/* global Promise */
;(function (exports) {
  'use strict';

  var OAUTH3 = exports.OAUTH3 = {
    clientUri: function (location) {
      return OAUTH3.uri.normalize(location.host + location.pathname);
    }
  , error: {
      parse: function (providerUri, params) {
        var err = new Error(params.error_description || params.error.message || "Unknown error with provider '" + providerUri + "'");
        err.uri = params.error_uri || params.error.uri;
        err.code = params.error.code || params.error;
        return err;
      }
    }
  , _base64: {
      atob: function (base64) {
        // atob must be called from the global context
        // http://stackoverflow.com/questions/9677985/uncaught-typeerror-illegal-invocation-in-chrome
        return (exports.atob || require('atob'))(base64);
      }
    , btoa: function (b64) {
        // for directive passing in .well-known/oauth3
        // http://stackoverflow.com/questions/9677985/uncaught-typeerror-illegal-invocation-in-chrome
        return (exports.btoa || require('btoa'))(b64);
      }
    , decodeUrlSafe: function (b64) {
        // URL-safe Base64 to Base64
        // https://en.wikipedia.org/wiki/Base64
        // https://gist.github.com/catwell/3046205
        var mod = b64.length % 4;
        if (2 === mod) { b64 += '=='; }
        if (3 === mod) { b64 += '='; }
        b64 = b64.replace(/-/g, '+').replace(/_/g, '/');
        return OAUTH3._base64.atob(b64);
      }
    , encodeUrlSafe: function (b64) {
        // for directive passing in .well-known/oauth3
        // Base64 to URL-safe Base64
        b64 = OAUTH3._base64.btoa(b64);
        b64 = b64.replace(/\+/g, '-').replace(/\//g, '_');
        b64 = b64.replace(/=+/g, '');
        return b64;
      }
    }
  , uri: {
      normalize: function (uri) {
        if ('string' !== typeof uri) {
          console.error((new Error('stack')).stack);
        }
        // tested with
        //   example.com
        //   example.com/
        //   http://example.com
        //   https://example.com/
        return uri
          .replace(/^(https?:\/\/)?/i, '')
          .replace(/\/?$/, '')
          ;
      }
    }
  , url: {
      normalize: function (url) {
        if ('string' !== typeof url) {
          console.error((new Error('stack')).stack);
        }
        // tested with
        //   example.com
        //   example.com/
        //   http://example.com
        //   https://example.com/
        return url
          .replace(/^(https?:\/\/)?/i, 'https://')
          .replace(/\/?$/, '')
          ;
      }
    , resolve: function (base, next) {
        if (/^https:\/\//i.test(next)) {
          return next;
        }
        return this.normalize(base) + '/' + this._normalizePath(next);
      }
    , _normalizePath: function (path) {
        return path.replace(/^\//, '').replace(/\/$/, '');
      }
    }
  , query: {
      parse: function (search) {
        // needed for .well-known/oauth3
        // parse a query or a hash
        if (-1 !== ['#', '?'].indexOf(search[0])) {
          search = search.substring(1);
        }
        // Solve for case of search within hash
        // example: #/authorization_dialog/?state=...&redirect_uri=...
        var queryIndex = search.indexOf('?');
        if (-1 !== queryIndex) {
          search = search.substr(queryIndex + 1);
        }

        var args = search.split('&');
        var argsParsed = {};
        var i, arg, kvp, key, value;

        for (i = 0; i < args.length; i += 1) {
          arg = args[i];
          if (-1 === arg.indexOf('=')) {
            argsParsed[decodeURIComponent(arg).trim()] = true;
          }
          else {
            kvp = arg.split('=');
            key = decodeURIComponent(kvp[0]).trim();
            value = decodeURIComponent(kvp[1]).trim();
            argsParsed[key] = value;
          }
        }
        return argsParsed;
      }
    , stringify: function (params) {
        var qs = [];

        Object.keys(params).forEach(function (key) {
          // TODO nullify instead?
          if ('undefined' === typeof params[key]) {
            return;
          }

          if ('scope' === key) {
            params[key] = OAUTH3.scope.stringify(params[key]);
          }

          qs.push(encodeURIComponent(key) + '=' + encodeURIComponent(params[key]));
        });

