From 05b417acfa10a970a442b264aa4e9037cb26721b Mon Sep 17 00:00:00 2001
From: Michael Mayer <michael@lastzero.net>
Date: Tue, 26 Jan 2021 13:00:54 +0100
Subject: [PATCH] Metadata: Apply existing time zone when changing TakenAt

---
 internal/entity/photo.go      | 29 ++++++++++++++++-------------
 internal/entity/photo_test.go | 16 ++++++++++++----
 2 files changed, 28 insertions(+), 17 deletions(-)

diff --git a/internal/entity/photo.go b/internal/entity/photo.go
index 129e9a1c9..196b33292 100644
--- a/internal/entity/photo.go
+++ b/internal/entity/photo.go
@@ -857,6 +857,11 @@ func (m *Photo) SetTakenAt(taken, local time.Time, zone, source string) {
 		return
 	}
 
+	// Default local time to taken if zero or invalid.
+	if local.IsZero() || local.Year() < 1000 {
+		local = taken
+	}
+
 	// Round times to avoid jitter.
 	taken = taken.Round(time.Second).UTC()
 	local = local.Round(time.Second)
@@ -866,23 +871,21 @@ func (m *Photo) SetTakenAt(taken, local time.Time, zone, source string) {
 		return
 	}
 
+	// Set UTC time and date source.
 	m.TakenAt = taken
 	m.TakenSrc = source
 
-	if local.IsZero() || local.Year() < 1000 {
-		m.TakenAtLocal = m.TakenAt
-	} else {
-		m.TakenAtLocal = local
-	}
-
-	// Set time zone.
-	if zone != "" {
+	// Convert time and set zone as needed.
+	if loc, err := time.LoadLocation(zone); err == nil && zone != "" {
+		// Apply new time zone.
 		m.TimeZone = zone
-	}
-
-	// Apply time zone.
-	if m.TimeZone != "" {
-		m.TakenAt = m.GetTakenAt()
+		m.TakenAtLocal = m.TakenAt.In(loc)
+	} else if m.TimeZone == "" {
+		// Ignore time zone.
+		m.TakenAtLocal = local
+	} else if loc, err := time.LoadLocation(m.TimeZone); err == nil {
+		// Apply existing time zone.
+		m.TakenAtLocal = m.TakenAt.In(loc)
 	}
 
 	m.UpdateDateFields()
diff --git a/internal/entity/photo_test.go b/internal/entity/photo_test.go
index 222822732..e4becfee0 100644
--- a/internal/entity/photo_test.go
+++ b/internal/entity/photo_test.go
@@ -575,11 +575,19 @@ func TestPhoto_SetTakenAt(t *testing.T) {
 		assert.Equal(t, time.Date(2013, 11, 11, 9, 7, 18, 0, time.UTC), m.TakenAt)
 		assert.Equal(t, time.Date(2013, 11, 11, 9, 7, 18, 0, time.UTC), m.TakenAtLocal)
 
-		m.SetTakenAt(time.Date(2013, 11, 11, 9, 7, 18, 0, time.UTC),
-			time.Date(2013, 11, 11, 9, 7, 18, 0, time.UTC), "Europe/Berlin", SrcName)
+		newTime := time.Date(2013, 11, 11, 9, 7, 18, 0, time.UTC)
+		newLoc, _ := time.LoadLocation("Europe/Berlin")
 
-		assert.Equal(t, time.Date(2013, 11, 11, 8, 7, 18, 0, time.UTC), m.TakenAt)
-		assert.Equal(t, time.Date(2013, 11, 11, 9, 7, 18, 0, time.UTC), m.TakenAtLocal)
+		m.SetTakenAt(newTime, newTime, "Europe/Berlin", SrcName)
+
+		/*
+			t.Logf("TakenAt: %s\n", m.TakenAt)
+			t.Logf("TakenAtLocal: %s\n", m.TakenAtLocal)
+			t.Logf("Expected: %s\n", newTime.In(newLoc))
+		*/
+
+		assert.Equal(t, newTime, m.TakenAt)
+		assert.Equal(t, newTime.In(newLoc), m.TakenAtLocal)
 	})
 	t.Run("time > max year", func(t *testing.T) {
 		m := PhotoFixtures.Get("Photo15")