<?php

/*
 * File: stupid_template_engine.php
 * The implementation of the Stupid Template Engine.
 * 
 * About: License
 * This file is licensed under the MIT/X11 License.
 * See COPYING for more details.
 */

/*
 * Namespace: ste
 * Everything in this file is in this namespace.
 */
namespace ste;

abstract class ASTNode {
	public $tpl;
	public $offset;
	public function __construct($tpl, $off) {
		$this->tpl    = $tpl;
		$this->offset = $off;
	}
}

class TextNode extends ASTNode {
	public $text;
	public function __construct($tpl, $off, $text = "") {
		parent::__construct($tpl, $off);
		$this->text = $text;
	}
}

class TagNode extends ASTNode {
	public $name;
	public $params = array();
	public $sub = array();
	public function __construct($tpl, $off, $name = "") {
		parent::__construct($tpl, $off);
		$this->name = $name;
	}
}

class VariableNode extends ASTNode {
	public $name;
	public $arrayfields = array();
	public function transcompile() {
		$varaccess = '@$ste->vars[' . (is_numeric($this->name) ? $this->name : '"' . escape_text($this->name) . '"'). ']';
		foreach($this->arrayfields as $af) {
			if((count($af) == 1) and ($af[0] instanceof TextNode) and is_numeric($af[0]->text)) {
				$varaccess .= '[' . $af->text . ']';
			} else {
				$varaccess .= '[' . implode(".", array_map(function($node) {
					if($node instanceof TextNode) {
						return "\"" . escape_text($node->text) . "\"";
					} else if($node instanceof VariableNode) {
						return $node->transcompile();
					}
				}, $af)). ']';
			}
		}
		return $varaccess;
	}
}

class ParseCompileError extends \Exception {
	public $msg;
	public $tpl;
	public $off;
	
	public function __construct($msg, $tpl, $offset, $code = 0, $previous = NULL) {
		$this->msg = $msg;
		$this->tpl = $tpl;
		$this->off = $offset;
		$this->message = "$msg (Template $tpl, Offset $offset)";
	}
	
	public function rewrite($code) {
		$line = substr_count(str_replace("\r\n", "\n", substr($code, 0, $this->off)), "\n") + 1;
		$this->message = "{$this->msg} (Template {$this->tpl}, Line $line)";
		$this->is_rewritten = true;
	}
}

/*
 * Class: RuntimeError
 * An Exception that a tag can throw, if a non-fatal runtime error occurred.
 * By default this will return in no output at all. But if <STECore::$mute_runtime_errors> is false, this will generate a error message instead of the tag's output.
 */
class RuntimeError      extends \Exception {}

/*
 * Class: FatalRuntimeError
 * An Exception a tag can throw, if a fatal (irreparable) runtime error occurred.
 * This Exception will always "bubble up" so you probably want to catch them. Remember that this exception is also in the namespace ste!
 */
class FatalRuntimeError extends \Exception {}

/*
 * Class: Parser
 * The class, where the parser lives in. Can not be constructed manually.
 * Use the static method parse.
 */
class Parser {
	private $text;
	private $name;
	private $off;
	private $len;
	
	const PARSE_SHORT = 1;
	const PARSE_TAG   = 2;
	
	const ESCAPES_DEFAULT = '$?~{}|\\';
	
	private function __construct($text, $name) {
		$this->text = $text;
		$this->name = $name;
		$this->off  = 0;
		$this->len  = mb_strlen($text);
	}
	
	private function next($n = 1) {
		if($n <= 0) {
			throw new \InvalidArgumentException("\$n must be > 0");
		}
		$c = mb_substr($this->text, $this->off, $n);
		$this->off = min($this->off + $n, $this->len);
		return $c;
	}
	
	
	private function back($n = 1) {
		if($n <= 0) {
			throw new \InvalidArgumentException("\$n must be > 0");
		}
		$this->off = max($this->off - $n, 0);
	}
	
	private function search_off($needle) {
		return mb_strpos($this->text, $needle, $this->off);
	}
	
	private function search_multi($needles) {
		$oldoff = $this->off;
		
		$minoff = $this->len;
		$which = NULL;
		
		foreach($needles as $key => $needle) {
			if(($off = $this->search_off($needle)) === false) {
				continue;
			}

			if($off < $minoff) {
				$minoff = $off;
				$which = $key;
			}
		}
		
		$this->off = $minoff + (($which === NULL) ? 0 : mb_strlen((string) $needles[$which]));
		
		return array($which, $minoff, mb_substr($this->text, $oldoff, $minoff - $oldoff), $oldoff);
	}
	
	private function search($needle) {
		$oldoff = $this->off;
		
		$off = $this->search_off($needle);
		if($off === false) {
			$this->off = $this->len;
			return array(false, mb_substr($this->text, $oldoff), $oldoff);
		}
		
		$this->off = $off + mb_strlen($needle);
		return array($off, mb_substr($this->text, $oldoff, $off - $oldoff), $oldoff);
	}
	
	private function take_while($cb) {
		$s = "";
		while($c = $this->next()) {
			if(!call_user_func($cb, $c)) {
				$this->back();
				return $s;
			}
			$s .= $c;
		}
		return $s;
	}
	
	private function skip_ws() {
		$this->take_while("ctype_space");
	}
	
	private function get_name() {
		$off = $this->off;
		$name = $this->take_while(function($c) { return ctype_alnum($c) || ($c == "_"); });
		if(mb_strlen($name) == 0) {
			throw new ParseCompileError("Expected a name (alphanumeric chars + '_', at least one char)");
		}
		return $name;
	}
	
	/*
	 * Function: parse
	 * Parses the input into an AST.
	 *
	 * You only need this function, if you want to manually trnascompile a template.
	 *
	 * Parameters:
	 *	$text - The input code.
	 *	$name - The name of the template.
	 *
	 * Returns:
	 *	An array of <ASTNode> objects.
	 *
	 * Throws:
	 *	<ParseCompileError>
	 */
	public static function parse($text, $name) {
		$obj = new self($text, $name);
		$res = $obj->parse_text(
			self::ESCAPES_DEFAULT, /* Escapes */
			self::PARSE_SHORT | self::PARSE_TAG /* Flags */
		);
		return self::tidyup_ast($res[0]);
	}
	
	private static function tidyup_ast($ast) {
		$out = array();
		
		$prevtext = NULL;
		$first = true;
		
		foreach($ast as $node) {
			if($node instanceof TextNode) {
				if($prevtext === NULL) {
					$prevtext = $node;
				} else {
					$prevtext->text .= $node->text;
				}
			} else {
				if($prevtext !== NULL) {
					if($first) {
						$prevtext->text = ltrim($prevtext->text);
					}
					if($prevtext->text != "") {
						$out[] = $prevtext;
					}
				}
				$prevtext = NULL;
				$first = false;
				
				if($node instanceof TagNode) {
					$node->sub = self::tidyup_ast($node->sub);
					foreach($node->params as $k => &$v) {
						$v = self::tidyup_ast($v);
					}
					unset($v);
				} else { /* VariableNode */
					foreach($node->arrayfields as &$v) {
						$v = self::tidyup_ast($v);
					}
					unset($v);
				}
				
