import from unified repo

csgo/sharecode.go

@@ -0,0 +1,57 @@
+package csgo
+
+import (
+	"encoding/hex"
+	"fmt"
+	"math/big"
+	"regexp"
+	"strings"
+)
+
+//goland:noinspection SpellCheckingInspection
+var DICT = "ABCDEFGHJKLMNOPQRSTUVWXYZabcdefhijkmnopqrstuvwxyz23456789"
+var sharecodeRexEx = regexp.MustCompile("^CSGO(?:-?[\\w]{5}){5}$")
+
+func DecodeSharecode(code string) (uint64, uint64, uint32, error) {
+	if !sharecodeRexEx.MatchString(code) {
+		return 0, 0, 0, fmt.Errorf("not a CSGO sharecode: %s", code)
+	}
+
+	cleanCode := strings.ReplaceAll(code, "CSGO", "")
+	cleanCode = strings.ReplaceAll(cleanCode, "-", "")
+
+	chars := ReverseString(strings.Split(cleanCode, ""))
+	bigInt := new(big.Int)
+	dictLenBig := big.NewInt(int64(len(DICT)))
+
+	for _, c := range chars {
+		bigInt.Mul(bigInt, dictLenBig)
+		bigInt.Add(bigInt, big.NewInt(int64(strings.Index(DICT, c))))
+	}
+
+	bytes := make([]byte, 18)
+	bigInt.FillBytes(bytes)
+
+	matchId := new(big.Int)
+	matchId.SetString(hex.EncodeToString(Reverse(bytes[0:8])), 16)
+	outcomeId := new(big.Int)
+	outcomeId.SetString(hex.EncodeToString(Reverse(bytes[8:16])), 16)
+	tokenId := new(big.Int)
+	tokenId.SetString(hex.EncodeToString(Reverse(bytes[16:18])), 16)
+
+	return matchId.Uint64(), outcomeId.Uint64(), uint32(tokenId.Uint64()), nil
+}
+
+func Reverse(numbers []byte) []byte {
+	for i, j := 0, len(numbers)-1; i < j; i, j = i+1, j-1 {
+		numbers[i], numbers[j] = numbers[j], numbers[i]
+	}
+	return numbers
+}
+
+func ReverseString(numbers []string) []string {
+	for i, j := 0, len(numbers)-1; i < j; i, j = i+1, j-1 {
+		numbers[i], numbers[j] = numbers[j], numbers[i]
+	}
+	return numbers
+}