Add GroupByLastmod

Fixes #7408

2 files changed, 51 insertions, 0 deletions

diff --git a/resources/page/pagegroup.go b/resources/page/pagegroup.go
index fbb6e7e53..2d37a5d4d 100644
--- a/resources/page/pagegroup.go
+++ b/resources/page/pagegroup.go
@@ -284,6 +284,20 @@ func (p Pages) GroupByExpiryDate(format string, order ...string) (PagesGroup, er
 	return p.groupByDateField(sorter, formatter, order...)
 }
 
+// GroupByLastmod groups by the given page's Lastmod value in
+// the given format and with the given order.
+// Valid values for order is asc, desc, rev and reverse.
+// For valid format strings, see https://golang.org/pkg/time/#Time.Format
+func (p Pages) GroupByLastmod(format string, order ...string) (PagesGroup, error) {
+	sorter := func(p Pages) Pages {
+		return p.ByLastmod()
+	}
+	formatter := func(p Page) string {
+		return p.Lastmod().Format(format)
+	}
+	return p.groupByDateField(sorter, formatter, order...)
+}
+
 // GroupByParamDate groups by a date set as a param on the page in
 // the given format and with the given order.
 // Valid values for order is asc, desc, rev and reverse.
diff --git a/resources/page/pagegroup_test.go b/resources/page/pagegroup_test.go
index 26a25c381..fe6dbf94b 100644
--- a/resources/page/pagegroup_test.go
+++ b/resources/page/pagegroup_test.go
@@ -49,6 +49,7 @@ func preparePageGroupTestPages(t *testing.T) Pages {
 		p.date = cast.ToTime(src.date)
 		p.pubDate = cast.ToTime(src.date)
 		p.expiryDate = cast.ToTime(src.date)
+		p.lastMod = cast.ToTime(src.date).AddDate(3, 0, 0)
 		p.params["custom_param"] = src.param
 		p.params["custom_date"] = cast.ToTime(src.date)
 		pages = append(pages, p)
@@ -378,6 +379,42 @@ func TestGroupByParamDate(t *testing.T) {
 	}
 }
 
+func TestGroupByLastmod(t *testing.T) {
+	t.Parallel()
+	pages := preparePageGroupTestPages(t)
+	expect := PagesGroup{
+		{Key: "2015-04", Pages: Pages{pages[4], pages[2], pages[0]}},
+		{Key: "2015-03", Pages: Pages{pages[3]}},
+		{Key: "2015-01", Pages: Pages{pages[1]}},
+	}
+
+	groups, err := pages.GroupByLastmod("2006-01")
+	if err != nil {
+		t.Fatalf("Unable to make PagesGroup array: %s", err)
+	}
+	if !reflect.DeepEqual(groups, expect) {
+		t.Errorf("PagesGroup has unexpected groups. It should be %#v, got %#v", expect, groups)
+	}
+}
+
+func TestGroupByLastmodInReverseOrder(t *testing.T) {
+	t.Parallel()
+	pages := preparePageGroupTestPages(t)
+	expect := PagesGroup{
+		{Key: "2015-01", Pages: Pages{pages[1]}},
+		{Key: "2015-03", Pages: Pages{pages[3]}},
+		{Key: "2015-04", Pages: Pages{pages[0], pages[2], pages[4]}},
+	}
+
+	groups, err := pages.GroupByLastmod("2006-01", "asc")
+	if err != nil {
+		t.Fatalf("Unable to make PagesGroup array: %s", err)
+	}
+	if !reflect.DeepEqual(groups, expect) {
+		t.Errorf("PagesGroup has unexpected groups. It should be\n%#v, got\n%#v", expect, groups)
+	}
+}
+
 func TestGroupByParamDateInReverseOrder(t *testing.T) {
 	t.Parallel()
 	pages := preparePageGroupTestPages(t)