% @doc grids cache
-module(fd_gridsd).
-vsn("0.2.0").

-behavior(gen_server).

-export_type([
]).

-export([
    %% caller context
    get_url/2,

    %% api
    start_link/0,

    %% process context
    init/1, handle_call/3, handle_cast/2, handle_info/2,
    code_change/3, terminate/2
]).

-include("$zx_include/zx_logger.hrl").

-type mh_str()         :: string().

%% for craig's autism
-record(sp,
        {recipient :: string(),
         amount    :: non_neg_integer(),
         payload   :: binary()}).

-type search_pattern() :: #sp{}.

-record(s,
        {current_gen_height         :: pos_integer(),
         current_gen_hash           :: string(),
         current_gen_seen_mb_hashes :: [mh_str()],
         past_gen_seen_mb_hashes    :: [mh_str()],
         looking_for                :: [search_pattern()]}).
-type state() :: #s{}.


%%-----------------------------------------------------------------------------
%% caller context
%%-----------------------------------------------------------------------------

-spec get_url(Amount, Payload) -> {ok, URL, QR_PNG} | {error, term()}
    when Amount  :: none | pos_integer(),
         Payload :: none | binary(),
         URL     :: string(),
         QR_PNG  :: binary().

get_url(Amount, Payload) ->
    gen_server:call(?MODULE, {get_url, Amount, Payload}).


%% gen_server callbacks
start_link() ->
    gen_server:start_link({local, ?MODULE}, ?MODULE, none, []).


%%-----------------------------------------------------------------------------
%% process context below this line
%%-----------------------------------------------------------------------------

%% gen_server callbacks

init(none) ->
    tell("starting fd_gridsd"),
    InitState = #s{},
    {ok, InitState}.


handle_call({get_url, Amount, Payload}, From, State) ->
    case i_get_url(Amount, Payload, From, State) of
        {ok, URL, PNG, NewState} ->
            {reply, {ok, URL, PNG}, NewState};
        Error ->
            {reply, Error, State}
    end;
handle_call(Unexpected, From, State) ->
    tell("~tp: unexpected call from ~tp: ~tp", [?MODULE, Unexpected, From]),
    {noreply, State}.


handle_cast(Unexpected, State) ->
    tell("~tp: unexpected cast: ~tp", [?MODULE, Unexpected]),
    {noreply, State}.


handle_info(Unexpected, State) ->
    tell("~tp: unexpected info: ~tp", [?MODULE, Unexpected]),
    {noreply, State}.


code_change(_, State, _) ->
    {ok, State}.

terminate(_, _) ->
    ok.


%%-----------------------------------------------------------------------------
%% internals
%%-----------------------------------------------------------------------------

-spec i_get_url(Amount, Payload, From, State) -> Result
    when Amount  :: none | pos_integer(),
         Payload :: none | binary(),
         From    :: {pid(), reference()},
         State   :: state(),
         URL     :: string(),
         QR_PNG  :: binary().
         Result  :: {ok, URL, QR_PNG, NewState}
                  | {error, term()}.

i_get_url(Amount, Payload, From, State) ->
    NetworkId = fewd:network_id(),
    Pubkey    = fewd:pubkey(),
    URL       = gmgrids:encode({spend, NetworkId, Pubkey},
                               [{amount, Amount}, {payload, Payload}]),