feat: persist session state (folder, cursor, active pane) on exit and restore on launch

internal/config/session.go

@@ -0,0 +1,83 @@
+package config
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+
+	toml "github.com/pelletier/go-toml/v2"
+)
+
+// SessionState stores the UI state that should be restored on next launch.
+type SessionState struct {
+	ActivePane string         `toml:"active_pane"`
+	Left       PaneSession    `toml:"left"`
+	Right      PaneSession    `toml:"right"`
+}
+
+// PaneSession stores per-pane session state (path and selected entry name).
+type PaneSession struct {
+	Path      string `toml:"path"`
+	EntryName string `toml:"entry_name"`
+}
+
+// DefaultSessionPath returns the path to the session file.
+func DefaultSessionPath() (string, error) {
+	homeDir, err := os.UserHomeDir()
+	if err != nil {
+		return "", fmt.Errorf("resolve home dir: %w", err)
+	}
+	xdgDir := os.Getenv("XDG_CONFIG_HOME")
+	if xdgDir == "" {
+		xdgDir = filepath.Join(homeDir, ".config")
+	}
+	return filepath.Join(xdgDir, "vcom", "session.toml"), nil
+}
+
+// LoadSession reads the session state from disk.
+// Returns (SessionState, nil) on success, (empty, error) if file doesn't exist.
+func LoadSession() (SessionState, error) {
+	path, err := DefaultSessionPath()
+	if err != nil {
+		return SessionState{}, err
+	}
+
+	data, err := os.ReadFile(path)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return SessionState{}, nil
+		}
+		return SessionState{}, fmt.Errorf("read %s: %w", path, err)
+	}
+
+	var s SessionState
+	if err := toml.Unmarshal(data, &s); err != nil {
+		return SessionState{}, fmt.Errorf("parse %s: %w", path, err)
+	}
+	return s, nil
+}
+
+// SaveSession writes the session state to disk.
+func SaveSession(s SessionState) error {
+	path, err := DefaultSessionPath()
+	if err != nil {
+		return err
+	}
+
+	absPath, err := filepath.Abs(path)
+	if err != nil {
+		return fmt.Errorf("resolve %s: %w", path, err)
+	}
+	if err := os.MkdirAll(filepath.Dir(absPath), 0o755); err != nil {
+		return fmt.Errorf("mkdir %s: %w", filepath.Dir(absPath), err)
+	}
+
+	data, err := toml.Marshal(s)
+	if err != nil {
+		return fmt.Errorf("marshal session: %w", err)
+	}
+	if err := os.WriteFile(absPath, data, 0o644); err != nil {
+		return fmt.Errorf("write %s: %w", path, err)
+	}
+	return nil
+}