restructure retribution calculations table

app/Models/RetributionCalculation.php

@@ -0,0 +1,81 @@
+<?php
+
+namespace App\Models;
+
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\BelongsTo;
+use Carbon\Carbon;
+
+class RetributionCalculation extends Model
+{
+    protected $fillable = [
+        'calculation_id',
+        'building_type_id',
+        'floor_number',
+        'building_area',
+        'retribution_amount',
+        'calculation_detail',
+        'calculated_at'
+    ];
+
+    protected $casts = [
+        'floor_number' => 'integer',
+        'building_area' => 'decimal:2',
+        'retribution_amount' => 'decimal:2',
+        'calculation_detail' => 'array',
+        'calculated_at' => 'datetime'
+    ];
+
+    /**
+     * Building type relationship
+     */
+    public function buildingType(): BelongsTo
+    {
+        return $this->belongsTo(BuildingType::class, 'building_type_id');
+    }
+
+    /**
+     * Generate unique calculation ID
+     */
+    public static function generateCalculationId(): string
+    {
+        return 'RTB' . Carbon::now()->format('ymdHis') . rand(10, 99);
+    }
+
+    /**
+     * Create new calculation
+     */
+    public static function createCalculation(
+        int $buildingTypeId,
+        int $floorNumber,
+        float $buildingArea,
+        float $retributionAmount,
+        array $calculationDetail
+    ): self {
+        return self::create([
+            'calculation_id' => self::generateCalculationId(),
+            'building_type_id' => $buildingTypeId,
+            'floor_number' => $floorNumber,
+            'building_area' => $buildingArea,
+            'retribution_amount' => $retributionAmount,
+            'calculation_detail' => $calculationDetail,
+            'calculated_at' => Carbon::now()
+        ]);
+    }
+
+    /**
+     * Get formatted retribution amount
+     */
+    public function getFormattedAmount(): string
+    {
+        return 'Rp ' . number_format($this->retribution_amount, 2, ',', '.');
+    }
+
+    /**
+     * Get calculation breakdown
+     */
+    public function getCalculationBreakdown(): array
+    {
+        return $this->calculation_detail ?? [];
+    }
+}