from datetime import datetime, timezone
from uuid import uuid4, UUID
from fastapi import HTTPException

from fastapi_demo.app.domain.status import AssetStatus
from fastapi_demo.app.domain.transitions import ensure_transition_allowed
from fastapi_demo.app.infrastructure.repositories.assets_repo import AssetsRepo
from fastapi_demo.app.schemas.asset import (
    AssetCreate,
    AssetOut,
    AssetTransitionIn,
    AssetEventOut,
)


class AssetsService:
    def __init__(self, repo: AssetsRepo) -> None:
        self.repo = repo

    def create_asset(self, data: AssetCreate) -> AssetOut:
        now = datetime.now(timezone.utc)
        asset = AssetOut(
            id=uuid4(),
            name=data.name,
            serial=data.serial,
            status=AssetStatus.WARENEINGANG,
            revision=0,  # <-- neu
            updated_at=now,
        )
        self.repo.create(asset)
        return asset

    def get_asset(self, asset_id: UUID) -> AssetOut:
        asset = self.repo.get(asset_id)
        if not asset:
            raise HTTPException(status_code=404, detail="Asset nicht gefunden")
        return asset

    def transition(
        self, asset_id: UUID, data: AssetTransitionIn
    ) -> tuple[AssetOut, AssetEventOut]:
        asset = self.get_asset(asset_id)

        # Domain-Regel: Transition erlaubt?
        ensure_transition_allowed(asset.status, data.to_status)

        now = datetime.now(timezone.utc)

        # Repo macht atomar: revision check + status update + event insert
        updated_asset, event = self.repo.transition_with_revision(
            asset_id=asset_id,
            expected_revision=data.expected_revision,
            to_status=data.to_status,
            at=now,
            note=data.note,
        )
        return updated_asset, event

    def list_events(self, asset_id: UUID) -> list[AssetEventOut]:
        self.get_asset(asset_id)  # 404 falls nicht existiert
        return self.repo.list_events(asset_id)