feat(history): 会话列表lastMessage预览(B3) — 单查询无N+1
- history/session_preview.go: SessionMeta.LastMessage + 单条SQL(LEFT JOIN取每会话ORDER BY created_at DESC,rowid DESC LIMIT 1,走覆盖索引)
- ListSessions 迁出重写(签名不变), content折叠空白截前60rune
- gateway: historySessionSummary 增 lastMessage{role,content,createdAt}(omitempty), /sessions与/admin/sessions共用
- 新增测试(session_preview_test, history_lastmessage_test)
- Docs/api-client.md v0.22 同步
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AskaEth committed
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@@ -0,0 +1,103 @@
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package history
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import (
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"context"
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"database/sql"
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"fmt"
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"strings"
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)
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// This file owns the last-message preview carried in the session list
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// (GET /api/v1/sessions): a display-only summary of each session's newest message so a
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// client can render a conversation row without one request per session. The preview is
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// truncated for display and never feeds identity or permission decisions — identity
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// comes from channel actor metadata / JWT (project red line).
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// lastMessagePreviewRunes bounds the preview content so a long message cannot bloat the
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// session-list response. A longer message is whitespace-collapsed and truncated to this
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// many runes with an ellipsis.
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const lastMessagePreviewRunes = 60
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// MessageSummary is a display-only preview of a session's most recent message.
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type MessageSummary struct {
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Role string // "user" | "assistant"
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Content string // whitespace-collapsed, truncated preview
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CreatedAt int64 // Unix milliseconds
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}
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// listSessionsQuery reads every session plus its newest message in one statement. The
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// LEFT JOIN's correlated subquery resolves each session's newest row via the
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// (session_id, created_at DESC) index (rowid DESC breaks a same-millisecond tie by
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// insertion order), so a session with no messages still appears with NULL preview
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// columns. Ordering keeps the main session first, then subs oldest-first.
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const listSessionsQuery = `SELECT s.id, s.type, s.title, s.created_at,
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m.role, m.content, m.created_at
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FROM chat_sessions s
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LEFT JOIN chat_messages m ON m.rowid = (
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SELECT rowid FROM chat_messages
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WHERE session_id = s.id
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ORDER BY created_at DESC, rowid DESC
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LIMIT 1
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)
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ORDER BY (s.type = ?) DESC, s.created_at ASC`
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// ListSessions returns the main session first, then every sub session, oldest first,
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// each carrying a LastMessage preview of its newest message (nil when the session has
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// none). Sessions and previews are read in a single query, so the query count does not
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// grow with the number of sessions. The returned slice is non-nil.
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func (s *Store) ListSessions(ctx context.Context) ([]SessionMeta, error) {
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rows, err := s.db.QueryContext(ctx, listSessionsQuery, SessionMain)
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if err != nil {
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return nil, fmt.Errorf("history: list sessions: %w", err)
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}
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defer func() { _ = rows.Close() }()
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sessions := make([]SessionMeta, 0)
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for rows.Next() {
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meta, err := scanSessionMeta(rows)
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if err != nil {
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return nil, fmt.Errorf("history: scan session: %w", err)
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}
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sessions = append(sessions, meta)
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}
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if err := rows.Err(); err != nil {
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return nil, fmt.Errorf("history: iterate sessions: %w", err)
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}
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return sessions, nil
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}
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// scanSessionMeta reads one joined chat_sessions + last-message row. The three message
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// columns are NULL for a session that has never received a message, so they scan into
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// nullable holders and only produce a LastMessage when a row is present.
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func scanSessionMeta(sc rowScanner) (SessionMeta, error) {
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var (
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meta SessionMeta
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typeStr string
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role sql.NullString
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content sql.NullString
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lastAt sql.NullInt64
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)
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if err := sc.Scan(&meta.ID, &typeStr, &meta.Title, &meta.CreatedAt, &role, &content, &lastAt); err != nil {
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return SessionMeta{}, err
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}
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meta.Type = typeStr
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if role.Valid && lastAt.Valid {
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meta.LastMessage = &MessageSummary{
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Role: role.String,
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Content: previewContent(content.String),
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CreatedAt: lastAt.Int64,
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}
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}
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return meta, nil
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}
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// previewContent collapses whitespace runs (newlines included) to single spaces and
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// truncates to lastMessagePreviewRunes runes with an ellipsis. It is display-only.
