package subtle

import (
	"crypto/sha1"
	"crypto/sha256"
	"crypto/sha512"
	"errors"
	"hash"

	"xdx.jelly/xgcl/sm/sm3"
)

// hashDigestSize maps hash algorithms to their digest size in bytes.
var hashDigestSize = map[string]uint32{
	"SHA1":   uint32(20),
	"SHA256": uint32(32),
	"SHA384": uint32(48),
	"SHA512": uint32(64),
	"SM3":    uint32(32),
}
var errNilHashFunc = errors.New("nil hash function")

// GetHashDigestSize returns the digest size of the specified hash algorithm.
func GetHashDigestSize(hash string) (uint32, error) {
	digestSize, ok := hashDigestSize[hash]
	if !ok {
		return 0, errors.New("invalid hash algorithm")
	}
	return digestSize, nil
}

// GetHashFunc returns the corresponding hash function of the given hash name.
func GetHashFunc(hash string) func() hash.Hash {
	switch hash {
	case "SHA1":
		return sha1.New
	case "SHA256":
		return sha256.New
	case "SHA384":
		return sha512.New384
	case "SHA512":
		return sha512.New
	case "SM3":
		return sm3.New
	default:
		return nil
	}
}