# Fakultät für Mathematik (FfM)

import aiohttp
import asyncio
import bs4
import logging
import pathlib
import re

from .organizer import Organizer
from . import utils

__all__ = [
	"FfM",
]
logger = logging.getLogger(__name__)

class FfM:
	BASE_URL = "http://www.math.kit.edu/"
	LINK_RE = re.compile(r"^https?://www.math.kit.edu/.*/(.*\.pdf)$")

	RETRY_ATTEMPTS = 5
	RETRY_DELAY = 1 # seconds

	def __init__(self, base_path):
		self.base_path = base_path

		self._session = aiohttp.ClientSession()

	async def synchronize(self, urlpart, to_dir, transform=lambda x: x):
		logging.info(f"    Synchronizing {urlpart} to {to_dir} using the FfM synchronizer.")

		sync_path = pathlib.Path(self.base_path, to_dir)
		orga = Organizer(self.base_path, sync_path)

		orga.clean_temp_dir()

		await self._crawl(orga, urlpart, transform)

		orga.clean_sync_dir()
		orga.clean_temp_dir()

	async def close(self):
		await self._session.close()

	async def _crawl(self, orga, urlpart, transform):
		url = self.BASE_URL + urlpart
		async with self._session.get(url) as resp:
			text = await resp.text()
		soup = bs4.BeautifulSoup(text, "html.parser")

		for found in soup.find_all("a", href=self.LINK_RE):
			url = found["href"]
			filename = re.match(self.LINK_RE, url).group(1)
			logger.debug(f"Found file {filename} at {url}")

			old_path = pathlib.PurePath(filename)
			new_path = transform(old_path)
			if new_path is None:
				continue
			logger.debug(f"Transformed from {old_path} to {new_path}")

			temp_path = orga.temp_file()
			await self._download(url, temp_path)
			orga.add_file(temp_path, new_path)

	async def _download(self, url, to_path):
		for t in range(self.RETRY_ATTEMPTS):
			try:
				async with self._session.get(url) as resp:
					await utils.stream_to_path(resp, to_path)
			except aiohttp.client_exceptions.ServerDisconnectedError:
				logger.debug(f"Try {t+1} out of {self.RETRY_ATTEMPTS} failed, retrying in {self.RETRY_DELAY} s")
				await asyncio.sleep(self.RETRY_DELAY)
			else:
				return
		else:
			logger.error(f"Could not download {url}")
			raise utils.OutOfTriesException(f"Try {self.RETRY_ATTEMPTS} out of {self.RETRY_ATTEMPTS} failed.")