package updater

import (
	"fmt"
	"io/fs"
	"os"
	"path/filepath"
)

func replaceRegularFile(directory, target, pattern string, data []byte, syncer DirectorySyncer) error {
	if info, err := os.Lstat(target); err == nil {
		if info.Mode()&os.ModeSymlink != 0 || !info.Mode().IsRegular() {
			return fmt.Errorf("%w: file target is not a regular file", ErrUnsafeLayout)
		}
	} else if !os.IsNotExist(err) {
		return err
	}
	temporary, err := os.CreateTemp(directory, pattern)
	if err != nil {
		return err
	}
	temporaryPath := temporary.Name()
	defer os.Remove(temporaryPath)
	if err := temporary.Chmod(0o600); err != nil {
		_ = temporary.Close()
		return err
	}
	if _, err := temporary.Write(data); err != nil {
		_ = temporary.Close()
		return err
	}
	if err := temporary.Sync(); err != nil {
		_ = temporary.Close()
		return err
	}
	if err := temporary.Close(); err != nil {
		return err
	}
	if err := os.Rename(temporaryPath, target); err != nil {
		return err
	}
	return syncer.SyncDirectory(directory)
}

func readRegularFile(path string) ([]byte, error) {
	if err := validateRegularFile(path); err != nil {
		return nil, err
	}
	return os.ReadFile(path)
}

func removeRegularFile(path, directory string, syncer DirectorySyncer) error {
	info, err := os.Lstat(path)
	if os.IsNotExist(err) {
		return nil
	}
	if err != nil {
		return err
	}
	if info.Mode()&os.ModeSymlink != 0 || !info.Mode().IsRegular() {
		return fmt.Errorf("%w: refuse to remove non-regular file", ErrUnsafeLayout)
	}
	if err := os.Remove(path); err != nil {
		return err
	}
	return syncer.SyncDirectory(directory)
}

func renameDirectory(source, target string, layout updateLayout, syncer DirectorySyncer, description string) error {
	if source != layout.target && source != layout.staging && source != layout.backup {
		return fmt.Errorf("%w: source outside managed root", ErrUnsafeLayout)
	}
	if target != layout.target && target != layout.staging && target != layout.backup {
		return fmt.Errorf("%w: target outside managed root", ErrUnsafeLayout)
	}
	if err := os.Rename(source, target); err != nil {
		return fmt.Errorf("%s: %w", description, err)
	}
	if err := syncer.SyncDirectory(filepath.Dir(source)); err != nil {
		return err
	}
	if filepath.Dir(target) != filepath.Dir(source) {
		if err := syncer.SyncDirectory(filepath.Dir(target)); err != nil {
			return err
		}
	}
	return nil
}

func removeManagedTree(path string, layout updateLayout, syncer DirectorySyncer) error {
	if filepath.Dir(path) != filepath.Join(layout.root, backupsDirectoryName) && filepath.Dir(path) != filepath.Join(layout.root, stagingDirectoryName) {
		return fmt.Errorf("%w: refuse removal outside managed staging or backups", ErrUnsafeLayout)
	}
	if err := verifyTreeNoLinks(path); err != nil {
		return err
	}
	if err := os.RemoveAll(path); err != nil {
		return err
	}
	return syncer.SyncDirectory(filepath.Dir(path))
}

func verifyTreeNoLinks(path string) error {
	info, err := os.Lstat(path)
	if os.IsNotExist(err) {
		return nil
	}
	if err != nil {
		return err
	}
	if info.Mode()&os.ModeSymlink != 0 || !info.IsDir() {
		return fmt.Errorf("%w: managed tree is not a real directory", ErrUnsafeLayout)
	}
	return filepath.WalkDir(path, func(current string, entry fs.DirEntry, walkErr error) error {
		if walkErr != nil {
			return walkErr
		}
		if entry.Type()&os.ModeSymlink != 0 {
			return fmt.Errorf("%w: managed tree contains a symbolic link", ErrUnsafeLayout)
		}
		return nil
	})
}