				$out[] = $node;
			}
		}
		
		if($prevtext !== NULL) {
			if($first) {
				$prevtext->text = ltrim($prevtext->text);
			}
			if($prevtext->text != "") {
				$out[] = $prevtext;
			}
		}
		
		return $out;
	}
	
	private function parse_text($escapes, $flags, $breakon = NULL, $separator = NULL, $nullaction = NULL, $opentag = NULL, $openedat = -1) {
		$elems = array();
		$astlist = array();
		
		$needles = array(
			"commentopen" => "<ste:comment>",
			"rawopen" => "<ste:rawtext>",
			"escape" => '\\',
			"varcurlyopen" => '${',
			"var" => '$',
		);
		
		if($flags & self::PARSE_TAG) {
			$needles["tagopen"] = '<ste:';
			$needles["closetagopen"] = '</ste:';
		}
		if($flags & self::PARSE_SHORT) {
			$needles["shortifopen"] = '?{';
			$needles["shortcompopen"] = '~{';
		}
		
		if($separator !== NULL) {
			$needles["sep"] = $separator;
		}
		if($breakon !== NULL) {
			$needles["break"] = $breakon;
		}
		
		for(;;) {
			list($which, $off, $before, $offbefore) = $this->search_multi($needles);
			
			$astlist[] = new TextNode($this->name, $offbefore, $before);
			
			switch($which) {
			case NULL:
				if($nullaction === NULL) {
					$elems[] = $astlist;
					return $elems;
				} else {
					call_user_func($nullaction);
				}
				break;
			case "commentopen":
				list($off, $before, $offbefore) = $this->search("</ste:comment>");
				if($off === false) {
					throw new ParseCompileError("ste:comment was not closed", $this->name, $offbefore);
				}
				break;
			case "rawopen":
				$off_start = $off;
				list($off, $before, $offbefore) = $this->search("</ste:rawtext>");
				if($off === false) {
					throw new ParseCompileError("ste:rawtext was not closed", $this->name, $off_start);
				}
				$astlist[] = new TextNode($this->name, $off_start, $before);
				break;
			case "tagopen":
				$astlist[] = $this->parse_tag($off);
				break;
			case "closetagopen":
				$off_start = $off;
				$name = $this->get_name();
				$this->skip_ws();
				$off = $this->off;
				if($this->next() != ">") {
					throw new ParseCompileError("Expected '>' in closing ste-Tag", $this->name, $off);
				}
				
				if($opentag === NULL) {
					throw new ParseCompileError("Found closing ste:$name tag, but no tag was opened", $this->name, $off_start);
				}
				if($opentag != $name) {
					throw new ParseCompileError("Open ste:$opentag was not closed", $this->name, $openedat);
				}
				
				$elems[] = $astlist;
				return $elems;
			case "escape":
				$c = $this->next();
				if(mb_strpos($escapes, $c) !== false) {
					$astlist[] = new TextNode($this->name, $off, $c);
				} else {
					$astlist[] = new TextNode($this->name, $off, '\\');
					$this->back();
				}
				break;
			case "shortifopen":
				$shortelems = $this->parse_short("?{", $off);
				if(count($shortelems) != 3) {
					throw new ParseCompileError("A short if tag must have the form ?{..|..|..}", $this->name, $off);
				}
				
				list($cond, $then, $else) = $shortelems;
				$thentag = new TagNode($this->name, $off);
				$thentag->name = "then";
				$thentag->sub = $then;
				
				$elsetag = new TagNode($this->name, $off);
				$elsetag->name = "else";
				$elsetag->sub = $else;
				
				$iftag = new TagNode($this->name, $off);
				$iftag->name = "if";
				$iftag->sub = $cond;
				$iftag->sub[] = $thentag;
				$iftag->sub[] = $elsetag;
				
				$astlist[] = $iftag;
				break;
			case "shortcompopen":
				$shortelems = $this->parse_short("~{", $off);
				if(count($shortelems) != 3) {
					throw new ParseCompileError("A short comparasion tag must have the form ~{..|..|..}", $this->name, $off);
				}
				
				// TODO: What will happen, if a tag was in one of the elements?
				list($a, $op, $b) = $shortelems;
				$cmptag = new TagNode($this->name, $off);
				$cmptag->name = "cmp";
				$cmptag->params["text_a"] = $a;
				$cmptag->params["op"] = $op;
				$cmptag->params["text_b"] = $b;
				
				$astlist[] = $cmptag;
				break;
			case "sep":
				$elems[] = $astlist;
				$astlist = array();
				break;
			case "varcurlyopen":
				$astlist[] = $this->parse_var($off, true);
				break;
			case "var":
				$astlist[] = $this->parse_var($off, false);
				break;
			case "break":
				$elems[] = $astlist;
				return $elems;
			}
		}
		
		$elems[] = $astlist;
		return $elems;
	}
	
	private function parse_short($shortname, $openedat) {
		$tplname = $this->name;
		
		return $this->parse_text(
			self::ESCAPES_DEFAULT, /* Escapes */
			self::PARSE_SHORT | self::PARSE_TAG, /* Flags */
			'}', /* Break on */
			'|', /* Separator */
			function() use ($shortname, $tplname, $openedat) { /* NULL action */
				throw new ParseCompileError("Unclosed $shortname", $tplname, $openedat);
			},
			NULL, /* Open tag */
			$openedat /* Opened at */
		);
	}
	
	private function parse_var($openedat, $curly) {
		$varnode = new VariableNode($this->name, $openedat);
		$varnode->name = $this->get_name();
		$varnode->arrayfields = $this->parse_array();
		
		if(($curly) && ($this->next() != "}")) {
			throw new ParseCompileError("Unclosed '\${'", $this->name, $openedat);
		}
		return $varnode;
	}
	
	private function parse_array() {
		$tplname = $this->name;
		
		$arrayfields = array();
		
		while($this->next() == "[") {
			$openedat = $this->off - 1;
			$res = $this->parse_text(
				self::ESCAPES_DEFAULT, /* Escapes */
				0, /* Flags */
				']', /* Break on */
				NULL, /* Separator */
				function() use ($tplname, $openedat) { /* NULL action */
					throw new ParseCompileError("Unclosed array access '[...]'", $tplname, $openedat);
				},
				NULL, /* Open tag */
				$openedat /* Opened at */
			);
			$arrayfields[] = $res[0];
		}
		
		$this->back();
		return $arrayfields;
	}
	
	private function parse_tag($openedat) {
		$tplname = $this->name;
		
		$this->skip_ws();
		$tag = new TagNode($this->name, $openedat);
		$name = $tag->name = $this->get_name();
		$tag->params = array();
		$tag->sub = array();
		
		for(;;) {
			$this->skip_ws();
			
			switch($this->next()) {
			case '/': /* Self-closing tag */
				$this->skip_ws();
				if($this->next() != '>') {
					throw new ParseCompileError("Unclosed opening <ste: tag (expected >)", $this->name, $openedat);
				}
				
				return $tag;
			case '>':
				$sub = $this->parse_text(
					self::ESCAPES_DEFAULT, /* Escapes */
					self::PARSE_SHORT | self::PARSE_TAG, /* Flags */
					NULL, /* Break on */
					NULL, /* Separator */
					function() use ($name, $tplname, $openedat) { /* NULL action */
						throw new ParseCompileError("Open ste:$name tag was not closed", $tplname, $openedat);
					},
					$tag->name, /* Open tag */
					$openedat /* Opened at */
				);
				$tag->sub = $sub[0];
				return $tag;
			default:
				$this->back();
				
