import asyncio
import logging
import os
import re
from asyncio.exceptions import TimeoutError
from html import unescape
from time import time
from urllib.parse import unquote

import aiohttp
from aiohttp import ClientConnectorError

PROTOCOL = 'https://'
BASE_URL = 'telegram.org'
# its necessary to help crawler to find more links
HIDDEN_URLS = {
    # 'corefork.telegram.org',

    'telegram.org/privacy/gmailbot',
    'telegram.org/tos',
    'telegram.org/tour',
    'telegram.org/evolution',

    'desktop.telegram.org/changelog',
}
BASE_URL_REGEX = r'telegram.org'

# disable crawling sub links for specific domains and url patterns
CRAWL_RULES = {
    # every rule is regex
    # empty string means match any url
    # allow rules with high priority than deny
    'translations.telegram.org': {
        'allow': {
            r'^[^/]*$',  # root
            r'org/[^/]*/$',  # 1 lvl sub
            r'/en/[a-z_]+/$'  # 1 lvl after /en/
        },
        'deny': {
            '',  # all
        }
    },
    'bugs.telegram.org': {  # crawl first page of cards sorted by rating
        'deny': {
            # r'/c/[0-9]+/[0-9]+',  # disable comments
            '',
        },
    },
    'instantview.telegram.org': {
        'allow': {
            'contest/winners'
        },
        'deny': {
            'file/',

            r'templates/.+',
            'samples/',
            'contest/',
        },
    },
    'core.telegram.org': {
        'deny': {
            'file/',

            'tdlib/docs/classtd',

            'constructor/',
            'method/',
            'type/',
        },
    },
    'telegram.org': {
        'deny': {
            'file/',
        },
    }
}

DIRECT_LINK_REGEX = r'([-a-zA-Z0-9@:%._\+~#]{0,249}' + BASE_URL_REGEX + r')'
ABSOLUTE_LINK_REGEX = r'([-a-zA-Z0-9@:%._\+~#]{1,249}' + BASE_URL_REGEX + r'\b[-a-zA-Z0-9@:%_\+.~#?&\/\/=]*)'
RELATIVE_LINK_REGEX = r'\/([-a-zA-Z0-9\/@:%._\+~#]{0,249})'

DOM_ATTRS = ['href', 'src']

OUTPUT_FILENAME = os.environ.get('OUTPUT_FILENAME', 'tracked_links.txt')

# unsecure but so simple
CONNECTOR = aiohttp.TCPConnector(ssl=False)
TIMEOUT = aiohttp.ClientTimeout(total=30)

logging.basicConfig(format='%(message)s', level=logging.DEBUG)
logger = logging.getLogger(__name__)

VISITED_LINKS = set()
LINKS_TO_TRACK = set()


def should_exclude(url: str) -> bool:
    direct_link = re.findall(DIRECT_LINK_REGEX, url)[0]
    domain_rules = CRAWL_RULES.get(direct_link)
    if not domain_rules:
        return False

    allow_rules = domain_rules.get('allow', set())
    deny_rules = domain_rules.get('deny', set())

    exclude = False

    for regex in deny_rules:
        if re.search(regex, url):
            exclude = True
            break

    for regex in allow_rules:
        if re.search(regex, url):
            exclude = False
            break

    return exclude


def find_absolute_links(html: str) -> set[str]:
    absolute_links = set(re.findall(ABSOLUTE_LINK_REGEX, html))

    return {link for link in absolute_links if not should_exclude(link)}


def find_relative_links(html: str, cur_link: str) -> set[str]:
    direct_cur_link = re.findall(DIRECT_LINK_REGEX, cur_link)[0]
    # optimization. when we want to exclude domain
    if should_exclude(cur_link):
        return set()

    relative_links = set()
    for attr in DOM_ATTRS:
        regex = f'{attr}="{RELATIVE_LINK_REGEX}'
        links = re.findall(regex, html)

        for link in links:
            # bypass //www.apple and etc shit ;d
            if link.startswith('/'):
                # absolute links starting with double slash
                if find_absolute_links(link):
                    if not should_exclude(link[1::]):
                        relative_links.add(link[1::])
            else:
                url = f'{direct_cur_link}/{link}'
                if not should_exclude(url):
                    relative_links.add(url)

    return relative_links


def cleanup_links(links: set[str]) -> set[str]:
    cleaned_links = set()
    for tmp_link in links:
        # normalize link
        link = unquote(tmp_link)
        link = unescape(link)
        link = link.replace('www.', '')
        link = link.replace('http://', '').replace('https://', '')
        # skip anchor links
        if '#' in link:
            continue

        link_parts = link.split('.')
        if '@' in link_parts[0]:
            continue

        cleaned_links.add(link)

    return cleaned_links


async def crawl(url: str, session: aiohttp.ClientSession):
    # todo
    if url.endswith('.'):
        return

    without_trailing_slash = url[:-1:] if url.endswith('/') else url
    if without_trailing_slash in VISITED_LINKS:
        return
    VISITED_LINKS.add(without_trailing_slash)

    try:
        logger.info(f'[{len(VISITED_LINKS)}] Process {url}')
        async with session.get(f'{PROTOCOL}{url}', allow_redirects=False) as response:
            status_code = response.status
            content_type = response.headers.get('content-type')

            # if it was redirect to link with trailing slash - handle this url
            if 300 < status_code < 400:
                location = response.headers.get('location', '')
                # todo rewrite logic
                if without_trailing_slash in location:
                    if not should_exclude(location):
                        # nice shit bro
                        logger.info(f'Trailing slash. {location}')
                        cleaned_link = list(cleanup_links({location}))[0]
                        await asyncio.gather(crawl(cleaned_link, session))

            if status_code != 200:
                return

            if 'text/html' in content_type:
                LINKS_TO_TRACK.add(url)

                html = await response.text()
                absolute_links = cleanup_links(find_absolute_links(html))
                relative_links = cleanup_links(find_relative_links(html, url))

                sub_links = absolute_links | relative_links
                await asyncio.gather(*[crawl(url, session) for url in sub_links])
            elif 'application/javascript' in content_type:
                LINKS_TO_TRACK.add(url)
            elif 'text/css' in content_type:
                LINKS_TO_TRACK.add(url)
            elif 'application/json' in content_type:
                LINKS_TO_TRACK.add(url)
            else:
                # TODO track hashes of image/svg/video content types
                logger.info(f'Unhandled type: {content_type}')
    except UnicodeDecodeError:
        logger.warning('Codec can\'t decode byte. So its was a tgs file')
    except (TimeoutError, ClientConnectorError):
        await asyncio.gather(crawl(url, session))


async def start(url_list: set[str]):
    async with aiohttp.ClientSession(connector=CONNECTOR) as session:
        await asyncio.gather(*[crawl(url, session) for url in url_list])


if __name__ == '__main__':
    HIDDEN_URLS.add(BASE_URL)

    logger.info('Start crawling links...')
    start_time = time()
    asyncio.get_event_loop().run_until_complete(start(HIDDEN_URLS))
    logger.info(f'Stop crawling links. {time() - start_time} sec.')

    with open(OUTPUT_FILENAME, 'w') as f:
        f.write('\n'.join(sorted(LINKS_TO_TRACK)))