Add WALHeader & WALFrameHeader

db.go

@@ -0,0 +1,84 @@
+package litestream
+
+import (
+	"context"
+	"path/filepath"
+	"sync"
+)
+
+const (
+	MetaDirSuffix = "-litestream"
+
+	WALDirName  = "wal"
+	LogFilename = "log"
+)
+
+// Mode represents the journaling mode of a DB.
+type Mode int
+
+const (
+	ModeEmpty = Mode(iota + 1)
+	ModeJournal
+	ModeWAL
+)
+
+// DB represents an instance of a managed SQLite database in the file system.
+type DB struct {
+	path string
+	mode Mode // method of writing to DB
+	inTx bool // currently in transaction
+
+	walFile *WALFile // active wal segment
+
+	ctx    context.Context
+	cancel func()
+	wg     sync.WaitGroup
+}
+
+// NewDB returns a new instance of DB for a given path.
+func NewDB(path string) *DB {
+	db := &DB{path: path}
+	db.ctx, db.cancel = context.WithCancel(context.Background())
+	return db
+}
+
+// Path returns the path to the database.
+func (db *DB) Path() string {
+	return db.path
+}
+
+// MetaPath returns the path to the database metadata.
+func (db *DB) MetaPath() string {
+	dir, file := filepath.Split(db.path)
+	return filepath.Join(dir, "."+file+MetaDirSuffix)
+}
+
+// WALPath returns the path to the internal WAL directory.
+func (db *DB) WALPath() string {
+	return filepath.Join(db.MetaPath(), WALDirName)
+}
+
+// LogPath returns the path to the internal log directory.
+func (db *DB) LogPath() string {
+	return filepath.Join(db.MetaPath(), LogFilename)
+}
+
+// Open loads the configuration file
+func (db *DB) Open() error {
+	// TODO: Ensure sidecar directory structure exists.
+	// TODO: Read WAL segments.
+	return nil
+}
+
+// Close stops management of the database.
+func (db *DB) Close() error {
+	db.cancel()
+	db.wg.Wait()
+	// TODO: Close WAL segments.
+	return nil
+}
+
+// ActiveWALFile returns the active WAL file.
+func (db *DB) ActiveWALFile() *WALFile {
+	return db.walFile
+}