				$param = $this->get_name();
				
				$this->skip_ws();
				if($this->next() != '=') {
					throw new ParseCompileError("Expected '=' after tag parameter name", $this->name, $this->off - 1);
				}
				$this->skip_ws();
				
				$quot = $this->next();
				if(($quot != '"') && ($quot != "'")) {
					throw new ParseCompileError("Expected ' or \" after '=' of tag parameter", $this->name, $this->off - 1);
				}
				
				$off = $this->off - 1;
				$paramval = $this->parse_text(
					self::ESCAPES_DEFAULT . $quot, /* Escapes */
					0, /* Flags */
					$quot, /* Break on */
					NULL, /* Separator */
					function() use ($quot, $tplname, $off) { /* NULL action */
						throw new ParseCompileError("Open tag parameter value ($quot) was not closed", $tplname, $off);
					},
					NULL, /* Open tag */
					$off /* Opened at */
				);
				$tag->params[$param] = $paramval[0];
			}
		}
	}
}

function indent_code($code) {
	return implode(
		"\n",
		array_map(function($line) { return "\t$line"; }, explode("\n", $code))
	);
}

/* We could also just eval() the $infix_math code, but this is much cooler :-D (Parser inception) */
function shunting_yard($infix_math) {
	$operators = array(
		"+" => array("l", 2),
		"-" => array("l", 2),
		"*" => array("l", 3),
		"/" => array("l", 3),
		"^" => array("r", 4),
		"_" => array("r", 5),
		"(" => array("", 0), 
		")" => array("", 0)
	);
	
	preg_match_all("/\s*(?:(?:[+\\-\\*\\/\\^\\(\\)])|(\\d*[\\.]?\\d*))\\s*/s", $infix_math, $tokens, PREG_PATTERN_ORDER);
	$tokens_raw   = array_filter(array_map('trim', $tokens[0]), function($x) { return ($x === "0") || (!empty($x)); });
	$output_queue = array();
	$op_stack     = array();
	
	$lastpriority = NULL;
	/* Make - unary, if neccessary */
	$tokens = array();
	foreach($tokens_raw as $token) {
		$priority = isset($operators[$token]) ? $operators[$token][1] : -1;
		if(($token == "-") && (($lastpriority === NULL) || ($lastpriority >= 0))) {
			$priority = $operators["_"][1];
			$tokens[] = "_";
		} else {
			$tokens[] = $token;
		}
		$lastpriority = $priority;
	}
	
	while(!empty($tokens)) {
		$token = array_shift($tokens);
		if(is_numeric($token)) {
			$output_queue[] = $token;
		} else if($token == "(") {
			$op_stack[] = $token;
		} else if($token == ")") {
			$lbr_found = false;
			while(!empty($op_stack)) {
				$op = array_pop($op_stack);
				if($op == "(") {
					$lbr_found = true;
					break;
				}
				$output_queue[] = $op;
			}
			if(!$lbr_found) {
				throw new RuntimeError("Bracket mismatch.");
			}
		} else if(!isset($operators[$token])) {
			throw new RuntimeError("Invalid token ($token): Not a number, bracket or operator. Stop.");
		} else {
			$priority = $operators[$token][1];
			if($operators[$token][0] == "l") {
				while((!empty($op_stack)) and ($priority <= $operators[$op_stack[count($op_stack)-1]][1])) {
					$output_queue[] = array_pop($op_stack);
				}
			} else {
				while((!empty($op_stack)) and ($priority < $operators[$op_stack[count($op_stack)-1]][1])) {
					$output_queue[] = array_pop($op_stack);
				}
			}
			$op_stack[] = $token;
		}
	}
	
	while(!empty($op_stack)) {
		$op = array_pop($op_stack);
		if($op == "(") {
			throw new RuntimeError("Bracket mismatch...");
		}
		$output_queue[] = $op;
	}
	
	return $output_queue;
}

function pop2(&$array) {
	$rv = array(array_pop($array), array_pop($array));
	if(array_search(NULL, $rv, true) !== false) {
		throw new RuntimeError("Not enough numbers on stack. Invalid formula.");
	}
	return $rv;
}

function calc_rpn($rpn) {
	$stack = array();
	foreach($rpn as $token) {
		switch($token) {
		case "+":
			list($b, $a) = pop2($stack);
			$stack[] = $a + $b;
			break;
		case "-":
			list($b, $a) = pop2($stack);
			$stack[] = $a - $b;
			break;
		case "*":
			list($b, $a) = pop2($stack);
			$stack[] = $a * $b;
			break;
		case "/":
			list($b, $a) = pop2($stack);
			$stack[] = $a / $b;
			break;
		case "^":
			list($b, $a) = pop2($stack);
			$stack[] = pow($a, $b);
			break;
		case "_":
			$a = array_pop($stack);
			if($a === NULL) {
				throw new RuntimeError("Not enough numbers on stack. Invalid formula.");
			}
			$stack[] = -$a;
			break;
		default:
			$stack[] = $token;
			break;
		}
	}
	return array_pop($stack);
}

function loopbody($code) {
	return "try\n{\n" . indent_code($code) . "\n}\ncatch(\ste\BreakException \$e) { break; }\ncatch(\ste\ContinueException \$e) { continue; }\n";
}

$ste_builtins = array(
	"if" => function($ast) {
		$output = "";
		$condition = array();
		$then = NULL;
		$else = NULL;
		
		foreach($ast->sub as $node) {
			if(($node instanceof TagNode) and ($node->name == "then")) {
				$then = $node->sub;
			} else if(($node instanceof TagNode) and ($node->name == "else")) {
				$else = $node->sub;
			} else {
				$condition[] = $node;
			}
		}
		
		if($then === NULL) {
			throw new ParseCompileError("Transcompile error: Missing <ste:then> in <ste:if>.", $ast->tpl, $ast->offset);
		}
		
		$output .= "\$outputstack[] = \"\";\n\$outputstack_i++;\n";
		$output .= _transcompile($condition);
		$output .= "\$outputstack_i--;\nif(\$ste->evalbool(array_pop(\$outputstack)))\n{\n";
		$output .= indent_code(_transcompile($then));
		$output .= "\n}\n";
		if($else !== NULL) {
			$output .= "else\n{\n";
			$output .= indent_code(_transcompile($else));
			$output .= "\n}\n";
		}
		return $output;
	},
	"cmp" => function($ast) {
		$operators = array(
			array('eq', '=='),
			array('neq', '!='),
			array('lt', '<'),
			array('lte', '<='),
			array('gt', '>'),
			array('gte', '>=')
		);
		