        return qs.join('&');
      }
    }
  , scope: {
      stringify: function (scope) {
        if (Array.isArray(scope)) {
          scope = scope.join(' ');
        }
        return scope;
      }
    }
  , randomState: function () {
      // TODO put in different file for browser vs node
      try {
        return Array.prototype.slice.call(
          window.crypto.getRandomValues(new Uint8Array(16))
        ).map(function (ch) { return (ch).toString(16); }).join('');
      } catch(e) {
        return OAUTH3.utils._insecureRandomState();
      }
    }
  , _insecureRandomState: function () {
      var i;
      var ch;
      var str;
      // TODO use fisher-yates on 0..255 and select [0] 16 times
      // [security] https://medium.com/@betable/tifu-by-using-math-random-f1c308c4fd9d#.5qx0bf95a
      // https://github.com/v8/v8/blob/b0e4dce6091a8777bda80d962df76525dc6c5ea9/src/js/math.js#L135-L144
      // Note: newer versions of v8 do not have this bug, but other engines may still
      console.warn('[security] crypto.getRandomValues() failed, falling back to Math.random()');
      str = '';
      for (i = 0; i < 32; i += 1) {
        ch = Math.round(Math.random() * 255).toString(16);
        if (ch.length < 2) { ch = '0' + ch; }
        str += ch;
      }
      return str;
    }
  , jwt: {
      // decode only (no verification)
      decode: function (str) {

        // 'abc.qrs.xyz'
        // [ 'abc', 'qrs', 'xyz' ]
        // [ {}, {}, 'foo' ]
        // { header: {}, payload: {}, signature: '' }
        var parts = str.split(/\./g);
        var jsons = parts.slice(0, 2).map(function (urlsafe64) {
          var b64 = OAUTH3._base64.decodeUrlSafe(urlsafe64);
          return b64;
        });

        return {
          header: JSON.parse(jsons[0])
        , payload: JSON.parse(jsons[1])
        , signature: parts[2] // should remain url-safe base64
        };
      }
    , freshness: function (tokenMeta, staletime, _now) {
        staletime = staletime || (15 * 60);
        var now = _now || Date.now();
        var fresh = ((parseInt(tokenMeta.exp, 10) || 0) - Math.round(now / 1000));

        if (fresh >= staletime) {
          return 'fresh';
        }

        if (fresh <= 0) {
          return 'expired';
        }

        return 'stale';
      }
    }
  , urls: {
      discover: function (providerUri, opts) {
        if (!providerUri) {
          throw new Error("cannot discover without providerUri");
        }
        if (!opts.client_id) {
          throw new Error("cannot discover without options.client_id");
        }
        var clientId = OAUTH3.url.normalize(opts.client_id || opts.client_uri);
        providerUri = OAUTH3.url.normalize(providerUri);

        var params = {
          action: 'directives'
        , state: opts.state || OAUTH3.utils.randomState()
        , redirect_uri: clientId + (opts.client_callback_path || '/.well-known/oauth3/callback.html#/')
        , response_type: 'rpc'
        , _method: 'GET'
        , _pathname: '.well-known/oauth3/directives.json'
        , debug: opts.debug || undefined
        };

        var result = {
          url: providerUri + '/.well-known/oauth3/#/?' + OAUTH3.query.stringify(params)
        , state: params.state
        , method: 'GET'
        , query: params
        };

        return result;
      }
    , implicitGrant: function (directive, opts) {
        //
        // Example Implicit Grant Request
        // (for generating a browser-only session, not a session on your server)
        //
        // GET https://example.com/api/org.oauth3.provider/authorization_dialog
        //  ?response_type=token
        //  &scope=`encodeURIComponent('profile.login profile.email')`
        //  &state=`cryptoutil.random().toString('hex')`
        //  &client_id=xxxxxxxxxxx
        //  &redirect_uri=`encodeURIComponent('https://myapp.com/oauth3.html')`
        //
        // NOTE: `redirect_uri` itself may also contain URI-encoded components
        //

        opts = opts || {};
        var type = 'authorization_dialog';
        var responseType = 'token';

        var scope = opts.scope || directive.authn_scope;
        var args = directive[type];
        var uri = args.url;
        var state = opts.state || OAUTH3.utils.randomState();
        var params = {
          debug: opts.debug || undefined
        , client_uri: opts.client_uri || opts.clientUri || undefined
        , client_id: opts.client_id || opts.client_uri || undefined
        , state: state
        };
        var result;

        params.response_type = responseType;
        if (scope) {
          params.scope = OAUTH3.scope.stringify(scope);
        }
        if (!opts.redirect_uri) {
          // TODO consider making this optional
          //console.warn("auto-generating redirect_uri from hard-coded callback.html"
          //  + " (should be configurable... but then redirect_uri could just be manually-generated)");
          opts.redirect_uri = OAUTH3.url.resolve(
            OAUTH3.url.normalize(params.client_uri)
          , '.well-known/oauth3/callback.html'
          );
        }
        params.redirect_uri = opts.redirect_uri;

        uri += '?' + OAUTH3.query.stringify(params);

        result = {
          url: uri
        , state: state
        , method: args.method
        , query: params
        };

        return result;
      }
    , refreshToken: function (directive, opts) {
        // grant_type=refresh_token

