msgstore: implement a uid-based architecture

Change the message store architecture from an index-based to a uid-based
one. Key advantage of this design approach is that no reselect mechanism
is required anymore since it comes with the design for free.

Fixes: https://todo.sr.ht/~rjarry/aerc/43
Signed-off-by: Koni Marti <koni.marti@gmail.com>
Tested-by: Tim Culverhouse <tim@timculverhouse.com>
Acked-by: Robin Jarry <robin@jarry.cc>

5 files changed, 73 insertions, 86 deletions

diff --git a/commands/account/clear.go b/commands/account/clear.go
index 5bab7109..af7da324 100644
--- a/commands/account/clear.go
+++ b/commands/account/clear.go
@@ -51,8 +51,6 @@ func (Clear) Execute(aerc *widgets.Aerc, args []string) error {
 
 	if clearSelected {
 		defer store.Select(0)
-	} else {
-		store.SetReselect(store.Selected())
 	}
 	store.ApplyClear()
 	acct.SetStatus(statusline.SearchFilterClear())
diff --git a/commands/msg/delete.go b/commands/msg/delete.go
index 2d7ad0f2..d1443887 100644
--- a/commands/msg/delete.go
+++ b/commands/msg/delete.go
@@ -56,7 +56,7 @@ func (Delete) Execute(aerc *widgets.Aerc, args []string) error {
 					// no more messages in the list
 					if next == nil {
 						aerc.RemoveTab(h.msgProvider)
-						store.Select(len(store.Uids()))
+						acct.Messages().Select(0)
 						acct.Messages().Invalidate()
 						return
 					}
@@ -74,7 +74,7 @@ func (Delete) Execute(aerc *widgets.Aerc, args []string) error {
 				if next == nil {
 					// We deleted the last message, select the new last message
 					// instead of the first message
-					store.Select(len(store.Uids()))
+					acct.Messages().Select(0)
 				}
 			}
 			acct.Messages().Invalidate()
diff --git a/commands/msg/toggle-threads.go b/commands/msg/toggle-threads.go
index 05c2c5e1..af694bc0 100644
--- a/commands/msg/toggle-threads.go
+++ b/commands/msg/toggle-threads.go
@@ -34,7 +34,6 @@ func (ToggleThreads) Execute(aerc *widgets.Aerc, args []string) error {
 	if err != nil {
 		return err
 	}
-	store.SetReselect(store.Selected())
 	store.SetThreadedView(!store.ThreadedView())
 	acct.SetStatus(statusline.Threading(store.ThreadedView()))
 	acct.Messages().Invalidate()
diff --git a/lib/msgstore.go b/lib/msgstore.go
index 34c26761..61a6dd44 100644
--- a/lib/msgstore.go
+++ b/lib/msgstore.go
@@ -20,7 +20,7 @@ type MessageStore struct {
 	uids    []uint32
 	Threads []*types.Thread
 
-	selected        int
+	selectedUid     uint32
 	reselect        *models.MessageInfo
 	bodyCallbacks   map[uint32][]func(*types.FullMessage)
 	headerCallbacks map[uint32][]func(*types.MessageInfo)
@@ -57,6 +57,8 @@ type MessageStore struct {
 	dirInfoUpdateDelay    time.Duration
 }
 
+const MagicUid = 0xFFFFFFFF
+
 func NewMessageStore(worker *types.Worker,
 	dirInfo *models.DirectoryInfo,
 	defaultSortCriteria []*types.SortCriterion,
@@ -75,7 +77,7 @@ func NewMessageStore(worker *types.Worker,
 		DirInfo:  *dirInfo,
 		Messages: make(map[uint32]*models.MessageInfo),
 
-		selected:        0,
+		selectedUid:     MagicUid,
 		marked:          make(map[uint32]struct{}),
 		bodyCallbacks:   make(map[uint32][]func(*types.FullMessage)),
 		headerCallbacks: make(map[uint32][]func(*types.MessageInfo)),
@@ -197,9 +199,6 @@ func merge(to *models.MessageInfo, from *models.MessageInfo) {
 func (store *MessageStore) Update(msg types.WorkerMessage) {
 	update := false
 	directoryChange := false
-	if store.reselect == nil {
-		store.SetReselect(store.Selected())
-	}
 	switch msg := msg.(type) {
 	case *types.DirectoryInfo:
 		store.DirInfo = *msg.Info
@@ -367,7 +366,6 @@ func (store *MessageStore) SetThreadedView(thread bool) {
 		if store.threadedView {
 			store.runThreadBuilder()
 		}
-		store.Reselect()
 		return
 	}
 	store.Sort(store.sortCriteria, nil)
@@ -490,54 +488,20 @@ func (store *MessageStore) Uids() []uint32 {
 }
 
