// Copyright 2022 Martin Dosch.
// Use of this source code is governed by the BSD-2-clause
// license that can be found in the LICENSE file.

package main

import (
	"bytes"
	"crypto/rand"
	"fmt"
	"log"
	"math/big"
	"os"
)

func readFile(path string) (*bytes.Buffer, error) {
	file, err := os.Open(path)
	if err != nil {
		return nil, err
	}
	defer file.Close()
	buffer := new(bytes.Buffer)
	_, err = buffer.ReadFrom(file)
	if err != nil {
		return nil, err
	}

	return buffer, nil
}

func getRpad(messageLength int) string {
	var letters = []rune("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789.,;?!+-_§$%&/()=")
	lettersLength := int64(len(letters))
	length := 100 - messageLength%100
	s := make([]rune, length)
	for i := range s {
		pos, _ := rand.Int(rand.Reader, big.NewInt(lettersLength))
		s[i] = letters[pos.Int64()]
	}
	return string(s)
}

func getID() string {
	b := make([]byte, 12)
	_, err := rand.Read(b)
	if err != nil {
		log.Fatal(err)
	}
	id := fmt.Sprintf("%x-%x-%x", b[0:4], b[4:8], b[8:])
	return id
}

func getShortID() string {
	b := make([]byte, 4)
	_, err := rand.Read(b)
	if err != nil {
		log.Fatal(err)
	}
	id := fmt.Sprintf("%x", b[0:4])
	return id
}