// Some of the code comes from WebComponents.JS
// https://github.com/webcomponents/webcomponentsjs/blob/master/src/HTMLImports/path.js

import {RegExp, RegExpWrapper, StringWrapper, isPresent} from 'angular2/src/core/facade/lang';
import {UrlResolver} from 'angular2/src/core/services/url_resolver';

/**
 * Rewrites URLs by resolving '@import' and 'url()' URLs from the given base URL,
 * removes and returns the @import urls
 */
export function resolveStyleUrls(resolver: UrlResolver, baseUrl: string, cssText: string):
    StyleWithImports {
  var foundUrls = [];
  cssText = extractUrls(resolver, baseUrl, cssText, foundUrls);
  cssText = replaceUrls(resolver, baseUrl, cssText);
  return new StyleWithImports(cssText, foundUrls);
}

export class StyleWithImports {
  constructor(public style: string, public styleUrls: string[]) {}
}

function extractUrls(resolver: UrlResolver, baseUrl: string, cssText: string, foundUrls: string[]):
    string {
  return StringWrapper.replaceAllMapped(cssText, _cssImportRe, (m) => {
    var url = isPresent(m[1]) ? m[1] : m[2];
    foundUrls.push(resolver.resolve(baseUrl, url));
    return '';
  });
}

function replaceUrls(resolver: UrlResolver, baseUrl: string, cssText: string): string {
  return StringWrapper.replaceAllMapped(cssText, _cssUrlRe, (m) => {
    var pre = m[1];
    var originalUrl = m[2];
    if (RegExpWrapper.test(_dataUrlRe, originalUrl)) {
      // Do not attempt to resolve data: URLs
      return m[0];
    }
    var url = StringWrapper.replaceAll(originalUrl, _quoteRe, '');
    var post = m[3];

    var resolvedUrl = resolver.resolve(baseUrl, url);

    return pre + "'" + resolvedUrl + "'" + post;
  });
}

var _cssUrlRe = /(url\()([^)]*)(\))/g;
var _cssImportRe = /@import\s+(?:url\()?\s*(?:(?:['"]([^'"]*))|([^;\)\s]*))[^;]*;?/g;
var _quoteRe = /['"]/g;
var _dataUrlRe = /^['"]?data:/g;