		$code = "";
		
		if(isset($ast->params["var_b"])) {
			list($val, $pre) = _transcompile($ast->params["var_b"], true);
			$code .= $pre;
			$b = '$ste->get_var_by_name(' . $val . ')';
		} else if(isset($ast->params["text_b"])) {
			list($b, $pre) = _transcompile($ast->params["text_b"], true);
			$code .= $pre;
		} else {
			throw new ParseCompileError("Transcompile error: neiter var_b nor text_b set in <ste:cmp>.", $ast->tpl, $ast->offset);
		}
		
		if(isset($ast->params["var_a"])) {
			list($val, $pre) = _transcompile($ast->params["var_a"], true);
			$code .= $pre;
			$a = '$ste->get_var_by_name(' . $val . ')';
		} else if(isset($ast->params["text_a"])) {
			list($a, $pre) = _transcompile($ast->params["text_a"], true);
			$code .= $pre;
		} else {
			throw new ParseCompileError("Transcompile error: neiter var_a nor text_a set in <ste:cmp>.", $ast->tpl, $ast->offset);
		}
		
		if(!isset($ast->params["op"])) {
			throw new ParseCompileError("Transcompile error: op not given in <ste:cmp>.", $ast->tpl, $ast->offset);
		}
		if((count($ast->params["op"]) == 1) and ($ast->params["op"][0] instanceof TextNode)) {
			/* Operator is known at compile time, this saves *a lot* of output code! */
			$op = trim($ast->params["op"][0]->text);
			$op_php = NULL;
			foreach($operators as $v) {
				if($v[0] == $op) {
					$op_php = $v[1];
					break;
				}
			}
			if($op_php === NULL) {
				throw new ParseCompileError("Transcompile Error: Unknown operator in <ste:cmp>", $ast->tpl, $ast->offset);
			}
			$code .= "\$outputstack[\$outputstack_i] .= (($a) $op_php ($b)) ? 'yes' : '';\n";
		} else {
			list($val, $pre) = _transcompile($ast->params["op"], true);
			$code .= $pre . "switch(trim(" . $val . "))\n{\n\t";
			$code .= implode("", array_map(
					function($op) use ($a,$b)
					{
						list($op_stetpl, $op_php) = $op;
						return "case '$op_stetpl':\n\t\$outputstack[\$outputstack_i] .= (($a) $op_php ($b)) ? 'yes' : '';\n\tbreak;\n\t";
					}, $operators
				));
			$code .= "default: throw new \\ste\\RuntimeError('Unknown operator in <ste:cmp>.');\n}\n";
		}
		return $code;
	},
	"not" => function($ast) {
		$code = "\$outputstack[] = '';\n\$outputstack_i++;\n";
		$code .= _transcompile($ast->sub);
		$code .= "\$outputstack_i--;\n\$outputstack[\$outputstack_i] .= (!\$ste->evalbool(array_pop(\$outputstack))) ? 'yes' : '';\n";
		return $code;
	},
	"even" => function($ast) {
		$code = "\$outputstack[] = '';\n\$outputstack_i++;\n";
		$code .= _transcompile($ast->sub);
		$code .= "\$outputstack_i--;\n\$tmp_even = array_pop(\$outputstack);\n\$outputstack[\$outputstack_i] .= (is_numeric(\$tmp_even) and (\$tmp_even % 2 == 0)) ? 'yes' : '';\n";
		return $code;
	},
	"for" => function($ast) {
		$code = "";
		$loopname = "forloop_" . str_replace(".", "_", uniqid("",true));
		if(empty($ast->params["start"])) {
			throw new ParseCompileError("Transcompile error: Missing 'start' parameter in <ste:for>.", $ast->tpl, $ast->offset);
		}
		list($val, $pre) = _transcompile($ast->params["start"], true);
		$code .= $pre;
		$code .= "\$${loopname}_start = " . $val . ";\n";
		
		if(empty($ast->params["stop"])) {
			throw new ParseCompileError("Transcompile error: Missing 'end' parameter in <ste:for>.", $ast->tpl, $ast->offset);
		}
		list($val, $pre) = _transcompile($ast->params["stop"], true);
		$code .= $pre;
		$code .= "\$${loopname}_stop = " . $val . ";\n";
		
		$step = NULL; /* i.e. not known at compilation time */
		if(empty($ast->params["step"])) {
			$step = 1;
		} else if((count($ast->params["step"]) == 1) and ($ast->params["step"][0] instanceof TextNode)) {
			$step = $ast->params["step"][0]->text + 0;
		} else {
			list($val, $pre) = _transcompile($ast->params["step"], true);
			$code .= $pre;
			$code .= "\$${loopname}_step = " . $val . ";\n";
		}
		
		if(!empty($ast->params["counter"])) {
			list($val, $pre) = _transcompile($ast->params["counter"], true);
			$code .= $pre;
			$code .= "\$${loopname}_countername = " . $val . ";\n";
		}
		
		$loopbody = empty($ast->params["counter"]) ? "" : "\$ste->set_var_by_name(\$${loopname}_countername, \$${loopname}_counter);\n";
		$loopbody .= _transcompile($ast->sub);
		$loopbody = indent_code("{\n" . loopbody(indent_code($loopbody)) . "\n}\n");
		
		if($step === NULL) {
			$code .= "if(\$${loopname}_step == 0)\n\tthrow new \\ste\\RuntimeError('step can not be 0 in <ste:for>.');\n";
			$code .= "if(\$${loopname}_step > 0)\n{\n";
			$code .= "\tfor(\$${loopname}_counter = \$${loopname}_start; \$${loopname}_counter <= \$${loopname}_stop; \$${loopname}_counter += \$${loopname}_step)\n";
			$code .= $loopbody;
			$code .= "\n}\nelse\n{\n";
			$code .= "\tfor(\$${loopname}_counter = \$${loopname}_start; \$${loopname}_counter >= \$${loopname}_stop; \$${loopname}_counter += \$${loopname}_step)\n";
			$code .= $loopbody;
			$code .= "\n}\n";
		} else if($step == 0) {
			throw new ParseCompileError("Transcompile Error: step can not be 0 in <ste:for>.", $ast->tpl, $ast->offset);
		} else if($step > 0) {
			$code .= "for(\$${loopname}_counter = \$${loopname}_start; \$${loopname}_counter <= \$${loopname}_stop; \$${loopname}_counter += $step)\n$loopbody\n";
		} else {
			$code .= "for(\$${loopname}_counter = \$${loopname}_start; \$${loopname}_counter >= \$${loopname}_stop; \$${loopname}_counter += $step)\n$loopbody\n";
		}
		
		return $code;
	},
	"foreach" => function($ast) {
		$loopname = "foreachloop_" . str_replace(".", "_", uniqid("",true));
		$code = "";
		
		if(empty($ast->params["array"])) {
			throw new ParseCompileError("Transcompile Error: array not given in <ste:foreach>.", $ast->tpl, $ast->offset);
		}
		list($val, $pre) = _transcompile($ast->params["array"], true);
		$code .= $pre;
		$code .= "\$${loopname}_arrayvar = " . $val . ";\n";
		
		if(empty($ast->params["value"])) {
			throw new ParseCompileError("Transcompile Error: value not given in <ste:foreach>.", $ast->tpl, $ast->offset);
		}
		list($val, $pre) = _transcompile($ast->params["value"], true);
		$code .= $pre;
		$code .= "\$${loopname}_valuevar = " . $val . ";\n";
		
		if(!empty($ast->params["key"])) {
			list($val, $pre) = _transcompile($ast->params["key"], true);
			$code .= $pre;
			$code .= "\$${loopname}_keyvar = " . $val . ";\n";
		}
		
		if(!empty($ast->params["counter"])) {
			list($val, $pre) = _transcompile($ast->params["counter"], true);
			$code .= $pre;
			$code .= "\$${loopname}_countervar = " . $val . ";\n";
		}
		
