/*
 * css.normalize.js
 *
 * CSS Normalization
 *
 * CSS paths are normalized based on an optional basePath and the RequireJS config
 *
 * Usage:
 *   normalize(css, fromBasePath, toBasePath);
 *
 * css: the stylesheet content to normalize
 * fromBasePath: the absolute base path of the css relative to any root (but without ../ backtracking)
 * toBasePath: the absolute new base path of the css relative to the same root
 * 
 * Absolute dependencies are left untouched.
 *
 * Urls in the CSS are picked up by regular expressions.
 * These will catch all statements of the form:
 *
 * url(*)
 * url('*')
 * url("*")
 * 
 * @import '*'
 * @import "*"
 *
 * (and so also @import url(*) variations)
 *
 * For urls needing normalization
 *
 */

define(function () {

	// regular expression for removing double slashes
	// eg http://www.example.com//my///url/here -> http://www.example.com/my/url/here
	var slashes = /([^:])\/+/g
	var removeDoubleSlashes = function (uri) {
		return uri.replace(slashes, '$1/');
	}

	// given a relative URI, and two absolute base URIs, convert it from one base to another
	var protocolRegEx = /[^\:\/]*:\/\/([^\/])*/;
	var absUrlRegEx = /^(\/|data:)/;

	function convertURIBase(uri, fromBase, toBase) {
		if (uri.match(absUrlRegEx) || uri.match(protocolRegEx))
			return uri;
		uri = removeDoubleSlashes(uri);
		// if toBase specifies a protocol path, ensure this is the same protocol as fromBase, if not
		// use absolute path at fromBase
		var toBaseProtocol = toBase.match(protocolRegEx);
		var fromBaseProtocol = fromBase.match(protocolRegEx);
		if (fromBaseProtocol && (!toBaseProtocol || toBaseProtocol[1] != fromBaseProtocol[1] || toBaseProtocol[2] != fromBaseProtocol[2]))
			return absoluteURI(uri, fromBase);

		else {
			return relativeURI(absoluteURI(uri, fromBase), toBase);
		}
	};

	// given a relative URI, calculate the absolute URI
	function absoluteURI(uri, base) {
		if (uri.substr(0, 2) == './')
			uri = uri.substr(2);

		// absolute urls are left in tact
		if (uri.match(absUrlRegEx) || uri.match(protocolRegEx))
			return uri;

		var baseParts = base.split('/');
		var uriParts = uri.split('/');

		baseParts.pop();

		while (curPart = uriParts.shift())
			if (curPart == '..')
				baseParts.pop();
			else
				baseParts.push(curPart);

		return baseParts.join('/');
	};


	// given an absolute URI, calculate the relative URI
	function relativeURI(uri, base) {

		// reduce base and uri strings to just their difference string
		var baseParts = base.split('/');
		baseParts.pop();
		base = baseParts.join('/') + '/';
		i = 0;
		while (base.substr(i, 1) == uri.substr(i, 1))
			i++;
		while (base.substr(i, 1) != '/')
			i--;
		base = base.substr(i + 1);
		uri = uri.substr(i + 1);

		// each base folder difference is thus a backtrack
		baseParts = base.split('/');
		var uriParts = uri.split('/');
		out = '';
		while (baseParts.shift())
			out += '../';

		// finally add uri parts
		while (curPart = uriParts.shift())
			out += curPart + '/';

		return out.substr(0, out.length - 1);
	};

	var normalizeCSS = function (source, fromBase, toBase) {

		fromBase = removeDoubleSlashes(fromBase);
		toBase = removeDoubleSlashes(toBase);

		var urlRegEx = /@import\s*("([^"]*)"|'([^']*)')|url\s*\(\s*(\s*"([^"]*)"|'([^']*)'|[^\)]*\s*)\s*\)/ig;
		var result, url, source;

		while (result = urlRegEx.exec(source)) {
			url = result[3] || result[2] || result[5] || result[6] || result[4];
			var newUrl;
			newUrl = convertURIBase(url, fromBase, toBase);
			var quoteLen = result[5] || result[6] ? 1 : 0;
			source = source.substr(0, urlRegEx.lastIndex - url.length - quoteLen - 1) + newUrl + source.substr(urlRegEx.lastIndex - quoteLen - 1);
			urlRegEx.lastIndex = urlRegEx.lastIndex + (newUrl.length - url.length);
		}

		return source;
	};

	normalizeCSS.convertURIBase = convertURIBase;
	normalizeCSS.absoluteURI = absoluteURI;
	normalizeCSS.relativeURI = relativeURI;

	return normalizeCSS;
});