hivetaxi-sdk/lib/credentials/credential_provider_chain.js

HiveTaxi SDK for JavaScript

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

/**
 * Creates a credential provider chain that searches for HiveTaxi credentials
 * in a list of credential providers specified by the {providers} property.
 *
 * By default, the chain will use the {defaultProviders} to resolve credentials.
 * These providers will look in the environment using the
 * {HiveTaxi.EnvironmentCredentials} class with the 'HIVE' or 'HIVETAXI' prefixes.
 *
 * ## Setting Providers
 *
 * Each provider in the {providers} list should be a function that returns
 * a {HiveTaxi.Credentials} object, or a hardcoded credentials object. The function
 * form allows for delayed execution of the credential construction.
 *
 * ## Resolving Credentials from a Chain
 *
 * Call {resolve} to return the first valid credential object that can be
 * loaded by the provider chain.
 *
 * For example, to resolve a chain with a custom provider that checks a file
 * on disk after the set of {defaultProviders}:
 *
 * ```javascript
 * var diskProvider = new HiveTaxi.FileSystemCredentials('./creds.json');
 * var chain = new HiveTaxi.CredentialProviderChain();
 * chain.providers.push(diskProvider);
 * chain.resolve();
 * ```
 *
 * The above code will return the `diskProvider` object if the
 * file contains credentials and the `defaultProviders` do not contain
 * any credential settings.
 *
 * @!attribute providers
 *   @return [Array<HiveTaxi.Credentials, Function>]
 *     a list of credentials objects or functions that return credentials
 *     objects. If the provider is a function, the function will be
 *     executed lazily when the provider needs to be checked for valid
 *     credentials. By default, this object will be set to the
 *     {defaultProviders}.
 *   @see defaultProviders
 */
HiveTaxi.CredentialProviderChain = HiveTaxi.util.inherit(HiveTaxi.Credentials, {

  /**
   * Creates a new CredentialProviderChain with a default set of providers
   * specified by {defaultProviders}.
   */
  constructor: function CredentialProviderChain(providers) {
    if (providers) {
      this.providers = providers;
    } else {
      this.providers = HiveTaxi.CredentialProviderChain.defaultProviders.slice(0);
    }
  },

  /**
   * @!method  resolvePromise()
   *   Returns a 'thenable' promise.
   *   Resolves the provider chain by searching for the first set of
   *   credentials in {providers}.
   *
   *   Two callbacks can be provided to the `then` method on the returned promise.
   *   The first callback will be called if the promise is fulfilled, and the second
   *   callback will be called if the promise is rejected.
   *   @callback fulfilledCallback function(credentials)
   *     Called if the promise is fulfilled and the provider resolves the chain
   *     to a credentials object
   *     @param credentials [HiveTaxi.Credentials] the credentials object resolved
   *       by the provider chain.
   *   @callback rejectedCallback function(error)
   *     Called if the promise is rejected.
   *     @param err [Error] the error object returned if no credentials are found.
   *   @return [Promise] A promise that represents the state of the `resolve` method call.
   *   @example Calling the `resolvePromise` method.
   *     var promise = chain.resolvePromise();
   *     promise.then(function(credentials) { ... }, function(err) { ... });
   */

  /**
   * Resolves the provider chain by searching for the first set of
   * credentials in {providers}.
   *
   * @callback callback function(err, credentials)
   *   Called when the provider resolves the chain to a credentials object
   *   or null if no credentials can be found.
   *
   *   @param err [Error] the error object returned if no credentials are
   *     found.
   *   @param credentials [HiveTaxi.Credentials] the credentials object resolved
   *     by the provider chain.
   * @return [HiveTaxi.CredentialProviderChain] the provider, for chaining.
   */
  resolve: function resolve(callback) {
    if (this.providers.length === 0) {
      callback(new Error('No providers'));
      return this;
    }

    var index = 0;
    var providers = this.providers.slice(0);

    function resolveNext(err, creds) {
      if ((!err && creds) || index === providers.length) {
        callback(err, creds);
        return;
      }

      var provider = providers[index++];
      if (typeof provider === 'function') {
        creds = provider.call();
      } else {
        creds = provider;
      }

      if (creds.get) {
        creds.get(function(getErr) {
          resolveNext(getErr, getErr ? null : creds);
        });
      } else {
        resolveNext(null, creds);
      }
    }

    resolveNext();
    return this;
  }
});

/**
 * The default set of providers used by a vanilla CredentialProviderChain.
 *
 * In the browser:
 *
 * ```javascript
 * HiveTaxi.CredentialProviderChain.defaultProviders = []
 * ```
 *
 * In Node.js:
 *
 * ```javascript
 * HiveTaxi.CredentialProviderChain.defaultProviders = [
 *   function () { return new HiveTaxi.EnvironmentCredentials('HIVE'); },
 *   function () { return new HiveTaxi.EnvironmentCredentials('HIVETAXI'); },
 *   function () { return new HiveTaxi.SharedIniFileCredentials(); }
 * ]
 * ```
 */
HiveTaxi.CredentialProviderChain.defaultProviders = [];

/**
 * @api private
 */
HiveTaxi.CredentialProviderChain.addPromisesToClass = function addPromisesToClass(PromiseDependency) {
  this.prototype.resolvePromise = HiveTaxi.util.promisifyMethod('resolve', PromiseDependency);
};

/**
 * @api private
 */
HiveTaxi.CredentialProviderChain.deletePromisesFromClass = function deletePromisesFromClass() {
  delete this.prototype.resolvePromise;
};

HiveTaxi.util.addPromises(HiveTaxi.CredentialProviderChain);