#
# Copyright 2020 Laszlo Zeke
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#

from cachetools import cached, TTLCache, LRUCache
from feedformatter import Feed
from flask import abort, Flask, request
from io import BytesIO
from os import environ
import datetime
import gzip
import time
import json
import logging
import re
import urllib


VOD_URL_TEMPLATE = 'https://api.twitch.tv/helix/videos?user_id=%s&type=all'
USERID_URL_TEMPLATE = 'https://api.twitch.tv/helix/users?login=%s'
VODCACHE_LIFETIME = 10 * 60
USERIDCACHE_LIFETIME = 24 * 60 * 60
CHANNEL_FILTER = re.compile("^[a-zA-Z0-9_]{2,25}$")
TWITCH_CLIENT_ID = environ.get("TWITCH_CLIENT_ID")
TWITCH_SECRET = environ.get("TWITCH_SECRET")
TWITCH_OAUTH_TOKEN = ""
TWITCH_OAUTH_EXPIRE_EPOCH = 0
logging.basicConfig(level=logging.DEBUG if environ.get('DEBUG') else logging.INFO)

if not TWITCH_CLIENT_ID:
    raise Exception("Twitch API client id is not set.")
if not TWITCH_SECRET:
    raise Exception("Twitch API secret env variable not set.")


app = Flask(__name__)

def authorize():
    global TWITCH_OAUTH_TOKEN
    global TWITCH_OAUTH_EXPIRE_EPOCH

    # return if token has not expired
    if (TWITCH_OAUTH_EXPIRE_EPOCH >= round(time.time())):
        return

    logging.debug("requesting a new oauth token")
    data = {
        'client_id': TWITCH_CLIENT_ID,
        'client_secret': TWITCH_SECRET,
        'grant_type': 'client_credentials',
    }
    url = 'https://id.twitch.tv/oauth2/token'
    request = urllib.request.Request(url, data=urllib.parse.urlencode(data).encode("utf-8"), method='POST')
    retries = 0
    while retries < 3:
        try:
            result = urllib.request.urlopen(request, timeout=3)
            r = json.loads(result.read().decode("utf-8"))
            TWITCH_OAUTH_TOKEN = r['access_token']
            TWITCH_OAUTH_EXPIRE_EPOCH = int(r['expires_in']) + round(time.time())
            logging.debug("oauth token aquired")
            return
        except Exception as e:
            logging.warning("Fetch exception caught: %s" % e)
            retries += 1
    abort(503)

@app.route('/vod/<string:channel>', methods=['GET', 'HEAD'])
def vod(channel):
    if CHANNEL_FILTER.match(channel):
        return get_inner(channel)
    else:
        abort(404)


@app.route('/vodonly/<string:channel>', methods=['GET', 'HEAD'])
def vodonly(channel):
    if CHANNEL_FILTER.match(channel):
        return get_inner(channel, add_live=False)
    else:
        abort(404)


def get_inner(channel, add_live=True):
    userid_json = fetch_userid(channel)
    if not userid_json:
        abort(404)

    (channel_display_name, channel_id) = extract_userid(json.loads(userid_json)['data'][0])

    channel_json = fetch_vods(channel_id)
    if not channel_json:
        abort(404)

    decoded_json = json.loads(channel_json)['data']
    rss_data = construct_rss(channel, decoded_json, channel_display_name, add_live)
    headers = {'Content-Type': 'application/rss+xml'}

    if 'gzip' in request.headers.get("Accept-Encoding", ''):
        headers['Content-Encoding'] = 'gzip'
        rss_data = gzip.compress(rss_data)

    return rss_data, headers


@cached(cache=TTLCache(maxsize=3000, ttl=USERIDCACHE_LIFETIME))
def fetch_userid(channel_name):
    return fetch_json(channel_name, USERID_URL_TEMPLATE)


@cached(cache=TTLCache(maxsize=500, ttl=VODCACHE_LIFETIME))
def fetch_vods(channel_id):
    return fetch_json(channel_id, VOD_URL_TEMPLATE)


def fetch_json(id, url_template):
    #update the oauth token
    authorize()

    url = url_template % id
    headers = {
        'Authorization': 'Bearer '+TWITCH_OAUTH_TOKEN,
        'Client-Id': TWITCH_CLIENT_ID,
        'Accept-Encoding': 'gzip'
    }
    request = urllib.request.Request(url, headers=headers)
    retries = 0
    while retries < 3:
        try:
            result = urllib.request.urlopen(request, timeout=3)
            logging.debug('Fetch from twitch for %s with code %s' % (id, result.getcode()))
            if result.info().get('Content-Encoding') == 'gzip':
                logging.debug('Fetched gzip content')
                return gzip.decompress(result.read())
            return result.read()
        except Exception as e:
            logging.warning("Fetch exception caught: %s" % e)
            retries += 1
    abort(503)


def extract_userid(user_info):
    # Get the first id in the list
    userid = user_info['id']
    username = user_info['display_name']
    if username and userid:
        return username, userid
    else:
        logging.warning('Userid is not found in %s' % user_info)
        abort(404)


def construct_rss(channel_name, vods_info, display_name, add_live=True):
    feed = Feed()

    # Set the feed/channel level properties
    feed.feed["title"] = "%s's Twitch video RSS" % display_name
    feed.feed["link"] = "https://twitchrss.appspot.com/"
    feed.feed["author"] = "Twitch RSS Generated"
    feed.feed["description"] = "The RSS Feed of %s's videos on Twitch" % display_name
    feed.feed["ttl"] = '10'

    # Create an item
    try:
        if vods_info:
            for vod in vods_info:
                item = {}

                # @madiele: in twitch new API the current stream now it's not bundled in the same request
                # maybe to be re-implemented later on

                #if vod["status"] == "recording":
                #    if not add_live:
                #        continue
                #    link = "http://www.twitch.tv/%s" % channel_name
                #    item["title"] = "%s - LIVE" % vod['title']
                #    item["category"] = "live"
                #else:
                link = vod['url']
                item["title"] = vod['title']
                item["category"] = vod['type']

                item["link"] = link
                item["description"] = "<a href=\"%s\"><img src=\"%s\" /></a>" % (link, vod['thumbnail_url'].replace("%{width}", "512").replace("%{height}","288"))

                #@madiele: for some reason the new API does not have the game field anymore...
                #if vod.get('game'):
                #    item["description"] += "<br/>" + vod['game']

                if vod.get('description'):
                    item["description"] += "<br/>" + vod['description']
                d = datetime.datetime.strptime(vod['created_at'], '%Y-%m-%dT%H:%M:%SZ')
                item["pubDate"] = d.timetuple()
                item["guid"] = vod['id']
                #if vod["status"] == "recording":  # To show a different news item when recording is over
                #    item["guid"] += "_live"
                feed.items.append(item)
    except KeyError as e:
        logging.warning('Issue with json: %s\nException: %s' % (vods_info, e))
        abort(404)

    return feed.format_rss2_string()


# For debug
if __name__ == "__main__":
    app.run(host='127.0.0.1', port=8080, debug=True)