Make Pages.Prev/Next work like the other Prev/Next methods

Fixes #4500

3 files changed, 30 insertions, 26 deletions

diff --git a/resources/page/pages_prev_next.go b/resources/page/pages_prev_next.go
index 9293c9874..dd87aa4ce 100644
--- a/resources/page/pages_prev_next.go
+++ b/resources/page/pages_prev_next.go
@@ -13,13 +13,12 @@
 
 package page
 
-// Prev returns the previous page reletive to the given
-func (p Pages) Prev(cur Page) Page {
+// Next returns the next page reletive to the given
+func (p Pages) Next(cur Page) Page {
 	for x, c := range p {
 		if c.Eq(cur) {
 			if x == 0 {
-				// TODO(bep) consider return nil here to get it line with the other Prevs
-				return p[len(p)-1]
+				return nil
 			}
 			return p[x-1]
 		}
@@ -27,15 +26,14 @@ func (p Pages) Prev(cur Page) Page {
 	return nil
 }
 
-// Next returns the next page reletive to the given
-func (p Pages) Next(cur Page) Page {
+// Prev returns the previous page reletive to the given
+func (p Pages) Prev(cur Page) Page {
 	for x, c := range p {
 		if c.Eq(cur) {
 			if x < len(p)-1 {
 				return p[x+1]
 			}
-			// TODO(bep) consider return nil here to get it line with the other Nexts
-			return p[0]
+			return nil
 		}
 	}
 	return nil
diff --git a/resources/page/pages_prev_next_test.go b/resources/page/pages_prev_next_test.go
index a75335f00..689e102c2 100644
--- a/resources/page/pages_prev_next_test.go
+++ b/resources/page/pages_prev_next_test.go
@@ -38,18 +38,20 @@ func TestPrev(t *testing.T) {
 	t.Parallel()
 	c := qt.New(t)
 	pages := preparePageGroupTestPages(t)
-	c.Assert(pages[4], qt.Equals, pages.Prev(pages[0]))
-	c.Assert(pages[0], qt.Equals, pages.Prev(pages[1]))
-	c.Assert(pages[3], qt.Equals, pages.Prev(pages[4]))
+
+	c.Assert(pages.Prev(pages[3]), qt.Equals, pages[4])
+	c.Assert(pages.Prev(pages[1]), qt.Equals, pages[2])
+	c.Assert(pages.Prev(pages[4]), qt.IsNil)
 }
 
 func TestNext(t *testing.T) {
 	t.Parallel()
 	c := qt.New(t)
 	pages := preparePageGroupTestPages(t)
-	c.Assert(pages[1], qt.Equals, pages.Next(pages[0]))
-	c.Assert(pages[2], qt.Equals, pages.Next(pages[1]))
-	c.Assert(pages[0], qt.Equals, pages.Next(pages[4]))
+
+	c.Assert(pages.Next(pages[0]), qt.IsNil)
+	c.Assert(pages.Next(pages[1]), qt.Equals, pages[0])
+	c.Assert(pages.Next(pages[4]), qt.Equals, pages[3])
 }
 
 func prepareWeightedPagesPrevNext(t *testing.T) WeightedPages {
@@ -72,16 +74,20 @@ func TestWeightedPagesPrev(t *testing.T) {
 	t.Parallel()
 	c := qt.New(t)
 	w := prepareWeightedPagesPrevNext(t)
-	c.Assert(w[4].Page, qt.Equals, w.Prev(w[0].Page))
-	c.Assert(w[0].Page, qt.Equals, w.Prev(w[1].Page))
-	c.Assert(w[3].Page, qt.Equals, w.Prev(w[4].Page))
+
+	c.Assert(w.Prev(w[0].Page), qt.Equals, w[1].Page)
+	c.Assert(w.Prev(w[1].Page), qt.Equals, w[2].Page)
+	c.Assert(w.Prev(w[4].Page), qt.IsNil)
+
 }
 
 func TestWeightedPagesNext(t *testing.T) {
 	t.Parallel()
 	c := qt.New(t)
 	w := prepareWeightedPagesPrevNext(t)
-	c.Assert(w[1].Page, qt.Equals, w.Next(w[0].Page))
-	c.Assert(w[2].Page, qt.Equals, w.Next(w[1].Page))
-	c.Assert(w[0].Page, qt.Equals, w.Next(w[4].Page))
+
+	c.Assert(w.Next(w[0].Page), qt.IsNil)
+	c.Assert(w.Next(w[1].Page), qt.Equals, w[0].Page)
+	c.Assert(w.Next(w[4].Page), qt.Equals, w[3].Page)
+
 }
diff --git a/resources/page/weighted.go b/resources/page/weighted.go
index 48ed736ce..b2fc8b67b 100644
--- a/resources/page/weighted.go
+++ b/resources/page/weighted.go
@@ -95,13 +95,13 @@ func (wp WeightedPages) Pages() Pages {
 	return pages
 }
 
-// Prev returns the previous Page relative to the given Page in
+// Next returns the next Page relative to the given Page in
 // this weighted page set.
-func (wp WeightedPages) Prev(cur Page) Page {
+func (wp WeightedPages) Next(cur Page) Page {
 	for x, c := range wp {
 		if c.Page == cur {
 			if x == 0 {
-				return wp[len(wp)-1].Page
+				return nil
 			}
 			return wp[x-1].Page
 		}
@@ -109,15 +109,15 @@ func (wp WeightedPages) Prev(cur Page) Page {
 	return nil
 }
 
-// Next returns the next Page relative to the given Page in
+// Prev returns the previous Page relative to the given Page in
 // this weighted page set.
-func (wp WeightedPages) Next(cur Page) Page {
+func (wp WeightedPages) Prev(cur Page) Page {
 	for x, c := range wp {
 		if c.Page == cur {
 			if x < len(wp)-1 {
 				return wp[x+1].Page
 			}
-			return wp[0].Page
+			return nil
 		}
 	}
 	return nil