'use strict';

const functions = require('firebase-functions');
const admin = require('firebase-admin');
admin.initializeApp();

var db = admin.firestore();

const MAX_NOTIFICATIONS_PER_DAY = 150;

exports.sendPushNotification = functions.https.onRequest(async (req, res) => {
  console.log('Received payload', req.body);
  var today = getToday();
  var token = req.body.push_token;
  var ref = db.collection('rateLimits').doc(today).collection('tokens').doc(token);

  var payload = {
    notification: {
      body: req.body.message
    },
    android: {
        priority: 'HIGH',
        notification: {
            sound: 'default',
            icon: 'mini_icon',
            channel_id: 'ha_notify'
        }
    },
    token: token,
  };

  if(req.body.title) {
    payload.notification.title = req.body.title;
  }

  if(req.body.data) {
    if(req.body.data.android) {
      payload.android = req.body.data.android;
    }
    if(req.body.data.apns) {
      payload.apns = req.body.data.apns;
    }
    if(req.body.data.data) {
      payload.data = req.body.data.data;
    }
    if(req.body.data.webpush) {
      payload.webpush = req.body.data.webpush;
    }
  }

  console.log('Notification payload', JSON.stringify(payload));

  var docExists = false;
  var docData = {
    deliveredCount: 0,
    errorCount: 0,
    totalCount: 0,
  };

  try {
    let currentDoc = await ref.get();
    docExists = currentDoc.exists;
    if(currentDoc.exists) {
      docData = currentDoc.data();
    }
  } catch(err) {
    console.error('Error getting document!', err);
    return handleError(res, 'getDoc', err);
  }

  if(docData.deliveredCount > MAX_NOTIFICATIONS_PER_DAY) {
    return res.status(429).send({
      errorType: 'RateLimited',
      message: 'The given target has reached the maximum number of notifications allowed per day. Please try again later.',
      target: token,
      rateLimits: getRateLimitsObject(docData),
    });
  }

  docData.totalCount = docData.totalCount + 1;

  var messageId;
  try {
    messageId = await admin.messaging().send(payload);
    docData.deliveredCount = docData.deliveredCount + 1;
  } catch(err) {
    docData.errorCount = docData.errorCount + 1;
    await setRateLimitDoc(ref, docExists, docData, res);
    return handleError(res, 'sendNotification', err);
  }

  console.log('Successfully sent message:', messageId);

  await setRateLimitDoc(ref, docExists, docData, res);

  return res.status(201).send({
    messageId: messageId,
    sentPayload: payload,
    target: token,
    rateLimits: getRateLimitsObject(docData),
  });

});

async function setRateLimitDoc(ref, docExists, docData, res) {
  try {
    if(docExists) {
      console.log('Updating existing doc!');
      await ref.update(docData);
    } else {
      console.log('Creating new doc!');
      await ref.set(docData);
    }
  } catch(err) {
    if(docExists) {
      console.error('Error updating document!', err);
    } else {
      console.error('Error creating document!', err);
    }
    return handleError(res, 'setDocument', err);
  }
  return true;
}

function handleError(res, step, incomingError) {
  if (!incomingError) return null;
  console.error('InternalError during', step, incomingError);
  return res.status(500).send({
    errorType: 'InternalError',
    errorStep: step,
    message: incomingError.message,
  });
}

function getToday() {
  var today = new Date();
  var dd = String(today.getDate()).padStart(2, '0');
  var mm = String(today.getMonth() + 1).padStart(2, '0');
  var yyyy = today.getFullYear();
  return yyyy + mm + dd;
}

function getRateLimitsObject(doc) {
  var d = new Date();
  return {
    successful: (doc.deliveredCount || 0),
    errors: (doc.errorCount || 0),
    total: (doc.totalCount || 0),
    maximum: MAX_NOTIFICATIONS_PER_DAY,
    remaining: (MAX_NOTIFICATIONS_PER_DAY - doc.deliveredCount),
    resetsAt: new Date(d.getFullYear(), d.getMonth(), d.getDate()+1)
  };
}