/*
 *
 * Copyright 2015 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.
 *
 */

'use strict';

var grpc = require('../..');
var grpcMath = require('./math_grpc_pb');
var math = require('./math_pb');

/**
 * Server function for division. Provides the /Math/DivMany and /Math/Div
 * functions (Div is just DivMany with only one stream element). For each
 * DivArgs parameter, responds with a DivReply with the results of the division
 * @param {Object} call The object containing request and cancellation info
 * @param {function(Error, *)} cb Response callback
 */
function mathDiv(call, cb) {
  var req = call.request;
  var divisor = req.getDivisor();
  var dividend = req.getDividend();
  // Unary + is explicit coersion to integer
  if (req.getDivisor() === 0) {
    cb(new Error('cannot divide by zero'));
  } else {
    var response = new math.DivReply();
    response.setQuotient(Math.floor(dividend / divisor));
    response.setRemainder(dividend % divisor);
    cb(null, response);
  }
}

/**
 * Server function for Fibonacci numbers. Provides the /Math/Fib function. Reads
 * a single parameter that indicates the number of responses, and then responds
 * with a stream of that many Fibonacci numbers.
 * @param {stream} stream The stream for sending responses.
 */
function mathFib(stream) {
  // Here, call is a standard writable Node object Stream
  var previous = 0, current = 1;
  for (var i = 0; i < stream.request.getLimit(); i++) {
    var response = new math.Num();
    response.setNum(current);
    stream.write(response);
    var temp = current;
    current += previous;
    previous = temp;
  }
  stream.end();
}

/**
 * Server function for summation. Provides the /Math/Sum function. Reads a
 * stream of number parameters, then responds with their sum.
 * @param {stream} call The stream of arguments.
 * @param {function(Error, *)} cb Response callback
 */
function mathSum(call, cb) {
  // Here, call is a standard readable Node object Stream
  var sum = 0;
  call.on('data', function(data) {
    sum += data.getNum();
  });
  call.on('end', function() {
    var response = new math.Num();
    response.setNum(sum);
    cb(null, response);
  });
}

function mathDivMany(stream) {
  stream.on('data', function(div_args) {
    var divisor = div_args.getDivisor();
    var dividend = div_args.getDividend();
    if (divisor === 0) {
      stream.emit('error', new Error('cannot divide by zero'));
    } else {
      var response = new math.DivReply();
      response.setQuotient(Math.floor(dividend / divisor));
      response.setRemainder(dividend % divisor);
      stream.write(response);
    }
  });
  stream.on('end', function() {
    stream.end();
  });
}

function getMathServer() {
  var server = new grpc.Server();
  server.addService(grpcMath.MathService, {
    div: mathDiv,
    fib: mathFib,
    sum: mathSum,
    divMany: mathDivMany
  });
  return server;
}

if (require.main === module) {
  var server = getMathServer();
  server.bind('0.0.0.0:50051', grpc.ServerCredentials.createInsecure());
  server.start();
}

/**
 * See docs for server
 */
module.exports = getMathServer;