"""Render HTML for scraping"""
# -*- coding: utf-8 -*-

import os
import sys
from contextlib import contextmanager
from multiprocessing import Pool
import lxml.html

try:
    TimeoutError
except NameError:
    from multiprocessing import TimeoutError  # Python 2


def _render(source_html):
    """Return rendered HTML."""
    from PyQt5.QtCore import QEventLoop, QUrl
    from PyQt5.QtWebEngineWidgets import QWebEngineView
    from PyQt5.QtWidgets import QApplication

    class Render(QWebEngineView):
        """Render HTML with PyQt5 WebEngine."""

        def __init__(self, url):
            self.html = None
            self.app = QApplication(sys.argv)
            QWebEngineView.__init__(self)
            self.loadFinished.connect(self._loadFinished)
            self.loadFinished.connect(self._events_in_html)
            self.load(QUrl(url))
            self.show()
            while not self._events_in_html():
                self.app.processEvents(
                    QEventLoop.ExcludeUserInputEvents |
                    QEventLoop.ExcludeSocketNotifiers |
                    QEventLoop.WaitForMoreEvents)

            self.app.quit()

        def _events_in_html(self):
            if self.html is None:
                return False
            #print(len(lxml.html.fromstring(html).xpath('//*[@class="event"]')))
            elif len(lxml.html.fromstring(self.html).xpath('//*//div[@class="events-result-set"]/*'))>0:
            #if len(lxml.html.fromstring(html).xpath('//*[@class="events-result-set"]/*[@class="event"]'))>0:
                return True
            else:
                return False

        def _callable(self, data):
            self.html = data

        def _loadFinished(self, result):
            self.page().toHtml(self._callable)

    #with devnull():
    return Render(source_html).html

@contextmanager
def devnull():
    """Temporarily redirect stdout and stderr to /dev/null."""

    try:
        original_stderr = os.dup(sys.stderr.fileno())
        original_stdout = os.dup(sys.stdout.fileno())
        null = open(os.devnull, 'w')
        os.dup2(null.fileno(), sys.stderr.fileno())
        os.dup2(null.fileno(), sys.stdout.fileno())
        yield

    finally:
        if original_stderr is not None:
            os.dup2(original_stderr, sys.stderr.fileno())
        if original_stdout is not None:
            os.dup2(original_stdout, sys.stdout.fileno())
        if null is not None:
            null.close()

def render(html):
    """Perform render in a new process to prevent hangs."""

    tries = 3

    for _ in range(tries):
        pool = Pool(1)
        try:
            return pool.apply_async(_render, args=(html,)).get(timeout=120)
        except TimeoutError:
            continue
        finally:
            pool.terminate()

    raise TimeoutError('Timed out attempting to render HTML %d times' % tries)