-module(compat).
-export([unpack_issuer/1, unpack_signature/1]).
-include_lib("public_key/include/public_key.hrl").

unpack_issuer(Issuer) ->
    unpack_issuer(erlang:system_info(otp_release), Issuer).
unpack_signature(Signature) ->
    unpack_signature(erlang:system_info(otp_release), Signature).

%% @doc Dig out alg, params and key from issuer.
unpack_issuer("17", Issuer) ->
    #'SubjectPublicKeyInfo'{
       algorithm = #'AlgorithmIdentifier'{algorithm = Alg, parameters = Params},
       subjectPublicKey = {0, Key}} = Issuer,
    {Alg, Params, Key};
unpack_issuer("18", Issuer) ->
    #'SubjectPublicKeyInfo'{
       algorithm = #'AlgorithmIdentifier'{algorithm = Alg, parameters = Params},
       subjectPublicKey = Key} = Issuer,
    {Alg, Params, Key}.

%% @doc Unpack a #'Certificate'.signature, return the signature.
unpack_signature("17", Signature) ->
    {_, Sig} = Signature,
    Sig;
unpack_signature("18", Signature) ->
    Signature.