package es.xperiments.utils 
{
	import r1.deval.D;	
	
	/**
	 * @author xperiments
	 */
	public class PureASTemplate 
	{
		private static var tplMap : Array = new Array();
		private static var left : String = "<#";
		private static var right : String = "#>";
		//Delimiters can have regex special characters in them; the following two variables will hold escaped versions of them
		private static var escapedLeft : String = "<#";
		private static var escapedRight : String = "#>";
		private static var escapeRegex : RegExp = new RegExp( '(\\' + [ '$', '^', '?', '/', '.', '*', '+', '?', '|', '(', ')', '[', ']', '{', '}', '\\' ].join( '|\\' ) + ')', 'g' );
		private static var replaceLeft : RegExp = new RegExp( "<#", "g" );
		private static var regexLeftRight : RegExp = new RegExp( "<#" + "|" + "#>", "g" );
		private static var replaceSingleQuote : RegExp = new RegExp( "'", "g" );
		private static var replaceLineBreak : RegExp = new RegExp( "\\r|\\n", "g" );
		
		public static function parseTemplate( id : String, tpl : String, data : Object ):String
		{
			var unreplaceLineBreak : RegExp = new RegExp( "{lineBreak}", "g" );
			var tplID : String = id;
			var tplObj : Object = tplMap[tplID];
			if (!tplObj)
			{
				var leftjs : String = String.fromCharCode( 21 );
				var leftjsout : String = leftjs + "=";
				tpl = tpl.replace( replaceLeft, left + leftjs );
				var tplSplit : Array = tpl.split( regexLeftRight );
				var js:String = "function "+id+"( data ) { ";
					js += "var output=''; var ld='" + left + "'; var rd='" + right + "'; ";
				for (var i : uint = 0; i < tplSplit.length ; i++)
				{
					var line : String = tplSplit[i];
					if (PureASTemplate.stringStartsWith( line, leftjsout ))
					{
						js += " output+=" + line.substring( leftjsout.length ) + "; ";
					}
					else if (PureASTemplate.stringStartsWith( line, leftjs ))
					{
						js += " " + line.substring( leftjs.length ) + " ";
					}
					else
					{
						js += " output+='" + line.replace( replaceSingleQuote, "\\'" ).replace( replaceLineBreak, '{lineBreak}' ) + "'; ";
					}
				}
				js += " return output; }";
				tplObj = D.parseFunctions( js );
				tplMap[tplID] = tplObj;
			}
			return D.evalToString( id+'( data )', { data:data }, tplObj ).replace( unreplaceLineBreak, '\n' );
		}	

		public static function setDelimiters(l : String, r : String) : void
		{
			if (l != r)
			{
				left = l;
				escapedLeft = left.replace( escapeRegex, '\\$1' );
				replaceLeft = new RegExp( escapedLeft, "g" );

				right = r;
				escapedRight = right.replace( escapeRegex, '\\$1' );

				regexLeftRight = new RegExp( escapedLeft + "|" + escapedRight, "g" );
			}
		}

		private static function stringStartsWith(str : String, startsWith : String):Boolean
		{
			return str.substring( 0, startsWith.length ) == startsWith;
		}					
	}
}