<?php

/**
 * Brainf*ck interpreter.
 * 
 * This class was made so that brainf*ck doesn't f*ck with your brain anymore.
 *
 * A good tutorial for learning brainf*ck can be found at: 
 * http://nieko.net/data/bf.txt
 * 
 * @author Tom Reitsma <hide@address.com>
 * @version 0.8
 */

Class bf
{
	var $stack = array();
	var $pointer = 0;
	var $loop_points = array();
	var $code = null;
	var $result = "";
	
	/**
	 * load()
	 * 
	 * Sets the input for the brainf*ck code.
	 * If the given input is a file, it will get its contents, else it will load the given string.
	 *
	 * @param mixed $file
	 * @return void
	 */
	function load($file)
	{
		if(is_file($file))
		{
			$this->code = file_get_contents($file);
			
			if(strlen($this->code) == 0)
			{
				$this->code == null;
			}
		}
		else if(is_string($file))
		{
			$this->code = $file;
		}
		else 
		{
			die("File $file not found");
		}
	}
	
	/**
	 * execute()
	 * 
	 * Starts interpreting the given input, set by load()
	 * You can, aswell as in load, give a string to execute.
	 * This will overrule the previously loaded string or file.
	 * 
	 * @param string $code
	 * @return void
	 */
	function execute($code=false)
	{
		if($code == false && $this->code == null)
		{
			die("Interpretation failed: No code was found.");
		}
		
		if($code == false)
		{
			$code = $this->code;
		}
		
		for($i=0;$i<strlen($code);$i++)
		{
			$curChar = $code{$i};
			
			switch($curChar)
			{
				case '+':
					$this->stack[$this->pointer]++;
					if($this->stack[$this->pointer] > 255)
						$this->stack[$this->pointer] = 1;
					break;
					
				case '-':
					$this->stack[$this->pointer]--;
					if($this->stack[$this->pointer] < 0)
						$this->stack[$this->pointer] = 255;
					break;
					
				case '>':
					$this->pointer++;						
					break;
					
				case '<':
					$this->pointer--;
					break;
					
				case '.':
					$this->result .= chr($this->stack[$this->pointer]);
					break;
					
				case '[':
					$this->loop_points[] = $i;
					break;
					
				case ']':
					if($this->stack[$this->pointer] > 0)
						$i = $this->loop_points[sizeof($this->loop_points) - 1];
					else 
						array_pop($this->loop_points);
					break;
					
				case ',':
					$this->stack[$this->pointer] = chr($this->stack[$this->pointer]);
					break;
				
				// This is one of my own commands.
				// This echoes the byte under the current pointer
				// (for debug usage)
				case '#':
					$this->result .= " debug::". $this->stack[$this->pointer]." ";
					break;
					
				case '?':
					$this->result .= "<pre>[".print_r($this->stack, true)."]</pre>";
					break;
				
				// This resets the stack, the pointer and the all the loop points
				case '%':
					$this->stack = array();
					$this->pointer = 0;
					$this->loop_points = array();
					break;
					
				default:
					break;
			}
		}
		
		return $this->result;
	}
}

?>