From c1c8ecc9d6df31830a64618cb04f79ae34a3335a Mon Sep 17 00:00:00 2001
From: Hanchen Wang <hanchen.wang@mail.utoronto.ca>
Date: Wed, 11 May 2016 10:09:43 -0400
Subject: [PATCH] hugolib: Add GroupByExpireDate function

---
 hugolib/pageGroup.go      | 13 +++++++++++++
 hugolib/pageGroup_test.go | 18 ++++++++++++++++++
 2 files changed, 31 insertions(+)

diff --git a/hugolib/pageGroup.go b/hugolib/pageGroup.go
index 4f5286b8..814bf3e7 100644
--- a/hugolib/pageGroup.go
+++ b/hugolib/pageGroup.go
@@ -253,6 +253,19 @@ func (p Pages) GroupByPublishDate(format string, order ...string) (PagesGroup, e
 	return p.groupByDateField(sorter, formatter, order...)
 }
 
+// GroupByExpireDate groups by the given page's ExpireDate 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) GroupByExpiryDate(format string, order ...string) (PagesGroup, error) {
+	sorter := func(p Pages) Pages {
+		return p.ByExpiryDate()
+	}
+	formatter := func(p *Page) string {
+		return p.ExpiryDate.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.
 // For valid format strings, see https://golang.org/pkg/time/#Time.Format
diff --git a/hugolib/pageGroup_test.go b/hugolib/pageGroup_test.go
index c9b3cfaa..e7a97517 100644
--- a/hugolib/pageGroup_test.go
+++ b/hugolib/pageGroup_test.go
@@ -47,6 +47,7 @@ func preparePageGroupTestPages(t *testing.T) Pages {
 		p.Weight = s.weight
 		p.Date = cast.ToTime(s.date)
 		p.PublishDate = cast.ToTime(s.date)
+		p.ExpiryDate = cast.ToTime(s.date)
 		p.Params["custom_param"] = s.param
 		p.Params["custom_date"] = cast.ToTime(s.date)
 		pages = append(pages, p)
@@ -369,6 +370,23 @@ func TestGroupByPublishDateWithEmptyPages(t *testing.T) {
 	}
 }
 
+func TestGroupByExpiryDate(t *testing.T) {
+	pages := preparePageGroupTestPages(t)
+	expect := PagesGroup{
+		{Key: "2012-04", Pages: Pages{pages[4], pages[2], pages[0]}},
+		{Key: "2012-03", Pages: Pages{pages[3]}},
+		{Key: "2012-01", Pages: Pages{pages[1]}},
+	}
+
+	groups, err := pages.GroupByExpiryDate("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 TestGroupByParamDate(t *testing.T) {
 	pages := preparePageGroupTestPages(t)
 	expect := PagesGroup{
-- 
2.30.2