 func (store *MessageStore) Selected() *models.MessageInfo {
-	uids := store.Uids()
-	idx := len(uids) - store.selected - 1
-	if len(uids) == 0 || idx < 0 || idx >= len(uids) {
-		return nil
-	}
-	return store.Messages[uids[idx]]
-}
-
-func (store *MessageStore) SelectedIndex() int {
-	return store.selected
+	return store.Messages[store.selectedUid]
 }
 
-func (store *MessageStore) Select(index int) {
-	l := len(store.Uids())
-	switch {
-	case l+index < 0:
-		// negative index overruns length of list
-		store.selected = 0
-	case index < 0:
-		// negative index, select from bottom
-		store.selected = l + index
-	case index >= l:
-		// index greater than length, select last
-		store.selected = l - 1
-	default:
-		store.selected = index
+func (store *MessageStore) SelectedUid() uint32 {
+	if store.selectedUid == MagicUid && len(store.Uids()) > 0 {
+		uids := store.Uids()
+		store.selectedUid = uids[len(uids)-1]
 	}
-	store.updateVisual()
+	return store.selectedUid
 }
 
-func (store *MessageStore) Reselect() {
-	if store.reselect == nil {
-		return
-	}
-	uid := store.reselect.Uid
-	newIdx := 0
-	for idx, uidStore := range store.Uids() {
-		if uidStore == uid {
-			newIdx = len(store.Uids()) - idx - 1
-			break
-		}
-	}
-	store.reselect = nil
-	store.Select(newIdx)
-}
-
-func (store *MessageStore) SetReselect(info *models.MessageInfo) {
-	store.reselect = info
+func (store *MessageStore) Select(uid uint32) {
+	store.selectedUid = uid
+	store.updateVisual()
 }
 
 // Mark sets the marked state on a MessageInfo
@@ -648,15 +612,20 @@ func (store *MessageStore) updateVisual() {
 		store.ClearVisualMark()
 		return
 	}
-	uidLen := len(store.Uids())
-	// store.selected is the inverted form of the actual array
-	selectedIdx := uidLen - store.selected - 1
+
+	selectedIdx := store.FindIndexByUid(store.SelectedUid())
+	if selectedIdx < 0 {
+		store.ClearVisualMark()
+		return
+	}
+
 	var visUids []uint32
 	if selectedIdx > startIdx {
 		visUids = store.Uids()[startIdx : selectedIdx+1]
 	} else {
 		visUids = store.Uids()[selectedIdx : startIdx+1]
 	}
+
 	store.resetMark()
 	for _, uid := range visUids {
 		store.marked[uid] = struct{}{}
@@ -675,20 +644,31 @@ func (store *MessageStore) NextPrev(delta int) {
 	if len(uids) == 0 {
 		return
 	}
-	idx := store.SelectedIndex() + delta
-	if idx < 0 {
-		store.Select(0)
-	} else {
-		store.Select(idx)
+
+	uid := store.SelectedUid()
+
+	newIdx := store.FindIndexByUid(uid)
+	if newIdx < 0 {
+		store.Select(uids[len(uids)-1])
+	}
+
+	newIdx -= delta
+	if newIdx >= len(uids) {
+		newIdx = len(uids) - 1
+	} else if newIdx < 0 {
+		newIdx = 0
 	}
+
+	store.Select(uids[newIdx])
+
 	store.updateVisual()
+
 	nextResultIndex := len(store.results) - store.resultIndex - 2*delta
 	if nextResultIndex < 0 || nextResultIndex >= len(store.results) {
 		return
 	}
 	nextResultUid := store.results[nextResultIndex]
-	selectedUid := uids[len(uids)-store.selected-1]
-	if nextResultUid == selectedUid {
+	if nextResultUid == store.SelectedUid() {
 		store.resultIndex += delta
 	}
 }
@@ -734,21 +714,12 @@ func (store *MessageStore) SetFilter(args []string) {
 }
 
