<?php

namespace App\Domains\Purchase\Services;

use App\Domains\Cart\Models\Cart;
use App\Domains\Cart\Models\CartItem;
use App\Domains\Catalog\Models\ProductVariant;
use App\Domains\Purchase\Models\Purchase;
use App\Domains\Tenant\Models\Tenant;
use Illuminate\Support\Collection;
use Illuminate\Support\Facades\DB;
use Illuminate\Validation\ValidationException;
use Symfony\Component\HttpKernel\Exception\NotFoundHttpException;

class CheckoutService
{
    public function startCheckout(Tenant $tenant, int $userId, array $purchaseData): Purchase
    {
        $cartId = (int) $purchaseData['cart_id'];
        unset($purchaseData['cart_id']);

        return DB::transaction(function () use ($tenant, $userId, $purchaseData, $cartId): Purchase {
            $cart = $this->resolveCheckoutCart($tenant, $userId, $cartId);
            $cartItems = $cart->items()->lockForUpdate()->get();

            if ($cartItems->isEmpty()) {
                throw ValidationException::withMessages([
                    'cart_id' => 'The selected cart does not contain items.',
                ]);
            }

            $cartItems->load('variant.product');
            $cart->setRelation('items', $cartItems);
            $totalAmount = $cart->getTotalAmount();

            /** @var Purchase|null $purchase */
            $purchase = Purchase::query()
                ->where('cart_id', $cart->getKey())
                ->where('tenant_codigo', $tenant->codigo)
                ->where('user_id', $userId)
                ->whereIn('status', [Purchase::STATUS_CREATED, Purchase::STATUS_PENDING_PAYMENT])
                ->latest('id')
                ->first();

            if ($purchase === null) {
                /** @var Purchase $purchase */
                $purchase = Purchase::query()->create([
                    ...$purchaseData,
                    'cart_id' => $cart->getKey(),
                    'tenant_codigo' => $tenant->codigo,
                    'user_id' => $userId,
                    'status' => Purchase::STATUS_CREATED,
                    'payment_method' => null,
                    'total' => $totalAmount,
                ]);
            } else {
                $purchase->fill([
                    ...$purchaseData,
                    'status' => Purchase::STATUS_CREATED,
                    'payment_method' => null,
                    'total' => $totalAmount,
                ]);
                $purchase->save();
            }

            return $purchase->load(['items.variant.product', 'items.variant.definitions.productAttribute.attribute']);
        });
    }

    public function completePurchase(Purchase $purchase): Purchase
    {
        return DB::transaction(function () use ($purchase): Purchase {
            /** @var Purchase $purchase */
            $purchase = Purchase::query()
                ->lockForUpdate()
                ->findOrFail($purchase->getKey());

            if ($purchase->payment_method === null) {
                throw ValidationException::withMessages([
                    'payment_method' => 'The purchase payment method must be selected before finalizing.',
                ]);
            }

            if (in_array($purchase->status, [Purchase::STATUS_PAID, Purchase::STATUS_CANCELLED, Purchase::STATUS_REJECTED], true)) {
                return $purchase->load(['items.variant.product', 'items.variant.definitions.productAttribute.attribute']);
            }

            $purchase->update([
                'status' => Purchase::STATUS_PENDING_PAYMENT,
                'total' => $purchase->calculateCurrentTotalAmount(),
            ]);

            return $purchase->load(['items.variant.product', 'items.variant.definitions.productAttribute.attribute']);
        });
    }

    public function confirmPurchase(Purchase $purchase): void
    {
        DB::transaction(function () use ($purchase): void {
            /** @var Cart|null $cart */
            $cart = $purchase->cart()->lockForUpdate()->first();

            if ($cart === null) {
                throw ValidationException::withMessages([
                    'cart_id' => 'The purchase cart is no longer available.',
                ]);
            }

