state: store join util

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/state/state_test.go

@@ -94,6 +94,14 @@ func testStore(t *testing.T, s state.Store) {
 		}
 	})
 
+	t.Run("join store", func(t *testing.T) {
+		if entries, err := state.Join(s); err != nil {
+			t.Fatalf("Join: error = %v", err)
+		} else if len(entries) != 3 {
+			t.Fatalf("Join(s) = %#v", entries)
+		}
+	})
+
 	t.Run("clear aid 1", func(t *testing.T) {
 		do(1, func(c state.Cursor) {
 			if err := c.Destroy(tc[insertEntryOtherApp].ID); err != nil {

internal/state/util.go

@@ -0,0 +1,49 @@
+package state
+
+import (
+	"errors"
+	"maps"
+)
+
+var (
+	ErrDuplicate = errors.New("store contains duplicates")
+)
+
+// Join returns joined state entries of all active aids.
+func Join(s Store) (Entries, error) {
+	var (
+		aids    []int
+		entries = make(Entries)
+
+		el      int
+		res     Entries
+		loadErr error
+	)
+
+	if ln, err := s.List(); err != nil {
+		return nil, err
+	} else {
+		aids = ln
+	}
+
+	for _, aid := range aids {
+		if _, err := s.Do(aid, func(c Cursor) {
+			res, loadErr = c.Load()
+		}); err != nil {
+			return nil, err
+		}
+
+		if loadErr != nil {
+			return nil, loadErr
+		}
+
+		// save expected length
+		el = len(entries) + len(res)
+		maps.Copy(entries, res)
+		if len(entries) != el {
+			return nil, ErrDuplicate
+		}
+	}
+
+	return entries, nil
+}