		$loopbody = "";
		$code .= "\$${loopname}_array = \$ste->get_var_by_name(\$${loopname}_arrayvar);\n";
		$code .= "if(!is_array(\$${loopname}_array))\n\t\$${loopname}_array = array();\n";
		if(!empty($ast->params["counter"])) {
			$code .= "\$${loopname}_counter = -1;\n";
			$loopbody .= "\$${loopname}_counter++;\n\$ste->set_var_by_name(\$${loopname}_countervar, \$${loopname}_counter);\n";
		}
		
		$loopbody .= "\$ste->set_var_by_name(\$${loopname}_valuevar, \$${loopname}_value);\n";
		if(!empty($ast->params["key"])) {
			$loopbody .= "\$ste->set_var_by_name(\$${loopname}_keyvar, \$${loopname}_key);\n";
		}
		$loopbody .= "\n";
		$loopbody .= _transcompile($ast->sub);
		$loopbody = "{\n" . loopbody(indent_code($loopbody)) . "\n}\n";
		
		$code .= "foreach(\$${loopname}_array as \$${loopname}_key => \$${loopname}_value)\n$loopbody\n";
		
		return $code;
	},
	"infloop" => function($ast) {
		return "while(true)\n{\n" . indent_code(loopbody(indent_code(_transcompile($ast->sub)))) . "\n}\n";
	},
	"break" => function($ast) {
		return "throw new \\ste\\BreakException();\n";
	},
	"continue" => function($ast) {
		return "throw new \\ste\\ContinueException();\n";
	},
	"block" => function($ast) {
		if(empty($ast->params["name"])) {
			throw new ParseCompileError("Transcompile Error: name missing in <ste:block>.", $ast->tpl, $ast->offset);
		}
		
		$blknamevar = "blockname_" . str_replace(".", "_", uniqid("", true));
		
		list($val, $code) = _transcompile($ast->params["name"], true);
		$code .= "\$${blknamevar} = " . $val . ";\n";
		
		$tmpblk = uniqid("", true);
		$code .= "\$ste->blocks['$tmpblk'] = array_pop(\$outputstack);\n\$ste->blockorder[] = '$tmpblk';\n\$outputstack = array('');\n\$outputstack_i = 0;\n";
		
		$code .= _transcompile($ast->sub);
		
		$code .= "\$ste->blocks[\$${blknamevar}] = array_pop(\$outputstack);\n";
		$code .= "if(array_search(\$${blknamevar}, \$ste->blockorder) === false)\n\t\$ste->blockorder[] = \$${blknamevar};\n\$outputstack = array('');\n\$outputstack_i = 0;\n";
		
		return $code;
	},
	"load" => function($ast) {
		if(empty($ast->params["name"])) {
			throw new ParseCompileError("Transcompile Error: name missing in <ste:load>.", $ast->tpl, $ast->offset);
		}
		
		list($val, $code) = _transcompile($ast->params["name"], true);
		$code .= "\$outputstack[\$outputstack_i] .= \$ste->load(" . $val . ");\n";
		return $code;
	},
	"mktag" => function($ast) {
		$code = "";
		
		if(empty($ast->params["name"])) {
			throw new ParseCompileError("Transcompile Error: name missing in <ste:mktag>.", $ast->tpl, $ast->offset);
		}
		
		$fxbody = "\$outputstack = array(''); \$outputstack_i = 0;\$ste->vars['_tag_parameters'] = \$params;\n";
		
		list($tagname, $tagname_pre) = _transcompile($ast->params["name"], true);
		
		$usemandatory = "";
		if(!empty($ast->params["mandatory"])) {
			$usemandatory = " use (\$mandatory_params)";
			$code .= "\$outputstack[] = '';\n\$outputstack_i++;\n";
			$code .= _transcompile($ast->params["mandatory"]);
			$code .= "\$outputstack_i--;\n\$mandatory_params = explode('|', array_pop(\$outputstack));\n";
			
			$fxbody .= "foreach(\$mandatory_params as \$mp)\n{\n\tif(!isset(\$params[\$mp]))\n\t\tthrow new \\ste\\RuntimeError(\"\$mp missing in <ste:\" . $tagname . \">.\");\n}";
		}
		
		$fxbody .= _transcompile($ast->sub);
		$fxbody .= "return array_pop(\$outputstack);";
		
		$code .= "\$tag_fx = function(\$ste, \$params, \$sub)" . $usemandatory . "\n{\n" . indent_code($fxbody) . "\n};\n";
		$code .= $tagname_pre;
		$code .= "\$ste->register_tag($tagname, \$tag_fx);\n";
		
		return $code;
	},
	"tagcontent" => function($ast) {
		return "\$outputstack[\$outputstack_i] .= \$sub(\$ste);";
	},
	"set" => function($ast) {
		if(empty($ast->params["var"])) {
			throw new ParseCompileError("Transcompile Error: var missing in <ste:set>.", $ast->tpl, $ast->offset);
		}
		
		$code = "\$outputstack[] = '';\n\$outputstack_i++;\n";
		$code .= _transcompile($ast->sub);
		$code .= "\$outputstack_i--;\n";
		
		list($val, $pre) = _transcompile($ast->params["var"], true);
		$code .= $pre;
		$code .= "\$ste->set_var_by_name(" . $val . ", array_pop(\$outputstack));\n";
		
		return $code;
	},
	"get" => function($ast) {
		if(empty($ast->params["var"])) {
			throw new ParseCompileError("Transcompile Error: var missing in <ste:get>.", $ast->tpl, $ast->offset);
		}
		
		list($val, $pre) = _transcompile($ast->params["var"],  true);
		$code .= $pre;
		return "\$outputstack[\$outputstack_i] .= \$ste->get_var_by_name(" . $val . ");";
	},
	"calc" => function($ast) {
		$code = "\$outputstack[] = '';\n\$outputstack_i++;\n";
		$code .= _transcompile($ast->sub);
		$code .= "\$outputstack_i--;\n\$outputstack[\$outputstack_i] .= \$ste->calc(array_pop(\$outputstack));\n";
		
		return $code;
	}
);

function escape_text($text) {
	return addcslashes($text, "\r\n\t\$\0..\x1f\\\"\x7f..\xff");
}

function _transcompile($ast, $avoid_outputstack = false) { /* The real transcompile function, does not add boilerplate code. */
	$code = "";
	global $ste_builtins;
	
	$text_and_var_buffer = array();
	
	foreach($ast as $node) {
		if($node instanceof TextNode) {
			$text_and_var_buffer[] = '"' . escape_text($node->text) . '"';
		} else if($node instanceof VariableNode) {
			$text_and_var_buffer[] = $node->transcompile();
		} else if($node instanceof TagNode) {
			if(!empty($text_and_var_buffer)) {
				$code .= "\$outputstack[\$outputstack_i] .= " . implode (" . ", $text_and_var_buffer) . ";\n";
				$text_and_var_buffer = array();
			}
			if(isset($ste_builtins[$node->name])) {
				$code .= $ste_builtins[$node->name]($node);
			} else {
				$paramarray = "parameters_" . str_replace(".", "_", uniqid("", true));
				$code .= "\$$paramarray = array();\n";
				
				foreach($node->params as $pname => $pcontent) {
					list($pval, $pre) = _transcompile($pcontent, true);
					$code .= $pre . "\$${paramarray}['" . escape_text($pname) . "'] = " . $pval . ";\n";
				}
				
