var AWS = require('../core');

/**
 * Represents credentials retrieved from STS Web Identity Federation using
 * the Amazon Cognito Identity service.
 *
 * By default this provider gets credentials using the
 * {AWS.CognitoIdentity.getCredentialsForIdentity} service operation,
 * after first getting an `IdentityId` from {AWS.CognitoIdentity.getId}. This
 * operation requires an `IdentityPoolId` (Amazon Cognito Identity Pool ID).
 * If a `RoleArn` is provided, then this provider gets credentials using the
 * {AWS.STS.assumeRoleWithWebIdentity} service operation, after first getting
 * an Open ID token from {AWS.CognitoIdentity.getOpenIdToken}. These operations
 * require an `IdentityPoolId` (Amazon Cognito Identity Pool ID), and `RoleArn`
 * containing the ARN of the IAM trust policy for the Amazon Cognito role that
 * the user will log into.
 *
 * In addition, if this credential provider is used to provide authenticated
 * login, the `Logins` map may be set to the tokens provided by the respective
 * identity providers. See {constructor} for an example on creating a credentials
 * object with proper property values.
 *
 * ## Refreshing Credentials from Identity Service
 *
 * In addition to AWS credentials expiring after a given amount of time, the
 * login token from the identity provider will also expire. Once this token
 * expires, it will not be usable to refresh AWS credentials, and another
 * token will be needed. The SDK does not manage refreshing of the token value,
 * but this can be done through a "refresh token" supported by most identity
 * providers. Consult the documentation for the identity provider for refreshing
 * tokens. Once the refreshed token is acquired, you should make sure to update
 * this new token in the credentials object's {params} property. The following
 * code will update the WebIdentityToken, assuming you have retrieved an updated
 * token from the identity provider:
 *
 * ```javascript
 * AWS.config.credentials.params.Logins['graph.facebook.com'] = updatedToken;
 * ```
 *
 * Future calls to `credentials.refresh()` will now use the new token.
 *
 * @!attribute params
 *   @return [map] the map of params passed to
 *     {AWS.CognitoIdentity.getId},
 *     {AWS.CognitoIdentity.getOpenIdToken}, and
 *     {AWS.STS.assumeRoleWithWebIdentity}. To update the token, set the
 *     `params.WebIdentityToken` property.
 * @!attribute data
 *   @return [map] the raw data response from the call to
 *     {AWS.CognitoIdentity.getCredentialsForIdentity}, or
 *     {AWS.STS.assumeRoleWithWebIdentity}. Use this if you want to get
 *     access to other properties from the response.
 * @!attribute identityId
 *   @return [String] the Cognito ID returned by the last call to
 *     {AWS.CognitoIdentity.getOpenIdToken}. This ID represents the actual
 *     final resolved identity ID from Amazon Cognito.
 */
AWS.CognitoIdentityCredentials = AWS.util.inherit(AWS.Credentials, {
  /**
   * @api private
   */
  localStorageKey: {
    id: 'aws.cognito.identity-id.',
    providers: 'aws.cognito.identity-providers.'
  },

  /**
   * Creates a new credentials object.
   * @param (see AWS.CognitoIdentity.getId)
   * @param (see AWS.STS.assumeRoleWithWebIdentity)
   * @param (see AWS.CognitoIdentity.getOpenIdToken)
   * @example Creating a new credentials object
   *   AWS.config.credentials = new AWS.CognitoIdentityCredentials({
   *     IdentityPoolId: 'us-east-1:1699ebc0-7900-4099-b910-2df94f52a030',
   *     // optional, only necessary when the identity pool is not configured
   *     // to use IAM roles in the Amazon Cognito Console
   *     RoleArn: 'arn:aws:iam::1234567890:role/MYAPP-CognitoIdentity',
   *     Logins: { // optional tokens, used for authenticated login
   *       'graph.facebook.com': 'FBTOKEN',
   *       'www.amazon.com': 'AMAZONTOKEN',
   *       'accounts.google.com': 'GOOGLETOKEN'
   *     },
   *     RoleSessionName: 'web' // optional name, defaults to web-identity,
   *     // optional, only necessary when application runs in a browser
   *     // and multiple users are signed in at once
   *     LoginId: 'example@gmail.com'
   *   });
   * @see AWS.STS.assumeRoleWithWebIdentity
   * @see AWS.CognitoIdentity.getCredentialsForIdentity
   */
  constructor: function CognitoIdentityCredentials(params) {
    AWS.Credentials.call(this);
    this.expired = true;
    this.params = params;
    this.data = null;
    this.identityId = null;
    this.loadCachedId();
  },

  /**
   * Refreshes credentials using {AWS.CognitoIdentity.getCredentialsForIdentity},
   * or {AWS.STS.assumeRoleWithWebIdentity}.
   *
   * @callback callback function(err)
   *   Called when the STS service responds (or fails). When
   *   this callback is called with no error, it means that the credentials
   *   information has been loaded into the object (as the `accessKeyId`,
   *   `secretAccessKey`, and `sessionToken` properties).
   *   @param err [Error] if an error occurred, this value will be filled
   * @see get
   */
  refresh: function refresh(callback) {
    var self = this;
    self.createClients();
    self.data = null;
    self.identityId = null;
    self.getId(function(err) {
      if (!err) {
        if (!self.params.RoleArn) {
          self.getCredentialsForIdentity(callback);
        } else {
          self.getCredentialsFromSTS(callback);
        }
      } else {
        self.clearCachedId();
        callback(err);
      }
    });
  },

