// Copyright 2022 Paul Greenberg greenpau@outlook.com
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package system

import (
	"crypto/rand"
	"encoding/hex"
	"fmt"
	"os"
)

// GenerateKey generates a 256-bit symmetric key for PASETO v4 local tokens.
func GenerateKey(filePath string) error {
	key := make([]byte, 32)
	if _, err := rand.Read(key); err != nil {
		return fmt.Errorf("failed to generate random key: %w", err)
	}

	file, err := os.OpenFile(filePath, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600)
	if err != nil {
		return fmt.Errorf("failed to create key file: %w", err)
	}
	defer file.Close()

	_, err = fmt.Fprintln(file, hex.EncodeToString(key))
	return err
}
