<?php

namespace App\Services;

use App\Models\InventoryMovement;
use App\Models\Reservation;
use App\Models\Shortage;
use App\Models\SparePart;
use App\Models\SparePartOrder;
use Illuminate\Support\Collection;
use Illuminate\Support\Facades\DB;

/**
 * Сервис резервирования запчастей.
 *
 * Реализует алгоритм резервирования с учётом:
 * - FIFO по партиям (первыми резервируются старые поступления)
 * - Разделения по типу документов (with_documents)
 * - Создания дефицитов при нехватке
 */
class SparePartReservationService
{
    /**
     * Результат резервирования
     */
    public function __construct(
        private readonly ShortageService $shortageService
    ) {}

    /**
     * Зарезервировать запчасть для рекламации
     *
     * @param int $sparePartId ID запчасти
     * @param int $quantity Требуемое количество
     * @param bool $withDocuments С документами или без
     * @param int $reclamationId ID рекламации
     * @return ReservationResult
     */
    public function reserve(
        int $sparePartId,
        int $quantity,
        bool $withDocuments,
        int $reclamationId
    ): ReservationResult {
        return DB::transaction(function () use ($sparePartId, $quantity, $withDocuments, $reclamationId) {

            $sparePart = SparePart::findOrFail($sparePartId);

            // 1. Расчёт свободного остатка
            $physicalStock = SparePartOrder::query()
                ->where('spare_part_id', $sparePartId)
                ->where('with_documents', $withDocuments)
                ->where('status', SparePartOrder::STATUS_IN_STOCK)
                ->sum('available_qty');

            $activeReserves = Reservation::query()
                ->where('spare_part_id', $sparePartId)
                ->where('with_documents', $withDocuments)
                ->where('status', Reservation::STATUS_ACTIVE)
                ->sum('reserved_qty');

            $freeStock = $physicalStock - $activeReserves;

            // 2. Определение сколько можем зарезервировать
            $canReserve = min($quantity, max(0, $freeStock));
            $missing = $quantity - $canReserve;

            $reservations = collect();
            $shortage = null;

            // 3. Резервирование доступного количества (FIFO по партиям)
            if ($canReserve > 0) {
                $remainingToReserve = $canReserve;

                $orders = SparePartOrder::query()
                    ->where('spare_part_id', $sparePartId)
                    ->where('with_documents', $withDocuments)
                    ->where('status', SparePartOrder::STATUS_IN_STOCK)
                    ->where('available_qty', '>', 0)
                    ->orderBy('created_at', 'asc')
                    ->lockForUpdate()
                    ->get();

                foreach ($orders as $order) {
                    if ($remainingToReserve <= 0) break;

                    // Сколько уже зарезервировано из этой партии
                    $alreadyReserved = Reservation::query()
                        ->where('spare_part_order_id', $order->id)
                        ->where('status', Reservation::STATUS_ACTIVE)
                        ->sum('reserved_qty');

                    $freeInOrder = $order->available_qty - $alreadyReserved;
                    $toReserve = min($remainingToReserve, $freeInOrder);

                    if ($toReserve > 0) {
                        // Создаём движение типа reserve
                        $movement = InventoryMovement::create([
                            'spare_part_order_id' => $order->id,
                            'spare_part_id' => $sparePartId,
                            'qty' => $toReserve,
                            'movement_type' => InventoryMovement::TYPE_RESERVE,
                            'source_type' => InventoryMovement::SOURCE_RECLAMATION,
                            'source_id' => $reclamationId,
                            'with_documents' => $withDocuments,
                            'user_id' => auth()->id(),
                            'note' => "Резервирование для рекламации #{$reclamationId}",
                        ]);

                        // Создаём резерв
                        $reservation = Reservation::create([
                            'spare_part_id' => $sparePartId,
                            'spare_part_order_id' => $order->id,
                            'reclamation_id' => $reclamationId,
                            'reserved_qty' => $toReserve,
                            'with_documents' => $withDocuments,
                            'status' => Reservation::STATUS_ACTIVE,
                            'movement_id' => $movement->id,
                        ]);

