# System library imports.
from IPython.external.qt import QtGui
from pygments.formatters.html import HtmlFormatter
from pygments.lexer import RegexLexer, _TokenType, Text, Error
from pygments.lexers import PythonLexer
from pygments.styles import get_style_by_name


def get_tokens_unprocessed(self, text, stack=('root',)):
    """ Split ``text`` into (tokentype, text) pairs.

        Monkeypatched to store the final stack on the object itself.
    """
    pos = 0
    tokendefs = self._tokens
    if hasattr(self, '_saved_state_stack'):
        statestack = list(self._saved_state_stack)
    else:
        statestack = list(stack)
    statetokens = tokendefs[statestack[-1]]
    while 1:
        for rexmatch, action, new_state in statetokens:
            m = rexmatch(text, pos)
            if m:
                if type(action) is _TokenType:
                    yield pos, action, m.group()
                else:
                    for item in action(self, m):
                        yield item
                pos = m.end()
                if new_state is not None:
                    # state transition
                    if isinstance(new_state, tuple):
                        for state in new_state:
                            if state == '#pop':
                                statestack.pop()
                            elif state == '#push':
                                statestack.append(statestack[-1])
                            else:
                                statestack.append(state)
                    elif isinstance(new_state, int):
                        # pop
                        del statestack[new_state:]
                    elif new_state == '#push':
                        statestack.append(statestack[-1])
                    else:
                        assert False, "wrong state def: %r" % new_state
                    statetokens = tokendefs[statestack[-1]]
                break
        else:
            try:
                if text[pos] == '\n':
                    # at EOL, reset state to "root"
                    pos += 1
                    statestack = ['root']
                    statetokens = tokendefs['root']
                    yield pos, Text, u'\n'
                    continue
                yield pos, Error, text[pos]
                pos += 1
            except IndexError:
                break
    self._saved_state_stack = list(statestack)

# Monkeypatch!
RegexLexer.get_tokens_unprocessed = get_tokens_unprocessed


class PygmentsBlockUserData(QtGui.QTextBlockUserData):
    """ Storage for the user data associated with each line.
    """

    syntax_stack = ('root',)

    def __init__(self, **kwds):
        for key, value in kwds.iteritems():
            setattr(self, key, value)
        QtGui.QTextBlockUserData.__init__(self)

    def __repr__(self):
        attrs = ['syntax_stack']
        kwds = ', '.join([ '%s=%r' % (attr, getattr(self, attr))
                           for attr in attrs ])
        return 'PygmentsBlockUserData(%s)' % kwds


class PygmentsHighlighter(QtGui.QSyntaxHighlighter):
    """ Syntax highlighter that uses Pygments for parsing. """

    #---------------------------------------------------------------------------
    # 'QSyntaxHighlighter' interface
    #---------------------------------------------------------------------------

    def __init__(self, parent, lexer=None):
        super(PygmentsHighlighter, self).__init__(parent)

        self._document = self.document()
        self._formatter = HtmlFormatter(nowrap=True)
        self._lexer = lexer if lexer else PythonLexer()
        self.set_style('default')

    def highlightBlock(self, string):
        """ Highlight a block of text.
        """
        prev_data = self.currentBlock().previous().userData()
        if prev_data is not None:
            self._lexer._saved_state_stack = prev_data.syntax_stack
        elif hasattr(self._lexer, '_saved_state_stack'):
            del self._lexer._saved_state_stack

        # Lex the text using Pygments
        index = 0
        for token, text in self._lexer.get_tokens(string):
            length = len(text)
            self.setFormat(index, length, self._get_format(token))
            index += length

        if hasattr(self._lexer, '_saved_state_stack'):
            data = PygmentsBlockUserData(
                syntax_stack=self._lexer._saved_state_stack)
            self.currentBlock().setUserData(data)
            # Clean up for the next go-round.
            del self._lexer._saved_state_stack

    #---------------------------------------------------------------------------
    # 'PygmentsHighlighter' interface
    #---------------------------------------------------------------------------

    def set_style(self, style):
        """ Sets the style to the specified Pygments style.
        """
        if isinstance(style, basestring):
            style = get_style_by_name(style)
        self._style = style
        self._clear_caches()

    def set_style_sheet(self, stylesheet):
        """ Sets a CSS stylesheet. The classes in the stylesheet should
        correspond to those generated by:

            pygmentize -S <style> -f html

        Note that 'set_style' and 'set_style_sheet' completely override each
        other, i.e. they cannot be used in conjunction.
        """
        self._document.setDefaultStyleSheet(stylesheet)
        self._style = None
        self._clear_caches()

    #---------------------------------------------------------------------------
    # Protected interface
    #---------------------------------------------------------------------------

    def _clear_caches(self):
        """ Clear caches for brushes and formats.
        """
        self._brushes = {}
        self._formats = {}

    def _get_format(self, token):
        """ Returns a QTextCharFormat for token or None.
        """
        if token in self._formats:
            return self._formats[token]

        if self._style is None:
            result = self._get_format_from_document(token, self._document)
        else:
            result = self._get_format_from_style(token, self._style)

        self._formats[token] = result
        return result

    def _get_format_from_document(self, token, document):
        """ Returns a QTextCharFormat for token by
        """
        code, html = next(self._formatter._format_lines([(token, u'dummy')]))
        self._document.setHtml(html)
        return QtGui.QTextCursor(self._document).charFormat()

    def _get_format_from_style(self, token, style):
        """ Returns a QTextCharFormat for token by reading a Pygments style.
        """
        result = QtGui.QTextCharFormat()
        for key, value in style.style_for_token(token).items():
            if value:
                if key == 'color':
                    result.setForeground(self._get_brush(value))
                elif key == 'bgcolor':
                    result.setBackground(self._get_brush(value))
                elif key == 'bold':
                    result.setFontWeight(QtGui.QFont.Bold)
                elif key == 'italic':
                    result.setFontItalic(True)
                elif key == 'underline':
                    result.setUnderlineStyle(
                        QtGui.QTextCharFormat.SingleUnderline)
                elif key == 'sans':
                    result.setFontStyleHint(QtGui.QFont.SansSerif)
                elif key == 'roman':
                    result.setFontStyleHint(QtGui.QFont.Times)
                elif key == 'mono':
                    result.setFontStyleHint(QtGui.QFont.TypeWriter)
        return result

    def _get_brush(self, color):
        """ Returns a brush for the color.
        """
        result = self._brushes.get(color)
        if result is None:
            qcolor = self._get_color(color)
            result = QtGui.QBrush(qcolor)
            self._brushes[color] = result
        return result

    def _get_color(self, color):
        """ Returns a QColor built from a Pygments color string.
        """
        qcolor = QtGui.QColor()
        qcolor.setRgb(int(color[:2], base=16),
                      int(color[2:4], base=16),
                      int(color[4:6], base=16))
        return qcolor

