package jsondb

import (

	"errors"

	"io/ioutil"

	"os"

	"path"

	"testing"

	"github.com/stretchr/testify/require"

)

func TestWriteFileAtomically(t *testing.T) {

	dir, err := ioutil.TempDir("", "jsondb-test-")

	require.NoError(t, err)

	defer func() {

		err := os.RemoveAll(dir)

		require.NoError(t, err)

	}()

	t.Run("success", func(t *testing.T) {

		octopus := []byte("🐙\n")

		// use an uncommon mode to check it's set correctly

		perm := os.FileMode(0750)

		err = writeFileAtomically(dir, "octopus", perm, func(f *os.File) error {

			_, err := f.Write(octopus)

			return err

		})

		require.NoError(t, err)

		// ensure that there are no stray temporary files

		infos, err := ioutil.ReadDir(dir)

		require.NoError(t, err)

		require.Equal(t, 1, len(infos))

		require.Equal(t, "octopus", infos[0].Name())

		require.Equal(t, perm, infos[0].Mode())

		filename := path.Join(dir, "octopus")

		contents, err := ioutil.ReadFile(filename)

		require.NoError(t, err)

		require.Equal(t, octopus, contents)

		err = os.Remove(filename)

		require.NoError(t, err)

	})

	t.Run("error", func(t *testing.T) {

		err = writeFileAtomically(dir, "no-octopus", 0750, func(f *os.File) error {

			return errors.New("something went wrong")

		})

		require.Error(t, err)

		_, err := os.Stat(path.Join(dir, "no-octopus"))

		require.Error(t, err)

		// ensure there are no stray temporary files

		infos, err := ioutil.ReadDir(dir)

		require.NoError(t, err)

		require.Equal(t, 0, len(infos))

	})

}