<?php

namespace App\Domains\Purchase\Services\Checkout;

use App\Domains\Cart\Models\Cart;
use App\Domains\Cart\Models\CartItem;
use App\Domains\Catalog\Models\CatalogItem;
use App\Domains\Catalog\Models\Variant;
use App\Domains\Catalog\Services\CatalogInventoryService;
use App\Domains\Purchase\Models\Purchase;
use App\Domains\Purchase\Services\UserPurchaseLimitService;
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 StartCheckoutService
{
    public function __construct(
        private readonly CatalogInventoryService $inventory,
        private readonly UserPurchaseLimitService $purchaseLimits,
        private readonly CatalogSelectionResolver $selections,
        private readonly PurchaseItemSnapshotFactory $snapshots,
    ) {}

    /** @param array<string, mixed> $purchaseData */
    public function start(Tenant $tenant, int $userId, array $purchaseData): Purchase
    {
        return DB::transaction(function () use ($tenant, $userId, $purchaseData): Purchase {
            /** @var Tenant $tenant */
            $tenant = Tenant::query()
                ->lockForUpdate()
                ->findOrFail($tenant->getKey());

            $directItems = $purchaseData['direct_items'] ?? null;
            $cartId = isset($purchaseData['cart_id']) ? (int) $purchaseData['cart_id'] : null;
            unset($purchaseData['direct_items'], $purchaseData['cart_id']);

            if (is_array($directItems)) {
                return $this->startDirectItems(
                    $tenant,
                    $userId,
                    $purchaseData,
                    $directItems,
                );
            }

            if ($cartId === null) {
                throw ValidationException::withMessages([
                    'cart_id' => __('api.purchase.source_required'),
                ]);
            }

            return $this->startFromCart($tenant, $userId, $purchaseData, $cartId);
        });
    }

    /**
     * @param  array<string, mixed>  $purchaseData
     * @param  array<int, array<string, mixed>>  $directItems
     */
    private function startDirectItems(
        Tenant $tenant,
        int $userId,
        array $purchaseData,
        array $directItems,
    ): Purchase {
        $lines = collect(array_values($directItems))
            ->map(function (array $item, int $index): array {
                return [
                    'catalog_item_id' => (int) $item['catalog_item_id'],
                    'variant_id' => isset($item['variant_id']) ? (int) $item['variant_id'] : null,
                    'quantity' => (int) $item['cantidad'],
                    'field' => "direct_items.{$index}",
                ];
            })
            ->groupBy(fn (array $line): string => sprintf(
                '%d:%s',
                $line['catalog_item_id'],
                $line['variant_id'] === null ? 'none' : (string) $line['variant_id'],
            ))
            ->map(function (Collection $duplicateLines): array {
                $line = $duplicateLines->first();
                $line['quantity'] = (int) $duplicateLines->sum('quantity');

                return $line;
            })
            ->sortBy(fn (array $line): string => sprintf(
                '%020d:%020d',
                $line['catalog_item_id'],
                $line['variant_id'] ?? 0,
            ))
            ->values();

        $resolvedLines = $lines->map(function (array $line) use ($tenant): array {
            $selection = $this->selections->resolve(
                $tenant,
                $line['catalog_item_id'],
                $line['variant_id'],
                $line['field'],
            );

            return [
                ...$line,
                'selection' => $selection,
                'catalog_item' => $selection instanceof Variant
                    ? $selection->catalogItem
                    : $selection,
            ];
        });

        $resolvedLines
            ->groupBy(fn (array $line): int => $line['catalog_item']->getKey())
            ->each(function (Collection $catalogLines) use ($userId): void {
                /** @var CatalogItem $catalogItem */
                $catalogItem = $catalogLines->first()['catalog_item'];
                $this->purchaseLimits->assertCanPurchase(
                    $catalogItem,
                    $userId,
                    (int) $catalogLines->sum('quantity'),
                    field: 'direct_items',
                );
            });

        foreach ($resolvedLines as $line) {
            $availableQuantity = $this->inventory->availableQuantity($line['selection']);

            if ($availableQuantity !== null && $availableQuantity < $line['quantity']) {
                throw ValidationException::withMessages([
                    "{$line['field']}.cantidad" => __('api.purchase.direct_items_max_stock', [
                        'max' => $availableQuantity,
                    ]),
                ]);
            }

            try {
                $this->inventory->reserve($line['selection'], $line['quantity']);
            } catch (\InvalidArgumentException) {
                throw ValidationException::withMessages([
                    "{$line['field']}.cantidad" => __('api.purchase.insufficient_stock'),
                ]);
            }
        }

        $purchase = $this->createPurchase(
            $tenant,
            $userId,
            $purchaseData,
            (float) $resolvedLines->sum(
                fn (array $line): float => $line['selection']->getPrice() * $line['quantity'],
            ),
            null,
        );

        $directCartItems = $resolvedLines->map(fn (array $line): CartItem => $this->makeDirectCartItem(
            $line['selection'],
            $line['catalog_item_id'],
            $line['variant_id'],
            $line['quantity'],
        ));