            $cartItems = $cart->items()->lockForUpdate()->get();

            if ($cartItems->isEmpty()) {
                throw ValidationException::withMessages([
                    'cart_id' => 'The purchase cart does not contain items.',
                ]);
            }

            if ($purchase->items()->exists()) {
                return;
            }

            $cartItems->load('variant.product');
            $variants = $this->resolveTenantVariants($purchase->tenant, $cartItems);
            $purchaseItemsPayload = $this->buildPurchaseItemsPayload($cartItems, $variants);

            $purchase->items()->createMany($purchaseItemsPayload);
            $this->completeCartConversion($cart, $cartItems, $variants);
        });
    }

    /**
     * @return Collection<int, ProductVariant>
     */
    protected function resolveTenantVariants(Tenant $tenant, Collection $cartItems): Collection
    {
        $variantIds = $cartItems
            ->pluck('producto_variante_id')
            ->map(static fn (mixed $id): int => (int) $id)
            ->unique()
            ->values();

        /** @var Collection<int, ProductVariant> $variants */
        $variants = ProductVariant::query()
            ->with('product')
            ->whereIn('id', $variantIds)
            ->whereHas('product', fn ($query) => $query->where('tenant_codigo', $tenant->codigo))
            ->lockForUpdate()
            ->get()
            ->keyBy('id');

        if ($variants->count() !== $variantIds->count()) {
            throw ValidationException::withMessages([
                'cart_id' => 'One or more product variants do not belong to the tenant.',
            ]);
        }

        return $variants;
    }

    /**
     * @param  Collection<int, CartItem>  $cartItems
     * @return \Illuminate\Support\Collection<int, ProductVariant>
     */
    protected function resolveCheckoutCart(Tenant $tenant, int $userId, int $cartId): Cart
    {
        /** @var Cart|null $cart */
        $cart = Cart::query()
            ->lockForUpdate()
            ->find($cartId);

        if ($cart === null || $cart->tenant_codigo !== $tenant->codigo || $cart->user_id !== $userId) {
            throw new NotFoundHttpException('Cart not found for tenant.');
        }

        if ($cart->status !== 'active') {
            throw ValidationException::withMessages([
                'cart_id' => 'The selected cart is no longer active.',
            ]);
        }

        return $cart;
    }

    /**
     * @param  Collection<int, CartItem>  $cartItems
     * @param  Collection<int, ProductVariant>  $variants
     * @return array<int, array<string, mixed>>
     */
    protected function buildPurchaseItemsPayload(Collection $cartItems, Collection $variants): array
    {
        return $cartItems
            ->map(function (CartItem $item) use ($variants): array {
                /** @var ProductVariant $variant */
                $variant = $variants->get((int) $item['producto_variante_id']);
                $quantity = (int) $item['cantidad'];
                $unitPrice = (float) ($variant->product?->precio ?? 0);

                return [
                    'producto_variante_id' => $variant->getKey(),
                    'cantidad' => $quantity,
                    'precio_unitario' => $unitPrice,
                    'discount_total' => null,
                    'tax_total' => null,
                    'total' => $unitPrice * $quantity,
                ];
            })
            ->all();
    }

    /**
     * @param  Collection<int, CartItem>  $cartItems
     * @param  Collection<int, ProductVariant>  $variants
     */
    protected function completeCartConversion(Cart $cart, Collection $cartItems, Collection $variants): void
    {
        foreach ($cartItems as $item) {
            /** @var ProductVariant $variant */
            $variant = $variants->get((int) $item->producto_variante_id);
            $quantity = (int) $item->cantidad;

            try {
                $variant->confirmReservedStock($quantity);
            } catch (\InvalidArgumentException $exception) {
                throw ValidationException::withMessages([
                    'cart_id' => 'The selected cart has inconsistent stock state.',
                ]);
            }
        }

        $cart->status = 'converted';
        $cart->user_id = null;
        $cart->guest_token = null;
        $cart->save();
        $cart->delete();
    }
}