VatReducer.php

<?php

/**
 * Helper class designed to reduce the vat rates on order items when a
 * BookableProduct is added to cart.
 * 
 */
class VatReducer extends Object
{

    /**
     * The rate of VAT that will be removed from the item
     * 
     * @var float
     */
    protected $vat_rate;

    /**
     * Get the value of vat_rate
     *
     * @return float
     */ 
    public function getVatRate()
    {
        return $this->vat_rate;
    }

    /**
     * Set the value of vat_rate
     *
     * @param float $vat_rate The vat rate to set
     *
     * @return self
     */ 
    public function setVatRate(int $vat_rate)
    {
        $this->vat_rate = $vat_rate;

        return $this;
    }

    /**
     * The price that will be having VAT removed
     *
     * @var float
     */
    protected $price;

    /**
     * Get the value of price
     *
     * @return float
     */ 
    public function getPrice()
    {
        return $this->price;
    }

    /**
     * Set the value of price
     *
     * @param float $price The price to set
     *
     * @return self
     */ 
    public function setPrice(float $price)
    {
        $this->price = $price;

        return $this;
    }

    /**
     * The final price generated by the calculate function
     * 
     * @var float
     */
    protected $final_price;

    /**
     * Get the value of final_price
     *
     * @return float
     */ 
    public function getFinalPrice()
    {
        return $this->final_price;
    }

    /**
     * Floor a value to the provided precision
     * 
     * @param float $val       the value to floor
     * @param int   $precision the decimal precision (eg 2)
     */
    protected function floorp($val, $precision)
    {
        $mult = pow(10, $precision); // Can be cached in lookup table        
        return floor($val * $mult) / $mult;
    }

    /**
     * Create this object and setup params
     * 
     * @param float $price The inital price
     * @param float $vat   The rate of vat to use 
     */
    public function __construct(float $price, float $vat)
    {
        $this->setPrice($price);
        $this->setVatRate($vat);

        $this->calculate();
    }

    /**
     * Calculate the new final price, based on the submitted params and
     * save the value.
     */
    public function calculate()
    {
        $rate = $this->getVatRate();
        $price = $this->getPrice();
        $final_price = ($price / (100 + $rate)) * 100;
        $final_price = $this->floorp($final_price, 2);

        $this->final_price = $final_price;
    }
}