# -*- coding: utf-8 -*-

# Copyright (c) 2014 Detlev Offenbach <detlev@die-offenbachs.de>
#

"""
Module implementing a previewer widget for HTML, Markdown and ReST files.
"""

from __future__ import unicode_literals

import os
import threading
import re

from PyQt4.QtCore import pyqtSlot, pyqtSignal, Qt, QUrl, QSize, QThread
from PyQt4.QtGui import QWidget
from PyQt4.QtWebKit import QWebPage

from E5Gui.E5Application import e5App

from .Ui_PreviewerHTML import Ui_PreviewerHTML

import Utilities
import Preferences


class PreviewerHTML(QWidget, Ui_PreviewerHTML):
    """
    Class implementing a previewer widget for HTML, Markdown and ReST files.
    """
    def __init__(self, parent=None):
        """
        Constructor
        
        @param parent reference to the parent widget (QWidget)
        """
        super(PreviewerHTML, self).__init__(parent)
        self.setupUi(self)
        
        self.jsCheckBox.setChecked(
            Preferences.getUI("ShowFilePreviewJS"))
        self.ssiCheckBox.setChecked(
            Preferences.getUI("ShowFilePreviewSSI"))
        
        self.previewView.page().setLinkDelegationPolicy(
            QWebPage.DelegateAllLinks)
        
        self.__scrollBarPositions = {}
        self.__vScrollBarAtEnd = {}
        self.__hScrollBarAtEnd = {}
        
        self.__processingThread = PreviewProcessingThread()
        self.__processingThread.htmlReady.connect(self.__setHtml)

        self.__previewedPath = None
        self.__previewedEditor = None
    
    def shutdown(self):
        """
        Public method to perform shutdown actions.
        """
        self.__processingThread.wait()
    
    @pyqtSlot(bool)
    def on_jsCheckBox_clicked(self, checked):
        """
        Private slot to enable/disable JavaScript.
        
        @param checked state of the checkbox (boolean)
        """
        Preferences.setUI("ShowFilePreviewJS", checked)
        self.__setJavaScriptEnabled(checked)
    
    def __setJavaScriptEnabled(self, enable):
        """
        Private method to enable/disable JavaScript.
        
        @param enable flag indicating the enable state (boolean)
        """
        self.jsCheckBox.setChecked(enable)
        
        settings = self.previewView.settings()
        settings.setAttribute(settings.JavascriptEnabled, enable)
        
        self.processEditor()
    
    @pyqtSlot(bool)
    def on_ssiCheckBox_clicked(self, checked):
        """
        Private slot to enable/disable SSI.
        
        @param checked state of the checkbox (boolean)
        """
        Preferences.setUI("ShowFilePreviewSSI", checked)
        self.processEditor()
    
    def processEditor(self, editor=None):
        """
        Public slot to process an editor's text.
        
        @param editor editor to be processed (Editor)
        """
        if editor is None:
            editor = self.__previewedEditor
        else:
            self.__previewedEditor = editor
        
        if editor is not None:
            fn = editor.getFileName()
            
            if fn:
                extension = os.path.normcase(os.path.splitext(fn)[1][1:])
            else:
                extension = ""
            if extension in \
                Preferences.getEditor("PreviewHtmlFileNameExtensions") or \
               editor.getLanguage() == "HTML":
                language = "HTML"
            elif extension in \
                    Preferences.getEditor("PreviewMarkdownFileNameExtensions"):
                language = "Markdown"
            elif extension in \
                    Preferences.getEditor("PreviewRestFileNameExtensions"):
                language = "ReST"
            else:
                self.__setHtml(fn, self.tr(
                    "<p>No preview available for this type of file.</p>"))
                return
            
            if fn:
                project = e5App().getObject("Project")
                if project.isProjectFile(fn):
                    rootPath = project.getProjectPath()
                else:
                    rootPath = os.path.dirname(os.path.abspath(fn))
            else:
                rootPath = ""
            
            self.__processingThread.process(
                fn, language, editor.text(),
                self.ssiCheckBox.isChecked(), rootPath)

    def __setHtml(self, filePath, html):
        """
        Private method to set the HTML to the view and restore the scroll bars
        positions.
        