        // Example Refresh Token Request
        // (generally for 1st or 3rd party server-side, mobile, and desktop apps)
        //
        // POST https://example.com/api/oauth3/access_token
        //    { "grant_type": "refresh_token", "client_id": "<<id>>", "scope": "<<scope>>"
        //    , "username": "<<username>>", "password": "password" }
        //
        opts = opts || {};
        var type = 'access_token';
        var grantType = 'refresh_token';

        var scope = opts.scope || directive.authn_scope;
        var clientSecret = opts.client_secret;
        var args = directive[type];
        var params = {
          "grant_type": grantType
        , "refresh_token": opts.refresh_token || (opts.session && opts.session.refresh_token)
        , "response_type": 'token'
        , "client_id": opts.client_id || opts.client_uri
        , "client_uri": opts.client_uri
        //, "scope": undefined
        //, "client_secret": undefined
        , debug: opts.debug || undefined
        };
        var uri = args.url;
        var body;

        if (clientSecret) {
          // TODO not allowed in the browser
          console.warn("if this is a browser, you must not use client_secret");
          params.client_secret = clientSecret;
        }

        if (scope) {
          params.scope = OAUTH3.scope.stringify(scope);
        }

        if ('GET' === args.method.toUpperCase()) {
          uri += '?' + OAUTH3.query.stringify(params);
        } else {
          body = params;
        }

        return {
          url: uri
        , method: args.method
        , data: body
        };
      }
    , logout: function (directive, opts) {
        // action=logout

        // Example Logout Request
        // (generally for 1st or 3rd party server-side, mobile, and desktop apps)
        //
        // GET https://example.com/#/logout/
        //    ?client_id=<<id>>
        //    &access_token=<<token>>
        //    &sub=<<ppid>>
        //
        // Note that the use of # keeps certain parameters from traveling across
        // the network at all (and we use https anyway)
        //
        opts = opts || {};
        var action = 'logout';
        var args = directive[action];
        var state = opts.state || OAUTH3.utils.randomState();
        var params = {
          action: action
        //, response_type: 'confirmation'
        , client_id: opts.client_id || opts.client_uri
        , client_uri: opts.client_uri || opts.client_id
        , state: state
        , redirect_uri: opts.redirect_uri = OAUTH3.url.resolve(
            OAUTH3.url.normalize(opts.client_uri || opts.client_id)
          , '.well-known/oauth3/callback.html'
          )
        , debug: opts.debug
        };
        var uri = args.url;
        var body;

        if ('GET' === args.method.toUpperCase()) {
          uri += '?' + OAUTH3.query.stringify(params);
        } else {
          body = params;
        }

        return {
          url: OAUTH3.url.resolve(directive.issuer, uri)
        , method: args.method
        , state: state
        , data: body
        };
      }
    }
  , hooks: {
      directives: {
        get: function (providerUri) {
          providerUri = OAUTH3.uri.normalize(providerUri);
          return OAUTH3.PromiseA.resolve(OAUTH3.hooks.directives._getCached(providerUri)
            || OAUTH3.hooks.directives._get(providerUri))
            .then(function (directives) {
              // or do .then(this._set) to keep DRY?
            OAUTH3.hooks.directives._cache[providerUri] = directives;
            return directives;
          });
        }
      , _getCached: function (providerUri) {
          providerUri = OAUTH3.uri.normalize(providerUri);
          if (!OAUTH3.hooks.directives._cache) { OAUTH3.hooks.directives._cache = {}; }
          return OAUTH3.hooks.directives._cache[providerUri];
        }
      , set: function (providerUri, directives) {
          providerUri = OAUTH3.uri.normalize(providerUri);
          if (!OAUTH3.hooks.directives._cache) { OAUTH3.hooks.directives._cache = {}; }
          OAUTH3.hooks.directives._cache[providerUri] = directives;
          return OAUTH3.PromiseA.resolve(OAUTH3.hooks.directives._set(providerUri, directives));
        }
      , _get: function (providerUri) {
          console.warn('[Warn] Please implement OAUTH3.hooks.directives._get = function (providerUri) { return PromiseA<directives>; }');
          return JSON.parse(window.localStorage.getItem('directives-' + providerUri) || '{}');
        }
      , _set: function (providerUri, directives) {
          console.warn('[Warn] Please implement OAUTH3.hooks.directives._set = function (providerUri, directives) { return PromiseA<directives>; }');
          window.localStorage.setItem('directives-' + providerUri, JSON.stringify(directives));
          return directives;
        }
      }
    , session: {
        refresh: function (oldSession, newSession) {
          var providerUri = oldSession.provider_uri;
          var clientUri = oldSession.client_uri;