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func previewContent(content string) string {
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joined := strings.Join(strings.Fields(content), " ")
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runes := []rune(joined)
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if len(runes) <= lastMessagePreviewRunes {
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return joined
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}
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return string(runes[:lastMessagePreviewRunes]) + "…"
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}
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@@ -0,0 +1,134 @@
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package history
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import (
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"context"
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"strings"
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"testing"
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)
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// sessionOf returns the SessionMeta of one session from ListSessions, failing the test
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// when the session is absent.
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func sessionOf(t *testing.T, st *Store, id string) SessionMeta {
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t.Helper()
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sessions, err := st.ListSessions(context.Background())
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if err != nil {
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t.Fatalf("list sessions: %v", err)
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}
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for _, m := range sessions {
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if m.ID == id {
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return m
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}
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}
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t.Fatalf("session %q not found in %+v", id, sessions)
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return SessionMeta{}
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}
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func TestListSessionsLastMessagePreview(t *testing.T) {
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t.Parallel()
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st := newStore(t)
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ctx := context.Background()
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// The empty main session has no preview.
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if got := sessionOf(t, st, MainSessionID); got.LastMessage != nil {
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t.Fatalf("empty main LastMessage = %+v, want nil", got.LastMessage)
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}
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sub, err := st.NewSubSession(ctx, "owner")
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if err != nil {
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t.Fatalf("new sub: %v", err)
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}
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if err := st.Append(ctx, Message{SessionID: MainSessionID, Role: RoleUser, Content: "first", CreatedAt: 1000}); err != nil {
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t.Fatalf("append main user: %v", err)
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}
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if err := st.Append(ctx, Message{SessionID: MainSessionID, Role: RoleAssistant, Content: "latest reply", CreatedAt: 2000}); err != nil {
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t.Fatalf("append main assistant: %v", err)
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}
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if err := st.Append(ctx, Message{SessionID: sub, Role: RoleUser, Content: "sub question", CreatedAt: 1500}); err != nil {
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t.Fatalf("append sub: %v", err)
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}
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// Main stays first and carries its newest message, not the first one.
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sessions, err := st.ListSessions(ctx)
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if err != nil {
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t.Fatalf("list sessions: %v", err)
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}
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if len(sessions) != 2 || sessions[0].ID != MainSessionID {
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t.Fatalf("sessions = %+v, want main first", sessions)
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}
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main := sessions[0].LastMessage
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if main == nil || main.Role != RoleAssistant || main.Content != "latest reply" || main.CreatedAt != 2000 {
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t.Fatalf("main LastMessage = %+v, want assistant/latest reply/2000", main)
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}
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subPreview := sessions[1].LastMessage
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if subPreview == nil || subPreview.Role != RoleUser || subPreview.Content != "sub question" || subPreview.CreatedAt != 1500 {
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t.Fatalf("sub LastMessage = %+v, want user/sub question/1500", subPreview)
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}
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// A sub session created after the main one but never written has no preview.
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empty, err := st.NewSubSession(ctx, "owner")
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if err != nil {
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t.Fatalf("new empty sub: %v", err)
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}
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if got := sessionOf(t, st, empty); got.LastMessage != nil {
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t.Fatalf("empty sub LastMessage = %+v, want nil", got.LastMessage)
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}
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}
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func TestListSessionsLastMessageTruncatesAndCollapses(t *testing.T) {
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t.Parallel()
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st := newStore(t)
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ctx := context.Background()
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long := strings.Repeat("字", lastMessagePreviewRunes+10) + "\n\n尾部"
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if err := st.Append(ctx, Message{SessionID: MainSessionID, Role: RoleUser, Content: long, CreatedAt: 1000}); err != nil {
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t.Fatalf("append long: %v", err)
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}
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want := strings.Repeat("字", lastMessagePreviewRunes) + "…"
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if got := sessionOf(t, st, MainSessionID).LastMessage; got == nil || got.Content != want {
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t.Fatalf("truncated preview = %+v, want %q", got, want)
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}
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// Whitespace runs (including newlines) collapse to single spaces, and a short
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// message is returned whole.
