const { classes: Cc, interfaces: Ci, utils: Cu } = Components;

const THUMBNAIL_DIRECTORY = "thumbnails";

Cu.import("resource://gre/modules/XPCOMUtils.jsm", this);
Cu.import("resource://gre/modules/osfile.jsm", this);

XPCOMUtils.defineLazyGetter(this, "gCryptoHash", function() {
  return Cc["@mozilla.org/security/hash;1"].createInstance(Ci.nsICryptoHash);
});

XPCOMUtils.defineLazyGetter(this, "gUnicodeConverter", function() {
  let converter = Cc["@mozilla.org/intl/scriptableunicodeconverter"]
                    .createInstance(Ci.nsIScriptableUnicodeConverter);
  converter.charset = "utf8";
  return converter;
});
function PageThumbsStorageService() {}

PageThumbsStorageService.prototype = {
    classID: Components.ID("{97943eec-0e48-49ef-b7b7-cf4aa0109bb6}"),
    QueryInterface: XPCOMUtils.generateQI([Ci.nsIPageThumbsStorageService]),
    _xpcom_categories: [{
      service: true
    }],
    // The path for the storage
    _path: null,
    get path() {
      if (!this._path) {
        this._path = OS.Path.join(OS.Constants.Path.localProfileDir, THUMBNAIL_DIRECTORY);
      }
      return this._path;
    },

    getLeafNameForURL(aURL) {
      if (typeof aURL != "string") {
        throw new TypeError("Expecting a string");
      }
      let hash = this._calculateMD5Hash(aURL);
      return hash + ".png";
    },

    getFilePathForURL(aURL) {
      return OS.Path.join(this.path, this.getLeafNameForURL(aURL));
    },

    _calculateMD5Hash(aValue) {
      let hash = gCryptoHash;
      let value = gUnicodeConverter.convertToByteArray(aValue);

      hash.init(hash.MD5);
      hash.update(value, value.length);
      return this._convertToHexString(hash.finish(false));
    },

    _convertToHexString(aData) {
      let hex = "";
      for (let i = 0; i < aData.length; i++)
        hex += ("0" + aData.charCodeAt(i).toString(16)).slice(-2);
      return hex;
    },

};

this.NSGetFactory = XPCOMUtils.generateNSGetFactory([PageThumbsStorageService]);
