grokify/mogo

// encoding/guid supports encoding and decoding Guid values.
package guid

import (
    "fmt"
    "math/big"
    "regexp"

    "github.com/grokify/bitcoinmath"
)

const (
    // GuidPattern is a regexp pattern for GUIDs.
    GUIDPattern = `^([0-9a-fA-F]{8})-?([0-9a-fA-F]{4})-?([0-9a-fA-F]{4})-?([0-9a-fA-F]{4})-?([0-9a-fA-F]{12})$`
    guidReplace = "${1}-${2}-${3}-${4}-${5}"
)

var (
    rxGUID   = regexp.MustCompile(GUIDPattern)
    rxHyphen = regexp.MustCompile(`-`)
)

// ValidGUIDHex checks to see if a string is a valid GUID.
func ValidGUIDHex(guid string) bool {
    return rxGUID.MatchString(guid)
}

// GUIDToBigInt converts a GUID string, with or with out hypens, to a *big.Int.
func GUIDToBigInt(guid string) (*big.Int, error) {
    if !ValidGUIDHex(guid) {
        return nil, fmt.Errorf("not a valid GUID [%s]", guid)
    }
    bi := big.NewInt(0)
    bi.SetString(rxHyphen.ReplaceAllString(guid, ""), 16)
    return bi, nil
}

// GUIDToBase58 converts a GUID string to a Base58 string using the Bitcoin alphabet.
func GUIDToBase58(guid string) (string, error) {
    bi, err := GUIDToBigInt(guid)
    if err != nil {
        return "", err
    }
    return string(bitcoinmath.Big2Base58(bi)), nil
}

// Base58ToGUID converts a Base58 string to a GUID string, with or without hyphens, using the Bitcoin alphabet.
func Base58ToGUID(b58str string, inclHyphen bool) (string, error) {
    b58 := bitcoinmath.Base58(b58str)
    bi := b58.Base582Big()

    guid := fmt.Sprintf("%032s", bi.Text(16))

    if len(guid) != 32 {
        return "", fmt.Errorf("error converting base58 string to hex: %v", b58str)
    }

    if inclHyphen {
        guid = rxGUID.ReplaceAllString(guid, guidReplace)
    }

    return guid, nil
}