var AWS = require('./core');
var Api = require('./model/api');
var inherit = AWS.util.inherit;

/**
 * The service class representing an AWS service.
 *
 * @abstract
 *
 * @!attribute apiVersions
 *   @return [Array<String>] the list of API versions supported by this service.
 *   @readonly
 */
AWS.Service = inherit({
  /**
   * Create a new service object with a configuration object
   *
   * @param config [map] a map of configuration options
   */
  constructor: function Service(config) {
    if (!this.loadServiceClass) {
      throw AWS.util.error(new Error(),
        'Service must be constructed with `new\' operator');
    }
    var ServiceClass = this.loadServiceClass(config || {});
    if (ServiceClass) return new ServiceClass(config);
    this.initialize(config);
  },

  /**
   * @api private
   */
  initialize: function initialize(config) {
    this.config = new AWS.Config(AWS.config);
    if (config) this.config.update(config, true);

    this.config.endpoint = this.endpointFromTemplate(this.config.endpoint);
    this.setEndpoint(this.config.endpoint);
  },

  /**
   * @api private
   */
  loadServiceClass: function loadServiceClass(serviceConfig) {
    var config = serviceConfig;
    if (!AWS.util.isEmpty(this.api)) {
      return null;
    } else if (config.apiConfig) {
      return AWS.Service.defineServiceApi(this.constructor, config.apiConfig);
    } else if (!this.constructor.services) {
      return null;
    } else {
      config = new AWS.Config(AWS.config);
      config.update(serviceConfig, true);
      var version = config.apiVersions[this.constructor.serviceIdentifier];
      version = version || config.apiVersion;
      return this.getLatestServiceClass(version);
    }
  },

  /**
   * @api private
   */
  getLatestServiceClass: function getLatestServiceClass(version) {
    version = this.getLatestServiceVersion(version);
    if (this.constructor.services[version] === null) {
      AWS.Service.defineServiceApi(this.constructor, version);
    }

    return this.constructor.services[version];
  },

  /**
   * @api private
   */
  getLatestServiceVersion: function getLatestServiceVersion(version) {
    if (!this.constructor.services || this.constructor.services.length === 0) {
      throw new Error('No services defined on ' +
                      this.constructor.serviceIdentifier);
    }

    if (!version) {
      version = 'latest';
    } else if (AWS.util.isType(version, Date)) {
      version = AWS.util.date.iso8601(version).split('T')[0];
    }

    if (Object.hasOwnProperty(this.constructor.services, version)) {
      return version;
    }

    var keys = Object.keys(this.constructor.services).sort();
    var selectedVersion = null;
    for (var i = keys.length - 1; i >= 0; i--) {
      // versions that end in "*" are not available on disk and can be
      // skipped, so do not choose these as selectedVersions
      if (keys[i][keys[i].length - 1] !== '*') {
        selectedVersion = keys[i];
      }
      if (keys[i].substr(0, 10) <= version) {
        return selectedVersion;
      }
    }

    throw new Error('Could not find ' + this.constructor.serviceIdentifier +
                    ' API to satisfy version constraint `' + version + '\'');
  },

  /**
   * @api private
   */
  api: {},

  /**
   * @api private
   */
  defaultRetryCount: 3,

  /**
   * Calls an operation on a service with the given input parameters.
   *
   * @param operation [String] the name of the operation to call on the service.
   * @param params [map] a map of input options for the operation
   * @callback callback function(err, data)
   *   If a callback is supplied, it is called when a response is returned
   *   from the service.
   *   @param err [Error] the error object returned from the request.
   *     Set to `null` if the request is successful.
   *   @param data [Object] the de-serialized data returned from
   *     the request. Set to `null` if a request error occurs.
   */
  makeRequest: function makeRequest(operation, params, callback) {
    if (typeof params === 'function') {
      callback = params;
      params = null;
    }

    params = params || {};
    if (this.config.params) { // copy only toplevel bound params
      var rules = this.api.operations[operation];
      if (rules) {
        params = AWS.util.copy(params);
        AWS.util.each(this.config.params, function(key, value) {
          if (rules.input.members[key]) {
            if (params[key] === undefined || params[key] === null) {
              params[key] = value;
            }
          }
        });
      }
    }

    var request = new AWS.Request(this, operation, params);
    this.addAllRequestListeners(request);

    if (callback) request.send(callback);
    return request;
  },

  /**
   * Calls an operation on a service with the given input parameters, without
   * any authentication data. This method is useful for "public" API operations.
   *
   * @param operation [String] the name of the operation to call on the service.
   * @param params [map] a map of input options for the operation
   * @callback callback function(err, data)
   *   If a callback is supplied, it is called when a response is returned
   *   from the service.
   *   @param err [Error] the error object returned from the request.
   *     Set to `null` if the request is successful.
   *   @param data [Object] the de-serialized data returned from
   *     the request. Set to `null` if a request error occurs.
   */
  makeUnauthenticatedRequest: function makeUnauthenticatedRequest(operation, params, callback) {
    if (typeof params === 'function') {
      callback = params;
      params = {};
    }

    var request = this.makeRequest(operation, params).toUnauthenticated();
    return callback ? request.send(callback) : request;
  },

