From 766b57d52d583f46f8f2f36b0af68f1c5b171505 Mon Sep 17 00:00:00 2001
From: Kyle Corry <kylecorry31@gmail.com>
Date: Sat, 12 Sep 2020 15:27:22 -0400
Subject: [PATCH] Get more accurate sunrise/set times

---
 .../trailsensecore/domain/astronomy/Astro.kt  | 25 ++++++++++++++++---
 .../domain/time/TimeExtensions.kt             |  6 ++---
 .../domain/astronomy/AstroTest.kt             |  1 +
 3 files changed, 26 insertions(+), 6 deletions(-)

diff --git a/app/src/main/java/com/kylecorry/trailsensecore/domain/astronomy/Astro.kt b/app/src/main/java/com/kylecorry/trailsensecore/domain/astronomy/Astro.kt
index 8281266f..96c4650d 100644
--- a/app/src/main/java/com/kylecorry/trailsensecore/domain/astronomy/Astro.kt
+++ b/app/src/main/java/com/kylecorry/trailsensecore/domain/astronomy/Astro.kt
@@ -356,9 +356,12 @@ internal object Astro {
         coordinate: Coordinate,
         standardAltitude: Double = -0.8333
     ): RiseSetTransitTimes {
-        val ut = ut(date).toLocalDate().atStartOfDay()
-        val sr = meanSiderealTime(julianDay(ut))
-        val sun = solarCoordinates(julianDay(ut))
+        val ut = ut0hOnDate(date)
+        val jd = julianDay(ut)
+        val longitudeNutation = nutationInLongitude(jd)
+        val eclipticObliquity = trueObliquityOfEcliptic(jd)
+        val sr = apparentSiderealTime(jd, longitudeNutation, eclipticObliquity)
+        val sun = solarCoordinates(jd)
         val times = riseSetTransitTimes(
             coordinate.latitude,
             coordinate.longitude,
@@ -528,6 +531,22 @@ internal object Astro {
     private fun square(a: Double): Double {
         return a * a
     }
+
+
+    private fun ut0hOnDate(date: ZonedDateTime): LocalDateTime {
+        val localDate = date.toLocalDate()
+
+        for (i in -1..1){
+            val ut0h = ut(date.plusDays(i.toLong())).toLocalDate().atStartOfDay()
+            val local0h = utToLocal(ut0h, date.zone)
+            if (localDate == local0h.toLocalDate()){
+                return ut0h
+            }
+        }
+
+        return ut(date).toLocalDate().atStartOfDay()
+    }
+
 }
 
 data class AstroCoordinates(val declination: Double, val rightAscension: Double)
diff --git a/app/src/main/java/com/kylecorry/trailsensecore/domain/time/TimeExtensions.kt b/app/src/main/java/com/kylecorry/trailsensecore/domain/time/TimeExtensions.kt
index 5f26b40f..8de0c83f 100644
--- a/app/src/main/java/com/kylecorry/trailsensecore/domain/time/TimeExtensions.kt
+++ b/app/src/main/java/com/kylecorry/trailsensecore/domain/time/TimeExtensions.kt
@@ -28,8 +28,8 @@ fun Instant.toZonedDateTime(): ZonedDateTime {
 
 fun LocalDateTime.plusHours(hours: Double): LocalDateTime {
     val h = hours.toLong()
-    val m = ((hours % 1) * 60).toLong()
-    val s = (hours * 60) % 1
+    val m = (hours % 1) * 60
+    val s = (m % 1) * 60
     val ns = (1e9 * s).toLong()
-    return this.plusHours(h).plusMinutes(m).plusNanos(ns)
+    return this.plusHours(h).plusMinutes(m.toLong()).plusNanos(ns)
 }
\ No newline at end of file
diff --git a/app/src/test/java/com/kylecorry/trailsensecore/domain/astronomy/AstroTest.kt b/app/src/test/java/com/kylecorry/trailsensecore/domain/astronomy/AstroTest.kt
index 17de783f..4a093993 100644
--- a/app/src/test/java/com/kylecorry/trailsensecore/domain/astronomy/AstroTest.kt
+++ b/app/src/test/java/com/kylecorry/trailsensecore/domain/astronomy/AstroTest.kt
@@ -240,4 +240,5 @@ class AstroTest {
         assertEquals(-7.78507, coords.declination, 0.0001)
         assertEquals(-161.61917, coords.rightAscension, 0.0001)
     }
+
 }
\ No newline at end of file