Initial commit: SRDB - High-performance LSM-Tree database

- Core engine with MemTable, SST, WAL
- B+Tree indexing for SST files  
- Leveled compaction strategy
- Multi-table database management
- Schema validation and secondary indexes
- Query builder with complex conditions
- Web UI with HTMX for data visualization
- Command-line tools for diagnostics

wal/manager.go

@@ -0,0 +1,206 @@
+package wal
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"sort"
+	"strconv"
+	"strings"
+	"sync"
+)
+
+// Manager WAL 管理器，管理多个 WAL 文件
+type Manager struct {
+	dir           string
+	currentWAL    *WAL
+	currentNumber int64
+	mu            sync.Mutex
+}
+
+// NewManager 创建 WAL 管理器
+func NewManager(dir string) (*Manager, error) {
+	// 确保目录存在
+	err := os.MkdirAll(dir, 0755)
+	if err != nil {
+		return nil, err
+	}
+
+	// 读取当前 WAL 编号
+	number, err := readCurrentNumber(dir)
+	if err != nil {
+		// 如果读取失败，从 1 开始
+		number = 1
+	}
+
+	// 打开当前 WAL
+	walPath := filepath.Join(dir, fmt.Sprintf("%06d.wal", number))
+	wal, err := Open(walPath)
+	if err != nil {
+		return nil, err
+	}
+
+	// 保存当前编号
+	err = saveCurrentNumber(dir, number)
+	if err != nil {
+		wal.Close()
+		return nil, err
+	}
+
+	return &Manager{
+		dir:           dir,
+		currentWAL:    wal,
+		currentNumber: number,
+	}, nil
+}
+
+// Append 追加记录到当前 WAL
+func (m *Manager) Append(entry *Entry) error {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+
+	return m.currentWAL.Append(entry)
+}
+
+// Sync 同步当前 WAL 到磁盘
+func (m *Manager) Sync() error {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+
+	return m.currentWAL.Sync()
+}
+
+// Rotate 切换到新的 WAL 文件
+func (m *Manager) Rotate() (int64, error) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+
+	// 记录旧的 WAL 编号
+	oldNumber := m.currentNumber
+
+	// 关闭当前 WAL
+	err := m.currentWAL.Close()
+	if err != nil {
+		return 0, err
+	}
+
+	// 创建新 WAL
+	m.currentNumber++
+	walPath := filepath.Join(m.dir, fmt.Sprintf("%06d.wal", m.currentNumber))
+	wal, err := Open(walPath)
+	if err != nil {
+		return 0, err
+	}
+
+	m.currentWAL = wal
+
+	// 更新 CURRENT 文件
+	err = saveCurrentNumber(m.dir, m.currentNumber)
+	if err != nil {
+		return 0, err
+	}
+
+	return oldNumber, nil
+}
+
+// Delete 删除指定的 WAL 文件
+func (m *Manager) Delete(number int64) error {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+
+	walPath := filepath.Join(m.dir, fmt.Sprintf("%06d.wal", number))
+	return os.Remove(walPath)
+}
+
+// GetCurrentNumber 获取当前 WAL 编号
+func (m *Manager) GetCurrentNumber() int64 {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+
+	return m.currentNumber
+}
+
+// RecoverAll 恢复所有 WAL 文件
+func (m *Manager) RecoverAll() ([]*Entry, error) {
+	// 查找所有 WAL 文件
+	pattern := filepath.Join(m.dir, "*.wal")
+	files, err := filepath.Glob(pattern)
+	if err != nil {
+		return nil, err
+	}
+
+	if len(files) == 0 {
+		return nil, nil
+	}
+
+	// 按文件名排序（确保按时间顺序）
+	sort.Strings(files)
+
+	var allEntries []*Entry
+
+	// 依次读取每个 WAL
+	for _, file := range files {
+		reader, err := NewReader(file)
+		if err != nil {
+			continue
+		}
+
+		entries, err := reader.Read()
+		reader.Close()
+
+		if err != nil {
+			continue
+		}
+
+		allEntries = append(allEntries, entries...)
+	}
+
+	return allEntries, nil
+}
+
+// ListWALFiles 列出所有 WAL 文件
+func (m *Manager) ListWALFiles() ([]string, error) {
+	pattern := filepath.Join(m.dir, "*.wal")
+	files, err := filepath.Glob(pattern)
+	if err != nil {
+		return nil, err
+	}
+
+	sort.Strings(files)
+	return files, nil
+}
+
+// Close 关闭 WAL 管理器
+func (m *Manager) Close() error {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+
+	if m.currentWAL != nil {
+		return m.currentWAL.Close()
+	}
+
+	return nil
+}
+
+// readCurrentNumber 读取当前 WAL 编号
+func readCurrentNumber(dir string) (int64, error) {
+	currentPath := filepath.Join(dir, "CURRENT")
+	data, err := os.ReadFile(currentPath)
+	if err != nil {
+		return 0, err
+	}
+
+	number, err := strconv.ParseInt(strings.TrimSpace(string(data)), 10, 64)
+	if err != nil {
+		return 0, err
+	}
+
+	return number, nil
+}
+
+// saveCurrentNumber 保存当前 WAL 编号
+func saveCurrentNumber(dir string, number int64) error {
+	currentPath := filepath.Join(dir, "CURRENT")
+	data := []byte(fmt.Sprintf("%d\n", number))
+	return os.WriteFile(currentPath, data, 0644)
+}