From d21b9bb478097af8197ef8c091279061896b61bd Mon Sep 17 00:00:00 2001
From: Sergey Matveev <stargrave@stargrave.org>
Date: Fri, 22 Nov 2024 18:05:18 +0300
Subject: [PATCH] More tests

---
 leapsecs.go | 17 +++++-------
 tai.go      |  4 +--
 tai_test.go | 74 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 83 insertions(+), 12 deletions(-)

diff --git a/leapsecs.go b/leapsecs.go
index 4bad6a2..dc76829 100644
--- a/leapsecs.go
+++ b/leapsecs.go
@@ -29,18 +29,15 @@ var Leapsecs LeapsecsList
 
 // Add leap seconds to the time (convert TAI to UTC).
 func (leapsecs LeapsecsList) Add(tai time.Time) (utc time.Time) {
-	var i int
-	v := tai.Unix()
-	for ; i < len(leapsecs); i++ {
-		if v < leapsecs[i] {
-			break
+	orig := tai.Unix()
+	v := orig
+	v += Leapsecs1972
+	for _, leapsec := range Leapsecs {
+		if v >= leapsec {
+			v++
 		}
 	}
-	diff := Leapsecs1972 + int64(i)
-	if v+diff == leapsecs[i] {
-		diff++
-	}
-	utc = tai.Add(time.Second * time.Duration(diff))
+	utc = tai.Add(time.Second * time.Duration(v-orig))
 	return
 }
 
diff --git a/tai.go b/tai.go
index 52b9d73..8335213 100644
--- a/tai.go
+++ b/tai.go
@@ -51,12 +51,12 @@ func (tai *TAI64N) FromTime(src time.Time) {
 }
 
 func (tai *TAI64) Time() time.Time {
-	return time.Unix(int64(binary.BigEndian.Uint64(tai[:TAI64Size]))-Base, 0)
+	return time.Unix(int64(binary.BigEndian.Uint64(tai[:TAI64Size]))-Base, 0).In(time.UTC)
 }
 
 func (tai *TAI64N) Time() time.Time {
 	return time.Unix(
 		int64(binary.BigEndian.Uint64(tai[:TAI64Size]))-Base,
 		int64(binary.BigEndian.Uint32(tai[TAI64Size:])),
-	)
+	).In(time.UTC)
 }
diff --git a/tai_test.go b/tai_test.go
index bce160a..b48175c 100644
--- a/tai_test.go
+++ b/tai_test.go
@@ -17,6 +17,7 @@ package tai64n
 
 import (
 	"testing"
+	"testing/quick"
 	"time"
 )
 
@@ -93,6 +94,79 @@ func TestVectors(t *testing.T) {
 	if isLeap {
 		t.Fatal("unexpectedly leap")
 	}
+
+	tm, err = Decode("40000000586846a6")
+	if err != nil {
+		t.Fatal(err)
+	}
+	tm, isLeap = Leapsecs.Sub(tm)
+	ref = time.Date(2017, 1, 1, 0, 0, 1, 0, time.UTC)
+	if !tm.Equal(ref) {
+		t.Fatal("UTC != reference")
+	}
+	if isLeap {
+		t.Fatal("unexpectedly leap")
+	}
+}
+
+func TestLeaped(t *testing.T) {
+	tm := time.Date(2016, 12, 31, 23, 59, 59, 0, time.UTC)
+	tm = Leapsecs.Add(tm)
+	var tai TAI64
+	tai.FromTime(tm)
+	if tai.Encode() != "@40000000586846a3" {
+		t.Fatal("bad 2016-12-31 23:59:59")
+	}
+
+	tm = time.Date(2017, 1, 1, 0, 0, 0, 0, time.UTC)
+	tm = Leapsecs.Add(tm)
+	tai.FromTime(tm)
+	if tai.Encode() != "@40000000586846a5" {
+		t.Fatal("bad 2017-01-01 00:00:00")
+	}
+
+	tm = time.Date(2017, 1, 1, 0, 0, 1, 0, time.UTC)
+	tm = Leapsecs.Add(tm)
+	tai.FromTime(tm)
+	if tai.Encode() != "@40000000586846a6" {
+		t.Fatal("bad 2017-01-01 00:00:01")
+	}
+}
+
+func TestLeapsecsSymmetric(t *testing.T) {
+	f := func(secs int64) bool {
+		tm := time.Unix(secs, 0)
+		got, isLeap := Leapsecs.Sub(Leapsecs.Add(tm))
+		if isLeap {
+			return false
+		}
+		return tm == got
+	}
+	if err := quick.Check(f, nil); err != nil {
+		t.Error(err)
+	}
+}
+
+func Test1969(t *testing.T) {
+	tm := time.Date(1969, 1, 1, 0, 0, 0, 0, time.UTC)
+	tm = Leapsecs.Add(tm)
+	var tai TAI64
+	tai.FromTime(tm)
+	tm = tai.Time()
+	tm, _ = Leapsecs.Sub(tm)
+	if tm != time.Date(1969, 1, 1, 0, 0, 0, 0, time.UTC) {
+		t.Fatal("bad 1969 without ms")
+	}
+
+	tm = time.Date(1969, 1, 1, 0, 0, 0, 1, time.UTC)
+	tm = Leapsecs.Add(tm)
+	var tain TAI64N
+	tain.FromTime(tm)
+	tm = tain.Time()
+	tm, _ = Leapsecs.Sub(tm)
+	if tm != time.Date(1969, 1, 1, 0, 0, 0, 1, time.UTC) {
+		t.Fatal("bad 1969 with ms=1")
+	}
 }
 
 func BenchmarkTAI64(b *testing.B) {
-- 
2.48.1