  /**
   * Waits for a given state
   *
   * @param state [String] the state on the service to wait for
   * @param params [map] a map of parameters to pass with each request
   * @callback callback function(err, data)
   *   If a callback is supplied, it is called when a response is returned
   *   from the service.
   *   @param err [Error] the error object returned from the request.
   *     Set to `null` if the request is successful.
   *   @param data [Object] the de-serialized data returned from
   *     the request. Set to `null` if a request error occurs.
   */
  waitFor: function waitFor(state, params, callback) {
    var waiter = new AWS.ResourceWaiter(this, state);
    return waiter.wait(params, callback);
  },

  /**
   * @api private
   */
  addAllRequestListeners: function addAllRequestListeners(request) {
    var list = [AWS.events, AWS.EventListeners.Core, this.serviceInterface(),
                AWS.EventListeners.CorePost];
    for (var i = 0; i < list.length; i++) {
      if (list[i]) request.addListeners(list[i]);
    }

    // disable parameter validation
    if (!this.config.paramValidation) {
      request.removeListener('validate',
        AWS.EventListeners.Core.VALIDATE_PARAMETERS);
    }

    if (this.config.logger) { // add logging events
      request.addListeners(AWS.EventListeners.Logger);
    }

    this.setupRequestListeners(request);
  },

  /**
   * Override this method to setup any custom request listeners for each
   * new request to the service.
   *
   * @abstract
   */
  setupRequestListeners: function setupRequestListeners() {
  },

  /**
   * Gets the signer class for a given request
   * @api private
   */
  getSignerClass: function getSignerClass() {
    var version = this.api.signatureVersion;
    if (this.config.signatureVersion) version = this.config.signatureVersion;
    else if (this.isRegionV4()) version = 'v4';
    return AWS.Signers.RequestSigner.getVersion(version);
  },

  /**
   * @api private
   */
  serviceInterface: function serviceInterface() {
    switch (this.api.protocol) {
      case 'query': return AWS.EventListeners.Query;
      case 'json': return AWS.EventListeners.Json;
      case 'rest-json': return AWS.EventListeners.RestJson;
      case 'rest-xml': return AWS.EventListeners.RestXml;
    }
    if (this.api.protocol) {
      throw new Error('Invalid service `protocol\' ' +
        this.api.protocol + ' in API config');
    }
  },

  /**
   * @api private
   */
  successfulResponse: function successfulResponse(resp) {
    return resp.httpResponse.statusCode < 300;
  },

  /**
   * How many times a failed request should be retried before giving up.
   * the defaultRetryCount can be overriden by service classes.
   *
   * @api private
   */
  numRetries: function numRetries() {
    if (this.config.maxRetries !== undefined) {
      return this.config.maxRetries;
    } else {
      return this.defaultRetryCount;
    }
  },

  /**
   * @api private
   */
  retryDelays: function retryDelays() {
    var retryCount = this.numRetries();
    var delays = [];
    for (var i = 0; i < retryCount; ++i) {
      delays[i] = Math.pow(2, i) * 30;
    }
    return delays;
  },

  /**
   * @api private
   */
  retryableError: function retryableError(error) {
    if (this.networkingError(error)) return true;
    if (this.expiredCredentialsError(error)) return true;
    if (this.throttledError(error)) return true;
    if (error.statusCode >= 500) return true;
    return false;
  },

  /**
   * @api private
   */
  networkingError: function networkingError(error) {
    return error.code === 'NetworkingError';
  },

  /**
   * @api private
   */
  expiredCredentialsError: function expiredCredentialsError(error) {
    // TODO : this only handles *one* of the expired credential codes
    return (error.code === 'ExpiredTokenException');
  },

  /**
   * @api private
   */
  throttledError: function throttledError(error) {
    // this logic varies between services
    return (error.code === 'ProvisionedThroughputExceededException');
  },

  /**
   * @api private
   */
  endpointFromTemplate: function endpointFromTemplate(endpoint) {
    if (typeof endpoint !== 'string') return endpoint;

    var e = endpoint;
    e = e.replace(/\{service\}/g, this.api.endpointPrefix);
    e = e.replace(/\{region\}/g, this.config.region);
    e = e.replace(/\{scheme\}/g, this.config.sslEnabled ? 'https' : 'http');
    return e;
  },

