package files

import (
	"context"
	"errors"
	"fmt"
	"os"
	"path/filepath"
	"strings"
)

var (
	ErrUnsafeInstanceDataDirectory = errors.New("unsafe instance data directory")
	ErrInstanceDataNotDirectory    = errors.New("instance data path is not a directory")
)

// InstanceDataRemover deletes one explicitly authorized browser User Data Dir.
// Callers must check browser occupancy before invoking it.
type InstanceDataRemover interface {
	RemoveInstanceData(context.Context, string) error
}

type instanceDataRemover struct {
	lstat     func(string) (os.FileInfo, error)
	removeAll func(string) error
}

func NewInstanceDataRemover() InstanceDataRemover {
	return newInstanceDataRemover(os.Lstat, os.RemoveAll)
}

func newInstanceDataRemover(lstat func(string) (os.FileInfo, error), removeAll func(string) error) instanceDataRemover {
	return instanceDataRemover{lstat: lstat, removeAll: removeAll}
}

func (r instanceDataRemover) RemoveInstanceData(ctx context.Context, userDataDir string) error {
	if err := ctx.Err(); err != nil {
		return err
	}
	path, err := normalizeRemovableInstanceDataDir(userDataDir)
	if err != nil {
		return err
	}
	info, err := r.lstat(path)
	if errors.Is(err, os.ErrNotExist) {
		return nil
	}
	if err != nil {
		return fmt.Errorf("inspect instance data directory: %w", err)
	}
	if info.Mode()&(os.ModeSymlink|os.ModeIrregular) != 0 || isReparsePoint(info) {
		return fmt.Errorf("%w: links and reparse points are not removable", ErrUnsafeInstanceDataDirectory)
	}
	if !info.IsDir() {
		return ErrInstanceDataNotDirectory
	}
	if err := ctx.Err(); err != nil {
		return err
	}
	if err := r.removeAll(path); err != nil {
		return fmt.Errorf("remove instance data directory: %w", err)
	}
	return nil
}

func normalizeRemovableInstanceDataDir(value string) (string, error) {
	value = strings.TrimSpace(value)
	if value == "" || !filepath.IsAbs(value) {
		return "", fmt.Errorf("%w: path must be absolute", ErrUnsafeInstanceDataDirectory)
	}
	path := filepath.Clean(value)
	volumeRoot := filepath.Clean(filepath.VolumeName(path) + string(filepath.Separator))
	if strings.EqualFold(path, volumeRoot) {
		return "", fmt.Errorf("%w: volume root is not removable", ErrUnsafeInstanceDataDirectory)
	}
	return path, nil
}