          Object.keys(oldSession).forEach(function (key) {
            oldSession[key] = undefined;
          });
          Object.keys(newSession).forEach(function (key) {
            oldSession[key] = newSession[key];
          });

          // info about the session of this API call
          oldSession.provider_uri = providerUri;  // aud
          oldSession.client_uri = clientUri;      // azp

          // info about the newly-discovered token
          oldSession.token = OAUTH3.jwt.decode(oldSession.access_token).payload;

          oldSession.token.sub = oldSession.token.sub || oldSession.token.acx.id;
          oldSession.token.client_uri = clientUri;
          oldSession.token.provider_uri = providerUri;

          if (oldSession.refresh_token) {
            oldSession.refresh = OAUTH3.jwt.decode(oldSession.refresh_token).payload;
            oldSession.refresh.sub = oldSession.refresh.sub || oldSession.refresh.acx.id;
            oldSession.refresh.provider_uri = providerUri;
          }

          // set for a set of audiences
          return OAUTH3.PromiseA.resolve(OAUTH3.hooks.session.set(providerUri, oldSession));
        }
      , check: function (preq, opts) {
          opts = opts || {};
          if (!preq.session) {
            return OAUTH3.PromiseA.resolve(null);
          }
          var freshness = OAUTH3.jwt.freshness(preq.session.token, opts.staletime);

          switch (freshness) {
            case 'stale':
              return OAUTH3.hooks.session.stale(preq.session);
            case 'expired':
              return OAUTH3.hooks.session.expired(preq.session).then(function (newSession) {
                preq.session = newSession;
                return newSession;
              });
            //case 'fresh':
            default:
              return OAUTH3.PromiseA.resolve(preq.session);
          }
        }
      , stale: function (staleSession) {
          if (OAUTH3.hooks.session._stalePromise) {
            return OAUTH3.PromiseA.resolve(staleSession);
          }

          OAUTH3.hooks.session._stalePromise = OAUTH3._refreshToken(
            staleSession.provider_uri
          , { client_uri: staleSession.client_uri
            , session: staleSession
            , debug: staleSession.debug
            }
          ).then(function (newSession) {
            OAUTH3.hooks.session._stalePromise = null;
            return newSession; // oauth3.hooks.refreshSession(staleSession, newSession);
          }, function () {
            OAUTH3.hooks.session._stalePromise = null;
          });

          return OAUTH3.PromiseA.resolve(staleSession);
        }
      , expired: function (expiredSession) {
          return OAUTH3._refreshToken(
            expiredSession.provider_uri
          , { client_uri: expiredSession.client_uri
            , session: expiredSession
            , debug: expiredSession.debug
            }
          ).then(function (newSession) {
            return newSession; // oauth3.hooks.refreshSession(expiredSession, newSession);
          });
        }
      , _getCached: function (providerUri) {
          providerUri = OAUTH3.uri.normalize(providerUri);
          if (!OAUTH3.hooks.session._cache) { OAUTH3.hooks.session._cache = {}; }
          return OAUTH3.hooks.session._cache[providerUri];
        }
      , set: function (providerUri, newSession) {
          if (!providerUri) {
            console.error(new Error('no providerUri').stack);
            throw new Error("providerUri is not set");
          }
          providerUri = OAUTH3.uri.normalize(providerUri);
          if (!OAUTH3.hooks.session._cache) { OAUTH3.hooks.session._cache = {}; }
          OAUTH3.hooks.session._cache[providerUri] = newSession;
          return OAUTH3.PromiseA.resolve(OAUTH3.hooks.session._set(providerUri, newSession));
        }
      , get: function (providerUri) {
          providerUri = OAUTH3.uri.normalize(providerUri);
          if (!providerUri) {
            throw new Error("providerUri is not set");
          }

          return OAUTH3.PromiseA.resolve(OAUTH3.hooks.session._getCached(providerUri)
            || OAUTH3.hooks.session._get(providerUri)).then(function (session) {
            OAUTH3.hooks.session._cache[providerUri] = session;
            return session;
          });
        }
      , _get: function (providerUri) {
          console.warn('[Warn] Please implement OAUTH3.hooks.session._get = function (providerUri) { return PromiseA<savedSession>; }');
          return JSON.parse(window.localStorage.getItem('session-' + providerUri) || 'null');
        }
      , _set: function (providerUri, newSession) {
          console.warn('[Warn] Please implement OAUTH3.hooks.session._set = function (providerUri, newSession) { return PromiseA<newSession>; }');
          window.localStorage.setItem('session-' + providerUri, JSON.stringify(newSession));
          return newSession;
        }
      }
    }
  , discover: function (providerUri, opts) {
      if (!providerUri) {
        throw new Error('oauth3.discover(providerUri, opts) received providerUri as ' + providerUri);
      }

