import asyncio
import logging
from dataclasses import dataclass, field
from datetime import datetime, timezone
from hashlib import md5
from typing import *

import feedparser

USER_AGENT = "curl/7.64.1"

log = logging.getLogger(__name__)

FeedId = str
PostId = str


@dataclass
class Feed:
    id: FeedId
    url: str
    title: Optional[str] = None
    posts: List["Post"] = field(default_factory=list)
    etag: Optional[str] = None
    modified: Optional[str] = None
    active: bool = True
    next_url: Optional[str] = None

    @property
    def post_ids(self) -> Set[PostId]:
        return {p.id for p in self.posts}

    def load(self) -> None:
        """Load all posts from the current feed URL."""
        log.debug(f"Loading {self.url} ...")
        r = feedparser.parse(
            self.url, agent=USER_AGENT, etag=self.etag, modified=self.modified
        )
        log.debug(f"Loaded {self.url}: {r.get('status')} {r.headers}")
        if r.get("status") is None:
            log.error(f"Feed could not be loaded: {self.id}: {self.url}")
            return
        elif r.get("status") == 301:
            log.warning(f"Feed URL changed: {self.id}: {r.href}")
            self.url = r.href
        elif r.get("status") == 410:
            log.error(f"Feed is gone: {self.id}")
            self.active = False
            return

        if "etag" in r:
            self.etag = r.etag
        if "modified" in r:
            self.modified = r.modified
        if "title" in r.feed:
            self.title = r.feed.title

        posts = [Post.from_entry(e) for e in r.entries]
        for post in posts:
            if post.date is None:
                post.date = pubdate(r.feed)
        posts.sort(key=lambda e: e.date, reverse=True)
        self.posts = posts

        for link in r.feed.get("links", []):
            if link.get("rel") == "next":
                self.next_url = link.get("href")
                break
        else:
            self.next_url = None

    def load_next(self) -> Optional["Feed"]:
        if not self.next_url:
            return None
        feed = Feed(self.id, self.next_url)
        feed.load()
        return feed


@dataclass
class Post:
    id: PostId
    content: Optional[str] = None
    date: Optional[datetime] = None
    link: Optional[str] = None
    title: Optional[str] = None

    @classmethod
    def from_entry(cls, entry):
        content = entry.get("summary", "")
        title = entry.get("title", "")
        return cls(
            id=(
                entry.get("id")
                or entry.get("link")
                or md5(f"{title}|{content}".encode()).hexdigest()
            ),
            date=pubdate(entry),
            content=content,
            title=title,
            link=entry.get("link"),
        )


def pubdate(entry) -> Optional[datetime]:
    date = entry.get("published_parsed") or entry.get("updated_parsed")
    if date is None:
        return None
    return datetime(*date[:6], tzinfo=timezone.utc)