feat: add diagnostics and safe reset maintenance

internal/profile/diagnostic.go

@@ -0,0 +1,58 @@
+package profile
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"io/fs"
+	"os"
+
+	"golang.org/x/sys/unix"
+)
+
+// ReadOnlyLoad reads and validates Profile configuration without creating,
+// chmodding, chowning, locking, or replacing any filesystem object.
+func (s *FileStore) ReadOnlyLoad() (State, error) {
+	file, err := os.OpenFile(s.path, unix.O_RDONLY|unix.O_NOFOLLOW|unix.O_NONBLOCK, 0)
+	if errors.Is(err, fs.ErrNotExist) {
+		return State{}, nil
+	}
+	if err != nil {
+		return State{}, fmt.Errorf("open Profile configuration read-only: %w", err)
+	}
+	defer file.Close()
+	info, err := file.Stat()
+	if err != nil {
+		return State{}, fmt.Errorf("inspect Profile configuration: %w", err)
+	}
+	if !info.Mode().IsRegular() {
+		return State{}, errors.New("Profile configuration is not a regular file")
+	}
+	data, err := io.ReadAll(file)
+	if err != nil {
+		return State{}, fmt.Errorf("read Profile configuration: %w", err)
+	}
+	var state State
+	if err := json.Unmarshal(data, &state); err != nil {
+		return State{}, fmt.Errorf("parse Profile configuration: %w", err)
+	}
+	for _, candidate := range state.Profiles {
+		if _, err := ValidateAndNormalize(candidate); err != nil {
+			return State{}, fmt.Errorf("Profile %q is invalid: %w", candidate.Name, err)
+		}
+	}
+	if state.ActiveProfile != "" && indexProfile(state.Profiles, state.ActiveProfile) < 0 {
+		return State{}, fmt.Errorf("Active Profile %q does not exist", state.ActiveProfile)
+	}
+	return state, nil
+}
+
+func indexProfile(profiles []Profile, name string) int {
+	for i := range profiles {
+		if profiles[i].Name == name {
+			return i
+		}
+	}
+	return -1
+}