				$code .= "\$outputstack[\$outputstack_i] .= \$ste->call_tag('" . escape_text($node->name) . "', \$${paramarray}, ";
				$code .= empty($node->sub) ? "function(\$ste) { return ''; }" : transcompile($node->sub);
				$code .= ");\n";
			}
		}
	}
	
	if($avoid_outputstack && ($code == "")) {
		return array(implode (" . ", $text_and_var_buffer), "");
	}
	
	if(!empty($text_and_var_buffer)) {
		$code .= "\$outputstack[\$outputstack_i] .= ". implode (" . ", $text_and_var_buffer) . ";\n";
	}
	
	if($avoid_outputstack) {
		$tmpvar = "tmp_" . str_replace(".", "_", uniqid("",true));
		$code = "\$outputstack[] = '';\n\$outputstack_i++;" . $code;
		$code .= "\$$tmpvar = array_pop(\$outputstack);\n\$outputstack_i--;\n";
		return array("\$$tmpvar", $code);
	}
	
	return $code;
}

$ste_transc_boilerplate = "\$outputstack = array('');\n\$outputstack_i = 0;\n";

/*
 * Function: transcompile
 * Transcompiles an abstract syntax tree to PHP.
 * You only need this function, if you want to manually transcompile a template.
 * 
 * Parameters:
 * 	$ast - The abstract syntax tree to transcompile.
 * 
 * Returns:
 * 	PHP code. The PHP code is an anonymous function expecting a <STECore> instance as its parameter and returns a string (everything that was not pached into a section).
 */
function transcompile($ast) { /* Transcompile and add some boilerplate code. */
	global $ste_transc_boilerplate;
	return "function(\$ste)\n{\n" . indent_code($ste_transc_boilerplate . _transcompile($ast) . "return array_pop(\$outputstack);") . "\n}";
}

/*
 * Constants: Template modes
 * 
 * MODE_SOURCE - The Templates source
 * MODE_TRANSCOMPILED - The transcompiled template
 */
const MODE_SOURCE        = 0;
const MODE_TRANSCOMPILED = 1;

abstract class StorageAccessFailure extends \Exception { }

/*
 * Class: CantLoadTemplate
 * An exception that a <StorageAccess> implementation can throw, if it is unable to load a template.
 */
class CantLoadTemplate extends StorageAccessFailure { }

/*
 * Class: CantSaveTemplate
 * An exception that a <StorageAccess> implementation can throw, if it is unable to save a template.
 */
class CantSaveTemplate extends StorageAccessFailure { }

/*
 * Class: StorageAccess
 * An interface.
 * A StorageAccess implementation is used to access the templates from any storage.
 * This means, that you are not limited to store the Templates inside directories, you can also use a database or something else.
 */
interface StorageAccess {
	/*
	 * Function: load
	 * Loading a template.
	 * 
	 * Parameters:
	 * 	$tpl - The name of the template.
	 * 	&$mode - Which mode is preferred? One of the <Template modes>.
	 * 	         If <MODE_SOURCE>, the raw sourcecode is expected, if <MODE_TRANSCOMPILED> the transcompiled template *as a callable function* (expecting an <STECore> instance as first parameter) is expected.
	 * 	         If the transcompiled version is not available or older than the source, you can set this parameter to <MODE_SOURCE> and return the source.
	 * 
	 * Throws:
	 * 	A <CantLoadTemplate> exception if the template could not be loaded.
	 * 
	 * Returns:
	 * 	Either the sourcecode or a callable function (first, and only parameter: an <STECore> instance).
	 */
	public function load($tpl, &$mode);
	
	/*
	 * Function: save
	 * Saves a template.
	 * 
	 * Throws:
	 * 	A <CantSaveTemplate> exception if the template could not be saved.
	 * 
	 * Parameters:
	 * 	$tpl -The name of the template.
	 * 	$data - The data to be saved.
	 * 	$mode - A <Template mode> constant.
	 */
	public function save($tpl, $data, $mode);
}

/*
 * Class: FilesystemStorageAccess
 * The default <StorageAccess> implementation for loading / saving templates into a directory structure.
 */
class FilesystemStorageAccess implements StorageAccess {
	protected $sourcedir;
	protected $transcompileddir;
	
	/*
	 * Constructor: __construct
	 * 
	 * Parameters:
	 * 	$src - The directory with the sources (Writing permissions are not mandatory, because STE does not save template sources).
	 * 	$transc - The directory with the transcompiled templates (the PHP instance / the HTTP Server needs writing permissions to this directory).
	 */
	public function __construct($src, $transc) {
		$this->sourcedir        = $src;
		$this->transcompileddir = $transc;
	}
	
	public function load($tpl, &$mode) {
		$src_fn    = $this->sourcedir        . "/" . $tpl;
		$transc_fn = $this->transcompileddir . "/" . $tpl . ".php";
		
		if($mode == MODE_SOURCE) {
			$content = @file_get_contents($src_fn);
			if($content === false) {
				throw new CantLoadTemplate("Template not found.");
			}
			return $content;
		}
		
		$src_stat    = @stat($src_fn);
		$transc_stat = @stat($transc_fn);
		
		if(($src_stat === false) and ($transc_stat === false)) {
			throw new CantLoadTemplate("Template not found.");
		} else if($transc_stat === false) {
			$mode = MODE_SOURCE;
			return file_get_contents($src_fn);
		} else if($src_stat === false) {
			include($transc_fn);
			return $transcompile_fx;
		} else {
			if($src_stat["mtime"] > $transc_stat["mtime"]) {
				$mode = MODE_SOURCE;
				return file_get_contents($src_fn);
			} else {
				include($transc_fn);
				return $transcompile_fx;
			}
		}
	}
	
	public function save($tpl, $data, $mode) {
		$fn = (($mode == MODE_SOURCE) ? $this->sourcedir : $this->transcompileddir) . "/" . $tpl . (($mode == MODE_TRANSCOMPILED) ? ".php" : "");
		@mkdir(dirname($fn), 0777, true);
		if(file_put_contents($fn, "<?php \$transcompile_fx = $data; ?>") === false) {
			throw new CantSaveTemplate("Unable to save template.");
		}
	}
}

class BreakException    extends \Exception { }
class ContinueException extends \Exception { }

/*
 * Class: STECore
 * The Core of STE
 */
class STECore {
	private $tags;
	private $storage_access;
	private $cur_tpl_dir;
	
	/*
	 * Variables: Public variables
	 * 
	 * $blocks - Associative array of blocks (see the language definition).
	 * $blockorder - The order of the blocks (an array)
	 * $vars - Associative array of all template variables. Use this to pass data to your templates.
	 * $mute_runtime_errors - If true (default) a <RuntimeError> exception will result in no output from the tag, if false a error message will be written to output.
	 * $fatal_error_on_missing_tag - If true, STE will throw a <FatalRuntimeError> if a tag was called that was not registered, otherwise (default) a regular <RuntimeError> will be thrown and automatically handled by STE (see <$mute_runtime_errors>).
	 */
	public $blocks;
	public $blockorder;
	public $vars;
	public $mute_runtime_errors = true;
	public $fatal_error_on_missing_tag = false;
	
	/*
	 * Constructor: __construct
	 * 
	 * Parameters:
	 * 	$storage_access - An Instance of a <StorageAccess> implementation.
	 */
	public function __construct($storage_access) {
		$this->storage_access = $storage_access;
		$this->cur_tpl_dir = "/";
		STEStandardLibrary::_register_lib($this);
		$this->vars = array();
		$this->blockorder = array();
		$this->blocks = array();
	}
	
