// Copyright 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"
	"net/url"
	"os"
	"regexp"
	"strings"
)

func validUTF8(s string) string {
	// Remove invalid code points.
	s = strings.ToValidUTF8(s, "�")
	reg := regexp.MustCompile(`[\x{0000}-\x{0008}\x{000B}\x{000C}\x{000E}-\x{001F}]`)
	s = reg.ReplaceAllString(s, "�")

	return s
}

func validURI(s string) (*url.URL, error) {
	// Check if URI is valid
	uri, err := url.ParseRequestURI(s)
	return uri, fmt.Errorf("validURI: %w", err)
}

func readFile(path string) (*bytes.Buffer, error) {
	file, err := os.Open(path)
	if err != nil {
		return nil, fmt.Errorf("readFile: %w", err)
	}
	buffer := new(bytes.Buffer)
	_, err = buffer.ReadFrom(file)
	if err != nil {
		return nil, fmt.Errorf("readFile: %w", err)
	}
	err = file.Close()
	if err != nil {
		fmt.Println("error while closing file:", err)
	}
	return buffer, nil
}

func getRpad(messageLength int) string {
	rpadRunes := []rune("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789")
	length := defaultRpadMultiple - messageLength%defaultRpadMultiple
	max := big.NewInt(int64(len(rpadRunes)))
	rpad := make([]rune, length)
	for i := range rpad {
		randInt, err := rand.Int(rand.Reader, max)
		if err != nil {
			log.Fatal(err)
		}
		rpad[i] = rpadRunes[randInt.Int64()]
	}
	return string(rpad)
}

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

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