(function (exports) {
  'use strict';

  // NOTE: we assume that directive.provider_uri exists

  var core = {};

  core.stringifyscope = function (scope) {
    if (Array.isArray(scope)) {
      scope = scope.join(' ');
    }
    return scope;
  };

  core.querystringify = function (params) {
    var qs = [];

    Object.keys(params).forEach(function (key) {
      if ('scope' === key) {
        params[key] = core.stringifyscope(params[key]);
      }
      qs.push(encodeURIComponent(key) + '=' + encodeURIComponent(params[key]));
    });

    return qs.join('&');
  };

  core.authorizationCode = function (/*directive, scope, redirectUri, clientId*/) {
    //
    // Example Authorization Code Request
    // (not for use in the browser)
    //
    // GET https://example.com/api/org.oauth3.provider/authorization_dialog
    //  ?response_type=code
    //  &scope=`encodeURIComponent('profile.login profile.email')`
    //  &state=`Math.random()`
    //  &client_id=xxxxxxxxxxx
    //  &redirect_uri=`encodeURIComponent('https://myapp.com/oauth3.html')`
    //
    // NOTE: `redirect_uri` itself may also contain URI-encoded components
    //
    // NOTE: This probably shouldn't be done in the browser because the server
    //   needs to initiate the state. If it is done in a browser, the browser
    //   should probably request 'state' from the server beforehand
    //

    throw new Error("not implemented");
  };

  core.authorizationRedirect = function (directive, authorizationRedirect, opts) {
    //console.log('[authorizationRedirect]');
    //
    // Example Authorization Redirect - from Browser to Consumer API
    // (for generating a session securely on your own server)
    //
    // i.e. GET https://<<CONSUMER>>.com/api/org.oauth3.consumer/authorization_redirect/<<PROVIDER>>.com
    //
    // GET https://myapp.com/api/org.oauth3.consumer/authorization_redirect/`encodeURIComponent('example.com')`
    //  &scope=`encodeURIComponent('profile.login profile.email')`
    //
    // (optional)
    //  &state=`Math.random()`
    //  &redirect_uri=`encodeURIComponent('https://myapp.com/oauth3.html')`
    //
    // NOTE: This is not a request sent to the provider, but rather a request sent to the
    // consumer (your own API) which then sets some state and redirects.
    // This will initiate the `authorization_code` request on your server
    //
    opts = opts || {};

    var scope = opts.scope || directive.authn_scope;
    var providerUri = directive.provider_uri;

    var state = Math.random().toString().replace(/^0\./, '');
    var params = {};
    var slimProviderUri = encodeURIComponent(providerUri.replace(/^(https?|spdy):\/\//, ''));

    params.state = state;
    if (scope) {
      params.scope = scope;
    }
    if (opts.redirectUri) {
      // this is really only for debugging
      params.redirect_uri = opts.redirectUri;
    }
    // Note: the type check is necessary because we allow 'true'
    // as an automatic mechanism when it isn't necessary to specify
    if ('string' !== typeof authorizationRedirect) {
      // TODO oauth3.json for self?
      authorizationRedirect = 'https://' + window.location.host
        + '/api/org.oauth3.consumer/authorization_redirect/:provider_uri';
    }
    authorizationRedirect = authorizationRedirect
      .replace(/!(provider_uri)/, slimProviderUri)
      .replace(/:provider_uri/, slimProviderUri)
      .replace(/#{provider_uri}/, slimProviderUri)
      .replace(/{{provider_uri}}/, slimProviderUri)
      ;

    return {
      url: authorizationRedirect + '?' + core.querystringify(params)
    , method: 'GET'
    , state: state    // this becomes browser_state
    , params: params  // includes scope, final redirect_uri?
    };
  };

  core.implicitGrant = function (directive, opts) {
    //console.log('[implicitGrant]');
    //
    // 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=`Math.random()`
    //  &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 redirectUri = opts.redirectUri;
    var scope = opts.scope || directive.authn_scope;
    var clientId = opts.appId;
    var args = directive[type];
    var uri = args.url;
    var state = Math.random().toString().replace(/^0\./, '');
    var params = {};
    var loc;
    var result;

