feat(storage): add sqlite manager and storage config

internal/storage/storage.go

@@ -0,0 +1,114 @@
+package storage
+
+import (
+	"database/sql"
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+	"runtime"
+	"strings"
+	"sync"
+
+	_ "modernc.org/sqlite"
+
+	"github.com/stig/goaichat/internal/config"
+)
+
+// Manager handles access to the SQLite database storing chat sessions and metadata.
+type Manager struct {
+	path string
+	cfg  config.StorageConfig
+	mu   sync.Mutex
+	db   *sql.DB
+}
+
+// NewManager constructs a Manager and ensures the data directory exists.
+func NewManager(cfg config.Config) (*Manager, error) {
+	path, err := resolvePath(cfg.Storage)
+	if err != nil {
+		return nil, err
+	}
+
+	if err := ensureDir(filepath.Dir(path)); err != nil {
+		return nil, err
+	}
+
+	return &Manager{path: path, cfg: cfg.Storage}, nil
+}
+
+// Open lazily opens the SQLite database connection.
+func (m *Manager) Open() (*sql.DB, error) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+
+	if m.db != nil {
+		return m.db, nil
+	}
+
+	dsn := fmt.Sprintf("file:%s?_pragma=journal_mode(WAL)&_busy_timeout=5000", m.path)
+	db, err := sql.Open("sqlite", dsn)
+	if err != nil {
+		return nil, fmt.Errorf("open sqlite: %w", err)
+	}
+
+	if err := db.Ping(); err != nil {
+		_ = db.Close()
+		return nil, fmt.Errorf("ping sqlite: %w", err)
+	}
+
+	m.db = db
+	return db, nil
+}
+
+// Close releases the underlying database connection.
+func (m *Manager) Close() error {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+
+	if m.db == nil {
+		return nil
+	}
+
+	err := m.db.Close()
+	m.db = nil
+	return err
+}
+
+func resolvePath(cfg config.StorageConfig) (string, error) {
+	if strings.TrimSpace(cfg.Path) != "" {
+		return cfg.Path, nil
+	}
+
+	username := cfg.Username
+	if username == "" {
+		username = os.Getenv("USER")
+		if username == "" {
+			username = "default"
+		}
+	}
+
+	base := filepath.Join("/var/log/goaichat", username)
+	if cfg.BaseDir != "" {
+		base = cfg.BaseDir
+	}
+
+	return filepath.Join(base, "goaichat.db"), nil
+}
+
+func ensureDir(dir string) error {
+	if dir == "" {
+		return errors.New("directory path cannot be empty")
+	}
+	if err := os.MkdirAll(dir, 0o700); err != nil {
+		return fmt.Errorf("create data directory: %w", err)
+	}
+
+	if runtime.GOOS != "windows" {
+		if err := os.Chmod(dir, 0o700); err != nil {
+			return fmt.Errorf("chmod data directory: %w", err)
+		}
+	}
+
+	return nil
+}