import shutil

from flask import Blueprint, Response, redirect, request
from sqlalchemy import select

from l4d2host.paths import get_left4me_root

from l4d2web.auth import current_user, require_login
from l4d2web.db import session_scope
from l4d2web.models import BlueprintOverlay, Overlay
from l4d2web.services.overlay_creation import (
    create_overlay_directory,
    generate_overlay_path,
)


bp = Blueprint("overlay", __name__)


VALID_TYPES = {"external", "workshop"}


def _is_managed_path(overlay: Overlay) -> bool:
    return overlay.path == str(overlay.id)


def _can_edit_overlay(overlay: Overlay, user) -> bool:
    if user is None:
        return False
    if user.admin:
        return True
    if overlay.type == "external":
        return False
    if overlay.type == "workshop":
        return overlay.user_id == user.id
    return False


def _name_already_taken(db, name: str, scope_user_id: int | None, *, except_id: int | None = None) -> bool:
    query = select(Overlay).where(Overlay.name == name)
    if scope_user_id is None:
        query = query.where(Overlay.user_id.is_(None))
    else:
        query = query.where(Overlay.user_id == scope_user_id)
    if except_id is not None:
        query = query.where(Overlay.id != except_id)
    return db.scalar(query) is not None


@bp.post("/overlays")
@require_login
def create_overlay() -> Response:
    user = current_user()
    assert user is not None

    name = request.form.get("name", "").strip()
    overlay_type = request.form.get("type", "external").strip().lower()
    if not name:
        return Response("missing fields", status=400)
    if overlay_type not in VALID_TYPES:
        return Response(f"unknown overlay type: {overlay_type}", status=400)

    if overlay_type == "external":
        if not user.admin:
            return Response("admin only", status=403)
        scope_user_id: int | None = None
    else:  # workshop
        scope_user_id = user.id

    with session_scope() as db:
        if _name_already_taken(db, name, scope_user_id):
            return Response("overlay already exists", status=409)

        overlay = Overlay(name=name, path="", type=overlay_type, user_id=scope_user_id)
        db.add(overlay)
        db.flush()
        overlay.path = generate_overlay_path(overlay.id)
        db.flush()
        create_overlay_directory(overlay)
        new_id = overlay.id

    return redirect(f"/overlays/{new_id}")


@bp.post("/overlays/<int:overlay_id>")
@require_login
def update_overlay(overlay_id: int) -> Response:
    user = current_user()
    assert user is not None

    name = request.form.get("name", "").strip()
    if not name:
        return Response("missing fields", status=400)

    with session_scope() as db:
        overlay = db.scalar(select(Overlay).where(Overlay.id == overlay_id))
        if overlay is None:
            return Response(status=404)
        if not _can_edit_overlay(overlay, user):
            return Response(status=403)
        if _name_already_taken(db, name, overlay.user_id, except_id=overlay_id):
            return Response("overlay already exists", status=409)
        overlay.name = name

    return redirect(f"/overlays/{overlay_id}")


@bp.post("/overlays/<int:overlay_id>/delete")
@require_login
def delete_overlay(overlay_id: int) -> Response:
    user = current_user()
    assert user is not None

    with session_scope() as db:
        overlay = db.scalar(select(Overlay).where(Overlay.id == overlay_id))
        if overlay is None:
            return Response(status=404)
        if not _can_edit_overlay(overlay, user):
            return Response(status=403)
        in_use = db.scalar(select(BlueprintOverlay).where(BlueprintOverlay.overlay_id == overlay_id))
        if in_use is not None:
            return Response("overlay is in use", status=409)
        path_value = overlay.path
        path_is_managed = _is_managed_path(overlay)
        db.delete(overlay)

    if path_is_managed and path_value:
        target = get_left4me_root() / "overlays" / path_value
        if target.exists():
            shutil.rmtree(target)

    return redirect("/overlays")