From dae5722945d100832167fe2d7786bbbd6e9979a1 Mon Sep 17 00:00:00 2001
From: hhs <386998068@qq.com>
Date: Sun, 14 Jun 2026 17:52:21 +0800
Subject: [PATCH] =?UTF-8?q?feat:=20Phase=208.1=20=E2=80=94=20=E5=AE=9A?=
 =?UTF-8?q?=E4=B9=89=20MessageRepository=20=E6=8E=A5=E5=8F=A3=E5=92=8C?=
 =?UTF-8?q?=E6=B6=88=E6=81=AF=E8=A1=A8=E8=BF=81=E7=A7=BB=E8=84=9A=E6=9C=AC?=
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---
 backend/internal/store/message.go        | 40 ++++++++++++++++++++++++
 backend/migrations/002_messages.down.sql |  1 +
 backend/migrations/002_messages.up.sql   | 17 ++++++++++
 3 files changed, 58 insertions(+)
 create mode 100644 backend/internal/store/message.go
 create mode 100644 backend/migrations/002_messages.down.sql
 create mode 100644 backend/migrations/002_messages.up.sql

diff --git a/backend/internal/store/message.go b/backend/internal/store/message.go
new file mode 100644
index 0000000..629af20
--- /dev/null
+++ b/backend/internal/store/message.go
@@ -0,0 +1,40 @@
+package store
+
+import (
+	"context"
+	"errors"
+	"time"
+
+	"github.com/hhs/camtalk/internal/models"
+)
+
+var (
+	// ErrMessageNotFound 消息不存在。
+	ErrMessageNotFound = errors.New("message not found")
+)
+
+// MessageRepository 消息持久化接口。
+type MessageRepository interface {
+	// SaveMessage 保存一条消息。
+	SaveMessage(ctx context.Context, sessionID string, msg models.Message, tokensUsed int) error
+
+	// GetMessages 获取会话的消息列表（分页，按 created_at 升序）。
+	// beforeID 为 0 时从最新开始查询。
+	GetMessages(ctx context.Context, sessionID string, limit int, beforeID int64) ([]StoredMessage, error)
+
+	// GetLastMessage 获取会话的最后一条消息。
+	GetLastMessage(ctx context.Context, sessionID string) (*StoredMessage, error)
+
+	// GetMessageCount 获取会话的消息总数。
+	GetMessageCount(ctx context.Context, sessionID string) (int, error)
+}
+
+// StoredMessage 持久化消息模型（store 层）。
+type StoredMessage struct {
+	ID         int64     `json:"id"`
+	SessionID  string    `json:"-"`
+	Role       string    `json:"role"`
+	Content    string    `json:"content"`
+	TokensUsed int       `json:"tokens_used"`
+	CreatedAt  time.Time `json:"created_at"`
+}
diff --git a/backend/migrations/002_messages.down.sql b/backend/migrations/002_messages.down.sql
new file mode 100644
index 0000000..cbe8189
--- /dev/null
+++ b/backend/migrations/002_messages.down.sql
@@ -0,0 +1 @@
+DROP TABLE IF EXISTS messages;
diff --git a/backend/migrations/002_messages.up.sql b/backend/migrations/002_messages.up.sql
new file mode 100644
index 0000000..fe1e088
--- /dev/null
+++ b/backend/migrations/002_messages.up.sql
@@ -0,0 +1,17 @@
+-- 消息表
+CREATE TABLE IF NOT EXISTS messages (
+    id          BIGSERIAL PRIMARY KEY,
+    session_id  UUID NOT NULL,
+    role        VARCHAR(16) NOT NULL,  -- "user" | "assistant" | "system"
+    content     TEXT NOT NULL,
+    tokens_used INTEGER NOT NULL DEFAULT 0,
+    created_at  TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+
+-- 按会话查询消息（分页核心索引）
+CREATE INDEX IF NOT EXISTS idx_messages_session_id_created_at
+    ON messages(session_id, created_at);
+
+-- 按会话查询最后一条消息
+CREATE INDEX IF NOT EXISTS idx_messages_session_id_id_desc
+    ON messages(session_id, id DESC);