feat: 实现 SQLite 迁移备份、完整表结构与简单写入队列

internal/store/db.go

@@ -10,29 +10,105 @@ import (
 	_ "modernc.org/sqlite"
 )
 
-// OpenWriter 按 DEVELOPMENT 7.7 打开写连接（带 _txlock=immediate）。
+const dbFileName = "nixmsg.db"
+
+// DB 持有读写连接与写入队列。
+type DB struct {
+	Write *sql.DB
+	Read  *sql.DB
+	Queue *Queue
+}
+
+// Open 打开数据目录下的库：写连接、读连接池、迁移，并启动简单写入队列。
+// 若 nixmsg.db 尚不存在则跳过迁移前备份。
+func Open(dataDir, synchronous string) (*DB, error) {
+	if err := os.MkdirAll(dataDir, 0o755); err != nil {
+		return nil, fmt.Errorf("mkdir data_dir: %w", err)
+	}
+	dbPath := filepath.Join(dataDir, dbFileName)
+	existed, err := fileExists(dbPath)
+	if err != nil {
+		return nil, err
+	}
+
+	write, err := OpenWriter(dataDir, synchronous)
+	if err != nil {
+		return nil, err
+	}
+	if migErr := Migrate(write, dataDir, existed); migErr != nil {
+		_ = write.Close()
+		return nil, migErr
+	}
+	read, err := OpenReader(dataDir, synchronous)
+	if err != nil {
+		_ = write.Close()
+		return nil, err
+	}
+	q := NewQueue(write)
+	return &DB{Write: write, Read: read, Queue: q}, nil
+}
+
+// Close 停止写入队列并关闭连接。
+func (d *DB) Close() error {
+	var first error
+	if d.Queue != nil {
+		if err := d.Queue.Close(); err != nil {
+			first = err
+		}
+	}
+	if d.Read != nil {
+		if err := d.Read.Close(); err != nil && first == nil {
+			first = err
+		}
+	}
+	if d.Write != nil {
+		if err := d.Write.Close(); err != nil && first == nil {
+			first = err
+		}
+	}
+	return first
+}
+
+// OpenWriter 按 DEVELOPMENT 7.7 打开写连接（带 _txlock=immediate，MaxOpenConns=1）。
 func OpenWriter(dataDir, synchronous string) (*sql.DB, error) {
 	if err := os.MkdirAll(dataDir, 0o755); err != nil {
 		return nil, fmt.Errorf("mkdir data_dir: %w", err)
 	}
-	dsn, err := writeDSN(dataDir, synchronous)
+	dsn, err := buildDSN(dataDir, synchronous, true)
 	if err != nil {
 		return nil, err
 	}
 	db, err := sql.Open("sqlite", dsn)
 	if err != nil {
-		return nil, fmt.Errorf("open sqlite: %w", err)
+		return nil, fmt.Errorf("open sqlite writer: %w", err)
 	}
 	db.SetMaxOpenConns(1)
 	db.SetMaxIdleConns(1)
 	if err := db.Ping(); err != nil {
 		_ = db.Close()
-		return nil, fmt.Errorf("ping sqlite: %w", err)
+		return nil, fmt.Errorf("ping sqlite writer: %w", err)
 	}
 	return db, nil
 }
 
-func writeDSN(dataDir, synchronous string) (string, error) {
+// OpenReader 打开读连接池（DSN 不含 _txlock=immediate）。
+func OpenReader(dataDir, synchronous string) (*sql.DB, error) {
+	dsn, err := buildDSN(dataDir, synchronous, false)
+	if err != nil {
+		return nil, err
+	}
+	db, err := sql.Open("sqlite", dsn)
+	if err != nil {
+		return nil, fmt.Errorf("open sqlite reader: %w", err)
+	}
+	if err := db.Ping(); err != nil {
+		_ = db.Close()
+		return nil, fmt.Errorf("ping sqlite reader: %w", err)
+	}
+	return db, nil
+}
+
+func buildDSN(dataDir, synchronous string, writer bool) (string, error) {
 	sync := strings.ToUpper(strings.TrimSpace(synchronous))
 	if sync == "" {
 		sync = "FULL"
@@ -40,10 +116,28 @@ func writeDSN(dataDir, synchronous string) (string, error) {
 	if sync != "FULL" && sync != "NORMAL" {
 		return "", fmt.Errorf("invalid sqlite_synchronous: %s", synchronous)
 	}
-	dbPath := filepath.ToSlash(filepath.Join(dataDir, "nixmsg.db"))
-	return fmt.Sprintf(
-		"file:%s?_pragma=journal_mode(WAL)&_pragma=busy_timeout(5000)&_pragma=synchronous(%s)&_pragma=foreign_keys(ON)&_pragma=secure_delete(ON)&_txlock=immediate",
+	dbPath := filepath.ToSlash(filepath.Join(dataDir, dbFileName))
+	dsn := fmt.Sprintf(
+		"file:%s?_pragma=journal_mode(WAL)&_pragma=busy_timeout(5000)&_pragma=synchronous(%s)&_pragma=foreign_keys(ON)&_pragma=secure_delete(ON)",
 		dbPath,
 		sync,
-	), nil
+	)
+	if writer {
+		dsn += "&_txlock=immediate"
+	}
+	return dsn, nil
+}
+
+func fileExists(path string) (bool, error) {
+	st, err := os.Stat(path)
+	if err == nil {
+		if st.IsDir() {
+			return false, fmt.Errorf("db path is a directory: %s", path)
+		}
+		return true, nil
+	}
+	if os.IsNotExist(err) {
+		return false, nil
+	}
+	return false, err
 }