// Create a temporary file in the directory of the given destination
// file, then rename the temporary file over the destination file if
// writes to the temporary file complete without error.
//
// Used to atomically update files.
//
// Note: This is not guaranteed and depends on the sync semantics of the
// underlying filesystem.
package atomictemp

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

// Create a temporary file in the directory of the given destination
// file, then rename the temporary file over the destination file if
// writes to the temporary file complete without error.
//
// Used to atomically update files.
//
// Note: This is not guaranteed and depends on the sync semantics of the
// underlying filesystem.
func Create(dstPath string, fn func(io.Writer) error) error {
  // open temp output file
  f, err := os.CreateTemp(filepath.Dir(dstPath), "")
  if err != nil {
    return err
  }

  // build absolute path to temporary file
  // tmpPath := filepath.Join(filepath.Dir(dstPath), f.Name())
  defer os.Remove(f.Name())

  // invoke callback
  if err = fn(f); err != nil {
    return err
  }

  // close temp file
  if err = f.Close(); err != nil {
    return err
  }

  // rename to destination file, return result
  return os.Rename(f.Name(), dstPath)
}