from fastapi import APIRouter, Depends, HTTPException
from sqlalchemy import select
from sqlalchemy.exc import IntegrityError
from sqlalchemy.ext.asyncio import AsyncSession

from app.database import get_db
from app.models import Follow
from app.schemas.schemas import FollowCreate, FollowSchema

router = APIRouter()

VALID_FOLLOW_TYPES = {"bill", "member", "topic"}


@router.get("", response_model=list[FollowSchema])
async def list_follows(db: AsyncSession = Depends(get_db)):
    result = await db.execute(select(Follow).order_by(Follow.created_at.desc()))
    return result.scalars().all()


@router.post("", response_model=FollowSchema, status_code=201)
async def add_follow(body: FollowCreate, db: AsyncSession = Depends(get_db)):
    if body.follow_type not in VALID_FOLLOW_TYPES:
        raise HTTPException(status_code=400, detail=f"follow_type must be one of {VALID_FOLLOW_TYPES}")
    follow = Follow(follow_type=body.follow_type, follow_value=body.follow_value)
    db.add(follow)
    try:
        await db.commit()
        await db.refresh(follow)
    except IntegrityError:
        await db.rollback()
        # Already following — return existing
        result = await db.execute(
            select(Follow).where(
                Follow.follow_type == body.follow_type,
                Follow.follow_value == body.follow_value,
            )
        )
        return result.scalar_one()
    return follow


@router.delete("/{follow_id}", status_code=204)
async def remove_follow(follow_id: int, db: AsyncSession = Depends(get_db)):
    follow = await db.get(Follow, follow_id)
    if not follow:
        raise HTTPException(status_code=404, detail="Follow not found")
    await db.delete(follow)
    await db.commit()