	/*
	 * Function: register_tag
	 * Register a custom tag.
	 * 
	 * Parameters:
	 * 	$name - The name of the tag.
	 * 	$callback - A callable function (This must take three parameters: The <STECore> instance, an associative array of parameters, and a function representing the tags content(This expects the <STECore> instance as its only parameter and returns its text result, i.e to get the text, you neeed to call this function with the <STECore> instance as a parameter)).
	 * 
	 * Throws:
	 * 	An Exception if the tag could not be registered (if $callback is not callable or if $name is empty)
	 */
	public function register_tag($name, $callback) {
		if(!is_callable($callback)) {
			throw new \Exception("Can not register tag \"$name\", not callable.");
		}
		if(empty($name)) {
			throw new \Exception("Can not register tag, empty name.");
		}
		$this->tags[$name] = $callback;
	}
	
	/*
	 * Function: call_tag
	 * Calling a custom tag (builtin ones can not be called)
	 * 
	 * Parameters:
	 * 	$name - The Tag's name
	 * 	$params - Associative array of parameters
	 * 	$sub - A callable function (expecting an <STECore> instance as it's parameter) that represents the tag's content.
	 * 
	 * Throws:
	 * 	Might throw a <FatalRuntimeError> (see <$fatal_error_on_missing_tag>.
	 * 
	 * Returns:
	 * 	The output of the tag or, if a <RuntimeError> was thrown, the appropiate result (see <$mute_runtime_errors>).
	 */
	public function call_tag($name, $params, $sub) {
		try {
			if(!isset($this->tags[$name])) {
				if($this->fatal_error_on_missing_tag) {
					throw new FatalRuntimeError("Can not call tag \"$name\": Does not exist.");
				} else {
					throw new RuntimeError("Can not call tag \"$name\": Does not exist.");
				}
			}
			return call_user_func($this->tags[$name], $this, $params, $sub);
		} catch(RuntimeError $e) {
			if(!$this->mute_runtime_errors) {
				return "RuntimeError occurred on tag '$name': " . $e->getMessage();
			}
		}
	}
	
	public function calc($expression) {
		return calc_rpn(shunting_yard($expression));
	}
	
	/*
	 * Function: exectemplate
	 * Executes a template and returns the result. The huge difference to <load> is that this function will also output all blocks.
	 * 
	 * Parameters:
	 * 	$tpl - The name of the template to execute.
	 * 
	 * Throws:
	 * 	* A <CantLoadTemplate> exception if the template could not be loaded.
	 * 	* A <ParseCompileError> if the template could not be parsed or transcompiled.
	 * 	* A <FatalRuntimeError> if a tag threw it or if a tag was not found and <$fatal_error_on_missing_tag> is true.
	 * 	* Might also throw different exceptions, if a external tag threw it (but they should use <RuntimeError> or <FatalRuntimeError> to make it possible for STE to handle them correctly).
	 * 
	 * Returns:
	 * 	The output of the template.
	 */
	public function exectemplate($tpl) {
		$output = "";
		$lastblock = $this->load($tpl);
		
		foreach($this->blockorder as $blockname) {
			$output .= $this->blocks[$blockname];
		}
		
		return $output . $lastblock;
	}
	
	/*
	 * Function: get_var_reference
	 * Get a reference to a template variable using a variable name.
	 * This can be used,if your custom tag takes a variable name as a parameter.
	 * 
	 * Parameters:
	 * 	$name - The variables name.
	 * 	$create_if_not_exist - Should the variable be created, if it does not exist? Otherwise NULL will be returned, if the variable does not exist.
	 * 
	 * Throws:
	 * 	<RuntimeError> if the variable name can not be parsed (e.g. unbalanced brackets).
	 * 
	 * Returns:
	 * 	A Reference to the variable.
	 */
	
	public function &get_var_reference($name, $create_if_not_exist) {
		$ref = &$this->_get_var_reference($this->vars, $name, $create_if_not_exist);
		return $ref;
	}
	
	private function &_get_var_reference(&$from, $name, $create_if_not_exist) {
		$bracket_open = strpos($name, "[");
		if($bracket_open === false) {
			if(isset($from[$name]) or $create_if_not_exist) {
				$ref = &$from[$name];
				return $ref;
			} else {
				return NULL;
			}
		} else {
			$old_varname = $varname;
			$bracket_close = strpos($name, "]", $bracket_open);
			if($bracket_close === false) {
				throw new RuntimeError("Invalid varname \"$varname\". Missing closing \"]\".");
			}
			$varname = substr($name, 0, $bracket_open);
			$name    = substr($name, $bracket_open + 1, $bracket_close - $bracket_open - 1) . substr($name, $bracket_close + 1);
			if(!is_array($from[$varname])) {
				if($create_if_not_exist) {
					$from[$varname] = array();
				} else {
					return NULL;
				}
			}
			try {
				$ref = &$this->_get_var_reference($from[$varname], $name, $create_if_not_exist);
				return $ref;
			} catch(Exception $e) {
				throw new RuntimeError("Invalid varname \"$old_varname\". Missing closing \"]\".");
			}
		}
	}
	
	/*
	 * Function: set_var_by_name
	 * Set a template variable by its name.
	 * This can be used,if your custom tag takes a variable name as a parameter.
	 * 
	 * Parameters:
	 * 	$name - The variables name.
	 * 	$val - The new value.
	 * 
	 * Throws:
	 * 	<RuntimeError> if the variable name can not be parsed (e.g. unbalanced brackets).
	 */
	public function set_var_by_name($name, $val) {
		$ref = &$this->_get_var_reference($this->vars, $name, true);
		$ref = $val;
	}
	
	/*
	 * Function: get_var_by_name
	 * Get a template variable by its name.
	 * This can be used,if your custom tag takes a variable name as a parameter.
	 * 
	 * Parameters:
	 * 	$name - The variables name.
	 * 
	 * Throws:
	 * 	<RuntimeError> if the variable name can not be parsed (e.g. unbalanced brackets).
	 * 
	 * Returns:
	 * 	The variables value.
	 */
	public function get_var_by_name($name) {
		$ref = $this->_get_var_reference($this->vars, $name, false);
		return $ref === NULL ? "" : $ref;
	}
	
	/*
	 * Function: load
	 * Load a template and return its result (blocks not included, use <exectemplate> for this).
	 * 
	 * Parameters:
	 * 	$tpl - The name of the template to be loaded.
	 * 	$quiet - If true, do not output anything and do notmodify the blocks. This can be useful to load custom tags that are programmed in STE T/PL. Default: false.
	 * 
	 * Throws:
	 * 	* A <CantLoadTemplate> exception if the template could not be loaded.
	 * 	* A <ParseCompileError> if the template could not be parsed or transcompiled.
	 * 	* A <FatalRuntimeError> if a tag threw it or if a tag was not found and <$fatal_error_on_missing_tag> is true.
	 * 	* Might also throw different exceptions, if a external tag threw it (but they should use <RuntimeError> or <FatalRuntimeError> to make it possible for STE to handle them correctly).
	 * 
	 * Returns:
	 * 	The result of the template (if $quiet == false).
	 */
	public function load($tpl, $quiet = false) {
		$tpldir_b4 = $this->cur_tpl_dir;
		
