path: root/src/ste/Parser.php

<?php

// File: Parser.php

// Namespace: kch42\ste
namespace kch42\ste;

/*
 * 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 eof() {
		return ($this->off == $this->len);
	}
	
	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)", $this->name, $off);
		}
		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 = $this->get_name();
		if(!$this->eof()) {
			$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];
			}
		}
	}
}