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internal/database/conversation.go

@@ -4,6 +4,7 @@ import (
 	"database/sql"
 	"encoding/json"
 	"fmt"
+	"strings"
 	"time"
 
 	"github.com/google/uuid"
@@ -553,6 +554,102 @@ func (db *DB) GetMessages(conversationID string) ([]Message, error) {
 	return messages, nil
 }
 
+// turnSliceRange 根据任意一条消息 ID 定位「一轮对话」在 msgs 中的 [start, end) 下标区间（msgs 须已按时间升序，与 GetMessages 一致）。
+// 一轮 = 从某条 user 消息起，至下一条 user 之前（含中间所有 assistant）。
+func turnSliceRange(msgs []Message, anchorID string) (start, end int, err error) {
+	idx := -1
+	for i := range msgs {
+		if msgs[i].ID == anchorID {
+			idx = i
+			break
+		}
+	}
+	if idx < 0 {
+		return 0, 0, fmt.Errorf("message not found")
+	}
+	start = idx
+	for start > 0 && msgs[start].Role != "user" {
+		start--
+	}
+	if start < len(msgs) && msgs[start].Role != "user" {
+		start = 0
+	}
+	end = len(msgs)
+	for i := start + 1; i < len(msgs); i++ {
+		if msgs[i].Role == "user" {
+			end = i
+			break
+		}
+	}
+	return start, end, nil
+}
+
+// DeleteConversationTurn 删除锚点所在轮次的全部消息（用户提问 + 该轮助手回复等），并清空 last_react_*，避免与消息表不一致。
+func (db *DB) DeleteConversationTurn(conversationID, anchorMessageID string) (deletedIDs []string, err error) {
+	msgs, err := db.GetMessages(conversationID)
+	if err != nil {
+		return nil, err
+	}
+	start, end, err := turnSliceRange(msgs, anchorMessageID)
+	if err != nil {
+		return nil, err
+	}
+	if start >= end {
+		return nil, fmt.Errorf("empty turn range")
+	}
+	deletedIDs = make([]string, 0, end-start)
+	for i := start; i < end; i++ {
+		deletedIDs = append(deletedIDs, msgs[i].ID)
+	}
+
+	tx, err := db.Begin()
+	if err != nil {
+		return nil, fmt.Errorf("begin tx: %w", err)
+	}
+	defer func() { _ = tx.Rollback() }()
+
+	ph := strings.Repeat("?,", len(deletedIDs))
+	ph = ph[:len(ph)-1]
+	args := make([]interface{}, 0, 1+len(deletedIDs))
+	args = append(args, conversationID)
+	for _, id := range deletedIDs {
+		args = append(args, id)
+	}
+	res, err := tx.Exec(
+		"DELETE FROM messages WHERE conversation_id = ? AND id IN ("+ph+")",
+		args...,
+	)
+	if err != nil {
+		return nil, fmt.Errorf("delete messages: %w", err)
+	}
+	n, err := res.RowsAffected()
+	if err != nil {
+		return nil, err
+	}
+	if int(n) != len(deletedIDs) {
+		return nil, fmt.Errorf("deleted count mismatch")
+	}
+
+	_, err = tx.Exec(
+		`UPDATE conversations SET last_react_input = NULL, last_react_output = NULL, updated_at = ? WHERE id = ?`,
+		time.Now(), conversationID,
+	)
+	if err != nil {
+		return nil, fmt.Errorf("clear react data: %w", err)
+	}
+
+	if err := tx.Commit(); err != nil {
+		return nil, fmt.Errorf("commit: %w", err)
+	}
+
+	db.logger.Info("conversation turn deleted",
+		zap.String("conversationId", conversationID),
+		zap.Strings("deletedMessageIds", deletedIDs),
+		zap.Int("count", len(deletedIDs)),
+	)
+	return deletedIDs, nil
+}
+
 // ProcessDetail 过程详情事件
 type ProcessDetail struct {
 	ID             string    `json:"id"`

internal/database/conversation_turn_test.go

@@ -0,0 +1,39 @@
+package database
+
+import (
+	"testing"
+)
+
+func TestTurnSliceRange(t *testing.T) {
+	mk := func(id, role string) Message {
+		return Message{ID: id, Role: role}
+	}
+	msgs := []Message{
+		mk("u1", "user"),
+		mk("a1", "assistant"),
+		mk("u2", "user"),
+		mk("a2", "assistant"),
+	}
+	cases := []struct {
+		anchor string
+		start  int
+		end    int
+	}{
+		{"u1", 0, 2},
+		{"a1", 0, 2},
+		{"u2", 2, 4},
+		{"a2", 2, 4},
+	}
+	for _, tc := range cases {
+		s, e, err := turnSliceRange(msgs, tc.anchor)
+		if err != nil {
+			t.Fatalf("anchor %s: %v", tc.anchor, err)
+		}
+		if s != tc.start || e != tc.end {
+			t.Fatalf("anchor %s: got [%d,%d) want [%d,%d)", tc.anchor, s, e, tc.start, tc.end)
+		}
+	}
+	if _, _, err := turnSliceRange(msgs, "nope"); err == nil {
+		t.Fatal("expected error for missing id")
+	}
+}