      return OAUTH3.hooks.directives.get(providerUri).then(function (directives) {
        if (directives && directives.issuer) {
          return directives;
        }

        return OAUTH3._discoverHelper(providerUri, opts).then(function (directives) {
          directives.azp = directives.azp || OAUTH3.url.normalize(providerUri);
          directives.issuer = directives.issuer || OAUTH3.url.normalize(providerUri);
          // OAUTH3.PromiseA.resolve() is taken care of because this is wrapped
          return OAUTH3.hooks.directives.set(providerUri, directives);
        });
      });
    }
  , _discoverHelper: function(providerUri, opts) {
      return OAUTH3._browser.discover(providerUri, opts);
    }
  , request: function (preq, opts) {
      function fetch() {
        if (preq.session) {
          // TODO check session.token.aud against preq.url to make sure they match
          console.warn("[security] session audience checking has not been implemented yet (it's up to you to check)");
          preq.headers = preq.headers || {};
          preq.headers.Authorization = 'Bearer ' + (preq.session.access_token || preq.session.accessToken);
        }

        return OAUTH3._requestHelper(preq, opts);
      }

      if (!preq.session) {
        return fetch();
      }

      return OAUTH3.hooks.session.check(preq, opts).then(fetch);
    }
  , _requestHelper: function (preq, opts) {
      return OAUTH3._browser.request(preq, opts);
    }
  , implicitGrant: function(directives, opts) {
      var promise;
      var providerUri = directives.azp || directives.issuer || directives;

      if (opts.broker) {
        // Discovery can happen in-flow because we know that this is
        // a valid oauth3 provider
        promise = OAUTH3._discoverThenImplicitGrant(providerUri, opts);
      }
      else {
        // Discovery must take place before calling implicitGrant
        promise = OAUTH3._implicitGrant(OAUTH3.hooks.directives._getCached(providerUri), opts);
      }

      return promise.then(function (tokens) {
        // TODO abstract browser bits away
        try {
          OAUTH3._browser.closeFrame(tokens.state || opts._state, opts);
        } catch(e) {
          console.warn("[implicitGrant] TODO abstract browser bits away");
        }
        opts._state = undefined;
        return OAUTH3.hooks.session.refresh(
          opts.session || {
            provider_uri: providerUri
          , client_id: opts.client_id
          , client_uri: opts.client_uri || opts.clientUri
          }
        , tokens
        );
      });
    }
  , _discoverThenImplicitGrant: function(providerUri, opts) {
      opts.windowType = opts.windowType || 'popup';
      return OAUTH3.discover(providerUri, opts).then(function (directives) {
        return OAUTH3._implicitGrant(directives, opts).then(function (tokens) {
          return tokens;
        });
      });
    }
  , _implicitGrant: function(directives, opts) {
      // TODO this may need to be synchronous for browser security policy
      // Do some stuff
      var authReq = OAUTH3.urls.implicitGrant(
        directives
      , { redirect_uri: opts.redirect_uri
        , client_id: opts.client_id || opts.client_uri
        , client_uri: opts.client_uri || opts.client_id
        , state: opts._state || undefined
        , debug: opts.debug
        }
      );

      if (opts.debug) {
        window.alert("DEBUG MODE: Pausing so you can look at logs and whatnot :) Fire at will!");
      }

      return OAUTH3._browser.frameRequest(
        OAUTH3.url.resolve(directives.issuer, authReq.url)
      , authReq.state // state should recycle params
      , { windowType: opts.windowType
        , reuseWindow: opts.broker && '-broker'
        , debug: opts.debug
        }
      ).then(function (tokens) {
        if (tokens.error) {
          // TODO directives.audience
          return OAUTH3.PromiseA.reject(OAUTH3.error.parse(directives.issuer /*providerUri*/, tokens));
        }

        return tokens;
      });
    }
  , _refreshToken: function (providerUri, opts) {
      return OAUTH3.discover(providerUri, opts).then(function (directive) {
        var prequest = OAUTH3.urls.refreshToken(directive, opts);

