package safeio

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

func TestAtomicWriteFileWritesContentAndReplacesExisting(t *testing.T) {
	dir := t.TempDir()
	path := filepath.Join(dir, "data.txt")

	// Write initial content.
	if err := os.WriteFile(path, []byte("old"), 0o644); err != nil {
		t.Fatal(err)
	}

	// Atomic replace.
	if err := AtomicWriteFile(path, []byte("new"), 0o644); err != nil {
		t.Fatal(err)
	}

	got, err := os.ReadFile(path)
	if err != nil {
		t.Fatal(err)
	}
	if string(got) != "new" {
		t.Fatalf("content = %q, want %q", string(got), "new")
	}

	// No temp files left behind.
	entries, err := os.ReadDir(dir)
	if err != nil {
		t.Fatal(err)
	}
	for _, e := range entries {
		if e.Name() != "data.txt" {
			t.Fatalf("unexpected file in directory: %s", e.Name())
		}
	}
}

func TestAtomicWriteFileCreatesParentDirs(t *testing.T) {
	dir := t.TempDir()
	path := filepath.Join(dir, "sub", "dir", "file.txt")

	if err := AtomicWriteFile(path, []byte("hello"), 0o644); err != nil {
		t.Fatal(err)
	}

	got, err := os.ReadFile(path)
	if err != nil {
		t.Fatal(err)
	}
	if string(got) != "hello" {
		t.Fatalf("content = %q, want %q", string(got), "hello")
	}
}