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])
}