        return OAUTH3.request(prequest).then(function (req) {
          var data = req.data;
          data.provider_uri = providerUri;
          if (data.error) {
            return OAUTH3.PromiseA.reject(OAUTH3.error.parse(providerUri, data));
          }
          return OAUTH3.hooks.session.refresh(
            opts.session || { provider_uri: providerUri, client_uri: opts.client_uri || opts.clientUri }
          , data
          );
        });
      });
    }
  , logout: function(providerUri, opts) {
      return OAUTH3._logoutHelper(OAUTH3.hooks.directives._getCached(providerUri), opts);
    }
  , _logoutHelper: function(directives, opts) {
      var logoutReq = OAUTH3.urls.logout(
        directives
      , { client_id: (opts.client_id || opts.client_uri || OAUTH3.clientUri(OAUTH3._browser.window.location))
        , windowType: 'popup' // we'll figure out background later
        , broker: opts.broker
        //, state: opts._state
        , debug: opts.debug
        }
      );

      return OAUTH3._browser.frameRequest(
        OAUTH3.url.resolve(directives.issuer, logoutReq.url)
      , logoutReq.state // state should recycle params
      , { windowType: 'popup'
        , reuseWindow: opts.broker && '-broker'
        , debug: opts.debug
        }
      ).then(function (params) {
        OAUTH3._browser.closeFrame(params.state || opts._state, opts);

        if (params.error) {
          // TODO directives.audience
          return OAUTH3.PromiseA.reject(OAUTH3.error.parse(directives.issuer /*providerUri*/, params));
        }

        OAUTH3.hooks.session._cache = {};
        return params;
      });
    }


    //
    // Let the Code Waste begin!!
    //
  , _browser: {
      window: window
      // TODO we don't need to include this if we're using jQuery or angular
    , discover: function(providerUri, opts) {
        opts = opts || {};
        providerUri = OAUTH3.url.normalize(providerUri);

        if (providerUri.match(OAUTH3._browser.window.location.hostname)) {
          console.warn("It looks like you're a provider checking for your own directive,"
            + " so we we're just gonna use"
            + " OAUTH3.request({ method: 'GET', url: '.well-known/oauth3/directive.json' })");
          return OAUTH3.request({
            method: 'GET'
          , url: OAUTH3.url.normalize(providerUri) + '/.well-known/oauth3/directives.json'
          }).then(function (resp) {
            return resp.data;
          });
        }

        if (!(opts.client_id || opts.client_uri).match(OAUTH3._browser.window.location.hostname)) {
          console.warn("It looks like your client_id doesn't match your current window..."
            + " this probably won't end well");
          console.warn(opts.client_id || opts.client_uri, OAUTH3._browser.window.location.hostname);
        }

        var discReq = OAUTH3.urls.discover(
          providerUri
        , { client_id: (opts.client_id || opts.client_uri || OAUTH3.clientUri(OAUTH3._browser.window.location))
          , windowType: opts.broker && opts.windowType || 'background'
          , broker: opts.broker
          , state: opts._state || undefined
          , debug: opts.debug
          }
        );
        opts._state = discReq.state;
        //var discReq = OAUTH3.urls.discover(providerUri, opts);

        // hmm... we're gonna need a broker for this since switching windows is distracting,
        // popups are obnoxious, iframes are sometimes blocked, and most servers don't implement CORS
        // eventually it should be the browser (and postMessage may be a viable option now), but whatever...

        // TODO allow postMessage from providerUri in addition to callback
        // TODO allow node to open a desktop browser window
        opts._windowType = opts.windowType;
        opts.windowType = opts.windowType || 'background';
        return OAUTH3._browser.frameRequest(
          OAUTH3.url.resolve(providerUri, discReq.url)
        , discReq.state
          // why not just pass opts whole?
        , { windowType: opts.windowType
          , reuseWindow: opts.broker && '-broker'
          , debug: opts.debug
          }
        ).then(function (params) {
          opts.windowType = opts._windowType;

          // caller will call OAUTH3._browser.closeFrame(discReq.state, { debug: opts.debug || params.debug });
          if (params.error) {
            // TODO directives.issuer || directives.audience
            return OAUTH3.PromiseA.reject(OAUTH3.error.parse(providerUri, params));
          }