    params.state = state;
    params.response_type = responseType;
    if (scope) {
      if (Array.isArray(scope)) {
        scope = scope.join(' ');
      }
      params.scope = scope;
    }
    if (clientId) {
      // In OAuth3 client_id is optional for implicit grant
      params.client_id = clientId;
    }
    if (!redirectUri) {
      loc = window.location;
      redirectUri = loc.protocol + '//' + loc.host + loc.pathname;
      if ('/' !== redirectUri[redirectUri.length - 1]) {
        redirectUri += '/';
      }
      redirectUri += 'oauth3.html';
    }
    params.redirect_uri = redirectUri;

    uri += '?' + core.querystringify(params);

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

    return result;
  };

  core.loginCode = function (directive, username, opts) {
    //
    // Example Resource Owner Password Request
    // (generally for 1st party and direct-partner mobile apps, and webapps)
    //
    // POST https://api.example.com/api/org.oauth3.provider/otp
    //    { "request_otp": true, "client_id": "<<id>>", "scope": "<<scope>>"
    //    , "username": "<<username>>" }
    //
    opts = opts || {};
    var clientId = opts.appId || opts.clientId;

    var args = directive.otp;
    var params = {
      "username": username || opts.id || opts.username
    , "request_otp": true // opts.requestOtp || undefined
    //, "jwt": opts.jwt // TODO sign a proof
    };
    var uri = args.url;
    var body;
    if (opts.clientUri) {
      params.client_uri = opts.clientUri;
    }
    if (opts.clientAgreeTos) {
      params.client_agree_tos = opts.clientAgreeTos;
    }
    if (clientId) {
      params.client_id = clientId;
    }
    if ('GET' === args.method.toUpperCase()) {
      uri += '?' + core.querystringify(params);
    } else {
      body = params;
    }

    return {
      url: uri
    , method: args.method
    , data: body
    };
  };

  core.resourceOwnerPassword = function (directive, username, passphrase, opts) {
    //
    // Example Resource Owner Password Request
    // (generally for 1st party and direct-partner mobile apps, and webapps)
    //
    // POST https://example.com/api/org.oauth3.provider/access_token
    //    { "grant_type": "password", "client_id": "<<id>>", "scope": "<<scope>>"
    //    , "username": "<<username>>", "password": "password" }
    //
    opts = opts || {};
    var type = 'access_token';
    var grantType = 'password';

    var scope = opts.scope || directive.authn_scope;
    var clientId = opts.appId;
    var clientAgreeTos = opts.clientAgreeTos;
    var clientUri = opts.clientUri;
    var args = directive[type];
    var params = {
      "grant_type": grantType
    , "username": username
    , "password": passphrase
    //, "totp": opts.totp
    };
    var uri = args.url;
    var body;
    if (opts.totp) {
      params.totp = opts.totp;
    }

    if (clientId) {
      params.clientId = clientId;
    }
    if (clientUri) {
      params.clientUri = clientUri;
      params.clientAgreeTos = clientAgreeTos;
      if (!clientAgreeTos) {
        throw new Error('Developer Error: missing clientAgreeTos uri');
      }
    }

    if (scope) {
      if (Array.isArray(scope)) {
        scope = scope.join(' ');
      }
      params.scope = scope;
    }

    if ('GET' === args.method.toUpperCase()) {
      uri += '?' + core.querystringify(params);
    } else {
      body = params;
    }

    return {
      url: uri
    , method: args.method
    , data: body
    };
  };

  exports.OAUTH3 = exports.OAUTH3 || { core: core };
  exports.OAUTH3_CORE = core.OAUTH3_CORE = core;

  if ('undefined' !== typeof module) {
    module.exports = core;
  }
}('undefined' !== typeof exports ? exports : window));