suivicpt/app/Models/BudgetLine.php

<?php

declare(strict_types=1);

namespace App\Models;

use Illuminate\Database\Eloquent\Builder;
use Illuminate\Database\Eloquent\Model;
use Illuminate\Database\Eloquent\Relations\BelongsTo;

class BudgetLine extends Model
{
    protected $fillable = ['household_id', 'category_id', 'year', 'month', 'amount'];

    protected function casts(): array
    {
        return [
            'amount' => 'decimal:2',
        ];
    }

    public function household(): BelongsTo
    {
        return $this->belongsTo(Household::class);
    }

    public function category(): BelongsTo
    {
        return $this->belongsTo(Category::class);
    }

    public function scopeForYear(Builder $query, int $year): Builder
    {
        return $query->where('year', $year);
    }

    public function scopeDefaultLine(Builder $query): Builder
    {
        return $query->whereNull('month');
    }

    public function scopeForMonth(Builder $query, int $month): Builder
    {
        return $query->where('month', $month);
    }
}