-module(oidcc_session).
-behaviour(gen_server).

%% API.
-export([start_link/3]).
-export([start_link/4]).
-export([is_user_agent/2]).
-export([is_cookie_data/2]).
-export([is_peer_ip/2]).
-export([get_id/1]).
-export([get_provider/1]).
-export([get_scopes/1]).
-export([get_nonce/1]).
-export([get_pkce/1]).
-export([get_peer_ip/1]).
-export([get_user_agent/1]).
-export([get_cookie_data/1]).
-export([get_client_mod/1]).
-export([set_user_agent/2]).
-export([set_cookie_data/2]).
-export([set_peer_ip/2]).
-export([set_client_mod/2]).
-export([close/1]).


%% gen_server.
-export([init/1]).
-export([handle_call/3]).
-export([handle_cast/2]).
-export([handle_info/2]).
-export([terminate/2]).
-export([code_change/3]).

-record(state, {
          id = undefined,
          timeout = undefined,
          data = #{}
         }).

%% API.

start_link(Id, Nonce, ProviderId) ->
    {ok, Config} = oidcc:get_openid_provider_info(ProviderId),
    Scopes = maps:get(request_scopes, Config),
    start_link(Id, Nonce, ProviderId, Scopes).

start_link(Id, Nonce, ProviderId, Scopes0) ->
    Scopes = case Scopes0 of
                 undefined -> application:get_env(oidcc, scopes, [openid]);
                 _ -> Scopes0
             end,
    Pkce = generate_pkce_if_supported(ProviderId),
    gen_server:start_link(?MODULE, {Id, Nonce, Pkce, ProviderId, Scopes}, []).

-spec close(Pid ::pid()) -> ok.
close(Pid) ->
    gen_server:cast(Pid, close).

is_user_agent(UserAgent, Pid) ->
    gen_server:call(Pid, {is, user_agent, UserAgent}).

is_cookie_data(CookieData, Pid) ->
    gen_server:call(Pid, {is, cookie_data, CookieData}).

is_peer_ip(PeerIp, Pid) ->
    gen_server:call(Pid, {is, peer_ip, PeerIp}).

get_id(Pid) ->
    gen_server:call(Pid, get_id).

get_provider(Pid) ->
    gen_server:call(Pid, {get, provider}).

get_scopes(Pid) ->
    gen_server:call(Pid, {get, scopes}).

get_nonce(Pid) ->
    gen_server:call(Pid, {get, nonce}).

get_pkce(Pid) ->
    gen_server:call(Pid, {get, pkce}).

get_peer_ip(Pid) ->
    gen_server:call(Pid, {get, peer_ip}).

get_user_agent(Pid) ->
    gen_server:call(Pid, {get, user_agent}).

get_cookie_data(Pid) ->
    gen_server:call(Pid, {get, cookie_data}).

get_client_mod(Pid) ->
    gen_server:call(Pid, {get, client_mod}).

set_user_agent(UserAgent, Pid) ->
    gen_server:call(Pid, {set, user_agent, UserAgent}).

set_peer_ip(PeerIp, Pid) ->
    gen_server:call(Pid, {set, peer_ip, PeerIp }).

set_cookie_data(CookieData, Pid) ->
    gen_server:call(Pid, {set, cookie_data, CookieData }).

set_client_mod(ClientMod, Pid) ->
    gen_server:call(Pid, {set, client_mod, ClientMod }).
%% gen_server.

init({Id, Nonce, Pkce, ProviderId, Scopes}) ->
    Timeout = application:get_env(oidcc, session_timeout, 300000),
    Map = #{nonce => Nonce, scopes => Scopes, pkce => Pkce,
            provider => ProviderId},
    {ok, #state{id = Id, data = Map, timeout=Timeout}, Timeout}.

handle_call({get, Field}, _From, #state{data=Map, timeout=To} = State) ->
    Value = maps:get(Field, Map, undefined),
    {reply, {ok, Value}, State, To};
handle_call({set, Field, Value}, _From, #state{data=Map, timeout=To} = State) ->
    NewMap = maps:put(Field, Value, Map),
    {reply, ok, State#state{data=NewMap}, To};
handle_call({is, Field, InVal}, _From, #state{data=Map, timeout=To} = State) ->
    Value = maps:get(Field, Map, undefined),
    {reply, InVal == Value, State, To};

handle_call(get_id, _From, #state{id=Id, timeout=To} = State) ->
    {reply, {ok, Id}, State, To};
handle_call(_Request, _From, #state{timeout=To} = State) ->
    {reply, ignored, State, To}.

handle_cast(close, #state{id = Id} = State) ->
    ok = oidcc_session_mgr:session_terminating(Id),
    {stop, normal, State};
handle_cast(_Request, #state{timeout = To} = State) ->
    {noreply, State, To}.

handle_info(timeout, #state{id = Id} = State) ->
    ok = oidcc_session_mgr:session_terminating(Id),
    {stop, normal, State};
handle_info(_Info, #state{timeout=To} = State) ->
    {noreply, State, To}.



terminate(normal, _State) ->
    ok;
terminate(_Reason, #state{id = Id}) ->
    oidcc_session_mgr:session_terminating(Id),
    ok.

code_change(_OldVsn, State, _Extra) ->
    {ok, State}.

generate_pkce_if_supported(ProviderId) ->
    {ok, Config} = oidcc:get_openid_provider_info(ProviderId),
    UsePkce = maps:is_key(code_challenge_methods_supported, Config),
    Methods = maps:get(code_challenge_methods_supported, Config, [<<"S256">>]),
    generate_pkce(UsePkce, Methods).

generate_pkce(true, Methods) ->
    CodeVerifier = gen_code_verifier(),
    UseS256 = lists:member(<<"S256">>, Methods),
    apply_s256(UseS256, CodeVerifier);
generate_pkce(_, _) ->
    undefined.

apply_s256(true, CodeVerifier) ->
    #{
       verifier => CodeVerifier,
       challenge => base64url:encode(crypto:hash(sha256, CodeVerifier)),
       method => 'S256'
     };
apply_s256(_, CodeVerifier) ->
    #{
       verifier => CodeVerifier,
       challenge => CodeVerifier,
       method => plain
     }.

gen_code_verifier() ->
    base64:encode(crypto:strong_rand_bytes(64)).