TaxCalculator.php

<?php

/**
 * @author Dawid Góra <dawidgora@icloud.com>
 */
class TaxCalculator
{

    const TYPE_NET = 1;
    const TYPE_GROSS = 2;

    /**
     * @var float
     */
    private $netValue = 0.0;

    /**
     * @var float
     */
    private $grossValue = 0.0;

    /**
     * @var float
     */
    private $taxValue = 0.0;

    /**
     * @var Model_Tax
     */
    private $taxModel;

    /**
     * @var int
     */
    private $last = 0;

    /**
     * TaxCalculator constructor.
     * @param Model_Tax $taxModel
     */
    public function __construct(Model_Tax $taxModel = null)
    {
        if (!$taxModel || !$taxModel->loaded()) {
            $taxModel = Model_Tax::getDefault();
        }
        $this->taxModel = $taxModel;
    }

    /**
     * @return float
     */
    public function getNetValue()
    {
        return $this->netValue;
    }

    /**
     * @param float $netValue
     */
    public function setNetValue($netValue)
    {
        $this->netValue = $netValue;

        $this->taxValue = $this->netValue * $this->taxModel->getValue();
        $this->grossValue = $this->netValue + $this->taxValue;
        $this->last = self::TYPE_NET;
    }

    /**
     * @return float
     */
    public function getGrossValue()
    {
        return $this->grossValue;
    }

    /**
     * @param float $grossValue
     */
    public function setGrossValue($grossValue)
    {
        $this->grossValue = $grossValue;

        $this->taxValue = $this->grossValue * $this->taxModel->getValue() / (1 + $this->taxModel->getValue());
        $this->netValue = $this->grossValue - $this->taxValue;
        $this->last = self::TYPE_GROSS;
    }

    /**
     * @return float
     */
    public function getTaxValue()
    {
        return $this->taxValue;
    }

    /**
     * @return Model_Tax
     */
    public function getTaxModel()
    {
        return $this->taxModel;
    }

    /**
     * @param Model_Tax $taxModel
     */
    public function setTaxModel($taxModel)
    {
        $this->taxModel = $taxModel;

        if ($this->last === self::TYPE_NET) {
            $this->setNetValue($this->netValue);
        } elseif ($this->last === self::TYPE_GROSS) {
            $this->setGrossValue($this->grossValue);
        }
    }

}