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//
// PositionDecoder.swift
// ADSBDecoder
//
// Created by Jacky Jack on 14/06/2024.
//
import Foundation
import Collections
struct PositionData {
var cpr_lat: UInt32
var cpr_long: UInt32
var even: Bool
var cprtime: Int64
}
func cpr_mod(_ a: Int, _ b: Int) -> Int {
var res:Int = a % b;
if (res < 0) {
res += b
}
return res;
}
/* The NL function uses the precomputed table from 1090-WP-9-14 */
func cpr_NLFunction(_ _lat: Double) -> Int {
var lat:Double = _lat
if (lat < 0) {
lat = -lat
} /* Table is simmetric about the equator. */
if (lat < 10.47047130) {return 59}
if (lat < 14.82817437) {return 58}
if (lat < 18.18626357) {return 57}
if (lat < 21.02939493) {return 56}
if (lat < 23.54504487) {return 55}
if (lat < 25.82924707) {return 54}
if (lat < 27.93898710) {return 53}
if (lat < 29.91135686) {return 52}
if (lat < 31.77209708) {return 51}
if (lat < 33.53993436) {return 50}
if (lat < 35.22899598) {return 49}
if (lat < 36.85025108) {return 48}
if (lat < 38.41241892) {return 47}
if (lat < 39.92256684) {return 46}
if (lat < 41.38651832) {return 45}
if (lat < 42.80914012) {return 44}
if (lat < 44.19454951) {return 43}
if (lat < 45.54626723) {return 42}
if (lat < 46.86733252) {return 41}
if (lat < 48.16039128) {return 40}
if (lat < 49.42776439) {return 39}
if (lat < 50.67150166) {return 38}
if (lat < 51.89342469) {return 37}
if (lat < 53.09516153) {return 36}
if (lat < 54.27817472) {return 35}
if (lat < 55.44378444) {return 34}
if (lat < 56.59318756) {return 33}
if (lat < 57.72747354) {return 32}
if (lat < 58.84763776) {return 31}
if (lat < 59.95459277) {return 30}
if (lat < 61.04917774) {return 29}
if (lat < 62.13216659) {return 28}
if (lat < 63.20427479) {return 27}
if (lat < 64.26616523) {return 26}
if (lat < 65.31845310) {return 25}
if (lat < 66.36171008) {return 24}
if (lat < 67.39646774) {return 23}
if (lat < 68.42322022) {return 22}
if (lat < 69.44242631) {return 21}
if (lat < 70.45451075) {return 20}
if (lat < 71.45986473) {return 19}
if (lat < 72.45884545) {return 18}
if (lat < 73.45177442) {return 17}
if (lat < 74.43893416) {return 16}
if (lat < 75.42056257) {return 15}
if (lat < 76.39684391) {return 14}
if (lat < 77.36789461) {return 13}
if (lat < 78.33374083) {return 12}
if (lat < 79.29428225) {return 11}
if (lat < 80.24923213) {return 10}
if (lat < 81.19801349) {return 9}
if (lat < 82.13956981) {return 8}
if (lat < 83.07199445) {return 7}
if (lat < 83.99173563) {return 6}
if (lat < 84.89166191) {return 5}
if (lat < 85.75541621) {return 4}
if (lat < 86.53536998) {return 3}
if (lat < 87.00000000) {return 2}
else {return 1}
}
func cpr_NFunction(_ lat: Double, _ isodd: Int) -> Int {
var nl:Int = cpr_NLFunction(lat) - isodd;
if (nl < 1) {
nl = 1
}
return nl;
}
func cpr_DlonFunction(_ lat: Double, _ isodd: Int) -> Double {
return 360.0 / Double(cpr_NFunction(lat, isodd));
}
func mstime() -> Int64 {
var tv:timeval = timeval(tv_sec: 0, tv_usec: 0)