 func (store *MessageStore) ApplyClear() {
-	if store.reselect == nil {
-		store.SetReselect(store.Selected())
-	}
 	store.filter = []string{"filter"}
 	store.results = nil
 	if store.onFilterChange != nil {
 		store.onFilterChange(store)
 	}
-	cb := func(msg types.WorkerMessage) {
-		switch msg.(type) {
-		case *types.Done:
-			store.Reselect()
-		}
-	}
-	store.Sort(nil, cb)
+	store.Sort(nil, nil)
 }
 
 func (store *MessageStore) nextPrevResult(delta int) {
@@ -762,13 +733,7 @@ func (store *MessageStore) nextPrevResult(delta int) {
 	if store.resultIndex < 0 {
 		store.resultIndex = len(store.results) - 1
 	}
-	uids := store.Uids()
-	for i, uid := range uids {
-		if store.results[len(store.results)-store.resultIndex-1] == uid {
-			store.Select(len(uids) - i - 1)
-			break
-		}
-	}
+	store.Select(store.results[len(store.results)-store.resultIndex-1])
 	store.update()
 }
 
@@ -826,3 +791,13 @@ func (store *MessageStore) visualStartIdx() int {
 	}
 	return -1
 }
+
+// FindIndexByUid returns the index in store.Uids() or -1 if not found
+func (store *MessageStore) FindIndexByUid(uid uint32) int {
+	for idx, u := range store.Uids() {
+		if u == uid {
+			return idx
+		}
+	}
+	return -1
+}
diff --git a/widgets/msglist.go b/widgets/msglist.go
index a190c184..4c7c1c22 100644
--- a/widgets/msglist.go
+++ b/widgets/msglist.go
@@ -69,7 +69,9 @@ func (ml *MessageList) Draw(ctx *ui.Context) {
 
 	ml.UpdateScroller(ml.height, len(store.Uids()))
 	if store := ml.Store(); store != nil && len(store.Uids()) > 0 {
-		ml.EnsureScroll(store.SelectedIndex())
+		if idx := store.FindIndexByUid(store.SelectedUid()); idx >= 0 {
+			ml.EnsureScroll(len(store.Uids()) - idx - 1)
+		}
 	}
 
 	textWidth := ctx.Width()
@@ -244,7 +246,7 @@ func (ml *MessageList) drawRow(textWidth int, ctx *ui.Context, uid uint32, row i
 
 	var style tcell.Style
 	// current row
-	if row == ml.store.SelectedIndex()-ml.Scroll() {
+	if msg.Uid == ml.store.SelectedUid() {
 		style = uiConfig.GetComposedStyleSelected(config.STYLE_MSGLIST_DEFAULT, msg_styles)
 	} else {
 		style = uiConfig.GetComposedStyle(config.STYLE_MSGLIST_DEFAULT, msg_styles)
@@ -342,7 +344,6 @@ func (ml *MessageList) storeUpdate(store *lib.MessageStore) {
 	if ml.Store() != store {
 		return
 	}
-	store.Reselect()
 }
 
 func (ml *MessageList) SetStore(store *lib.MessageStore) {
@@ -352,7 +353,8 @@ func (ml *MessageList) SetStore(store *lib.MessageStore) {
 	ml.store = store
 	if store != nil {
 		ml.spinner.Stop()
-		ml.nmsgs = len(store.Uids())
+		uids := store.Uids()
+		ml.nmsgs = len(uids)
 		store.OnUpdate(ml.storeUpdate)
 		store.OnFilterChange(func(store *lib.MessageStore) {
 			if ml.Store() != store {
@@ -384,8 +386,21 @@ func (ml *MessageList) Selected() *models.MessageInfo {
 }
 
 func (ml *MessageList) Select(index int) {
+	// Note that the msgstore.Select function expects a uid as argument
+	// whereas the msglist.Select expects the message number
 	store := ml.Store()
-	store.Select(index)
+	uids := store.Uids()
+	if len(uids) == 0 {
+		return
+	}
+	uidIdx := len(uids) - index - 1
+	if uidIdx >= len(store.Uids()) {
+		uidIdx = 0
+	} else if uidIdx < 0 {
+		uidIdx = len(store.Uids()) - 1
+	}
+	store.Select(store.Uids()[uidIdx])
+
 	ml.Invalidate()
 }