From c08a739158c7eda24cb86dcc9c7a4c57d720112e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mike=20Schw=C3=B6rer?= <pubgit@mikescher.com>
Date: Thu, 21 Sep 2023 16:29:23 +0200
Subject: [PATCH] v0.0.268 added WeekStart() and WeekEnd()

---
 goextVersion.go              |  4 ++--
 timeext/calendarweek.go      | 28 ++++++++++++++++++++++++++++
 timeext/calendarweek_test.go | 25 +++++++++++++++++++++++++
 3 files changed, 55 insertions(+), 2 deletions(-)
 create mode 100644 timeext/calendarweek.go
 create mode 100644 timeext/calendarweek_test.go

diff --git a/goextVersion.go b/goextVersion.go
index ba66875..62d29fc 100644
--- a/goextVersion.go
+++ b/goextVersion.go
@@ -1,5 +1,5 @@
 package goext
 
-const GoextVersion = "0.0.267"
+const GoextVersion = "0.0.268"
 
-const GoextVersionTimestamp = "2023-09-21T14:15:02+0200"
+const GoextVersionTimestamp = "2023-09-21T16:29:23+0200"
diff --git a/timeext/calendarweek.go b/timeext/calendarweek.go
new file mode 100644
index 0000000..1de8974
--- /dev/null
+++ b/timeext/calendarweek.go
@@ -0,0 +1,28 @@
+package timeext
+
+import "time"
+
+func WeekStart(year, week int) time.Time {
+
+	// https://stackoverflow.com/a/52303730/1761622
+
+	// Start from the middle of the year:
+	t := time.Date(year, 7, 1, 0, 0, 0, 0, time.UTC)
+
+	// Roll back to Monday:
+	if wd := t.Weekday(); wd == time.Sunday {
+		t = t.AddDate(0, 0, -6)
+	} else {
+		t = t.AddDate(0, 0, -int(wd)+1)
+	}
+
+	// Difference in weeks:
+	_, w := t.ISOWeek()
+	t = t.AddDate(0, 0, (week-w)*7)
+
+	return t
+}
+
+func WeekEnd(year, week int) time.Time {
+	return WeekStart(year, week).AddDate(0, 0, 7).Add(time.Duration(-1))
+}
diff --git a/timeext/calendarweek_test.go b/timeext/calendarweek_test.go
new file mode 100644
index 0000000..9fbab0a
--- /dev/null
+++ b/timeext/calendarweek_test.go
@@ -0,0 +1,25 @@
+package timeext
+
+import (
+	"gogs.mikescher.com/BlackForestBytes/goext/tst"
+	"testing"
+	"time"
+)
+
+func TestWeekStart(t *testing.T) {
+
+	tst.AssertEqual(t, WeekStart(2018, 1).Format(time.RFC3339Nano), "2018-01-01T00:00:00Z")
+	tst.AssertEqual(t, WeekStart(2018, 2).Format(time.RFC3339Nano), "2018-01-08T00:00:00Z")
+	tst.AssertEqual(t, WeekStart(2019, 1).Format(time.RFC3339Nano), "2018-12-31T00:00:00Z")
+	tst.AssertEqual(t, WeekStart(2019, 2).Format(time.RFC3339Nano), "2019-01-07T00:00:00Z")
+
+}
+
+func TestWeekEnd(t *testing.T) {
+
+	tst.AssertEqual(t, WeekEnd(2018, 1).Format(time.RFC3339Nano), "2018-01-07T23:59:59.999999999Z")
+	tst.AssertEqual(t, WeekEnd(2018, 2).Format(time.RFC3339Nano), "2018-01-14T23:59:59.999999999Z")
+	tst.AssertEqual(t, WeekEnd(2019, 1).Format(time.RFC3339Nano), "2019-01-06T23:59:59.999999999Z")
+	tst.AssertEqual(t, WeekEnd(2019, 2).Format(time.RFC3339Nano), "2019-01-13T23:59:59.999999999Z")
+
+}