from fastapi import APIRouter, Depends, HTTPException
from pydantic import BaseModel
from sqlalchemy import select
from sqlalchemy.orm import Session

from app.core.auth_dependency import require_session
from app.db import get_db
from app.models.category import Category
from app.models.channel import Channel
from app.models.channel_category import channel_categories

router = APIRouter(dependencies=[Depends(require_session)])


class ChannelCategoriesUpdate(BaseModel):
    category_ids: list[int]


def _category_ids_by_channel(db: Session, channel_ids: list[int]) -> dict[int, list[int]]:
    if not channel_ids:
        return {}
    rows = db.execute(
        select(channel_categories.c.channel_id, channel_categories.c.category_id).where(
            channel_categories.c.channel_id.in_(channel_ids)
        )
    ).all()
    result: dict[int, list[int]] = {}
    for channel_id, category_id in rows:
        result.setdefault(channel_id, []).append(category_id)
    return result


def _serialize(channel: Channel, category_ids: list[int]) -> dict:
    return {
        "id": channel.id,
        "youtube_channel_id": channel.youtube_channel_id,
        "title": channel.title,
        "description": channel.description,
        "thumbnail_url": channel.thumbnail_url,
        "uploads_playlist_id": channel.uploads_playlist_id,
        "subscribed": channel.subscribed,
        "last_synced_at": channel.last_synced_at,
        "category_ids": category_ids,
    }


@router.get("/channels")
def list_channels(
    subscribed: bool | None = None,
    search: str | None = None,
    category_id: int | None = None,
    uncategorized: bool = False,
    db: Session = Depends(get_db),
) -> list[dict]:
    query = db.query(Channel)
    if subscribed is not None:
        query = query.filter(Channel.subscribed == subscribed)
    if search:
        query = query.filter(Channel.title.ilike(f"%{search}%"))

    if uncategorized:
        categorized_ids = select(channel_categories.c.channel_id)
        query = query.filter(~Channel.id.in_(categorized_ids))
    elif category_id is not None:
        channel_ids_in_category = select(channel_categories.c.channel_id).where(
            channel_categories.c.category_id == category_id
        )
        query = query.filter(Channel.id.in_(channel_ids_in_category))

    channels = query.order_by(Channel.title.asc()).all()
    category_map = _category_ids_by_channel(db, [c.id for c in channels])
    return [_serialize(c, category_map.get(c.id, [])) for c in channels]


@router.get("/channels/{channel_id}")
def get_channel(channel_id: int, db: Session = Depends(get_db)) -> dict:
    channel = db.get(Channel, channel_id)
    if channel is None:
        raise HTTPException(status_code=404, detail="Channel not found")
    category_map = _category_ids_by_channel(db, [channel_id])
    return _serialize(channel, category_map.get(channel_id, []))


@router.put("/channels/{channel_id}/categories")
def set_channel_categories(channel_id: int, payload: ChannelCategoriesUpdate, db: Session = Depends(get_db)) -> dict:
    channel = db.get(Channel, channel_id)
    if channel is None:
        raise HTTPException(status_code=404, detail="Channel not found")

    unique_ids = set(payload.category_ids)
    if unique_ids:
        found = db.query(Category.id).filter(Category.id.in_(unique_ids)).all()
        found_ids = {row[0] for row in found}
        missing = unique_ids - found_ids
        if missing:
            raise HTTPException(status_code=400, detail=f"Unknown category ids: {sorted(missing)}")

    db.execute(channel_categories.delete().where(channel_categories.c.channel_id == channel_id))
    if unique_ids:
        db.execute(
            channel_categories.insert(),
            [{"channel_id": channel_id, "category_id": cid} for cid in unique_ids],
        )
    db.commit()

    return _serialize(channel, sorted(unique_ids))