use std::collections::HashSet;
use std::sync::Arc;

use uuid::Uuid;

use crate::dto::{SetDeliveryOrderRequest, SetDeliveryOrderResponse};
use crate::error::ApplicationError;
use crate::ports::TourRepository;

/// Schreibt die Sortier-Reihenfolge aller Lieferungen einer Tour neu.
///
/// Eingabe-Validierung (vor DB-Aufruf):
/// * mindestens eine Id
/// * keine Duplikate
///
/// Die Mengen-Übereinstimmung mit der Tour wird in der Persistence
/// geprüft (braucht DB-Kontext).
pub struct SetDeliveryOrderUseCase {
    repository: Arc<dyn TourRepository>,
}

impl SetDeliveryOrderUseCase {
    pub fn new(repository: Arc<dyn TourRepository>) -> Self {
        Self { repository }
    }

    pub async fn execute(
        &self,
        tour_id: Uuid,
        request: SetDeliveryOrderRequest,
    ) -> Result<SetDeliveryOrderResponse, ApplicationError> {
        if request.delivery_ids.is_empty() {
            return Err(ApplicationError::Validation(
                "delivery_ids darf nicht leer sein".into(),
            ));
        }
        let mut seen = HashSet::with_capacity(request.delivery_ids.len());
        for id in &request.delivery_ids {
            if !seen.insert(*id) {
                return Err(ApplicationError::Validation(format!(
                    "delivery_id {id} kommt mehrfach vor"
                )));
            }
        }

        let order = self
            .repository
            .set_delivery_order(tour_id, &request.delivery_ids)
            .await?;

        Ok(SetDeliveryOrderResponse { tour_id, order })
    }
}