use std::sync::Arc;

use uuid::Uuid;

use holzleitner_domain::DeliveryCredit;

use crate::dto::{CreditAction, DeliveryCreditEventRequest};
use crate::error::ApplicationError;
use crate::ports::{CarRepository, DeliveryCreditRepository};

/// Obergrenze der Betrags-Gutschrift in Cent (150 €).
const MAX_CREDIT_CENTS: i64 = 15_000;

/// Wendet ein Gutschrift-Ereignis (`set`/`remove`) auf eine Lieferung an.
///
/// Validierung (fachlich, ohne DB):
/// * `Set`: Betrag Pflicht, `0 < amount ≤ 150 €` (beliebiger Betrag, keine
///   Schrittweite); Begründung Pflicht (nicht leer).
/// * `author_car_id` muss — falls gesetzt — zum Account gehören.
///
/// Den `active`-Check der Lieferung und die Idempotenz (`client_event_id`)
/// übernimmt das Repository mit der gelockten Zeile.
pub struct ApplyDeliveryCreditEventUseCase {
    repository: Arc<dyn DeliveryCreditRepository>,
    cars: Arc<dyn CarRepository>,
}

impl ApplyDeliveryCreditEventUseCase {
    pub fn new(
        repository: Arc<dyn DeliveryCreditRepository>,
        cars: Arc<dyn CarRepository>,
    ) -> Self {
        Self { repository, cars }
    }

    pub async fn execute(
        &self,
        delivery_id: Uuid,
        author_personalnummer: i64,
        request: DeliveryCreditEventRequest,
    ) -> Result<Option<DeliveryCredit>, ApplicationError> {
        if let Some(car_id) = request.author_car_id {
            self.cars
                .assert_owned_by_account(&[car_id], author_personalnummer)
                .await?;
        }

        let (amount_cents, reason) = match request.action {
            CreditAction::Set => {
                let amount = request.amount_cents.ok_or_else(|| {
                    ApplicationError::Validation("amount_cents required for set".into())
                })?;
                if amount <= 0 || amount > MAX_CREDIT_CENTS {
                    return Err(ApplicationError::Validation(format!(
                        "amount_cents must be in (0, {MAX_CREDIT_CENTS}]"
                    )));
                }
                let reason = request
                    .reason
                    .as_deref()
                    .map(str::trim)
                    .filter(|s| !s.is_empty())
                    .ok_or_else(|| {
                        ApplicationError::Validation("reason required for set".into())
                    })?
                    .to_owned();
                (amount, Some(reason))
            }
            // Remove: Betrag/Grund irrelevant.
            CreditAction::Remove => (0, None),
        };

        self.repository
            .apply_event(
                delivery_id,
                request.client_event_id,
                request.action,
                amount_cents,
                reason,
                author_personalnummer,
                request.author_car_id,
            )
            .await
    }
}