<?php

namespace App\Domains\Purchase\Services;

use App\Domains\Cart\Models\Cart;
use App\Domains\Cart\Models\CartItem;
use App\Domains\Bundle\Models\Bundle;
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('buyable');
            $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.buyable']);
        });
    }

    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.buyable']);
            }

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

            return $purchase->load(['items.buyable']);
        });
    }

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

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

            /** @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.',
                ]);
            }

            $cartItems->load('buyable');
            $this->verifyTenantBuyables($purchase->tenant, $cartItems);
            $purchaseItemsPayload = $this->buildPurchaseItemsPayload($cartItems);

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

    protected function verifyTenantBuyables(Tenant $tenant, Collection $cartItems): void
    {
        foreach ($cartItems as $item) {
            $buyable = $item->buyable;
            if ($buyable === null) {
                throw ValidationException::withMessages([
                    'cart_id' => 'One or more buyables could not be loaded.',
                ]);
            }

            if ($item->buyable_type === ProductVariant::class && $buyable->product->tenant_codigo !== $tenant->codigo) {
                throw ValidationException::withMessages([
                    'cart_id' => 'One or more product variants do not belong to the tenant.',
                ]);
            }

            if ($item->buyable_type === Bundle::class && $buyable->tenant_codigo !== $tenant->codigo) {
                throw ValidationException::withMessages([
                    'cart_id' => 'One or more bundles do not belong to the tenant.',
                ]);
            }
        }
    }

    /**
     * @param  Collection<int, CartItem>  $cartItems
     * @return 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
     * @return array<int, array<string, mixed>>
     */
    protected function buildPurchaseItemsPayload(Collection $cartItems): array
    {
        return $cartItems
            ->map(function (CartItem $item): array {
                $buyable = $item->buyable;
                $quantity = (int) $item['cantidad'];
                $unitPrice = $buyable?->getPrice() ?? 0;

                return [
                    'buyable_type' => $item->buyable_type,
                    'buyable_id' => $item->buyable_id,
                    'cantidad' => $quantity,
                    'precio_unitario' => $unitPrice,
                    'discount_total' => null,
                    'tax_total' => null,
                    'total' => $unitPrice * $quantity,
                ];
            })
            ->all();
    }

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

            try {
                $buyable->buy($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();
    }
}