package hkdf

import (
	stdhkdf "crypto/hkdf"
	"crypto/sha256"
)

// Extract computes HKDF-Extract(salt, ikm) using SHA-256.
// Note: parameter order is (salt, ikm) matching musiquay convention;
// stdlib expects (h, secret, salt) - mapping is applied internally.
func Extract(salt, ikm []byte) (v [32]byte) {
	if len(salt) == 0 {
		salt = []byte{:32}
	}
	prk, _ := stdhkdf.Extract(sha256.New, ikm, salt)
	var out [32]byte
	copy(out[:], prk)
	return out
}

// Expand derives length bytes of keying material from prk using SHA-256 HKDF-Expand.
func Expand(prk, info []byte, length int32) (buf []byte) {
	out, _ := stdhkdf.Expand(sha256.New, prk, info, length)
	return out
}