var mst:Int64=0;
gettimeofday(&tv, nil);
mst = Int64(tv.tv_sec)*1000;
mst += Int64(tv.tv_usec)/1000;
return mst;
}
class PositionDecoder {
var long: Double = 0.0
var lat: Double = 0.0
var ready: Bool = false
var newposition: Bool = false
//initialise first values so this values is nonsence
var queue: Deque<PositionData> = []
init() {
}
func addEvenPosition(_ cpr_lat: UInt32,_ cpr_long: UInt32, _ cprtime: Int64) {
queue.append(PositionData(cpr_lat:cpr_lat, cpr_long:cpr_long, even:true, cprtime: cprtime))
}
func addOddPosition(_ cpr_lat: UInt32,_ cpr_long: UInt32, _ cprtime: Int64) {
queue.append(PositionData(cpr_lat:cpr_lat,cpr_long:cpr_long,even:false, cprtime: cprtime))
}
func getPosition() -> (Double, Double)? {
if (ready) {
return (lat, long)
}
return nil
}
//TODO: allways adds to queue newer frees the queue
func calcPosition() -> Bool {
if (queue.count > 2) {
let el1 = queue[queue.count-1]
let el2 = queue[queue.count-2]
if (el1.even == el2.even) {
//ready = false
return false
}
} else {
ready = false
print("Position queue to short to calculate values")
return false
}
//last to elements are evan and odd
let el1 = queue[queue.count-1]
let el2 = queue[queue.count-2]
let cpr_even = el1.even ? el1 : el2
let cpr_odd = (!el1.even) ? el1 : el2
//print("Position queue is ready to calculate location \(cpr_even) \(cpr_odd)")
// from here https://github.com/antirez/dump1090/blob/master/dump1090.c#L1718
let AirDlat0:Double = 360.0/60.0
let AirDlat1:Double = 360.0/59.0
let lat0 = Int(cpr_even.cpr_lat)
let lat1 = Int(cpr_odd.cpr_lat)
let lon0 = Int(cpr_even.cpr_long)
let lon1 = Int(cpr_odd.cpr_long)
//latitude index
let j:Int = Int(floor(((59.0*Double(lat0) - 60.0*Double(lat1)) / 131072.0) + 0.5))
var rlat0:Double = AirDlat0 * (Double(cpr_mod(j,60)) + Double(lat0) / 131072.0)
var rlat1:Double = AirDlat1 * (Double(cpr_mod(j,59)) + Double(lat1) / 131072.0)
if (rlat0 >= 270.0) {
rlat0 -= 360.0
}
if (rlat1 >= 270.0) {
rlat1 -= 360.0
}
/* Check that both are in the same latitude zone, or abort. */
if (cpr_NLFunction(rlat0) != cpr_NLFunction(rlat1)) {
print("Not same lat?!")
return false
}
/* Compute ni and the longitude index m */
if (cpr_even.cprtime > cpr_odd.cprtime) {
/* Use even packet. */
let ni:Int = cpr_NFunction(rlat0,0);
let m:Int = Int(
floor((((Double(lon0) * (Double(cpr_NLFunction(rlat0))-1.0)) -
(Double(lon1) * Double(cpr_NLFunction(rlat0)))) / 131072.0) + 0.5)
);
self.long = Double(cpr_DlonFunction(rlat0,0)) * (Double(cpr_mod(m,ni))+Double(lon0)/131072.0);
self.lat = rlat0;
} else {
/* Use odd packet. */
let ni:Int = cpr_NFunction(rlat1,1);
let m:Int = Int(floor((((Double(lon0) * (Double(cpr_NLFunction(rlat1))-1.0)) -
(Double(lon1) * Double(cpr_NLFunction(rlat1)))) / 131072.0) + 0.5));
self.long = cpr_DlonFunction(rlat1,1) * (Double(cpr_mod(m,ni))+Double(lon1)/131072.0);
self.lat = rlat1;
}
if (self.long > 180) {
self.long -= 360
}
ready = true
return true
}
}
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