package core

import (
	"os"
	"path/filepath"
)

// AtomicWriteFile writes data to a file atomically by first writing to a
// temporary file in the same directory, syncing, then renaming over the target.
// This prevents data loss / corruption on crash.
func AtomicWriteFile(path string, data []byte, perm os.FileMode) error {
	dir := filepath.Dir(path)
	tmp, err := os.CreateTemp(dir, ".tmp-*")
	if err != nil {
		return err
	}
	tmpPath := tmp.Name()

	if _, err := tmp.Write(data); err != nil {
		tmp.Close()
		os.Remove(tmpPath)
		return err
	}
	if err := tmp.Sync(); err != nil {
		tmp.Close()
		os.Remove(tmpPath)
		return err
	}
	if err := tmp.Close(); err != nil {
		os.Remove(tmpPath)
		return err
	}
	if err := os.Chmod(tmpPath, perm); err != nil {
		os.Remove(tmpPath)
		return err
	}
	return os.Rename(tmpPath, path)
}