package kdbx

import "errors"

// argon2 variants, filled in by argon2impl.go.
const (
	argon2d  = 0
	argon2i  = 1
	argon2id = 2
)

// argon2KDF derives the transformed key for a file that uses Argon2.
func argon2KDF(kdf variantDict, composite []byte, variant int) ([]byte, error) {
	salt := kdf.bytes("S")
	par, okP := kdf.uint64("P")
	mem, okM := kdf.uint64("M")
	iter, okI := kdf.uint64("I")
	if len(salt) == 0 || !okP || !okM || !okI {
		return nil, errors.New("kdbx: Argon2 parameters are missing or malformed")
	}
	if ver, ok := kdf.uint64("V"); ok && ver != 0x13 {
		return nil, unsupported("Argon2 version %#x", ver)
	}
	if len(kdf.bytes("K")) != 0 || len(kdf.bytes("A")) != 0 {
		return nil, unsupported("Argon2 secret key or associated data")
	}
	// M is in bytes in KDBX, in kibibytes in Argon2 itself.
	return argon2Key(composite, salt, uint32(iter), uint32(mem/1024), uint8(par), 32, variant)
}