fix: delete instance data and remove legacy shared workspace support

internal/api/instance_data.go

@@ -0,0 +1,57 @@
+package api
+
+import (
+	"errors"
+	"os"
+	"strings"
+
+	"git.misaka.ren/m1saka/dsh-web/internal/store"
+)
+
+// Call only with the instance lock held, after Docker resources are removed.
+func (a *API) removeInstanceData(i store.Instance) error {
+	for _, id := range []string{i.UID, i.ID} {
+		if id == "" || id == "." || id == ".." || strings.ContainsAny(id, "/\\") {
+			return errors.New("invalid instance storage path")
+		}
+	}
+	for _, parts := range [][]string{{"workspaces", i.UID, "instances", i.ID}, {"backups", i.UID, i.ID}} {
+		if err := a.removeDataDirectory(parts); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// Walk parents without following symlinks; RemoveAll unlinks child symlinks.
+func (a *API) removeDataDirectory(parts []string) error {
+	root, err := os.OpenRoot(a.root)
+	if err != nil {
+		return err
+	}
+	defer func() { root.Close() }()
+	for _, part := range parts[:len(parts)-1] {
+		st, err := root.Lstat(part)
+		if errors.Is(err, os.ErrNotExist) {
+			return nil
+		}
+		if err != nil {
+			return err
+		}
+		if !st.IsDir() {
+			return errors.New("unsafe storage path")
+		}
+		next, err := root.OpenRoot(part)
+		if err != nil {
+			return err
+		}
+		actual, err := next.Stat(".")
+		if err != nil || !os.SameFile(st, actual) {
+			next.Close()
+			return errors.New("storage path changed")
+		}
+		root.Close()
+		root = next
+	}
+	return root.RemoveAll(parts[len(parts)-1])
+}