        @param filePath file path of the previewed editor (string)
        @param html processed HTML text ready to be shown (string)
        """
        self.__saveScrollBarPositions()
        self.__previewedPath = Utilities.normcasepath(
            Utilities.fromNativeSeparators(filePath))
        self.previewView.page().mainFrame().contentsSizeChanged.connect(
            self.__restoreScrollBarPositions)
        self.previewView.setHtml(html, baseUrl=QUrl.fromLocalFile(filePath))
    
    @pyqtSlot(str)
    def on_previewView_titleChanged(self, title):
        """
        Private slot to handle a change of the title.
        
        @param title new title (string)
        """
        if title:
            self.titleLabel.setText(self.tr("Preview - {0}").format(title))
        else:
            self.titleLabel.setText(self.tr("Preview"))
    
    def __saveScrollBarPositions(self):
        """
        Private method to save scroll bar positions for a previewed editor.
        """
        frame = self.previewView.page().mainFrame()
        if frame.contentsSize() == QSize(0, 0):
            return  # no valid data, nothing to save
        
        pos = frame.scrollPosition()
        self.__scrollBarPositions[self.__previewedPath] = pos
        self.__hScrollBarAtEnd[self.__previewedPath] = \
            frame.scrollBarMaximum(Qt.Horizontal) == pos.x()
        self.__vScrollBarAtEnd[self.__previewedPath] = \
            frame.scrollBarMaximum(Qt.Vertical) == pos.y()

    def __restoreScrollBarPositions(self):
        """
        Private method to restore scroll bar positions for a previewed editor.
        """
        try:
            self.previewView.page().mainFrame().contentsSizeChanged.disconnect(
                self.__restoreScrollBarPositions)
        except TypeError:
            # not connected, simply ignore it
            pass
        
        if self.__previewedPath not in self.__scrollBarPositions:
            return
        
        frame = self.previewView.page().mainFrame()
        frame.setScrollPosition(
            self.__scrollBarPositions[self.__previewedPath])
        
        if self.__hScrollBarAtEnd[self.__previewedPath]:
            frame.setScrollBarValue(
                Qt.Horizontal, frame.scrollBarMaximum(Qt.Horizontal))
        
        if self.__vScrollBarAtEnd[self.__previewedPath]:
            frame.setScrollBarValue(
                Qt.Vertical, frame.scrollBarMaximum(Qt.Vertical))
    
    @pyqtSlot(QUrl)
    def on_previewView_linkClicked(self, url):
        """
        Private slot handling the clicking of a link.
        
        @param url url of the clicked link (QUrl)
        """
        e5App().getObject("UserInterface").launchHelpViewer(url.toString())


class PreviewProcessingThread(QThread):
    """
    Class implementing a thread to process some text into HTML usable by the
    previewer view.
    
    @signal htmlReady(str,str) emitted with the file name and processed HTML
        to signal the availability of the processed HTML
    """
    htmlReady = pyqtSignal(str, str)
    
    def __init__(self, parent=None):
        """
        Constructor
        
        @param parent reference to the parent object (QObject)
        """
        super(PreviewProcessingThread, self).__init__()
        
        self.__lock = threading.Lock()
    
    def process(self, filePath, language, text, ssiEnabled, rootPath):
        """
        Public method to convert the given text to HTML.
        
        @param filePath file path of the text (string)
        @param language language of the text (string)
        @param text text to be processed (string)
        @param ssiEnabled flag indicating to do some (limited) SSI processing
            (boolean)
        @param rootPath root path to be used for SSI processing (str)
        """
        with self.__lock:
            self.__filePath = filePath
            self.__language = language
            self.__text = text
            self.__ssiEnabled = ssiEnabled
            self.__rootPath = rootPath
            self.__haveData = True
            if not self.isRunning():
                self.start(QThread.LowPriority)
    
    def run(self):
        """
        Public thread method to convert the stored data.
        """
        while True:
            # exits with break
            with self.__lock:
                filePath = self.__filePath
                language = self.__language
                text = self.__text
                ssiEnabled = self.__ssiEnabled
                rootPath = self.__rootPath
                self.__haveData = False
            
            html = self.__getHtml(language, text, ssiEnabled, filePath,
                                  rootPath)
            
            with self.__lock:
                if not self.__haveData:
                    self.htmlReady.emit(filePath, html)
                    break
                # else - next iteration
    
    def __getHtml(self, language, text, ssiEnabled, filePath, rootPath):
        """
        Private method to process the given text depending upon the given
        language.
        