  /**
   * Clears the cached Cognito ID associated with the currently configured
   * identity pool ID. Use this to manually invalidate your cache if
   * the identity pool ID was deleted.
   */
  clearCachedId: function clearCache() {
    this.identityId = null;
    delete this.params.IdentityId;

    var poolId = this.params.IdentityPoolId;
    var loginId = this.params.LoginId || '';
    delete this.storage[this.localStorageKey.id + poolId + loginId];
    delete this.storage[this.localStorageKey.providers + poolId + loginId];
  },

  /**
   * Retrieves a Cognito ID, loading from cache if it was already retrieved
   * on this device.
   *
   * @callback callback function(err, identityId)
   *   @param err [Error, null] an error object if the call failed or null if
   *     it succeeded.
   *   @param identityId [String, null] if successful, the callback will return
   *     the Cognito ID.
   * @note If not loaded explicitly, the Cognito ID is loaded and stored in
   *   localStorage in the browser environment of a device.
   * @api private
   */
  getId: function getId(callback) {
    var self = this;
    if (typeof self.params.IdentityId === 'string') {
      return callback(null, self.params.IdentityId);
    }

    self.cognito.getId(function(err, data) {
      if (!err && data.IdentityId) {
        self.params.IdentityId = data.IdentityId;
        callback(null, data.IdentityId);
      } else {
        callback(err);
      }
    });
  },


  /**
   * @api private
   */
  loadCredentials: function loadCredentials(data, credentials) {
    if (!data || !credentials) return;
    credentials.expired = false;
    credentials.accessKeyId = data.Credentials.AccessKeyId;
    credentials.secretAccessKey = data.Credentials.SecretKey;
    credentials.sessionToken = data.Credentials.SessionToken;
    credentials.expireTime = data.Credentials.Expiration;
  },

  /**
   * @api private
   */
  getCredentialsForIdentity: function getCredentialsForIdentity(callback) {
    var self = this;
    self.cognito.getCredentialsForIdentity(function(err, data) {
      if (!err) {
        self.cacheId(data);
        self.data = data;
        self.loadCredentials(self.data, self);
      } else {
        self.clearCachedId();
      }
      callback(err);
    });
  },

  /**
   * @api private
   */
  getCredentialsFromSTS: function getCredentialsFromSTS(callback) {
    var self = this;
    self.cognito.getOpenIdToken(function(err, data) {
      if (!err) {
        self.cacheId(data);
        self.params.WebIdentityToken = data.Token;
        self.webIdentityCredentials.refresh(function(webErr) {
          if (!webErr) {
            self.data = self.webIdentityCredentials.data;
            self.sts.credentialsFrom(self.data, self);
          } else {
            self.clearCachedId();
          }
          callback(webErr);
        });
      } else {
        self.clearCachedId();
        callback(err);
      }
    });
  },

  /**
   * @api private
   */
  loadCachedId: function loadCachedId() {
    var self = this;

    // in the browser we source default IdentityId from localStorage
    if (AWS.util.isBrowser() && !self.params.IdentityId) {
      var id = self.getStorage('id');
      if (id && self.params.Logins) {
        var actualProviders = Object.keys(self.params.Logins);
        var cachedProviders =
          (self.getStorage('providers') || '').split(',');

        // only load ID if at least one provider used this ID before
        var intersect = cachedProviders.filter(function(n) {
          return actualProviders.indexOf(n) !== -1;
        });
        if (intersect.length !== 0) {
          self.params.IdentityId = id;
        }
      } else if (id) {
        self.params.IdentityId = id;
      }
    }
  },

  /**
   * @api private
   */
  createClients: function() {
    this.webIdentityCredentials = this.webIdentityCredentials ||
      new AWS.WebIdentityCredentials(this.params);
    this.cognito = this.cognito ||
      new AWS.CognitoIdentity({params: this.params});
    this.sts = this.sts || new AWS.STS();
  },

  /**
   * @api private
   */
  cacheId: function cacheId(data) {
    this.identityId = data.IdentityId;
    this.params.IdentityId = this.identityId;

    // cache this IdentityId in browser localStorage if possible
    if (AWS.util.isBrowser()) {
      this.setStorage('id', data.IdentityId);

      if (this.params.Logins) {
        this.setStorage('providers', Object.keys(this.params.Logins).join(','));
      }
    }
  },

  /**
   * @api private
   */
  getStorage: function getStorage(key) {
    return this.storage[this.localStorageKey[key] + this.params.IdentityPoolId + (this.params.LoginId || '')];
  },

  /**
   * @api private
   */
  setStorage: function setStorage(key, val) {
    try {
      this.storage[this.localStorageKey[key] + this.params.IdentityPoolId + (this.params.LoginId || '')] = val;
    } catch (_) {}
  },

  /**
   * @api private
   */
  storage: (function() {
    try {
      return AWS.util.isBrowser() && window.localStorage !== null && typeof window.localStorage === 'object' ?
             window.localStorage : {};
    } catch (_) {
      return {};
    }
  })()
});