		/* Resolve ".", ".." and protect from possible LFI */
		$tpl = str_replace("\\", "/", $tpl);
		if($tpl[0] != "/") {
			$tpl = $this->cur_tpl_dir . "/" . $tpl;
		}
		$pathex = array_filter(explode("/", $tpl), function($s) { return ($s != ".") and (!empty($s)); });
		$pathex = array_merge($pathex);
		while(($i = array_search("..", $pathex)) !== false) {
			if($i == 0) {
				$pathex = array_slice($pathex, 1);
			} else {
				$pathex = array_merge(array_slice($pathex, 0, $i), array_slice($pathex, $i + 2));
			}
		}
		$tpl = implode("/", $pathex);
		$this->cur_tpl_dir = dirname($tpl);
		
		if($quiet) {
			$blocks_back     = clone $this->blocks;
			$blockorder_back = clone $this->blockorder;
		}
		
		$mode = MODE_TRANSCOMPILED;
		$content = $this->storage_access->load($tpl, $mode);
		if($mode == MODE_SOURCE) {
			try {
				$ast     = Parser::parse($content, $tpl);
				$transc  = transcompile($ast);
			} catch(ParseCompileError $e) {
				$e->rewrite($content);
				throw $e;
			}
			$this->storage_access->save($tpl, $transc, MODE_TRANSCOMPILED);
			eval("\$content = $transc;");
		}
		
		$output = $content($this);
		
		$this->cur_tpl_dir = $tpldir_b4;
		
		if($quiet) {
			$this->blocks     = $blocks_back;
			$this->blockorder = $blockorder_back;
		} else {
			return $output;
		}
	}
	
	/*
	 * Function: evalbool
	 * Test, if a text represents false (an empty / only whitespace text) or true (everything else).
	 * 
	 * Parameters:
	 * 	$txt - The text to test.
	 * 
	 * Returns:
	 * 	true/false.
	 */
	public function evalbool($txt) {
		return trim($txt . "") != "";
	}
}

class STEStandardLibrary {
	static public function _register_lib($ste) {
		foreach(get_class_methods(__CLASS__) as $method) {
			if($method[0] != "_") {
				$ste->register_tag($method, array(__CLASS__, $method));
			}
		}
	}
	
	static public function escape($ste, $params, $sub) {
		if($ste->evalbool($params["lines"])) {
			return nl2br(htmlspecialchars(str_replace("\r\n", "\n", $sub($ste))));
		} else {
			return htmlspecialchars($sub($ste));
		}
	}
	
	static public function strlen($ste, $params, $sub) {
		return strlen($sub($ste));
	}
	
	static public function arraylen($ste, $params, $sub) {
		if(empty($params["array"])) {
			throw new RuntimeError("Missing array parameter in <ste:arraylen>.");
		}
		$a = $ste->get_var_by_name($params["array"], false);
		return (is_array($a)) ? count($a) : "";
	}
	
	static public function inc($ste, $params, $sub) {
		if(empty($params["var"])) {
			throw new RuntimeError("Missing var parameter in <ste:inc>.");
		}
		$ref = &$ste->get_var_reference($params["var"], true);
		$ref++;
	}
	
	static public function dec($ste, $params, $sub) {
		if(empty($params["var"])) {
			throw new RuntimeError("Missing var parameter in <ste:dec>.");
		}
		$ref = &$ste->get_var_reference($params["var"], true);
		$ref--;
	}
	
	static public function date($ste, $params, $sub) {
		return @strftime($sub($ste), empty($params["timestamp"]) ? @time() : (int) $params["timestamp"]);
	}
	
	static public function in_array($ste, $params, $sub) {
		if(empty($params["array"])) {
			throw new RuntimeError("Missing array parameter in <ste:in_array>.");
		}
		$ar = &$ste->get_var_reference($params["array"], false);
		if(!is_array($ar)) {
			return "";
		}
		return in_array($sub($ste), $ar) ? "y" : "";
	}
	
	static public function join($ste, $params, $sub) {
		if(empty($params["array"])) {
			throw new RuntimeError("Missing array parameter in <ste:join>.");
		}
		return implode($sub($ste), $ste->get_var_by_name($params["array"]));
	}
	
	static public function split($ste, $params, $sub) {
		if(empty($params["array"])) {
			throw new RuntimeError("Missing array parameter in <ste:split>.");
		}
		if(empty($params["delim"])) {
			throw new RuntimeError("Missing delim parameter in <ste:split>.");
		}
		$ste->set_var_by_name($params["array"], explode($params["delim"], $sub($ste)));
	}
	
	static public function array_add($ste, $params, $sub) {
		if(empty($params["array"])) {
			throw new RuntimeError("Missing array parameter in <ste:array_add>.");
		}
		
		$ar = &$ste->get_var_reference($params["array"], true);
		if(empty($params["key"])) {
			$ar[] = $sub($ste);
		} else {
			$ar[$params["key"]] = $sub($ste);
		}
	}
	
	static public function array_filter($ste, $params, $sub)
	{
		if(empty($params["array"])) {
			throw new RuntimeError("Missing array parameter in <ste:array_filter>.");
		}
		
		$ar = $ste->get_var_by_name($params["array"]);
		if(!is_array($ar)) {
			throw new RuntimeError("Variable at 'array' is not an array.");
		}
		
		$keys = array_keys($ar);
		
		if(!empty($params["keep_by_keys"])) {
			$keep_by_keys = &$ste->get_var_reference($params["keep_by_keys"], false);
			if(!is_array($keep_by_keys)) {
				throw new RuntimeError("Variable at 'keep_by_keys' is not an array.");
			}
			$delkeys = array_filter($keys, function($k) use ($keep_by_keys) { return !in_array($k, $keep_by_keys); });
			foreach($delkeys as $dk) {
				unset($ar[$dk]);
			}
			$keys = array_keys($ar);
		}
		if(!empty($params["keep_by_values"])) {
			$keep_by_values = &$ste->get_var_reference($params["keep_by_values"], false);
			if(!is_array($keep_by_values)) {
				throw new RuntimeError("Variable at 'keep_by_values' is not an array.");
			}
			$ar = array_filter($ar, function($v) use ($keep_by_values) { return in_array($v, $keep_by_values); });
			$keys = array_keys($ar);
		}
		if(!empty($params["delete_by_keys"])) {
			$delete_by_keys = &$ste->get_var_reference($params["delete_by_keys"], false);
			if(!is_array($delete_by_keys)) {
				throw new RuntimeError("Variable at 'delete_by_keys' is not an array.");
			}
			$delkeys = array_filter($keys, function($k) use ($delete_by_keys) { return in_array($k, $delete_by_keys); });
			foreach($delkeys as $dk) {
				unset($ar[$dk]);
			}
			$keys = array_keys($ar);
		}
		if(!empty($params["delete_by_values"])) {
			$delete_by_values = &$ste->get_var_reference($params["delete_by_values"], false);
			if(!is_array($delete_by_values)) {
				throw new RuntimeError("Variable at 'delete_by_values' is not an array.");
			}
			$ar = array_filter($ar, function($v) use ($delete_by_values) { return !in_array($v, $delete_by_values); });
			$keys = array_keys($ar);
		}
		
		$ste->set_var_by_name($params["array"], $ar);
	}
}

?>