<?php

include_once('PolishNotationValidator.php');

use PolishNotationValidator as Validator;

/**
 * PolishNotation class
 *
 * Polish notation calculator.
 *
 * @author Ralph Moran - ralphmoran2003@gmail.com
 * @version 1.0
 * @copyright 2018
 */
class PolishNotation extends Validator{

    /**
     * __construct( String $sPNPattern )
     *
     * Take a pattern and calculate the results.
     *
     * @param string $pattern
     * @example new PolishNotation("/ 56 9")
     * @return int
     */
    public function __construct( String $sPNPattern ){

        $this->sPNPattern   = $sPNPattern                                     ;
        $this->aStackTokens = array_reverse( explode(" ", $this->sPNPattern) );

        try{
            if( $this->isValid() ){
                echo 'RESULT.- "' . $this->sPNPattern . '" = ' . $this->getResult() . PHP_EOL;
            }

        }catch(Exception $e){
            echo 'ERROR.- ' . $e->getMessage() . PHP_EOL;
        }

    }

    /**
     * getResult()
     *
     * Walks through $this->aTempStackResults to get the result
     *
     * @return integer | Exception
     */
    protected function getResult()
    {
        foreach( $this->aStackTokens as $sOperator ){

            if ( !is_numeric($sOperator) && $sOperator !== '' ){
                $iOp_1 = array_pop( $this->aTempStackResults );
                $iOp_2 = array_pop( $this->aTempStackResults );

                @eval('$this->iResult = ' .  $iOp_1 . $sOperator . $iOp_2 . ';');

                array_push( $this->aTempStackResults, $this->iResult );
            }else{
                array_push( $this->aTempStackResults, $sOperator );
            }
        };

        // At the end left 2 or more tokens, Prefix notation format is not valid
        if ( count($this->aTempStackResults) >= 2 ){
            throw new Exception('"' . $this->sPNPattern . '" is not a valid pattern');
        }

        return $this->iResult;
    }

}

new PolishNotation( '/ 10 2' );
new PolishNotation( '/ = 10 2' );
new PolishNotation( '/ ( 10 2' );
new PolishNotation( '/ 10 2)' );
new PolishNotation( ' / 10 + 2' );
new PolishNotation( ' / 10 + 2 -' );
new PolishNotation( '/ 10' );
new PolishNotation( '- + * 2 3 * 5 4 9' );
new PolishNotation( '+ * + 1 2 3 4' );