# This file is part of ReText
# Copyright: 2012-2021 Dmitry Shachnev
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 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 General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

from ReText.editor import getColor
from enum import IntFlag, auto
import re

from PyQt5.QtCore import Qt
from PyQt5.QtGui import QFont, QSyntaxHighlighter, QTextCharFormat

reHtmlTags     = re.compile('<[^<>@]*>')
reHtmlSymbols  = re.compile(r'&#?\w+;')
reHtmlStrings  = re.compile('"[^"<]*"(?=[^<]*>)')
reHtmlComments = re.compile('<!--[^<>]*-->')
reAsterisks    = re.compile(r'(?<!\*)\*[^ \*][^\*]*\*')
reUnderline    = re.compile(r'(?<!_|\w)_[^_]+_(?!\w)')
reDblAsterisks = re.compile(r'(?<!\*)\*\*((?!\*\*).)*\*\*')
reDblUnderline = re.compile(r'(?<!_|\w)__[^_]+__(?!\w)')
reTrpAsterisks = re.compile(r'\*{3,3}[^\*]+\*{3,3}')
reTrpUnderline = re.compile('___[^_]+___')
reMkdHeaders   = re.compile('^#.+')
reMkdLinksImgs = re.compile(r'(?<=\[)[^\[\]]*(?=\])')
reMkdLinkRefs  = re.compile(r'(?<=\]\()[^\(\)]*(?=\))')
reBlockQuotes  = re.compile('^ *>.+')
reReSTDirects  = re.compile(r'\.\. [a-z]+::')
reReSTRoles    = re.compile('(:[a-z-]+:)(`.+?`)')
reReSTLinks    = re.compile('(`.+?<)(.+?)(>`__?)')
reReSTLinkRefs = re.compile(r'\.\. _`?(.*?)`?: (.*)')
reReSTFldLists = re.compile('^ *:(.*?):')
reTextileHdrs  = re.compile(r'^h[1-6][()<>=]*\.\s.+')
reTextileQuot  = re.compile(r'^bq\.\s.+')
reMkdCodeSpans = re.compile('`[^`]*`')
reMkdMathSpans = re.compile(r'\\[\(\[].*?\\[\)\]]')
reReSTCodeSpan = re.compile('``.+?``')
reWords        = re.compile('[^_\\W]+')
reSpacesOnEnd  = re.compile(r'\s+$')


class Formatter:
	def __init__(self, funcs=None):
		self._funcs = funcs or []

	def __or__(self, other):
		result = Formatter(self._funcs.copy())
		if isinstance(other, Formatter):
			result._funcs.extend(other._funcs)
		elif isinstance(other, QFont.Weight):
			result._funcs.append(lambda f: f.setFontWeight(other))
		return result

	def format(self, charFormat):
		for func in self._funcs:
			func(charFormat)

NF = Formatter()
ITAL = Formatter([lambda f: f.setFontItalic(True)])
UNDL = Formatter([lambda f: f.setFontUnderline(True)])

def FG(colorName):
	func = lambda f: f.setForeground(getColor(colorName))
	return Formatter([func])

def QString_length(text):
	# In QString, surrogate pairs are represented using multiple QChars,
	# so the length of QString is not always equal to the number of graphemes
	# in it (which is the case with Python strings).
	return sum(2 if ord(char) > 65535 else 1 for char in text)


class Markup(IntFlag):
	Mkd = auto()
	ReST = auto()
	Textile = auto()
	HTML = auto()

	# Special value which means that no other markup is allowed inside this pattern
	CodeSpan = auto()


docTypesMapping = {
	'Markdown': Markup.Mkd,
	'reStructuredText': Markup.ReST,
	'Textile': Markup.Textile,
	'html': Markup.HTML,
}


