Add pagination to Out of sync item list (fixes #1509)

internal/model/model.go

@@ -375,53 +375,71 @@ func (m *Model) NeedSize(folder string) (nfiles int, bytes int64) {
 	return
 }
 
-// NeedFiles returns the list of currently needed files in progress, queued,
-// and to be queued on next puller iteration. Also takes a soft cap which is
-// only respected when adding files from the model rather than the runner queue.
-func (m *Model) NeedFolderFiles(folder string, max int) ([]db.FileInfoTruncated, []db.FileInfoTruncated, []db.FileInfoTruncated) {
+// NeedFiles returns paginated list of currently needed files in progress, queued,
+// and to be queued on next puller iteration, as well as the total number of
+// files currently needed.
+func (m *Model) NeedFolderFiles(folder string, page, perpage int) ([]db.FileInfoTruncated, []db.FileInfoTruncated, []db.FileInfoTruncated, int) {
 	m.fmut.RLock()
 	defer m.fmut.RUnlock()
 
-	if rf, ok := m.folderFiles[folder]; ok {
-		var progress, queued, rest []db.FileInfoTruncated
-		var seen map[string]bool
+	total := 0
 
-		runner, ok := m.folderRunners[folder]
-		if ok {
-			progressNames, queuedNames := runner.Jobs()
-
-			progress = make([]db.FileInfoTruncated, len(progressNames))
-			queued = make([]db.FileInfoTruncated, len(queuedNames))
-			seen = make(map[string]bool, len(progressNames)+len(queuedNames))
-
-			for i, name := range progressNames {
-				if f, ok := rf.GetGlobalTruncated(name); ok {
-					progress[i] = f
-					seen[name] = true
-				}
-			}
-
-			for i, name := range queuedNames {
-				if f, ok := rf.GetGlobalTruncated(name); ok {
-					queued[i] = f
-					seen[name] = true
-				}
-			}
-		}
-		left := max - len(progress) - len(queued)
-		if max < 1 || left > 0 {
-			rf.WithNeedTruncated(protocol.LocalDeviceID, func(f db.FileIntf) bool {
-				left--
-				ft := f.(db.FileInfoTruncated)
-				if !seen[ft.Name] {
-					rest = append(rest, ft)
-				}
-				return max < 1 || left > 0
-			})
-		}
-		return progress, queued, rest
+	rf, ok := m.folderFiles[folder]
+	if !ok {
+		return nil, nil, nil, 0
 	}
-	return nil, nil, nil
+
+	var progress, queued, rest []db.FileInfoTruncated
+	var seen map[string]struct{}
+
+	skip := (page - 1) * perpage
+	get := perpage
+
+	runner, ok := m.folderRunners[folder]
+	if ok {
+		allProgressNames, allQueuedNames := runner.Jobs()
+
+		var progressNames, queuedNames []string
+		progressNames, skip, get = getChunk(allProgressNames, skip, get)
+		queuedNames, skip, get = getChunk(allQueuedNames, skip, get)
+
+		progress = make([]db.FileInfoTruncated, len(progressNames))
+		queued = make([]db.FileInfoTruncated, len(queuedNames))
+		seen = make(map[string]struct{}, len(progressNames)+len(queuedNames))
+
+		for i, name := range progressNames {
+			if f, ok := rf.GetGlobalTruncated(name); ok {
+				progress[i] = f
+				seen[name] = struct{}{}
+			}
+		}
+
+		for i, name := range queuedNames {
+			if f, ok := rf.GetGlobalTruncated(name); ok {
+				queued[i] = f
+				seen[name] = struct{}{}
+			}
+		}
+	}
+
+	rest = make([]db.FileInfoTruncated, 0, perpage)
+	rf.WithNeedTruncated(protocol.LocalDeviceID, func(f db.FileIntf) bool {
+		total++
+		if skip > 0 {
+			skip--
+			return true
+		}
+		if get > 0 {
+			ft := f.(db.FileInfoTruncated)
+			if _, ok := seen[ft.Name]; !ok {
+				rest = append(rest, ft)
+				get--
+			}
+		}
+		return true
+	})
+
+	return progress, queued, rest, total
 }
 
 // Index is called when a new device is connected and we receive their full index.
@@ -1616,3 +1634,17 @@ func symlinkInvalid(isLink bool) bool {
 	}
 	return false
 }
+
+// Skips `skip` elements and retrieves up to `get` elements from a given slice.
+// Returns the resulting slice, plus how much elements are left to skip or
+// copy to satisfy the values which were provided, given the slice is not
+// big enough.
+func getChunk(data []string, skip, get int) ([]string, int, int) {
+	l := len(data)
+	if l <= skip {
+		return []string{}, skip - l, get
+	} else if l < skip+get {
+		return data[skip:l], 0, get - (l - skip)
+	}
+	return data[skip : skip+get], 0, 0
+}