package hexutility

import (
	"encoding/binary"
	"encoding/hex"
)

func MustDecodeHex(in string) []byte {
	in = strip0x(in)
	if len(in)%2 == 1 {
		in = "0" + in
	}
	payload, err := hex.DecodeString(in)
	if err != nil {
		panic(err)
	}
	return payload
}

func strip0x(str string) string {
	if len(str) >= 2 && str[0] == '0' && (str[1] == 'x' || str[1] == 'X') {
		return str[2:]
	}
	return str
}

// EncodeTs encodes a TimeStamp (BlockNumber or TxNumber or other uin64) as big endian
func EncodeTs(number uint64) []byte {
	enc := make([]byte, 8)
	binary.BigEndian.PutUint64(enc, number)
	return enc
}

// Encode encodes b as a hex string with 0x prefix.
func Encode(b []byte) string {
	enc := make([]byte, len(b)*2+2)
	copy(enc, "0x")
	hex.Encode(enc[2:], b)
	return string(enc)
}

func FromHex(s string) []byte {
	if Has0xPrefix(s) {
		s = s[2:]
	}
	if len(s)%2 == 1 {
		s = "0" + s
	}
	return Hex2Bytes(s)
}

// Has0xPrefix validates str begins with '0x' or '0X'.
func Has0xPrefix(str string) bool {
	return len(str) >= 2 && str[0] == '0' && (str[1] == 'x' || str[1] == 'X')
}

// Hex2Bytes returns the bytes represented by the hexadecimal string str.
func Hex2Bytes(str string) []byte {
	h, _ := hex.DecodeString(str)
	return h
}

// IsHex validates whether each byte is valid hexadecimal string.
func IsHex(str string) bool {
	if len(str)%2 != 0 {
		return false
	}
	for _, c := range []byte(str) {
		if !isHexCharacter(c) {
			return false
		}
	}
	return true
}

// isHexCharacter returns bool of c being a valid hexadecimal.
func isHexCharacter(c byte) bool {
	return ('0' <= c && c <= '9') || ('a' <= c && c <= 'f') || ('A' <= c && c <= 'F')
}

func MustDecodeString(s string) []byte {
	r, err := hex.DecodeString(s)
	if err != nil {
		panic(err)
	}
	return r
}