var linebot = require('linebot');

var express = require('express');

var translate = require('google-translate-api');

var bot = linebot({

  channelId: '請輸入LineBot的channelId',

  channelSecret: '請輸入LineBot的channelSecret',

  channelAccessToken: '請輸入LineBot的channelAccessToken'

});

var users=[];

//預設翻譯語言是英文

var defaultLangNum=2;

//以下各國語言陣列，可自行加減，語言代碼參照，請參考以下連結

//https://cloud.google.com/translate/docs/languages

var languages=[

    {language: '繁體中文', code: 'zh-tw'},

    {language: '簡體中文', code: 'zh-cn'},

    {language: '英文', code: 'en'},

    {language: '日文', code: 'ja'},

    {language: '韓文', code: 'ko'},

    {language: '泰文', code: 'th'},

    {language: '越南文', code: 'vi'},

    {language: '印尼文', code: 'id'},

    {language: '德文', code: 'de'},

    {language: '法文', code: 'fr'},

    {language: '俄文', code: 'ru'}

];

//取得第一次交談時的歡迎詞

var welcomeStr=getWelcomeStr();

bot.on('message', function(event) {

   var myReply='';

   var myId=event.source.userId;

   if (event.message.type === 'text') {

      if (users[myId]===undefined){

         users[myId]=[];

         users[myId].userId=myId;

         users[myId].defaultLangNum=defaultLangNum;

         myReply=welcomeStr+'目前的設定的翻譯語言為：'+languages[users[myId].defaultLangNum].language;

      }else if(event.message.text==='?'){

         myReply=welcomeStr+'目前的設定的翻譯語言為：'+languages[users[myId].defaultLangNum].language;

      }else if(!isNaN(event.message.text)){

         if (Number(event.message.text)<languages.length)

            setLanguage(myId,Number(event.message.text));

      }else{

         translate(event.message.text, {to: languages[users[myId].defaultLangNum].code}).then(res => {

         bot.push(myId,res.text);

         }).catch(err => {

            console.error(err);

         });

      }

      event.reply(myReply).then(function(data) {

         // success 

         console.log(myReply);

      }).catch(function(error){   

         // error 

         console.log('error');

      });

   }

});

//傳送訊息的函式

function sendMessage(eve,msg){

   eve.reply(msg).then(function(data) {

      // success 

      return true;

   }).catch(function(error) {

      // error 

      return false;

   });

}

//此為設定翻譯語言之函式

function setLanguage(userId,myLangNum){

   users[userId].defaultLangNum=myLangNum;

   bot.push(userId,'翻譯的語言已設定為：'+languages[myLangNum].language);

}

//此為處理語言設定字串之函式

function getWelcomeStr(){

   var myResult='您好，歡迎來到吉哥的即時翻譯LineBot，讓您用Line就可以翻譯各國語言。您可以輸入各國語言，轉換成您想要翻譯的語言，所以，請先設定您想要轉換成的語言，輸入數字即可設定完成：\n';

   for(var i=0;i<languages.length;i++){

      myResult+=(i+'：'+languages[i].language+'\n');

   }

   myResult+='?：列出語言設定指令\n';

   return myResult;

}

const app = express();

const linebotParser = bot.parser();

app.post('/', linebotParser);

//因為 express 預設走 port 3000，而 heroku 上預設卻不是，要透過下列程式轉換

var server = app.listen(process.env.PORT || 8080, function() {

  var port = server.address().port;

  console.log("App now running on port", port);

});