#!/usr/bin/env python3

import logging
import re
import os
import signal
import sys

from itertools import chain
import multiprocessing
from multiprocessing import Pool
from multiprocessing.util import Finalize
from pathlib import Path
from urllib.parse import urlparse

from fontTools.subset import Options, Subsetter, load_font
from selenium import webdriver

from config import config

logging.basicConfig(format='[%(relativeCreated)d] %(message)s')
logger = logging.getLogger('websubset')
logger.setLevel(logging.INFO)

options = Options()
options.parse_opts(config['ftsubset_options'])
if options.with_zopfli:
    from fontTools.ttLib import sfnt
    sfnt.USE_ZOPFLI = True

if config['screenshots']:
    from io import BytesIO
    from PIL import Image, ImageChops
    def gen_font_face(font):
        if 'fontfile' not in font:
            return ''
        return ''.join([
            '@font-face{',
            'font-family:"', font['family'], '";',
            'font-weight:', font['weight'], ';',
            'font-style:', font['style'], ';',
            'src: url("', font["fontfile"], '") format("opentype");',
            '}'])

    REPLACE_FONTS_SCRIPT = ''.join([
        "let style = document.createElement('style'); style.innerHTML = '",
        ''.join(gen_font_face(font) for font in config['fonts']),
        "'; document.body.appendChild(style);"])

EXTRACT_SCRIPT = r'''
    let whitelist = new Set(arguments[0]);
    let walker = document.createTreeWalker(document.body, NodeFilter.SHOW_TEXT);
    let node, dict = new Map();
    while (node = walker.nextNode()) {
        let cs = getComputedStyle(node.parentNode);
        let css = k => cs.getPropertyValue(k);
        if (css('display') == 'none')
            continue;
        let k = css('font-family').replace(/"/g, '').replace(/,.*/, '') + ';' +
                css('font-weight') + ';' +
                css('font-style');
        if (!whitelist.has(k))
            continue;
        const t = node.nodeValue;
        if (dict.has(k))
            for (let c of t)
                dict.get(k).add(c);
        else
            dict.set(k, new Set(t));
    }
    let dict2 = {};
    dict.forEach((v, k) => dict2[k] = [...v.keys()].join(''));
    return dict2;
'''

DRIVER = None
def stop_driver():
    global DRIVER
    if DRIVER:
        DRIVER.quit()
        DRIVER = None
def hook_sys(name):
    orig_hook = getattr(sys, name)
    def my_hook(*args, **kwargs):
        stop_driver()
        orig_hook(*args, **kwargs)
    setattr(sys, name, my_hook)
def hook_sig(signum):
    orig_handler = signal.getsignal(signum)
    if orig_handler is None:
        raise Exception('{signum} handler is None')
    def term_handler(*_):
        stop_driver()
        signal.signal(signum, orig_handler)
        os.kill(os.getpid(), signum)
    signal.signal(signum, term_handler)
def start_wworker(driver_name):
    hook_sig(signal.SIGTERM)
    global DRIVER
    if driver_name == 'chrome':
        chrome_options = webdriver.chrome.options.Options()
        chrome_options.headless = True
        chrome_options.experimental_options["prefs"] = {
            "profile.default_content_setting_values.images": 2
        }
        DRIVER = webdriver.Chrome(options=chrome_options, desired_capabilities={'detach': True})
    elif driver_name == 'firefox':
        firefox_profile = webdriver.FirefoxProfile()
        firefox_profile.set_preference('permissions.default.image', 2)
        firefox_options = webdriver.firefox.options.Options()
        firefox_options.headless = True
        DRIVER = webdriver.Firefox(firefox_profile=firefox_profile, options=firefox_options)
    else:
        raise Exception('unknown driver name')
    Finalize(DRIVER, stop_driver, exitpriority=16)

def is_uri(path):
    parsed = urlparse(path)
    return parsed.scheme and parsed.netloc
def make_uri(path):
    if is_uri(path):
        return path
    else:
        return Path(path).resolve().as_uri()

