<?php
/**
 * Provides the calculatable trait, to be used by something of which
 * subtotal, VAT and total can be calculated.
 *
 * @author Camil Staps
 *
 * BusinessAdmin: administrative software for small companies
 * Copyright (C) 2015 Camil Staps (ViviSoft)
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

/**
 * The calculatable interface, to be used by something of which subtotal, VAT
 * and total can be calculated
 */
interface Calculatable {
	const SUBTOTAL = 1;
	const VAT = 2;
	const TOTAL = 3;

	/**
	 * Calculate the subtotal
	 *
	 * @return float                        The subtotal
	 */
	function calculateSubtotal();

	/**
	 * Calculate the VAT
	 *
	 * @return float                        The VAT
	 */
	function calculateVAT();

	/**
	 * Calculate the total
	 *
	 * @return float                        The total
	 */
	function calculateTotal();

	/**
	 * Calculate and possibly format
	 *
	 * Subtotal: the sum of the prices of the assignments excl. VAT
	 * VAT: the sum of all the VAT from all the assignments
	 * Total: the sum of subtotal and total
	 *
	 * @param int $what                     Any of Calculatable::SUBTOTAL, Calculatable::VAT and Calculatable::TOTAL
	 * @param int $round                    How many decimals to round the result on
	 * @param bool $format                  Whether to format the number nicely (for output) or not (for calculations)
	 *
	 * @throws PDOException                 If something went wrong with the database
	 *
	 * @return float|bool                   The calculated value rounded to $round decimals, or false on incorrect input
	 */
	function calculate($what = Calculatable::TOTAL, $round = 2, $format = true);
}

/**
 * The calculatable trait, to be used by something of which subtotal, VAT and
 * total can be calculated
 */
trait StandardCalculatable {
	abstract public function calculateSubtotal();
	abstract public function calculateVAT();

	/**
	 * Calculate the total
	 *
	 * @return float                        The total
	 */
	public function calculateTotal() {
		return $this->calculateSubtotal() + $this->calculateVAT();
	}

	/**
	 * Calculate and possibly format
	 *
	 * Subtotal: the sum of the prices of the assignments excl. VAT
	 * VAT: the sum of all the VAT from all the assignments
	 * Total: the sum of subtotal and total
	 *
	 * @param int $what                     Any of Calculatable::SUBTOTAL, Calculatable::VAT and Calculatable::TOTAL
	 * @param int $round                    How many decimals to round the result on
	 * @param bool $format                  Whether to format the number nicely (for output) or not (for calculations)
	 *
	 * @throws PDOException                 If something went wrong with the database
	 *
	 * @return float|bool                   The calculated value rounded to $round decimals, or false on incorrect input
	 */
	public function calculate($what = Calculatable::TOTAL, $round = 2, $format = true) {
		$return = 0;
		switch ($what) {
			case Calculatable::SUBTOTAL:
				$return = $this->calculateSubtotal();
				break;
			case Calculatable::VAT:
				$return = $this->calculateVAT();
				break;
			case Calculatable::TOTAL:
				$return = $this->calculateTotal();
				break;
			default:
				return false;
		}
		if ($format) {
			return number_format($return, $round);
		} else {
			return $return;
		}
	}
}