const functions = require('firebase-functions');
const admin = require('firebase-admin');
admin.initializeApp();
// Listens for new messages added to /messages/:pushId/original and creates an
// uppercase version of the message to /messages/:pushId/uppercase
exports.takecurrdata = functions.database.ref('loc')
    .onUpdate((snapshot, context) => {
    
      // Grab the current value of what was written to the Realtime Database.
      var data = snapshot.after.val();
      var latarray =snapshot.after.child('targetloc').child('lati').val();
      var lonarray =snapshot.after.child('targetloc').child('longi').val();
      console.log(latarray);
      console.log(snapshot.after.child('targetloc').val()); 
      var ai=0;
      var d = 0;
      var smallest = 1000000;
      var last = latarray.length;
      admin.database().ref().child('count').set(parseFloat(last-1))
      while(ai < last){
            
            var lati = parseFloat(latarray[ai]);
            var longi = parseFloat(lonarray[ai]);
            console.log(lati);
            console.log(longi);
            var clati = parseFloat(snapshot.after.child('currloc').child('lati').val());
            var clongi =parseFloat(snapshot.after.child('currloc').child('longi').val());
            console.log(clati);
            console.log(clongi);
            const R = 6371e3; // metres
            const φ1 = lati * Math.PI/180; // φ, λ in radians
            const φ2 = clati * Math.PI/180;
            const Δφ = (clati-lati) * Math.PI/180;
            const Δλ = (clongi-longi) * Math.PI/180;
            const a = Math.sin(Δφ/2) * Math.sin(Δφ/2) + Math.cos(φ1) * Math.cos(φ2) *Math.sin(Δλ/2) * Math.sin(Δλ/2);
            const c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
            d = R * c; // in metres
            if(d < smallest){
                 smallest =d;
                  }
            if(ai === last - 1){
                 console.log(smallest);
                 admin.database().ref().child('distance').set(parseFloat(smallest));
            }
            ai++;
       } 
      // You must return a Promise when performing asynchronous tasks inside a Functions such as
      // writing to the Firebase Realtime Database.
      // Setting an "uppercase" sibling in the Realtime Database returns a Promise.
      
    });