store: implement the simplified index handling

Simplify the index handling for moving to the next or previous message.
Same for moving to the next or previous search results. Moving of the
index variable relies on the iterator package's StartIndex and EndIndex
functions.

Signed-off-by: Koni Marti <koni.marti@gmail.com>
Acked-by: Robin Jarry <robin@jarry.cc>

lib/iterator/index.go

@@ -21,6 +21,9 @@ func FixBounds(i, lower, upper int) int {
 // WrapBounds will wrap the index i around its upper- or lower-bound if
 // out-of-bound
 func WrapBounds(i, lower, upper int) int {
+	if upper <= 0 {
+		return lower
+	}
 	switch {
 	case i > upper:
 		i = lower + (i-upper-1)%upper

lib/msgstore.go

@@ -593,29 +593,20 @@ func (store *MessageStore) NextPrev(delta int) {
 	if len(uids) == 0 {
 		return
 	}
+
 	iter := store.iterFactory.NewIterator(uids)
 
-	uid := store.SelectedUid()
-
-	newIdx := store.FindIndexByUid(uid)
+	newIdx := store.FindIndexByUid(store.SelectedUid())
 	if newIdx < 0 {
 		store.Select(uids[iter.StartIndex()])
 		return
 	}
-
-	low, high := iter.EndIndex(), iter.StartIndex()
-	sign := -1
-	if high < low {
-		low, high = high, low
-		sign = 1
-	}
-	newIdx += sign * delta
-	if newIdx >= len(uids) {
-		newIdx = high
-	} else if newIdx < 0 {
-		newIdx = low
-	}
-
+	newIdx = iterator.MoveIndex(
+		newIdx,
+		delta,
+		iter,
+		iterator.FixBounds,
+	)
 	store.Select(uids[newIdx])
 
 	if store.BuildThreads() && store.ThreadedView() {
@@ -631,15 +622,7 @@ func (store *MessageStore) NextPrev(delta int) {
 	if store.marker != nil {
 		store.marker.UpdateVisualMark()
 	}
-
-	nextResultIndex := len(store.results) - store.resultIndex - 2*delta
-	if nextResultIndex < 0 || nextResultIndex >= len(store.results) {
-		return
-	}
-	nextResultUid := store.results[nextResultIndex]
-	if nextResultUid == store.SelectedUid() {
-		store.resultIndex += delta
-	}
+	store.updateResults()
 }
 
 func (store *MessageStore) Next() {
@@ -690,18 +673,35 @@ func (store *MessageStore) ApplyClear() {
 	store.Sort(nil, nil)
 }
 
+func (store *MessageStore) updateResults() {
+	if len(store.results) == 0 || store.resultIndex < 0 {
+		return
+	}
+	uid := store.SelectedUid()
+	for i, u := range store.results {
+		if uid == u {
+			store.resultIndex = i
+			break
+		}
+	}
+}
+
 func (store *MessageStore) nextPrevResult(delta int) {
 	if len(store.results) == 0 {
 		return
 	}
-	store.resultIndex += delta
-	if store.resultIndex >= len(store.results) {
-		store.resultIndex = 0
-	}
+	iter := store.iterFactory.NewIterator(store.results)
 	if store.resultIndex < 0 {
-		store.resultIndex = len(store.results) - 1
+		store.resultIndex = iter.StartIndex()
+	} else {
+		store.resultIndex = iterator.MoveIndex(
+			store.resultIndex,
+			delta,
+			iter,
+			iterator.WrapBounds,
+		)
 	}
-	store.Select(store.results[len(store.results)-store.resultIndex-1])
+	store.Select(store.results[store.resultIndex])
 	store.update(false)
 }