OPT_DEFAULT in flags:
            raise ValueError("%s and %s are mutually exclusive" % (TextSyntaxes.OPT_HIDDEN, TextSyntaxes.OPT_DEFAULT))

        syntaxes = TextSyntaxes.params_data['syntaxes']
        syntaxes[name] = {"to": to_xhtml_cb, "from": from_xhtml_cb, "flags": flags}
        if TextSyntaxes.OPT_DEFAULT in flags:
            syntaxes = TextSyntaxes.params_data['default'] = name

        self._updateParamOptions()

    def _removeMarkups(self, xhtml):
        """
        Remove XHTML markups from the given string.
        @param xhtml: the XHTML string to be cleaned
        @return: the cleaned string
        """
        cleaner = clean.Cleaner(kill_tags=['style'])
        cleaned = cleaner.clean_html(html.fromstring(xhtml))
        return html.tostring(cleaned, encoding=unicode, method="text")