from fastapi import FastAPI, HTTPException, Response, Depends
from sqlmodel import Session, select
from typing import Annotated
import datetime, re

from database.feed import Feed, FeedCreate, FeedPublic, FeedUpdate
from database.blacklist import Blacklist, BlacklistCreate
from utils.feed_generator import generate_feed_of_user, USER_NOT_FOUND, CANNOT_ACCESS_INSTANCE
from utils.database import get_session, create_db_and_tables

app = FastAPI()
SessionDep = Annotated[Session, Depends(get_session)]


@app.on_event("startup")
def on_startup():
    create_db_and_tables()


@app.get("/feed/{user_handle}")
def get_feed_of_user(user_handle: str, session: SessionDep):
    # validate user's handle
    HANDLE_PATTERN = "@[a-zA-Z0-9_]+@[^\t\n\r\f\v]+"
    if re.match(HANDLE_PATTERN, user_handle) is None:
        return HTTPException(status_code=400, detail="The handle is invalid.")

    # check if there is the user in blacklist
    black_user = session.exec(select(Blacklist).where(Blacklist.handle == user_handle)).first()
    if black_user:
        return HTTPException(status_code=401, detail="The user is in blacklist.")

    # get feed on database
    feed_db = session.exec(select(Feed).where(Feed.handle == user_handle)).first()
    
    # return cached feed if it has been cached for less than 10 minutes
    if feed_db and ((feed_db.updated_at + datetime.timedelta(minutes=10)) - datetime.datetime.now()).total_seconds() > 0:
        return Response(content=feed_db.feed, media_type="application/xml")

    feed = generate_feed_of_user(user_handle)

    if feed == USER_NOT_FOUND:
        return HTTPException(status_code=404, detail="The user cannot be found.")
    if feed == CANNOT_ACCESS_INSTANCE:
        return HTTPException(status_code=400, detail="Cannot access the instance.")
    
    # cache new feed
    if feed_db:
        feed_data = FeedUpdate(feed=feed, updated_at=datetime.datetime.now()).model_dump(exclude_unset=True)
        feed_db.sqlmodel_update(feed_data)
    else:
        feed_db = Feed.model_validate(FeedCreate(handle=user_handle, feed=feed))
    session.add(feed_db)
    session.commit()
    session.refresh(feed_db)
    
    return Response(content=feed, media_type="application/xml")