//.CommonJS
var CSSOM = {
	CSSValue: require('./CSSValue').CSSValue
};
///CommonJS


/**
 * @constructor
 * @see http://msdn.microsoft.com/en-us/library/ms537634(v=vs.85).aspx
 *
 */
CSSOM.CSSValueExpression = function CSSValueExpression(token, idx) {
	this._token = token;
	this._idx = idx;
};

CSSOM.CSSValueExpression.prototype = new CSSOM.CSSValue();
CSSOM.CSSValueExpression.prototype.constructor = CSSOM.CSSValueExpression;

/**
 * parse css expression() value
 *
 * @return {Object}
 *         - error:
 *         or
 *         - idx:
 *         - expression:
 *
 * Example:
 *
 * .selector {
 *		zoom: expression(documentElement.clientWidth > 1000 ? '1000px' : 'auto');
 * }
 */
CSSOM.CSSValueExpression.prototype.parse = function() {
	var token = this._token,
			idx = this._idx;

	var character = '',
			expression = '',
			error = '',
			info,
			paren = [];


	for (; ; ++idx) {
		character = token.charAt(idx);

		// end of token
		if (character === '') {
			error = 'css expression error: unfinished expression!';
			break;
		}

		switch(character) {
			case '(':
				paren.push(character);
				expression += character;
				break;

			case ')':
				paren.pop(character);
				expression += character;
				break;

			case '/':
				if ((info = this._parseJSComment(token, idx))) { // comment?
					if (info.error) {
						error = 'css expression error: unfinished comment in expression!';
					} else {
						idx = info.idx;
						// ignore the comment
					}
				} else if ((info = this._parseJSRexExp(token, idx))) { // regexp
					idx = info.idx;
					expression += info.text;
				} else { // other
					expression += character;
				}
				break;

			case "'":
			case '"':
				info = this._parseJSString(token, idx, character);
				if (info) { // string
					idx = info.idx;
					expression += info.text;
				} else {
					expression += character;
				}
				break;

			default:
				expression += character;
				break;
		}

		if (error) {
			break;
		}

		// end of expression
		if (paren.length === 0) {
			break;
		}
	}

	var ret;
	if (error) {
		ret = {
			error: error
		};
	} else {
		ret = {
			idx: idx,
			expression: expression
		};
	}

	return ret;
};


/**
 *
 * @return {Object|false}
 *          - idx:
 *          - text:
 *          or
 *          - error:
 *          or
 *          false
 *
 */
CSSOM.CSSValueExpression.prototype._parseJSComment = function(token, idx) {
	var nextChar = token.charAt(idx + 1),
			text;

	if (nextChar === '/' || nextChar === '*') {
		var startIdx = idx,
				endIdx,
				commentEndChar;

		if (nextChar === '/') { // line comment
			commentEndChar = '\n';
		} else if (nextChar === '*') { // block comment
			commentEndChar = '*/';
		}

		endIdx = token.indexOf(commentEndChar, startIdx + 1 + 1);
		if (endIdx !== -1) {
			endIdx = endIdx + commentEndChar.length - 1;
			text = token.substring(idx, endIdx + 1);
			return {
				idx: endIdx,
				text: text
			};
		} else {
			var error = 'css expression error: unfinished comment in expression!';
			return {
				error: error
			};
		}
	} else {
		return false;
	}
};


/**
 *
 * @return {Object|false}
 *					- idx:
 *					- text:
 *					or 
 *					false
 *
 */
CSSOM.CSSValueExpression.prototype._parseJSString = function(token, idx, sep) {
	var endIdx = this._findMatchedIdx(token, idx, sep),
			text;

	if (endIdx === -1) {
		return false;
	} else {
		text = token.substring(idx, endIdx + sep.length);

		return {
			idx: endIdx,
			text: text
		};
	}
};


/**
 * parse regexp in css expression
 *
 * @return {Object|false}
 *				- idx:
 *				- regExp:
 *				or 
 *				false
 */

/*

all legal RegExp
 
/a/
(/a/)
[/a/]
[12, /a/]

!/a/

+/a/
-/a/
* /a/
/ /a/
%/a/

===/a/
!==/a/
==/a/
!=/a/
>/a/
>=/a/
</a/
<=/a/

&/a/
|/a/
^/a/
~/a/
<</a/
>>/a/
>>>/a/

&&/a/
||/a/
?/a/
=/a/
,/a/

		delete /a/
				in /a/
instanceof /a/
				new /a/
		typeof /a/
			void /a/

*/
CSSOM.CSSValueExpression.prototype._parseJSRexExp = function(token, idx) {
	var before = token.substring(0, idx).replace(/\s+$/, ""),
			legalRegx = [
				/^$/,
				/\($/,
				/\[$/,
				/\!$/,
				/\+$/,
				/\-$/,
				/\*$/,
				/\/\s+/,
				/\%$/,
				/\=$/,
				/\>$/,
				/<$/,
				/\&$/,
				/\|$/,
				/\^$/,
				/\~$/,
				/\?$/,
				/\,$/,
				/delete$/,
				/in$/,
				/instanceof$/,
				/new$/,
				/typeof$/,
				/void$/
			];

	var isLegal = legalRegx.some(function(reg) {
		return reg.test(before);
	});

	if (!isLegal) {
		return false;
	} else {
		var sep = '/';

		// same logic as string
		return this._parseJSString(token, idx, sep);
	}
};


/**
 *
 * find next sep(same line) index in `token`
 *
 * @return {Number}
 *
 */
CSSOM.CSSValueExpression.prototype._findMatchedIdx = function(token, idx, sep) {
	var startIdx = idx,
			endIdx;

	var NOT_FOUND = -1;

	while(true) {
		endIdx = token.indexOf(sep, startIdx + 1);

		if (endIdx === -1) { // not found
			endIdx = NOT_FOUND;
			break;
		} else {
			var text = token.substring(idx + 1, endIdx),
					matched = text.match(/\\+$/);
			if (!matched || matched[0] % 2 === 0) { // not escaped
				break;
			} else {
				startIdx = endIdx;
			}
		}
	}

	// boundary must be in the same line(js sting or regexp)
	var nextNewLineIdx = token.indexOf('\n', idx + 1);
	if (nextNewLineIdx < endIdx) {
		endIdx = NOT_FOUND;
	}


	return endIdx;
};




//.CommonJS
exports.CSSValueExpression = CSSOM.CSSValueExpression;
///CommonJS