// Package fileutil provides narrow filesystem helpers for durable artifacts.
package fileutil

import (
	"encoding/json"
	"fmt"
	"os"
	"path/filepath"
)

func WriteFileAtomic(path string, data []byte) error {
	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
		return fmt.Errorf("create directory %q: %w", filepath.Dir(path), err)
	}
	tmp, err := os.CreateTemp(filepath.Dir(path), "."+filepath.Base(path)+".*.tmp")
	if err != nil {
		return fmt.Errorf("create temporary file for %q: %w", path, err)
	}
	tmpName := tmp.Name()
	defer os.Remove(tmpName)
	if _, err := tmp.Write(data); err != nil {
		tmp.Close()
		return fmt.Errorf("write temporary file for %q: %w", path, err)
	}
	if err := tmp.Close(); err != nil {
		return fmt.Errorf("close temporary file for %q: %w", path, err)
	}
	if err := os.Rename(tmpName, path); err != nil {
		return fmt.Errorf("save %q: %w", path, err)
	}
	return nil
}

func WriteJSONAtomic(path string, value any) error {
	data, err := json.MarshalIndent(value, "", "  ")
	if err != nil {
		return fmt.Errorf("marshal %q: %w", path, err)
	}
	return WriteFileAtomic(path, data)
}

func CopyFileAtomic(source string, target string) error {
	data, err := os.ReadFile(source)
	if err != nil {
		return fmt.Errorf("read %q: %w", source, err)
	}
	return WriteFileAtomic(target, data)
}