package main

import (
	"crypto/hmac"
	"crypto/sha256"
	"encoding/hex"
	"net/url"
	"sort"
	"strings"
)

func VerifyTelegramInitData(initData, botToken string) (map[string]string, bool) {
	values, _ := url.ParseQuery(initData)

	hash := values.Get("hash")
	values.Del("hash")

	var data []string
	for k, v := range values {
		data = append(data, k+"="+v[0])
	}
	sort.Strings(data)

	checkString := strings.Join(data, "\n")

	secret := sha256.Sum256([]byte(botToken))
	h := hmac.New(sha256.New, secret[:])
	h.Write([]byte(checkString))

	expected := hex.EncodeToString(h.Sum(nil))

	return valuesToMap(values), expected == hash
}

func valuesToMap(v url.Values) map[string]string {
	m := make(map[string]string)
	for k, val := range v {
		m[k] = val[0]
	}
	return m
}