Faster unfragment. (#57)

The old implementation was N^2 which could take a long time for
subtitles with many items. Break out of the loop after we are
beyond the end time for the item that is being compared.

Also support unfragmenting nested items, eg:

1 -> 4 and 2 -> 5 will be combined into 1 -> 5.

Author: j0sh

subtitles.go

@@ -619,20 +619,25 @@ func (s *Subtitles) Unfragment() {
 		return
 	}
 
+	// Order
+	s.Order()
+
 	// Loop through items
 	for i := 0; i < len(s.Items)-1; i++ {
 		for j := i + 1; j < len(s.Items); j++ {
 			// Items are the same
-			if s.Items[i].String() == s.Items[j].String() && s.Items[i].EndAt == s.Items[j].StartAt {
-				s.Items[i].EndAt = s.Items[j].EndAt
+			if s.Items[i].String() == s.Items[j].String() && s.Items[i].EndAt >= s.Items[j].StartAt {
+				// Only override end time if longer
+				if s.Items[i].EndAt < s.Items[j].EndAt {
+					s.Items[i].EndAt = s.Items[j].EndAt
+				}
 				s.Items = append(s.Items[:j], s.Items[j+1:]...)
 				j--
+			} else if s.Items[i].EndAt < s.Items[j].StartAt {
+				break
 			}
 		}
 	}
-
-	// Order
-	s.Order()
 }
 
 // Write writes subtitles to a file

subtitles_test.go

@@ -126,6 +126,72 @@ func TestSubtitles_Fragment(t *testing.T) {
 	assert.Equal(t, 5*time.Second, s.Items[2].EndAt)
 }
 
+func TestSubtitles_Unfragment(t *testing.T) {
+	itemText := func(s string) []astisub.Line {
+		return []astisub.Line{{Items: []astisub.LineItem{{Text: s}}}}
+	}
+	items := []*astisub.Item{{
+		Lines:   itemText("subtitle-1"),
+		StartAt: 1 * time.Second,
+		EndAt:   2 * time.Second,
+	}, {
+		Lines:   itemText("subtitle-2"),
+		StartAt: 2 * time.Second,
+		EndAt:   5 * time.Second,
+	}, {
+		Lines:   itemText("subtitle-3"),
+		StartAt: 3 * time.Second,
+		EndAt:   4 * time.Second,
+	}, {
+		// gap and nested within first subtitle-2; should not override end time
+		Lines:   itemText("subtitle-2"),
+		StartAt: 3 * time.Second,
+		EndAt:   4 * time.Second,
+	}, {
+		Lines: itemText("subtitle-3"),
+		// gap and start time equals previous end time
+		StartAt: 4 * time.Second,
+		EndAt:   5 * time.Second,
+	}, {
+		// should not be combined
+		Lines:   itemText("subtitle-3"),
+		StartAt: 6 * time.Second,
+		EndAt:   7 * time.Second,
+	}, {
+		// test correcting for out-of-orderness
+		Lines:   itemText("subtitle-1"),
+		StartAt: 0 * time.Second,
+		EndAt:   3 * time.Second,
+	}}
+
+	s := &astisub.Subtitles{Items: items}
+
+	s.Unfragment()
+
+	expected := []astisub.Item{{
+		Lines:   itemText("subtitle-1"),
+		StartAt: 0 * time.Second,
+		EndAt:   3 * time.Second,
+	}, {
+		Lines:   itemText("subtitle-2"),
+		StartAt: 2 * time.Second,
+		EndAt:   5 * time.Second,
+	}, {
+		Lines:   itemText("subtitle-3"),
+		StartAt: 3 * time.Second,
+		EndAt:   5 * time.Second,
+	}, {
+		Lines:   itemText("subtitle-3"),
+		StartAt: 6 * time.Second,
+		EndAt:   7 * time.Second,
+	}}
+
+	assert.Equal(t, len(expected), len(s.Items))
+	for i := range expected {
+		assert.Equal(t, expected[i], *s.Items[i])
+	}
+}
+
 func TestSubtitles_Merge(t *testing.T) {
 	var s1 = &astisub.Subtitles{Items: []*astisub.Item{{EndAt: 3 * time.Second, StartAt: time.Second}, {EndAt: 8 * time.Second, StartAt: 5 * time.Second}, {EndAt: 12 * time.Second, StartAt: 10 * time.Second}}, Regions: map[string]*astisub.Region{"region_0": {ID: "region_0"}, "region_1": {ID: "region_1"}}, Styles: map[string]*astisub.Style{"style_0": {ID: "style_0"}, "style_1": {ID: "style_1"}}}
 	var s2 = &astisub.Subtitles{Items: []*astisub.Item{{EndAt: 4 * time.Second, StartAt: 2 * time.Second}, {EndAt: 7 * time.Second, StartAt: 6 * time.Second}, {EndAt: 11 * time.Second, StartAt: 9 * time.Second}, {EndAt: 14 * time.Second, StartAt: 13 * time.Second}}, Regions: map[string]*astisub.Region{"region_1": {ID: "region_1"}, "region_2": {ID: "region_2"}}, Styles: map[string]*astisub.Style{"style_1": {ID: "style_1"}, "style_2": {ID: "style_2"}}}