class ReTextHighlighter(QSyntaxHighlighter):
	dictionary = None
	docType = None

	patterns = (
		# regex,         color,                                markups
		(reMkdCodeSpans, FG('codeSpans'),                      Markup.Mkd | Markup.CodeSpan),
		(reMkdMathSpans, FG('codeSpans'),                      Markup.Mkd | Markup.CodeSpan),
		(reReSTCodeSpan, FG('codeSpans'),                      Markup.ReST | Markup.CodeSpan),
		(reHtmlTags,     FG('htmlTags') | QFont.Weight.Bold,   Markup.Mkd | Markup.Textile | Markup.HTML),
		(reHtmlSymbols,  FG('htmlSymbols') | QFont.Weight.Bold, Markup.Mkd | Markup.HTML),
		(reHtmlStrings,  FG('htmlStrings') | QFont.Weight.Bold, Markup.Mkd | Markup.HTML),
		(reHtmlComments, FG('htmlComments'),                   Markup.Mkd | Markup.HTML),
		(reAsterisks,    ITAL,                                 Markup.Mkd | Markup.ReST),
		(reUnderline,    ITAL,                                 Markup.Mkd | Markup.Textile),
		(reDblAsterisks, NF | QFont.Weight.Bold,               Markup.Mkd | Markup.ReST | Markup.Textile),
		(reDblUnderline, NF | QFont.Weight.Bold,               Markup.Mkd),
		(reTrpAsterisks, ITAL | QFont.Weight.Bold,             Markup.Mkd),
		(reTrpUnderline, ITAL | QFont.Weight.Bold,             Markup.Mkd),
		(reMkdHeaders,   NF | QFont.Weight.Black,              Markup.Mkd),
		(reMkdLinksImgs, FG('markdownLinks'),                  Markup.Mkd),
		(reMkdLinkRefs,  ITAL | UNDL,                          Markup.Mkd),
		(reBlockQuotes,  FG('blockquotes'),                    Markup.Mkd),
		(reReSTDirects,  FG('restDirectives') | QFont.Weight.Bold, Markup.ReST),
		(reReSTRoles,    NF, FG('restRoles') | QFont.Weight.Bold, FG('htmlStrings'), Markup.ReST),
		(reTextileHdrs,  NF | QFont.Weight.Black,              Markup.Textile),
		(reTextileQuot,  FG('blockquotes'),                    Markup.Textile),
		(reAsterisks,    NF | QFont.Weight.Bold,               Markup.Textile),
		(reDblUnderline, ITAL,                                 Markup.Textile),
		(reReSTLinks,    NF, NF, ITAL | UNDL, NF,              Markup.ReST),
		(reReSTLinkRefs, NF, FG('markdownLinks'), ITAL | UNDL, Markup.ReST),
		(reReSTFldLists, NF, FG('restDirectives'),             Markup.ReST),
	)

	def highlightBlock(self, text):
		# Syntax highlighter
		codeSpans = set()
		if self.docType in docTypesMapping:
			markup = docTypesMapping[self.docType]
			for pattern, *formatters, markups in self.patterns:
				if not (markup & markups):
					continue
				for match in pattern.finditer(text):
					start, end = match.start(), match.end()
					if markups & Markup.CodeSpan:
						codeSpans.add((start, end))
					elif any(start < codeEnd and end > codeStart
					         for codeStart, codeEnd in codeSpans):
						# Ignore any syntax if its match intersects with code spans.
						# See https://github.com/retext-project/retext/issues/529
						continue
					for i, formatter in enumerate(formatters):
						charFormat = QTextCharFormat()
						formatter.format(charFormat)
						self.setFormat(QString_length(text[:match.start(i)]),
						               QString_length(match.group(i)),
						               charFormat)
		for match in reSpacesOnEnd.finditer(text):
			charFormat = QTextCharFormat()
			charFormat.setBackground(getColor('whitespaceOnEnd'))
			self.setFormat(QString_length(text[:match.start()]),
			               QString_length(match.group(0)),
			               charFormat)
		# Spell checker
		if self.dictionary:
			charFormat = QTextCharFormat()
			charFormat.setUnderlineColor(Qt.GlobalColor.red)
			charFormat.setUnderlineStyle(QTextCharFormat.UnderlineStyle.SpellCheckUnderline)
			for match in reWords.finditer(text):
				finalFormat = QTextCharFormat()
				finalFormat.merge(charFormat)
				finalFormat.merge(self.format(match.start()))
				if not self.dictionary.check(match.group(0)):
					self.setFormat(QString_length(text[:match.start()]),
					               QString_length(match.group(0)),
					               finalFormat)
