feat: complete v0.3.1 agent workflow

internal/session/index.go

@@ -0,0 +1,58 @@
+package session
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"path/filepath"
+	"sort"
+
+	"agentu/internal/safeio"
+)
+
+const sessionIndexFile = "index.json"
+
+type sessionIndex struct {
+	Sessions []SessionMeta `json:"sessions"`
+}
+
+func metaFromSession(sess *Session) SessionMeta {
+	return SessionMeta{
+		ID:           sess.ID,
+		Name:         sess.Name,
+		CreatedAt:    sess.CreatedAt,
+		UpdatedAt:    sess.UpdatedAt,
+		Provider:     sess.Provider,
+		Model:        sess.Model,
+		MessageCount: len(sess.Messages),
+	}
+}
+
+func (s *Store) saveIndexFromSessions(metas []SessionMeta) error {
+	sort.Slice(metas, func(i, j int) bool {
+		return metas[i].UpdatedAt.After(metas[j].UpdatedAt)
+	})
+	idx := sessionIndex{Sessions: metas}
+	data, err := json.MarshalIndent(idx, "", "  ")
+	if err != nil {
+		return fmt.Errorf("marshal session index: %w", err)
+	}
+	path := filepath.Join(s.dir, sessionIndexFile)
+	return safeio.AtomicWriteFile(path, data, 0o644)
+}
+
+func (s *Store) loadIndex() ([]SessionMeta, error) {
+	path := filepath.Join(s.dir, sessionIndexFile)
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return nil, err
+	}
+	var idx sessionIndex
+	if err := json.Unmarshal(data, &idx); err != nil {
+		return nil, err
+	}
+	sort.Slice(idx.Sessions, func(i, j int) bool {
+		return idx.Sessions[i].UpdatedAt.After(idx.Sessions[j].UpdatedAt)
+	})
+	return idx.Sessions, nil
+}