  /**
   * @api private
   */
  setEndpoint: function setEndpoint(endpoint) {
    if (endpoint) {
      this.endpoint = new AWS.Endpoint(endpoint, this.config);
    } else if (this.hasGlobalEndpoint()) {
      this.endpoint = new AWS.Endpoint(this.api.globalEndpoint, this.config);
    } else {
      var host = this.api.endpointPrefix + '.' + this.config.region +
                 this.endpointSuffix();
      this.endpoint = new AWS.Endpoint(host, this.config);
    }
  },

  /**
   * @api private
   */
  hasGlobalEndpoint: function hasGlobalEndpoint() {
    if (this.isRegionV4()) return false;
    return this.api.globalEndpoint;
  },

  /**
   * @api private
   */
  endpointSuffix: function endpointSuffix() {
    var suffix = '.amazonaws.com';
    if (this.isRegionCN()) return suffix + '.cn';
    else return suffix;
  },

  /**
   * @api private
   */
  isRegionCN: function isRegionCN() {
    if (!this.config.region) return false;
    return this.config.region.match(/^cn-/) ? true : false;
  },

  /**
   * @api private
   */
  isRegionV4: function isRegionV4() {
    return this.isRegionCN();
  },

  /**
   * @api private
   */
  paginationConfig: function paginationConfig(operation, throwException) {
    var paginator = this.api.operations[operation].paginator;
    if (!paginator) {
      if (throwException) {
        var e = new Error();
        throw AWS.util.error(e, 'No pagination configuration for ' + operation);
      }
      return null;
    }

    return paginator;
  }
});

AWS.util.update(AWS.Service, {

  /**
   * Adds one method for each operation described in the api configuration
   *
   * @api private
   */
  defineMethods: function defineMethods(svc) {
    AWS.util.each(svc.prototype.api.operations, function iterator(method) {
      if (svc.prototype[method]) return;
      svc.prototype[method] = function (params, callback) {
        return this.makeRequest(method, params, callback);
      };
    });
  },

  /**
   * Defines a new Service class using a service identifier and list of versions
   * including an optional set of features (functions) to apply to the class
   * prototype.
   *
   * @param serviceIdentifier [String] the identifier for the service
   * @param versions [Array<String>] a list of versions that work with this
   *   service
   * @param features [Object] an object to attach to the prototype
   * @return [Class<Service>] the service class defined by this function.
   */
  defineService: function defineService(serviceIdentifier, versions, features) {
    if (!Array.isArray(versions)) {
      features = versions;
      versions = [];
    }

    var svc = inherit(AWS.Service, features || {});

    if (typeof serviceIdentifier === 'string') {
      AWS.Service.addVersions(svc, versions);

      var identifier = svc.serviceIdentifier || serviceIdentifier;
      svc.serviceIdentifier = identifier;
    } else { // defineService called with an API
      svc.prototype.api = serviceIdentifier;
      AWS.Service.defineMethods(svc);
    }

    return svc;
  },

  /**
   * @api private
   */
  addVersions: function addVersions(svc, versions) {
    if (!Array.isArray(versions)) versions = [versions];

    svc.services = svc.services || {};
    for (var i = 0; i < versions.length; i++) {
      if (svc.services[versions[i]] === undefined) {
        svc.services[versions[i]] = null;
      }
    }

    svc.apiVersions = Object.keys(svc.services).sort();
  },

  /**
   * @api private
   */
  defineServiceApi: function defineServiceApi(superclass, version, apiConfig) {
    var svc = inherit(superclass, {
      serviceIdentifier: superclass.serviceIdentifier
    });

    function setApi(api) {
      if (api.isApi) {
        svc.prototype.api = api;
      } else {
        svc.prototype.api = new Api(api);
      }
    }

    if (typeof version === 'string') {
      if (apiConfig) {
        setApi(apiConfig);
      } else {
        try {
          var apis = AWS.util.nodeRequire('aws-sdk-apis');
          setApi(apis.load(superclass.serviceIdentifier, version));
        } catch (err) {
          throw AWS.util.error(err, {
            message: 'Could not find API configuration ' +
              superclass.serviceIdentifier + '-' + version
          });
        }
      }
      if (!superclass.services.hasOwnProperty(version)) {
        superclass.apiVersions = superclass.apiVersions.concat(version).sort();
      }
      superclass.services[version] = svc;
    } else {
      setApi(version);
    }

    AWS.Service.defineMethods(svc);
    return svc;
  }
});
