/**
 * @license
 * Copyright 2017 gRPC authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */

/**
 * @module
 * @private
 */

'use strict';

var _ = require('lodash');

module.exports = function(grpc) {

  let exports = {};

  /**
   * Get a function that deserializes a specific type of protobuf.
   * @param {function()} cls The constructor of the message type to deserialize
   * @param {bool=} binaryAsBase64 Deserialize bytes fields as base64 strings
   *     instead of Buffers. Defaults to false
   * @param {bool=} longsAsStrings Deserialize long values as strings instead of
   *     objects. Defaults to true
   * @return {function(Buffer):cls} The deserialization function
   */
  exports.deserializeCls = function deserializeCls(cls, options) {
    /**
     * Deserialize a buffer to a message object
     * @param {Buffer} arg_buf The buffer to deserialize
     * @return {cls} The resulting object
     */
    return function deserialize(arg_buf) {
      // Convert to a native object with binary fields as Buffers (first argument)
      // and longs as strings (second argument)
      return cls.decode(arg_buf).toRaw(options.binaryAsBase64,
                                       options.longsAsStrings);
    };
  };

  var deserializeCls = exports.deserializeCls;

  /**
   * Get a function that serializes objects to a buffer by protobuf class.
   * @param {function()} Cls The constructor of the message type to serialize
   * @return {function(Cls):Buffer} The serialization function
   */
  exports.serializeCls = function serializeCls(Cls) {
    /**
     * Serialize an object to a Buffer
     * @param {Object} arg The object to serialize
     * @return {Buffer} The serialized object
     */
    return function serialize(arg) {
      return new Buffer(new Cls(arg).encode().toBuffer());
    };
  };

  var serializeCls = exports.serializeCls;

  /**
   * Get the fully qualified (dotted) name of a ProtoBuf.Reflect value.
   * @param {ProtoBuf.Reflect.Namespace} value The value to get the name of
   * @return {string} The fully qualified name of the value
   */
  exports.fullyQualifiedName = function fullyQualifiedName(value) {
    if (value === null || value === undefined) {
      return '';
    }
    var name = value.name;
    var parent_name = fullyQualifiedName(value.parent);
    if (parent_name !== '') {
      name = parent_name + '.' + name;
    }
    return name;
  };

  var fullyQualifiedName = exports.fullyQualifiedName;

  /**
   * Return a map from method names to method attributes for the service.
   * @param {ProtoBuf.Reflect.Service} service The service to get attributes for
   * @param {Object=} options Options to apply to these attributes
   * @return {Object} The attributes map
   */
  exports.getProtobufServiceAttrs = function getProtobufServiceAttrs(service,
                                                                     options) {
    var prefix = '/' + fullyQualifiedName(service) + '/';
    var binaryAsBase64, longsAsStrings;
    if (options) {
      binaryAsBase64 = options.binaryAsBase64;
      longsAsStrings = options.longsAsStrings;
    }
    /* This slightly awkward construction is used to make sure we only use
       lodash@3.10.1-compatible functions. A previous version used
       _.fromPairs, which would be cleaner, but was introduced in lodash
       version 4 */
    return _.zipObject(_.map(service.children, function(method) {
      return _.camelCase(method.name);
    }), _.map(service.children, function(method) {
      return {
        originalName: method.name,
        path: prefix + method.name,
        requestStream: method.requestStream,
        responseStream: method.responseStream,
        requestType: method.resolvedRequestType,
        responseType: method.resolvedResponseType,
        requestSerialize: serializeCls(method.resolvedRequestType.build()),
        requestDeserialize: deserializeCls(method.resolvedRequestType.build(),
                                           options),
        responseSerialize: serializeCls(method.resolvedResponseType.build()),
        responseDeserialize: deserializeCls(method.resolvedResponseType.build(),
                                            options)
      };
    }));
  };

  var getProtobufServiceAttrs = exports.getProtobufServiceAttrs;

  /**
   * Load a gRPC object from an existing ProtoBuf.Reflect object.
   * @param {ProtoBuf.Reflect.Namespace} value The ProtoBuf object to load.
   * @param {Object=} options Options to apply to the loaded object
   * @return {Object<string, *>} The resulting gRPC object
   */
  exports.loadObject = function loadObject(value, options) {
    var result = {};
    if (!value) {
      return value;
    }
    if (value.hasOwnProperty('ns')) {
      return loadObject(value.ns, options);
    }
    if (value.className === 'Namespace') {
      _.each(value.children, function(child) {
        result[child.name] = loadObject(child, options);
      });
      return result;
    } else if (value.className === 'Service') {
      return grpc.makeGenericClientConstructor(getProtobufServiceAttrs(value, options),
                                               options);
    } else if (value.className === 'Message' || value.className === 'Enum') {
      return value.build();
    } else {
      return value;
    }
  };

  /**
   * The primary purpose of this method is to distinguish between reflection
   * objects from different versions of ProtoBuf.js. This is just a heuristic,
   * checking for properties that are (currently) specific to this version of
   * ProtoBuf.js
   * @param {Object} obj The object to check
   * @return {boolean} Whether the object appears to be a Protobuf.js 5
   *   ReflectionObject
   */
  exports.isProbablyProtobufJs5 = function isProbablyProtobufJs5(obj) {
    return _.isArray(obj.children) && (typeof obj.build === 'function');
  };

  return exports;
};