        @param language language of the text (string)
        @param text to be processed (string)
        @param ssiEnabled flag indicating to do some (limited) SSI processing
            (boolean)
        @param filePath file path of the text (string)
        @param rootPath root path to be used for SSI processing (str)
        @return processed HTML text (string)
        """
        if language == "HTML":
            if ssiEnabled:
                return self.__processSSI(text, filePath, rootPath)
            else:
                return text
        elif language == "Markdown":
            return self.__convertMarkdown(text)
        elif language == "ReST":
            return self.__convertReST(text)
        else:
            return self.tr(
                "<p>No preview available for this type of file.</p>")
    
    def __processSSI(self, txt, filename, root):
        """
        Private method to process the given text for SSI statements.
        
        Note: Only a limited subset of SSI statements are supported.
        
        @param txt text to be processed (string)
        @param filename name of the file associated with the given text
            (string)
        @param root directory of the document root (string)
        @return processed HTML (string)
        """
        if not filename:
            return txt
        
        # SSI include
        incRe = re.compile(
            r"""<!--#include[ \t]+(virtual|file)=[\"']([^\"']+)[\"']\s*-->""",
            re.IGNORECASE)
        baseDir = os.path.dirname(os.path.abspath(filename))
        docRoot = root if root != "" else baseDir
        while True:
            incMatch = incRe.search(txt)
            if incMatch is None:
                break
            
            if incMatch.group(1) == "virtual":
                incFile = Utilities.normjoinpath(docRoot, incMatch.group(2))
            elif incMatch.group(1) == "file":
                incFile = Utilities.normjoinpath(baseDir, incMatch.group(2))
            else:
                incFile = ""
            if os.path.exists(incFile):
                try:
                    f = open(incFile, "r")
                    incTxt = f.read()
                    f.close()
                except (IOError, OSError):
                    # remove SSI include
                    incTxt = ""
            else:
                # remove SSI include
                incTxt = ""
            txt = txt[:incMatch.start(0)] + incTxt + txt[incMatch.end(0):]
        
        return txt
    
    def __convertReST(self, text):
        """
        Private method to convert ReST text into HTML.
        
        @param text text to be processed (string)
        @return processed HTML (string)
        """
        try:
            import docutils.core    # __IGNORE_EXCEPTION__ __IGNORE_WARNING__
        except ImportError:
            return self.tr(
                """<p>ReStructuredText preview requires the"""
                """ <b>python-docutils</b> package.<br/>Install it with"""
                """ your package manager or see"""
                """ <a href="http://pypi.python.org/pypi/docutils">"""
                """this page.</a></p>""")
        
        return docutils.core.publish_string(text, writer_name='html')\
            .decode("utf-8")
    
    def __convertMarkdown(self, text):
        """
        Private method to convert Markdown text into HTML.
        
        @param text text to be processed (string)
        @return processed HTML (string)
        """
        try:
            import markdown     # __IGNORE_EXCEPTION__ __IGNORE_WARNING__
        except ImportError:
            return self.tr(
                """<p>Markdown preview requires the <b>python-markdown</b> """
                """package.<br/>Install it with your package manager or see """
                """<a href="http://pythonhosted.org/Markdown/install.html">"""
                """installation instructions.</a></p>""")
        
        try:
            import mdx_mathjax  # __IGNORE_EXCEPTION__ __IGNORE_WARNING__
        except ImportError:
            #mathjax doesn't require import statement if installed as extension
            pass

        extensions = ['fenced_code', 'nl2br', 'extra']
        
        # version 2.0 supports only extension names, not instances
        if markdown.version_info[0] > 2 or \
                (markdown.version_info[0] == 2 and
                 markdown.version_info[1] > 0):
            class _StrikeThroughExtension(markdown.Extension):
                """
                Class is placed here, because it depends on imported markdown,
                and markdown import is lazy.
                
                (see http://achinghead.com/
                python-markdown-adding-insert-delete.html this page for
                details)
                """
                DEL_RE = r'(~~)(.*?)~~'

                def extendMarkdown(self, md, md_globals):
                    # Create the del pattern
                    del_tag = markdown.inlinepatterns.SimpleTagPattern(
                        self.DEL_RE, 'del')
                    # Insert del pattern into markdown parser
                    md.inlinePatterns.add('del', del_tag, '>not_strong')
            
            extensions.append(_StrikeThroughExtension())

        try:
            return markdown.markdown(text, extensions + ['mathjax'])
        except (ImportError, ValueError):
            # markdown raises ValueError or ImportError, depends on version
            # It is not clear, how to distinguish missing mathjax from other
            # errors. So keep going without mathjax.
            return markdown.markdown(text, extensions)
