/*
 * Copyright (c) 2014 The Polymer Project Authors. All rights reserved.
 * This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
 * The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
 * The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
 * Code distributed by Google as part of the polymer project is also
 * subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
 */

(function(scope) {

var urlResolver = {
  resolveDom: function(root, url) {
    url = url || baseUrl(root);
    this.resolveAttributes(root, url);
    this.resolveStyles(root, url);
    // handle template.content
    var templates = root.querySelectorAll('template');
    if (templates) {
      for (var i = 0, l = templates.length, t; (i < l) && (t = templates[i]); i++) {
        if (t.content) {
          this.resolveDom(t.content, url);
        }
      }
    }
  },
  resolveTemplate: function(template) {
    this.resolveDom(template.content, baseUrl(template));
  },
  resolveStyles: function(root, url) {
    var styles = root.querySelectorAll('style');
    if (styles) {
      for (var i = 0, l = styles.length, s; (i < l) && (s = styles[i]); i++) {
        this.resolveStyle(s, url);
      }
    }
  },
  resolveStyle: function(style, url) {
    url = url || baseUrl(style);
    style.textContent = this.resolveCssText(style.textContent, url);
  },
  resolveCssText: function(cssText, baseUrl, keepAbsolute) {
    cssText = replaceUrlsInCssText(cssText, baseUrl, keepAbsolute, CSS_URL_REGEXP);
    return replaceUrlsInCssText(cssText, baseUrl, keepAbsolute, CSS_IMPORT_REGEXP);
  },
  resolveAttributes: function(root, url) {
    if (root.hasAttributes && root.hasAttributes()) {
      this.resolveElementAttributes(root, url);
    }
    // search for attributes that host urls
    var nodes = root && root.querySelectorAll(URL_ATTRS_SELECTOR);
    if (nodes) {
      for (var i = 0, l = nodes.length, n; (i < l) && (n = nodes[i]); i++) {
        this.resolveElementAttributes(n, url);
      }
    }
  },
  resolveElementAttributes: function(node, url) {
    url = url || baseUrl(node);
    URL_ATTRS.forEach(function(v) {
      var attr = node.attributes[v];
      var value = attr && attr.value;
      var replacement;
      if (value && value.search(URL_TEMPLATE_SEARCH) < 0) {
        if (v === 'style') {
          replacement = replaceUrlsInCssText(value, url, false, CSS_URL_REGEXP);
        } else {
          replacement = resolveRelativeUrl(url, value);
        }
        attr.value = replacement;
      }
    });
  }
};

var CSS_URL_REGEXP = /(url\()([^)]*)(\))/g;
var CSS_IMPORT_REGEXP = /(@import[\s]+(?!url\())([^;]*)(;)/g;
var URL_ATTRS = ['href', 'src', 'action', 'style', 'url'];
var URL_ATTRS_SELECTOR = '[' + URL_ATTRS.join('],[') + ']';
var URL_TEMPLATE_SEARCH = '{{.*}}';
var URL_HASH = '#';

function baseUrl(node) {
  var u = new URL(node.ownerDocument.baseURI);
  u.search = '';
  u.hash = '';
  return u;
}

function replaceUrlsInCssText(cssText, baseUrl, keepAbsolute, regexp) {
  return cssText.replace(regexp, function(m, pre, url, post) {
    var urlPath = url.replace(/["']/g, '');
    urlPath = resolveRelativeUrl(baseUrl, urlPath, keepAbsolute);
    return pre + '\'' + urlPath + '\'' + post;
  });
}

function resolveRelativeUrl(baseUrl, url, keepAbsolute) {
  // do not resolve '/' absolute urls
  if (url && url[0] === '/') {
    return url;
  }
  var u = new URL(url, baseUrl);
  return keepAbsolute ? u.href : makeDocumentRelPath(u.href);
}

function makeDocumentRelPath(url) {
  var root = baseUrl(document.documentElement);
  var u = new URL(url, root);
  if (u.host === root.host && u.port === root.port &&
      u.protocol === root.protocol) {
    return makeRelPath(root, u);
  } else {
    return url;
  }
}

// make a relative path from source to target
function makeRelPath(sourceUrl, targetUrl) {
  var source = sourceUrl.pathname;
  var target = targetUrl.pathname;
  var s = source.split('/');
  var t = target.split('/');
  while (s.length && s[0] === t[0]){
    s.shift();
    t.shift();
  }
  for (var i = 0, l = s.length - 1; i < l; i++) {
    t.unshift('..');
  }
  // empty '#' is discarded but we need to preserve it.
  var hash = (targetUrl.href.slice(-1) === URL_HASH) ? URL_HASH : targetUrl.hash;
  return t.join('/') + targetUrl.search + hash;
}

// exports
scope.urlResolver = urlResolver;

})(Polymer);