package files

import (
	"fmt"
	"os"
	"path/filepath"
	"runtime"
)

func EnsureDir(path string, perm os.FileMode) error {
	if err := os.MkdirAll(path, perm); err != nil {
		return fmt.Errorf("mkdir %s: %w", path, err)
	}
	return nil
}

func WriteFileAtomic(path string, data []byte, perm os.FileMode) error {
	dir := filepath.Dir(path)
	if err := EnsureDir(dir, 0o755); err != nil {
		return err
	}
	f, err := os.CreateTemp(dir, ".tmp-*")
	if err != nil {
		return fmt.Errorf("create temp: %w", err)
	}
	tmp := f.Name()
	ok := false
	defer func() {
		_ = f.Close()
		if !ok {
			_ = os.Remove(tmp)
		}
	}()

	if _, err := f.Write(data); err != nil {
		return fmt.Errorf("write temp: %w", err)
	}
	if err := f.Chmod(perm); err != nil {
		return fmt.Errorf("chmod temp: %w", err)
	}
	if err := f.Sync(); err != nil {
		return fmt.Errorf("fsync temp: %w", err)
	}
	if err := f.Close(); err != nil {
		return fmt.Errorf("close temp: %w", err)
	}

	if err := ReplaceFile(tmp, path); err != nil {
		return err
	}
	ok = true
	return nil
}

func ReplaceFile(tmpPath, dstPath string) error {
	if err := os.Rename(tmpPath, dstPath); err == nil {
		return nil
	} else if runtime.GOOS == "windows" {
		_ = os.Remove(dstPath)
		if err2 := os.Rename(tmpPath, dstPath); err2 != nil {
			return fmt.Errorf("rename %s -> %s: %w", tmpPath, dstPath, err2)
		}
		return nil
	} else {
		return fmt.Errorf("rename %s -> %s: %w", tmpPath, dstPath, err)
	}
}