create stock and stock logs

app/Models/Stock.php

@@ -0,0 +1,56 @@
+<?php
+
+namespace App\Models;
+
+use Illuminate\Database\Eloquent\Factories\HasFactory;
+use Illuminate\Database\Eloquent\Model;
+
+class Stock extends Model
+{
+    use HasFactory;
+
+    protected $fillable = [
+        'product_id',
+        'dealer_id',
+        'quantity'
+    ];
+
+    public function product()
+    {
+        return $this->belongsTo(Product::class);
+    }
+
+    public function dealer()
+    {
+        return $this->belongsTo(Dealer::class);
+    }
+
+    public function stockLogs()
+    {
+        return $this->hasMany(StockLog::class);
+    }
+
+    // Method untuk mengupdate stock
+    public function updateStock($newQuantity, $source, $description = null)
+    {
+        $previousQuantity = $this->quantity;
+        $quantityChange = $newQuantity - $previousQuantity;
+        
+        $this->quantity = $newQuantity;
+        $this->save();
+
+        // Buat log perubahan
+        StockLog::create([
+            'stock_id' => $this->id,
+            'source_type' => get_class($source),
+            'source_id' => $source->id,
+            'previous_quantity' => $previousQuantity,
+            'new_quantity' => $newQuantity,
+            'quantity_change' => $quantityChange,
+            'description' => $description,
+            'user_id' => auth()->id()
+        ]);
+
+        return $this;
+    }
+}