          // TODO params should have response_type indicating json, binary, etc
          var directives = JSON.parse(OAUTH3._base64.decodeUrlSafe(params.result || params.directives));
          // caller will call OAUTH3.hooks.directives.set(providerUri, directives);
          return directives;
        });
      }
    , request: function (preq, _sys) {
        return new OAUTH3.PromiseA(function (resolve, reject) {
          var xhr;
          try {
            xhr = new XMLHttpRequest(_sys);
          } catch(e) {
            xhr = new XMLHttpRequest();
          }
          xhr.onreadystatechange = function () {
            var data;
            if (xhr.readyState !== XMLHttpRequest.DONE) {
              // nothing to do here
              return;
            }

            if (xhr.status !== 200) {
              reject(new Error('bad status code: ' + xhr.status));
              return;
            }

            try {
              data = JSON.parse(xhr.responseText);
            } catch(e) {
              data = xhr.responseText;
            }

            resolve({
              request: xhr
            , data: data
            , status: xhr.status
            });
          };
          xhr.open(preq.method || 'GET', preq.url, true);
          var headers = preq.headers || {};
          if (preq.data) {
            headers['Content-Type'] = 'application/json'; // TODO XXX TODO utf8
          }
          Object.keys(headers).forEach(function (key) {
            xhr.setRequestHeader(key, headers[key]);
          });
          xhr.send(JSON.stringify(preq.data));
        });
      }
    , frameRequest: function (url, state, opts) {
        opts = opts || {};
        var previousFrame = OAUTH3._browser._frames[state];

        var windowType = opts.windowType;
        if (!windowType) {
          windowType = 'popup';
        }

        var timeout = opts.timeout;
        if (opts.debug) {
          timeout = timeout || 3 * 60 * 1000;
        }
        else {
          timeout = timeout || ('background' === windowType ? 15 * 1000 : 3 * 60 * 1000);
        }

        return new OAUTH3.PromiseA(function (resolve, reject) {
          // TODO periodically garbage collect expired handlers from window object
          var tok;

          function cleanup() {
            delete window['--oauth3-callback-' + state];
            clearTimeout(tok);
            tok = null;
            // the actual close is done later (by the caller) so that the window/frame
            // can be reused or self-closes synchronously itself / by parent
            // (probably won't ever happen, but that's a negotiable implementation detail)
          }


          window['--oauth3-callback-' + state] = function (params) {
            resolve(params);
            cleanup();
          };

          tok = setTimeout(function () {
            var err = new Error(
              "the '" + windowType + "' request did not complete within " + Math.round(timeout / 1000) + "s"
            );
            err.code = "E_TIMEOUT";
            reject(err);
            cleanup();
          }, timeout);

          setTimeout(function () {
            if (!OAUTH3._browser._frames[state]) {
              reject(new Error("TODO: open the iframe first and discover oauth3 directives before popup"));
              cleanup();
            }
          }, 0);

          if ('background' === windowType) {
            if (previousFrame) {
              previousFrame.location = url;
              //promise = previousFrame.promise;
            }
            else {
              OAUTH3._browser._frames[state] = OAUTH3._browser.iframe(url, state, opts);
            }
          } else if ('popup' === windowType) {
            if (previousFrame) {
              previousFrame.location = url;
              if (opts.debug) {
                previousFrame.focus();
              }
            }
            else {
              OAUTH3._browser._frames[state] = OAUTH3._browser.frame(url, state, opts);
            }
          } else if ('inline' === windowType) {
            // callback function will never execute and would need to redirect back to current page
            // rather than the callback.html
            url += '&original_url=' + OAUTH3._browser.window.location.href;
            OAUTH3._browser.window.location = url;
            //promise = OAUTH3.PromiseA.resolve({ url: url });
            return;
          } else {
            throw new Error("login framing method options.windowType="
              + opts.windowType + " not type yet implemented");
          }

        }).then(function (params) {
          if (params.error) {
            // TODO directives.issuer || directives.audience
            return OAUTH3.PromiseA.reject(OAUTH3.error.parse('https://oauth3.org', params));
          }
          return params;
        });
      }
    , closeFrame: function (state, opts) {
        opts = opts || {};
        function close() {
          try {
            OAUTH3._browser._frames[state].close();
          } catch(e) {
            try {
              OAUTH3._browser._frames[state].remove();
            } catch(e) {
              console.error(new Error("Could not clase window/iframe. closeFrame may have been called twice."));
            }
          }

          delete OAUTH3._browser._frames[state];
        }

        if (opts.debug) {
          if (window.confirm("DEBUG MODE: okay to close oauth3 window?")) {
            close();
          }
        }
        else {
          close();
        }
      }
    , _frames: {}
    , iframe: function (url, state, opts) {
        var framesrc = '<iframe class="js-oauth3-iframe" src="' + url + '" ';
        if (opts.debug) {
          framesrc += ' width="' + (opts.height || 600) + 'px"'
            + ' height="' + (opts.width || 720) + 'px"'
            + ' style="opacity: 0.8;" frameborder="1"';
        }
        else {
          framesrc += ' width="1px" height="1px" frameborder="0"';
        }
        framesrc += '></iframe>';

