var util = require('./util');
var defaultConfig = {};

function Client(options) {
  this.options = options =
    util.clone(util.defaults(options || {}, defaultConfig));

  if (!options.server) {
    throw 'The server config option is required';
  }

  this._server = options.server;
  this._nextId = 0;
}

Client.prototype._makeRequest = function () {
  var method, params, callback, id;
  var args = Array.prototype.slice.call(arguments);
  var lastArg = args.length - 1;
  var request = {
    jsonrpc: '2.0'
  };

  if (util.isObject(args[0]) &&
    !util.isUndefined(args[0]) && !util.isNull(args[0])
  ) {
    // called with a config object
    method = args[0].method;
    params = args[0].params;
    request.callback = args[0].callback;
  } else {
    // called with a method name and optional params and callback
    method = args[0];
    params = args.slice(1);
  }

  if (!util.isString(method)) {
    throw 'Method must be a string';
  }

  if (params === null ||
    (!util.isArray(params) && !util.isObject(params))
  ) {
    throw 'Params must be an object or array';
  }

  request.method = method;
  if (params) {
    request.params = params;
  }

  return request;
};

Client.prototype._send = function (request, callback) {
  try {
    request = JSON.stringify(request);
  } catch (e) {
    throw 'Could not serialize request to JSON';
  }

  if (callback) {
    this._server.respond(request, function (error, response) {
      callback(error, JSON.parse(response));
    });
  } else {
    this._server.respond(request);
  }
};

Client.prototype.request = function () {
  var request = this._makeRequest.apply(this, arguments);
  var callback;
  var response;

  request.id = this._nextId++;

  if (request.callback) {
    callback = request.callback;
    delete request.callback;
  } else if (util.isArray(request.params) &&
    util.isFunction(request.params[request.params.length - 1])
  ) {
    callback = request.params.pop();
  }

  this._send(request, function (error, response) {
    if (callback) {
      if (error) {
        return callback(error, null);
      }

      callback(response.error || null, response.result || null);
    }
  });
};

Client.prototype.notify = function () {
  var request = this._makeRequest.apply(this, arguments);

  delete request.callback;

  this._send(request);
};

function parseArgs(args) {
  args = args.split(/,\s*/);
  var result = {};

  for (var i = 0; i < args.length; i++) {
    result[args[i]] = i;
  }

  return result;
}

function keys(o) {
  if (Object.prototype.keys) {
    return o.keys();
  }

  var result = [];
  for (var k in o) {
    if (o.hasOwnProperty(k)) {
      result.push(k);
    }
  }

  return result;
}

module.exports = Client;