                        $reservations->push($reservation);
                        $remainingToReserve -= $toReserve;
                    }
                }
            }

            // 4. Создание дефицита при нехватке
            if ($missing > 0) {
                $shortage = Shortage::create([
                    'spare_part_id' => $sparePartId,
                    'reclamation_id' => $reclamationId,
                    'with_documents' => $withDocuments,
                    'required_qty' => $quantity,
                    'reserved_qty' => $canReserve,
                    'missing_qty' => $missing,
                    'status' => Shortage::STATUS_OPEN,
                    'note' => "Дефицит при резервировании для рекламации #{$reclamationId}",
                ]);
            }

            return new ReservationResult(
                reserved: $canReserve,
                missing: $missing,
                reservations: $reservations,
                shortage: $shortage
            );
        });
    }

    /**
     * Отменить резервы для рекламации
     *
     * @param int $reclamationId ID рекламации
     * @param int|null $sparePartId ID запчасти (опционально, если нужно отменить для конкретной)
     * @param bool|null $withDocuments Тип документов (опционально)
     * @return int Количество отменённых единиц
     */
    public function cancelForReclamation(
        int $reclamationId,
        ?int $sparePartId = null,
        ?bool $withDocuments = null
    ): int {
        return DB::transaction(function () use ($reclamationId, $sparePartId, $withDocuments) {
            $query = Reservation::query()
                ->where('reclamation_id', $reclamationId)
                ->where('status', Reservation::STATUS_ACTIVE);

            if ($sparePartId !== null) {
                $query->where('spare_part_id', $sparePartId);
            }

            if ($withDocuments !== null) {
                $query->where('with_documents', $withDocuments);
            }

            $reservations = $query->lockForUpdate()->get();
            $totalCancelled = 0;

            foreach ($reservations as $reservation) {
                $this->cancelReservation($reservation, "Отмена резерва для рекламации #{$reclamationId}");
                $totalCancelled += $reservation->reserved_qty;
            }

            // Также закрываем связанные дефициты
            $shortageQuery = Shortage::query()
                ->where('reclamation_id', $reclamationId)
                ->where('status', Shortage::STATUS_OPEN);

            if ($sparePartId !== null) {
                $shortageQuery->where('spare_part_id', $sparePartId);
            }

            if ($withDocuments !== null) {
                $shortageQuery->where('with_documents', $withDocuments);
            }

            $shortageQuery->update(['status' => Shortage::STATUS_CLOSED]);

            return $totalCancelled;
        });
    }

    /**
     * Отменить конкретный резерв
     */
    public function cancelReservation(Reservation $reservation, string $reason = ''): bool
    {
        if (!$reservation->isActive()) {
            return false;
        }

        return DB::transaction(function () use ($reservation, $reason) {
            $reservation->status = Reservation::STATUS_CANCELLED;
            $reservation->save();

            // Создаём движение отмены
            InventoryMovement::create([
                'spare_part_order_id' => $reservation->spare_part_order_id,
                'spare_part_id' => $reservation->spare_part_id,
                'qty' => $reservation->reserved_qty,
                'movement_type' => InventoryMovement::TYPE_RESERVE_CANCEL,
                'source_type' => InventoryMovement::SOURCE_RECLAMATION,
                'source_id' => $reservation->reclamation_id,
                'with_documents' => $reservation->with_documents,
                'user_id' => auth()->id(),
                'note' => $reason,
            ]);

            return true;
        });
    }

    /**
     * Изменить количество резерва для рекламации
     *
     * @param int $reclamationId ID рекламации
     * @param int $sparePartId ID запчасти
     * @param bool $withDocuments Тип документов
     * @param int $newQuantity Новое требуемое количество
     * @return ReservationResult
     */
    public function adjustReservation(
        int $reclamationId,
        int $sparePartId,
        bool $withDocuments,
        int $newQuantity
    ): ReservationResult {
        return DB::transaction(function () use ($reclamationId, $sparePartId, $withDocuments, $newQuantity) {

