import os

from sqlalchemy.exc import IntegrityError
from fastapi import FastAPI, HTTPException
from fastapi.responses import RedirectResponse

from dependencies.models import UrlMapping
from dependencies.database import database, Base, engine
from schemas import UrlPayload
from utils import generate_shortcode

app = FastAPI()

@app.on_event("startup")
async def startup():
    await database.connect()
    Base.metadata.create_all(bind=engine) # TODO: create all tables if not present (ONLY DEVELOPMENT)

@app.on_event("shutdown")
async def shutdown():
    await database.disconnect()



@app.get("/{shortcode}")
async def redirect_to_original_url(shortcode: str):
    # TODO: do validation check for valid shortcode
    if not shortcode:
        raise HTTPException(status_code=400, detail="Shortcode is not valid")

    query = UrlMapping.__table__.select().where(UrlMapping.shortcode == shortcode)
    url_mapping = await database.fetch_one(query)

    if url_mapping:
        return RedirectResponse(url=url_mapping.url, status_code=302)
    else:
        raise HTTPException(status_code=404, detail="Shortcode not found")

@app.post("/shorten")
async def create_url_shortcode(url_payload: UrlPayload):
    original_url = str(url_payload.url) # convert to string from HttpUrl
    shortcode = generate_shortcode()

    try:
        query = UrlMapping.__table__.insert().values({
            "url": original_url,
            "shortcode": shortcode
        })
        await database.execute(query)

        return {"shortcode": shortcode, "original_url": original_url}
    except IntegrityError as e:
        if 'shortcode' in str(e):
            raise HTTPException(status_code=409, detail="Shortcode already in use")
        else:
            raise HTTPException(status_code=500, detail="Internal Server Error")