SpiceManagementSystem/app/Models/Batch.php

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Model;

class Batch extends Model
{
    protected $fillable = [
        'lot_number', 'product_id', 'size_id', 'recipe_id',
        'units_produced', 'quantity_g', 'produced_at', 'expires_at',
    ];

    protected $casts = [
        'produced_at' => 'date',
        'expires_at'  => 'date',
    ];

    public function product()
    {
        return $this->belongsTo(Product::class);
    }

    public function size()
    {
        return $this->belongsTo(ProductSize::class);
    }

    public function recipe()
    {
        return $this->belongsTo(Recipe::class);
    }

    public function origins()
    {
        return $this->hasMany(BatchOrigin::class);
    }

    protected static function booted(): void
    {
        // Auto-calculate quantity_g before saving
        static::saving(function (Batch $batch) {
            if ($batch->units_produced && $batch->size_id) {
                $gramsPerUnit = $batch->size?->packing?->size ?? 0;
                $batch->quantity_g = $batch->units_produced * $gramsPerUnit;
            }
        });

        static::created(function (Batch $batch) {
            $batch->deductSpices();
        });

        static::updated(function (Batch $batch) {
            if ($batch->wasChanged(['recipe_id', 'size_id', 'units_produced'])) {
                $batch->restoreSpices(
                    $batch->getOriginal('recipe_id'),
                    $batch->getOriginal('quantity_g'),
                );
                $batch->deductSpices();
            }
        });

        static::deleting(function (Batch $batch) {
            $batch->restoreSpices($batch->recipe_id, $batch->quantity_g);
        });
    }

    private function deductSpices(): void
    {
        if (! $this->quantity_g || ! $this->recipe_id) {
            return;
        }

        $recipe = Recipe::with('spices')->find($this->recipe_id);

        foreach ($recipe->spices as $spice) {
            $grams = $this->quantity_g * $spice->pivot->amount_in_percent / 100;
            $spice->decrement('quantity', $grams);
        }
    }

    private function restoreSpices(int $recipeId, float $quantityG): void
    {
        if (! $quantityG || ! $recipeId) {
            return;
        }

        $recipe = Recipe::with('spices')->find($recipeId);

        foreach ($recipe->spices as $spice) {
            $grams = $quantityG * $spice->pivot->amount_in_percent / 100;
            $spice->increment('quantity', $grams);
        }
    }
}