        $purchase->items()->createMany(
            $this->snapshots->fromCartItems($directCartItems),
        );

        return $this->loadPurchase($purchase);
    }

    /** @param array<string, mixed> $purchaseData */
    private function startFromCart(
        Tenant $tenant,
        int $userId,
        array $purchaseData,
        int $cartId,
    ): Purchase {
        $cart = $this->resolveCart($tenant, $userId, $cartId);
        $cartItems = $cart->items()->lockForUpdate()->get();

        if ($cartItems->isEmpty()) {
            throw ValidationException::withMessages([
                'cart_id' => __('api.purchase.empty_cart'),
            ]);
        }

        $this->loadCartItems($cartItems);
        $this->verifyTenantItems($tenant, $cartItems);
        $this->assertCartPurchaseLimits($tenant, $userId, $cartItems);
        $cart->setRelation('items', $cartItems);

        $purchase = $this->createPurchase(
            $tenant,
            $userId,
            $purchaseData,
            $cart->getTotalAmount(),
            $cart->getKey(),
        );
        $purchase->items()->createMany($this->snapshots->fromCartItems($cartItems));

        // The purchase owns the reservation until checkout finishes. The cart is
        // retained so it can be restored if the purchase is cancelled or expires.
        $cart->update([
            'status' => 'checkout',
            'guest_token' => null,
        ]);

        return $this->loadPurchase($purchase);
    }

    private function resolveCart(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' => __('api.purchase.inactive_cart'),
            ]);
        }

        return $cart;
    }

    /** @param Collection<int, CartItem> $cartItems */
    private function verifyTenantItems(Tenant $tenant, Collection $cartItems): void
    {
        foreach ($cartItems as $item) {
            if ($item->selectedItem() === null) {
                throw ValidationException::withMessages([
                    'cart_id' => __('api.purchase.catalog_item_missing'),
                ]);
            }

            if ($item->catalogItem?->tenant_code !== $tenant->codigo) {
                throw ValidationException::withMessages([
                    'cart_id' => __('api.purchase.catalog_item_wrong_tenant'),
                ]);
            }
        }
    }

    /** @param Collection<int, CartItem> $cartItems */
    private function assertCartPurchaseLimits(
        Tenant $tenant,
        int $userId,
        Collection $cartItems,
    ): void {
        $quantities = $cartItems
            ->groupBy('catalog_item_id')
            ->map(fn (Collection $items): int => (int) $items->sum('cantidad'))
            ->sortKeys();

        $catalogItems = CatalogItem::query()
            ->where('tenant_code', $tenant->codigo)
            ->whereKey($quantities->keys())
            ->orderBy('id')
            ->lockForUpdate()
            ->get()
            ->keyBy('id');

        foreach ($quantities as $catalogItemId => $quantity) {
            /** @var CatalogItem $catalogItem */
            $catalogItem = $catalogItems->get($catalogItemId);
            $this->purchaseLimits->assertCanPurchase(
                $catalogItem,
                $userId,
                $quantity,
                field: 'cart_id',
            );
        }
    }

    /** @param array<string, mixed> $purchaseData */
    private function createPurchase(
        Tenant $tenant,
        int $userId,
        array $purchaseData,
        float $total,
        ?int $cartId,
    ): Purchase {
        return Purchase::query()->create([
            ...$purchaseData,
            'cart_id' => $cartId,
            'tenant_codigo' => $tenant->codigo,
            'user_id' => $userId,
            'status' => Purchase::STATUS_CREATED,
            'payment_method' => null,
            'expires_at' => now()->addMinutes(
                max(1, (int) config('purchase.checkout_expiration_minutes', 30)),
            ),
            'total' => $total,
        ]);
    }

    private function makeDirectCartItem(
        CatalogItem|Variant $selection,
        int $catalogItemId,
        ?int $variantId,
        int $quantity,
    ): CartItem {
        $catalogItem = $selection instanceof Variant ? $selection->catalogItem : $selection;
        $catalogItem->loadMissing(['inventory', 'attachments']);

        if ($selection instanceof Variant) {
            $selection->loadMissing([
                'inventory',
                'attachments',
                'catalogItem',
                'definitions.itemAttribute.attribute',
            ]);
        }

        $item = new CartItem([
            'catalog_item_id' => $catalogItemId,
            'variant_id' => $variantId,
            'cantidad' => $quantity,
        ]);
        $item->setRelation('catalogItem', $catalogItem);
        $item->setRelation('variant', $selection instanceof Variant ? $selection : null);

        return $item;
    }

    /** @param Collection<int, CartItem> $cartItems */
    private function loadCartItems(Collection $cartItems): void
    {
        $cartItems->load([
            'catalogItem.inventory',
            'catalogItem.attachments',
            'variant.inventory',
            'variant.attachments',
            'variant.catalogItem',
            'variant.definitions.itemAttribute.attribute',
            'variant.eventDates',
            'variant.eventDate',
        ]);
    }

    private function loadPurchase(Purchase $purchase): Purchase
    {
        return $purchase->load(['items.imageAttachment']);
    }
}