DirectSum.php

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<?php

namespace Matrix\Operators;

use Matrix\Matrix;
use Matrix\Exception;

class DirectSum extends Operator
{
    public function execute($value): Operator
    {
        if (is_array($value)) {
            $value = new Matrix($value);
        }

        if ($value instanceof Matrix) {
            return $this->directSumMatrix($value);
        }

        throw new Exception('Invalid argument for addition');
    }

    private function directSumMatrix($value): Operator
    {
        $originalColumnCount = count($this->matrix[0]);
        $originalRowCount = count($this->matrix);
        $valColumnCount = $value->columns;
        $valRowCount = $value->rows;
        $value = $value->toArray();

        for ($row = 0; $row < $this->rows; ++$row) {
            $this->matrix[$row] = array_merge($this->matrix[$row], array_fill(0, $valColumnCount, 0));
        }

        $this->matrix = array_merge(
            $this->matrix,
            array_fill(0, $valRowCount, array_fill(0, $originalColumnCount, 0))
        );

        for ($row = $originalRowCount; $row < $originalRowCount + $valRowCount; ++$row) {
            array_splice(
                $this->matrix[$row],
                $originalColumnCount,
                $valColumnCount,
                $value[$row - $originalRowCount]
            );
        }

        return $this;
    }
}