def extract(path, whitelist, screenshots):
    logger.info('fetching %s', path)
    DRIVER.get(make_uri(path))
    if screenshots:
        logger.info('replacing fonts for %s', path)
        DRIVER.execute_script(REPLACE_FONTS_SCRIPT)
        logger.info('taking pre-screenshot for %s', path)
        height = DRIVER.execute_script('return document.body.parentNode.scrollHeight')
        DRIVER.set_window_size(2000, height)
        screenshot = DRIVER.find_element_by_tag_name('body').screenshot_as_png
    else:
        screenshot = None
    logger.info('extracting text from %s', path)
    return (path, DRIVER.execute_script(EXTRACT_SCRIPT, whitelist), screenshot)

def get_fontdesc(fonts, fontspec):
    font_match = dict(zip(('family', 'weight', 'style'), fontspec.split(';')))
    for font in fonts:
        if font_match.items() <= font.items():
            return font
    return None

def subset(fontdesc, text, fts_opts):
    fontfile = fontdesc['fontfile']
    logger.info('subsetting %s', fontfile)
    font = load_font(fontfile, fts_opts, dontLoadGlyphNames=True)
    subsetter = Subsetter(options=fts_opts)
    if 'extratext' in fontdesc:
        text += fontdesc['extratext']
    subsetter.populate(text=text)
    subsetter.subset(font)
    ret = []
    for flavor in ['woff', 'woff2']:
        if 'outfile' in fontdesc and flavor in fontdesc['outfile']:
            outfile = fontdesc['outfile'][flavor]
        else:
            outfile = re.sub(r'\.otf$', f'.subset.{flavor}', fontfile)
        if outfile == fontfile:
            raise Exception('cannot overwrite font file')
        ret.append((font, flavor, outfile))
    return ret

def write_subset(font, flavor, outfile):
    logger.info('writing %s', outfile)
    font.flavor = flavor
    font.save(outfile)

def verify(path, screenshot_begin_png):
    logger.info('refetching %s', path)
    DRIVER.get(make_uri(path))
    logger.info('taking post-screenshot for %s', path)
    height = DRIVER.execute_script('return document.body.parentNode.scrollHeight')
    DRIVER.set_window_size(2000, height)
    screenshot_end_png = DRIVER.find_element_by_tag_name('body').screenshot_as_png

    logger.info('checking screenshot for %s', path)
    screenshot_begin = Image.open(BytesIO(screenshot_begin_png))
    screenshot_end = Image.open(BytesIO(screenshot_end_png))
    if ImageChops.difference(screenshot_begin, screenshot_end).getbbox():
        raise Exception(f'screenshots do not match for {path}')

class LocalPool:
    def __init__(self, driver_name):
        start_wworker(driver_name)

    def starmap(self, func, args, *_):
        return [func(*arg) for arg in args]

    def close(self):
        stop_driver()

def main(argv):
    ncpus = len(os.sched_getaffinity(0))
    nfontfiles = sum('fontfile' in font for font in config['fonts'])
    nwworkers = min(len(argv) - 1, ncpus)
    nfworkers = min(nfontfiles * 2, ncpus)
    logger.info('starting %d web workers, %d font workers', nwworkers, nfworkers)
    with Pool(nfworkers) as fpool, \
         Pool(nwworkers, start_wworker, (config['selenium_driver_name'],)) as wpool:
        all_font_texts = {}
        screenshots = []
        whitelist = [
                ';'.join((f['family'], f['weight'], f['style']))
                for f in config['fonts']]
        extract_args = ((arg, whitelist, config['screenshots']) for arg in sys.argv[1:])
        extracted = wpool.starmap(extract, extract_args)
        for path, font_texts, screenshot in extracted:
            if config['screenshots']:
                screenshots.append((path, screenshot))
            for fontspec, text in font_texts.items():
                if fontspec in all_font_texts:
                    all_font_texts[fontspec] |= set(text)
                else:
                    all_font_texts[fontspec] = set(text)
        if not config['screenshots']:
            logger.info('shutting down web workers early')
            wpool.close()
        subset_args = (
                (get_fontdesc(config['fonts'], fontspec), ''.join(text), options)
                for fontspec, text in all_font_texts.items())
        subsetted = fpool.starmap(subset, subset_args)
        fpool.starmap(write_subset, chain(*subsetted))
        if config['screenshots']:
            wpool.starmap(verify, screenshots, 1)
    if multiprocessing.active_children():
        logger.info('waiting for workers')
        for proc in multiprocessing.active_children():
            proc.join()
    logger.info('exiting successfully')

if __name__ == '__main__':
    main(sys.argv)