        var frame = OAUTH3._browser.window.document.createElement('div');
        frame.innerHTML = framesrc;
        OAUTH3._browser.window.document.body.appendChild(frame);

        return frame;
      }
    , frame: function (url, state, opts) {

        // TODO allow size changes (via directive even)
        return window.open(
          url
        , 'oauth3-login-' + (opts.reuseWindow || state)
        , 'height=' + (opts.height || 720) + ',width=' + (opts.width || 620)
        );
      }
    }
  , api: function (providerUri, opts) {
      if (!OAUTH3.api[opts.api]) {
        return OAUTH3.PromiseA.reject(new Error("No API for '" + providerUri + "'"));
      }

      return OAUTH3.api[opts.api](providerUri, opts);
    }
  };
  OAUTH3.login = OAUTH3.implicitGrant;

  // TODO get rid of these
  OAUTH3.utils = {
    clientUri: OAUTH3.clientUri
  , query: OAUTH3.query
  , scope: OAUTH3.scope
  , uri: OAUTH3.uri
  , url: OAUTH3.url
  , _error: OAUTH3.error
  , _formatError: OAUTH3.error
  , _urlSafeBase64ToBase64: OAUTH3._urlSafeBase64ToBase64
  , randomState: OAUTH3.randomState
  , _insecureRandomState: OAUTH3._insecureRandomState
  };

  if ('undefined' !== typeof Promise) {
    OAUTH3.PromiseA = Promise;
  }

  // this is not necessary, but it's relatively small
  // and gives people the 3-line examples they love so much
  OAUTH3.create = function (location/*, opts*/) {
    if (!location) {
      location = OAUTH3._browser.window.location;
    }

    var result = {
      _clientUri: OAUTH3.clientUri(location)
    , _providerUri: null
    , init: function (location) {
        var me = this;
        var p = OAUTH3.PromiseA.resolve();

        if (location) {
          this._clientUri = OAUTH3.clientUri(location);
        }
        if (this._providerUri) {
          p = OAUTH3.discover(this._providerUri, { client_id: this._clientUri }).then(function (/*directives*/) {
            $('.js-signin').removeAttr('disabled');
          });
        }

        return OAUTH3.discover(this._clientUri, { client_id: this._clientUri }).then(function (clientDirectives) {
          me._clientDirectives = clientDirectives;
          return p.then(function () {
            return clientDirectives;
          });
        });
      }
    , setProvider: function (providerUri) {
        var me = this;
        me._providerUri = providerUri;
        return me.init().then(function () {
          // this should be synchronous the second time around
          return OAUTH3.discover(me._providerUri, { client_id: me._clientUri }).then(function (directives) {
            me._providerDirectives = directives;
            return directives;
          });
        });
      }
    , checkSession: function () {
        return OAUTH3.hooks.session.get(this._providerUri);
      }
    , login: function (opts) {
        var me = this;
        if (me.session()) {
          me._session = true;
          return OAUTH3.PromiseA.resolve(me.session());
        }

        opts = opts || {};
        opts.client_uri = me._clientUri;

        return OAUTH3.implicitGrant(me._providerDirectives, opts).then(function (session) {
          me._session = true;
          return session;
        });
      }
    , session: function () {
        return JSON.parse(JSON.stringify(OAUTH3.hooks.session._getCached(this._providerUri) || null));
      }
    , request: function (preq, opts) {
        opts = opts || {};
        preq.client_uri = this._clientUri;
        preq.client_id = this._clientUri;
        preq.method = preq.method || 'GET';
        if (this._session) {
          preq.session = preq.session || OAUTH3.hooks.session._getCached(this._providerUri);
        }
        // TODO maybe use a baseUrl from the directives file?
        preq.url = OAUTH3.url.resolve(this._providerUri, preq.url);
        return OAUTH3.request(preq, opts);
      }
    , logout: function (opts) {
        opts = opts || {};
        opts.client_uri = this._clientUri;
        opts.client_id = this._clientUri;
        opts.session = OAUTH3.hooks.session._getCached(this._providerUri);

        return OAUTH3.logout(this._providerUri, opts);
      }
    , api: function (api, opts) {
        opts = opts || {};
        opts.api = api;
        opts.session = OAUTH3.hooks.session._getCached(this._providerUri);
        return OAUTH3.api(this._providerUri, opts);
      }
    };
    result.authenticate = result.login;
    result.authorize = result.login;
    result.expire = result.logout;
    return result;
  };

}('undefined' !== typeof exports ? exports : window));