'use strict';
let express = require("express"),
    bodyParser= require("body-parser"),
    app = express(),
    request = require('request'),
    config = require('config'),
    images = require("./pics");

app.use(bodyParser.urlencoded({ extended : false}));
app.use(bodyParser.json());

let users = {};

app.listen(process.env.PORT || 8989, () => console.log('Example app listening on por 8989!'));

app.get('/', (req, res) => res.send('Hello World!'));


// Adds support for GET requests to our webhook
app.get('/webhook', (req, res) => {

  // Your verify token, Should be a random string.
  let VERIFY_TOKEN = "2016104171";

  // Parse the query params
  let mode = req.query['hub.mode'];
  let token = req.query['hub.verify_token'];
  let challenge = req.query['hub.challenge'];


  // Checks if a token and mode is in the query string of the request
  if(mode && token) {

    // Checks the mode and token sent is correcct
    if (mode === 'subscribe' && token === VERIFY_TOKEN) {

      // Responds with the challenge token from the request
      console.log('WEBHOOK_VERIFIED');
      res.status(200).send(challenge);

    } else {
      // Responds with '403 Forbidden' if verify tokens do not match
      res.sendStatus(403);
    }
  }
});

// Creates the endpoint for our webhook
app.post('/webhook', (req, res) => {

  let body = req.body;

  if (body.object === 'page') {

    // Iterates over each entry - there may be multiple if batched
    body.entry.forEach(function(entry) {

      // Gets the message. entry.messaging is an array, but
      // will only ever contain one message, so we get index 0
      let webhook_event = entry.messaging[0];
      console.log(webhook_event);

      // Get the sender PSID
      let sender_psid = webhook_event.sender.id;
      console.log('Sender PSID: ' + sender_psid);

      // Check if the event is a message or postback and
      // pass the event to the appropriate handler function
      if (webhook_event.message) {
        handleMessage(sender_psid, webhook_event.message);
      } else if (webhook_event.postback) {
        handlePostback(sender_psid, webhook_event.postback);
      }
    });

    // Returns a '200 OK' response to all requests
    res.status(200).send('EVENT_RECEIVED');
  } else {
    // Returns a '404 Not Found' if event is not from a page subscription
    res.sendStatus(404);
  }

});

// Views - handle Message, handle Postback

// Handles message events
const handleMessage = (sender_psid, received_message) => {
  let response;

  if(received_message.text){

    // Create the payload for a basic text message
    response = askTemplate()
  }

  // Sends the reponse message
  callSendAPI(sender_psid, response;
}

const handlePostback = (sender_psid, received_postback) => {
  let response;

  // Get the payload for the postback
  let payload = received_postback.payload;

  // Set the response based on the postback payload
  if (payload === 'CAT_PICS') {
    response = imageTemplate('cats', sender_psid);
    callSendAPI(sender_psid, response, function(){
      callSendAPI(sender_psid, askTemplate('Show me more'));
    });
  } else if (payload === 'DOG_PICS') {
    response = imageTemplate('dogs', sender_psid);
    callSendAPI(sender_psid, response, function(){
      callSendAPI(sender_psid, askTemplate('Show me more'));
    });
  } else if(payload === 'GET_STARTED'){
    response = askTemplate('Are you a Cat or Dog Person?');
    callSendAPI(sender_psid, response);
  }
  // Send the message to acknowledge the postback
}

const askTemplate = (text) => {
  return {
    "attachment":{
      "type":"template",
      "payload":{
        "template_type":"button",
        "text": text,
        "buttons":[
          {
            "type":"postback",
            "title":"Cats",
            "payload":"CAT_PICS"
          },
          {
            "type":"postback",
            "title":"Dogs",
            "payload":"DOG_PICS"
          }
        ]
      }
    }
  }
}

// Sends response messages via the Send API
const callSendAPI = (sender_psid, response, cb = null) => {
  // Construct the message body
  let request_body = {
    "recipient": {
      "id": sender_psid
    },
    "message": response
  };

  // Send the HTTP request to the Messenger Platform
  request({
    "uri": "https://graph.facebook.com/v2.6/me/messages",
    "qs": { "access_token": config.get('facebook.page.access_token') },
    "method": "POST",
    "json": request_body
  }, (err, res, body) => {
    if (!err) {
      if(cb){
        cb();
      }
    } else {
      console.error("Unable to send message:" + err);
    }
  });
}

const imageTemplate= (type, sender_id) => {
  return {
    "attachment":{
      "type":"image",
      "payload":{
        "url": getImage(type, sender_id),
        "is_reusable":true
      }
    }
  }
}

let users = {};

const getImage= (type, sender_id) => {
  // create user if doesn't exist
  if(users[sender_id] === undefined){
    users = Object.assign({
      [sender_id] : {
        'cats_count' : 0,
        'dogs_count' : 0
      }
    }, users);
  }

  let count = images[type].length, // total available images by type
      user = users[sender_id], // // user requesting image
      user_type_count = user[type+'_count'];


  // update user before returning image
  let updated_user = {
    [sender_id] : Object.assign(user, {
      [type+'_count'] : count === user_type_count + 1 ? 0 : user_type_count + 1
    })
  };
  // update users
  users = Object.assign(users, updated_user);

  console.log(users);
  return images[type][user_type_count];
}