            // Получаем текущие резервы
            $currentReserved = Reservation::query()
                ->where('reclamation_id', $reclamationId)
                ->where('spare_part_id', $sparePartId)
                ->where('with_documents', $withDocuments)
                ->where('status', Reservation::STATUS_ACTIVE)
                ->sum('reserved_qty');

            $diff = $newQuantity - $currentReserved;

            if ($diff > 0) {
                // Нужно дорезервировать
                return $this->reserve($sparePartId, $diff, $withDocuments, $reclamationId);
            } elseif ($diff < 0) {
                // Нужно освободить часть резерва
                $toRelease = abs($diff);
                $released = 0;

                // Освобождаем в обратном порядке FIFO (сначала новые)
                $reservations = Reservation::query()
                    ->where('reclamation_id', $reclamationId)
                    ->where('spare_part_id', $sparePartId)
                    ->where('with_documents', $withDocuments)
                    ->where('status', Reservation::STATUS_ACTIVE)
                    ->orderBy('created_at', 'desc')
                    ->lockForUpdate()
                    ->get();

                foreach ($reservations as $reservation) {
                    if ($released >= $toRelease) break;

                    $releaseFromThis = min($toRelease - $released, $reservation->reserved_qty);

                    if ($releaseFromThis === $reservation->reserved_qty) {
                        // Отменяем весь резерв
                        $this->cancelReservation($reservation, "Уменьшение резерва");
                    } else {
                        // Частичная отмена — создаём новый резерв на остаток
                        $reservation->reserved_qty -= $releaseFromThis;
                        $reservation->save();

                        // Движение частичной отмены
                        InventoryMovement::create([
                            'spare_part_order_id' => $reservation->spare_part_order_id,
                            'spare_part_id' => $sparePartId,
                            'qty' => $releaseFromThis,
                            'movement_type' => InventoryMovement::TYPE_RESERVE_CANCEL,
                            'source_type' => InventoryMovement::SOURCE_RECLAMATION,
                            'source_id' => $reclamationId,
                            'with_documents' => $withDocuments,
                            'user_id' => auth()->id(),
                            'note' => "Частичная отмена резерва",
                        ]);
                    }

                    $released += $releaseFromThis;
                }

                // Обновляем дефицит если есть
                $shortage = Shortage::query()
                    ->where('reclamation_id', $reclamationId)
                    ->where('spare_part_id', $sparePartId)
                    ->where('with_documents', $withDocuments)
                    ->where('status', Shortage::STATUS_OPEN)
                    ->first();

                if ($shortage) {
                    $shortage->required_qty = $newQuantity;
                    $shortage->recalculate();
                }

                // Пересчитываем фактически зарезервированное количество после изменений
                $actualReserved = Reservation::query()
                    ->where('reclamation_id', $reclamationId)
                    ->where('spare_part_id', $sparePartId)
                    ->where('with_documents', $withDocuments)
                    ->where('status', Reservation::STATUS_ACTIVE)
                    ->sum('reserved_qty');

                return new ReservationResult(
                    reserved: (int) $actualReserved,
                    missing: max(0, $newQuantity - $actualReserved),
                    reservations: collect(),
                    shortage: $shortage
                );
            }

            // diff = 0, ничего не делаем
            return new ReservationResult(
                reserved: $currentReserved,
                missing: 0,
                reservations: collect(),
                shortage: null
            );
        });
    }

    /**
     * Получить все активные резервы для рекламации
     */
    public function getReservationsForReclamation(int $reclamationId): Collection
    {
        return Reservation::query()
            ->where('reclamation_id', $reclamationId)
            ->where('status', Reservation::STATUS_ACTIVE)
            ->with(['sparePart', 'sparePartOrder'])
            ->get();
    }
}

/**
 * Результат операции резервирования
 */
class ReservationResult
{
    public function __construct(
        public readonly int $reserved,
        public readonly int $missing,
        public readonly Collection $reservations,
        public readonly ?Shortage $shortage
    ) {}

    public function isFullyReserved(): bool
    {
        return $this->missing === 0;
    }

    public function hasShortage(): bool
    {
        return $this->shortage !== null;
    }

    public function getTotalRequested(): int
    {
        return $this->reserved + $this->missing;
    }
}