feat(cart): add Cart and CartItem models with item management methods

app/Domains/Cart/Models/Cart.php

@@ -0,0 +1,152 @@
+<?php
+
+namespace App\Domains\Cart\Models;
+
+use App\Domains\Catalog\Models\ProductVariant;
+use App\Models\User;
+use Illuminate\Database\Eloquent\Attributes\Fillable;
+use Illuminate\Database\Eloquent\Factories\HasFactory;
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\BelongsTo;
+use Illuminate\Database\Eloquent\Relations\HasMany;
+use Illuminate\Support\Facades\DB;
+use Illuminate\Validation\ValidationException;
+
+#[Fillable([
+    'user_id',
+    'guest_token',
+    'status',
+])]
+class Cart extends Model
+{
+    use HasFactory;
+
+    protected $table = 'carritos';
+
+    protected function casts(): array
+    {
+        return [
+            'user_id' => 'integer',
+        ];
+    }
+
+    /**
+     * @return BelongsTo<User, $this>
+     */
+    public function user(): BelongsTo
+    {
+        return $this->belongsTo(User::class);
+    }
+
+    /**
+     * @return HasMany<CartItem, $this>
+     */
+    public function items(): HasMany
+    {
+        return $this->hasMany(CartItem::class, 'cart_id');
+    }
+
+    public function addItem(int $productVariantId, int $quantity): CartItem
+    {
+        if ($quantity <= 0) {
+            throw ValidationException::withMessages([
+                'cantidad' => 'La cantidad debe ser mayor a cero.',
+            ]);
+        }
+
+        return DB::transaction(function () use ($productVariantId, $quantity) {
+            /** @var ProductVariant $variant */
+            $variant = ProductVariant::query()
+                ->lockForUpdate()
+                ->findOrFail($productVariantId);
+
+            if ($variant->stock < $quantity) {
+                throw ValidationException::withMessages([
+                    'cantidad' => 'Stock insuficiente para la variante solicitada.',
+                ]);
+            }
+
+            /** @var CartItem|null $item */
+            $item = $this->items()
+                ->where('producto_variante_id', $productVariantId)
+                ->lockForUpdate()
+                ->first();
+
+            if ($item) {
+                $item->cantidad += $quantity;
+                $item->save();
+            } else {
+                $item = $this->items()->create([
+                    'producto_variante_id' => $productVariantId,
+                    'cantidad' => $quantity,
+                ]);
+            }
+
+            $variant->decrement('stock', $quantity);
+
+            return $item->fresh();
+        });
+    }
+
+    public function updateItem(int $productVariantId, int $quantity): CartItem
+    {
+        if ($quantity <= 0) {
+            throw ValidationException::withMessages([
+                'cantidad' => 'La cantidad debe ser mayor a cero.',
+            ]);
+        }
+
+        return DB::transaction(function () use ($productVariantId, $quantity) {
+            /** @var CartItem $item */
+            $item = $this->items()
+                ->where('producto_variante_id', $productVariantId)
+                ->lockForUpdate()
+                ->firstOrFail();
+
+            /** @var ProductVariant $variant */
+            $variant = ProductVariant::query()
+                ->lockForUpdate()
+                ->findOrFail($productVariantId);
+
+            $delta = $quantity - $item->cantidad;
+
+            if ($delta > 0 && $variant->stock < $delta) {
+                throw ValidationException::withMessages([
+                    'cantidad' => 'Stock insuficiente para actualizar la cantidad solicitada.',
+                ]);
+            }
+
+            $item->cantidad = $quantity;
+            $item->save();
+
+            if ($delta > 0) {
+                $variant->decrement('stock', $delta);
+            }
+
+            if ($delta < 0) {
+                $variant->increment('stock', abs($delta));
+            }
+
+            return $item->fresh();
+        });
+    }
+
+    public function removeItem(int $productVariantId): void
+    {
+        DB::transaction(function () use ($productVariantId) {
+            /** @var CartItem $item */
+            $item = $this->items()
+                ->where('producto_variante_id', $productVariantId)
+                ->lockForUpdate()
+                ->firstOrFail();
+
+            /** @var ProductVariant $variant */
+            $variant = ProductVariant::query()
+                ->lockForUpdate()
+                ->findOrFail($productVariantId);
+
+            $variant->increment('stock', $item->cantidad);
+            $item->delete();
+        });
+    }
+}

app/Domains/Cart/Models/CartItem.php

@@ -0,0 +1,46 @@
+<?php
+
+namespace App\Domains\Cart\Models;
+
+use App\Domains\Catalog\Models\ProductVariant;
+use Illuminate\Database\Eloquent\Attributes\Fillable;
+use Illuminate\Database\Eloquent\Factories\HasFactory;
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\BelongsTo;
+
+#[Fillable([
+    'cart_id',
+    'producto_variante_id',
+    'cantidad',
+])]
+class CartItem extends Model
+{
+    use HasFactory;
+
+    protected $table = 'carrito_items';
+
+    protected function casts(): array
+    {
+        return [
+            'cart_id' => 'integer',
+            'producto_variante_id' => 'integer',
+            'cantidad' => 'integer',
+        ];
+    }
+
+    /**
+     * @return BelongsTo<Cart, $this>
+     */
+    public function cart(): BelongsTo
+    {
+        return $this->belongsTo(Cart::class, 'cart_id');
+    }
+
+    /**
+     * @return BelongsTo<ProductVariant, $this>
+     */
+    public function variant(): BelongsTo
+    {
+        return $this->belongsTo(ProductVariant::class, 'producto_variante_id');
+    }
+}