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sub, err := st.NewSubSession(ctx, "owner")
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if err != nil {
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t.Fatalf("new sub: %v", err)
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}
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if err := st.Append(ctx, Message{SessionID: sub, Role: RoleUser, Content: " 你好\n\t世界 ", CreatedAt: 1000}); err != nil {
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t.Fatalf("append spaced: %v", err)
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}
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if got := sessionOf(t, st, sub).LastMessage; got == nil || got.Content != "你好 世界" {
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t.Fatalf("collapsed preview = %+v, want %q", got, "你好 世界")
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}
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}
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func TestListSessionsLastMessageTieBreaksByInsertion(t *testing.T) {
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t.Parallel()
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st := newStore(t)
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ctx := context.Background()
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// Two messages sharing a millisecond timestamp: the later insert is the newest.
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for _, content := range []string{"older", "newer"} {
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if err := st.Append(ctx, Message{SessionID: MainSessionID, Role: RoleAssistant, Content: content, CreatedAt: 5000}); err != nil {
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t.Fatalf("append %s: %v", content, err)
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}
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}
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if got := sessionOf(t, st, MainSessionID).LastMessage; got == nil || got.Content != "newer" {
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t.Fatalf("tie-break preview = %+v, want newer", got)
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}
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}
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func TestPreviewContentBounds(t *testing.T) {
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t.Parallel()
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if got := previewContent(""); got != "" {
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t.Fatalf("empty preview = %q, want empty", got)
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}
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exact := strings.Repeat("a", lastMessagePreviewRunes)
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if got := previewContent(exact); got != exact {
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t.Fatalf("exact-length preview changed: %q", got)
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}
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over := strings.Repeat("a", lastMessagePreviewRunes+1)
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if got := previewContent(over); got != exact+"…" {
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t.Fatalf("over-length preview = %q, want ellipsis", got)
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}
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}
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@@ -109,6 +109,11 @@ type SessionMeta struct {
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Type string // "main" | "sub"
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Title string
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CreatedAt int64
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// LastMessage is a display-only preview of the session's newest message, filled
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// by ListSessions in the same query. It is nil for a session with no messages.
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// A client uses it to render the conversation row without a per-session request;
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// identity and permissions never derive from it.
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LastMessage *MessageSummary
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}
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// HistoryStore abstracts the chat-history store so callers (the gateway) and tests can
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@@ -481,36 +486,6 @@ func (s *Store) NewSubSession(ctx context.Context, ownerID string) (string, erro
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return sessionID, nil
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}
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// ListSessions returns the main session first, then every sub session, oldest first. The
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// returned slice is non-nil.
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func (s *Store) ListSessions(ctx context.Context) ([]SessionMeta, error) {
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rows, err := s.db.QueryContext(ctx, `SELECT id, type, title, created_at FROM chat_sessions
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ORDER BY (type = ?) DESC, created_at ASC`, SessionMain)
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if err != nil {
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return nil, fmt.Errorf("history: list sessions: %w", err)
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}
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defer func() { _ = rows.Close() }()
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sessions := make([]SessionMeta, 0)
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for rows.Next() {
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var (
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meta SessionMeta
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typeStr string
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createdAt int64
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)
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if err := rows.Scan(&meta.ID, &typeStr, &meta.Title, &createdAt); err != nil {
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return nil, fmt.Errorf("history: scan session: %w", err)
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}
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meta.Type = typeStr
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meta.CreatedAt = createdAt
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sessions = append(sessions, meta)
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}
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if err := rows.Err(); err != nil {
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return nil, fmt.Errorf("history: iterate sessions: %w", err)
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}
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return sessions, nil
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}
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// ensureMainSession inserts the fixed main session row when it is absent, so ListSessions
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// always reports the main session even before any message is written.
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func (s *Store) ensureMainSession(ctx context.Context) error {
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