<?php

namespace Core;

class Gauss
{

    /**
     * @var array
     */
    protected $matrix;

    /**
     * @var integer
     */
    protected $matrixSize;

    /**
     * Gauss constructor.
     */
    public function __construct()
    {
        $this->matrix = include(ROOT . "/etc/matrix.php");
        $this
            ->setMatrixSize()
            ->printMatrix();
    }

    /**
     * @return array
     */
    public function resolve(): array
    {
        $tmp = 0.0;
        $xx = [];
        $k = 0;
        $i = 0;
        $j = 0;

        /**
         * Прямой ход (верхнетреугольный вид)
         */
        for ($i = 0; $i < $this->matrixSize; $i++) {
            $tmp = $this->matrix[$i][$i];
            for ($j = $this->matrixSize; $j >= $i; $j--) {
                $this->matrix[$i][$j] /= $tmp;
            }

            for ($j = $i + 1; $j < $this->matrixSize; $j++) {
                $tmp = $this->matrix[$j][$i];
                for ($k = $this->matrixSize; $k >= $i; $k--) {
                    $this->matrix[$j][$k] -= $tmp * $this->matrix[$i][$k];
                }
            }
        }

        /**
         * Обратный ход
         */
        $xx[$this->matrixSize - 1] = $this->matrix[$this->matrixSize - 1][$this->matrixSize];
        for ($i = $this->matrixSize - 2; $i >= 0; $i--) {
            $xx[$i] = $this->matrix[$i][$this->matrixSize];
            for ($j = $i + 1; $j < $this->matrixSize; $j++) {
                $xx[$i] -= $this->matrix[$i][$j] * $xx[$j];
            }
        }
        return $xx;
    }

    /**
     * @return Gauss
     */
    protected function printMatrix(): Gauss
    {
        echo "Your matrix" . PHP_EOL;
        foreach ($this->matrix as $element) {
            $string = implode("\t", $element);
            echo "$string \r\n";
        }
        return $this;
    }

    /**
     * @return Gauss
     */
    protected function setMatrixSize(): Gauss
    {
        $this->matrixSize = count($this->matrix);
        return $this;
    }
}