invoiceninja/app/Models/InvoiceItem.php

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\SoftDeletes;
use Laracasts\Presenter\PresentableTrait;

/**
 * Class InvoiceItem.
 */
class InvoiceItem extends EntityModel
{
    use PresentableTrait;
    use SoftDeletes;

    /**
     * @var string
     */
    protected $presenter = 'App\Ninja\Presenters\InvoiceItemPresenter';

    /**
     * @var array
     */
    protected $dates = ['deleted_at'];

    /**
     * @return mixed
     */
    public function getEntityType()
    {
        return ENTITY_INVOICE_ITEM;
    }

    /**
     * @var array
     */
    protected $fillable = [
        'tax_name1',
        'tax_rate1',
        'tax_name2',
        'tax_rate2',
        'invoice_item_type_id',
        'discount',
    ];

    /**
     * @return \Illuminate\Database\Eloquent\Relations\BelongsTo
     */
    public function invoice()
    {
        return $this->belongsTo('App\Models\Invoice');
    }

    /**
     * @return mixed
     */
    public function user()
    {
        return $this->belongsTo('App\Models\User')->withTrashed();
    }

    /**
     * @return \Illuminate\Database\Eloquent\Relations\BelongsTo
     */
    public function product()
    {
        return $this->belongsTo('App\Models\Product');
    }

    /**
     * @return \Illuminate\Database\Eloquent\Relations\BelongsTo
     */
    public function account()
    {
        return $this->belongsTo('App\Models\Account');
    }

    public function amount()
    {
        $amount = $this->cost * $this->qty;

        if ($this->discount != 0) {
            if ($this->invoice->is_amount_discount) {
                $amount -= $this->discount;
            } else {
                $amount -= $amount * $this->discount / 100;
            }
        }

        $preTaxAmount = $amount;

        if ($this->tax_rate1) {
            $amount += $preTaxAmount * $this->tax_rate1 / 100;
        }

        if ($this->tax_rate2) {
            $amount += $preTaxAmount * $this->tax_rate2 / 100;
        }

        return $amount;
    }

    public function markFeePaid()
    {
        if ($this->invoice_item_type_id == INVOICE_ITEM_TYPE_PENDING_GATEWAY_FEE) {
            $this->invoice_item_type_id = INVOICE_ITEM_TYPE_PAID_GATEWAY_FEE;
            $this->save();
        }
    }

    public function hasTaxes()
    {
        if ($this->tax_name1 || $this->tax_rate1) {
            return true;
        }

        if ($this->tax_name2 || $this->tax_rate2) {
            return false;
        }

        return false;
    }

    public function costWithDiscount()
    {
        $cost = $this->cost;

        if ($this->discount != 0) {
            if ($this->invoice->is_amount_discount) {
                $cost -= $discount / $this->qty;
            } else {
                $cost -= $cost * $discount / 100;
            }
        }

        return $cost;
    }

}