%%% @doc
%%% GRIDS URL parsing
%%%
%%% GRID(S): Gajumaru Remote Instruction Dispatch (Serialization)
%%% GRIDS is a Gajumaru protocol for encoding wallet instructions as URLs.
%%% Version 1 of the protocol consists of two verbs with two contexts each, collapsed to
%%% four symbols for brevity.
%%%
%%% The GRIDS schema begins with "grids://" or "grid://"
%%% Which way this is interpreted can vary depending on the verb.
%%%
%%% The typical "host" component is either an actual hostname or address and an optional
%%% port number (the defaut port being 3013), or a Gajumaru chain network IDi (in which
%%% case the port number is ignored if provided). Which way this field is interpreted
%%% depends on the verb.
%%%
%%% The first element of the path after the host component indicates the protocol version.
%%% Only version 1 exists at the time of this release.
%%%
%%% The next element of the path after the version is a single letter that indicates which
%%% action to take. The following actions are available:
%%%   "s": Spend on Chain
%%%     Constructs a spend transaction to the address indicated in the path component
%%%     indicated in the final path element. Two qargs are valid in the trailing arguments
%%%     section: "a" for amount (in Pucks, not Gajus!), and "p" for data payload.
%%%     In this context the "host" field in the URL is interpreted as a chain network ID.
%%%   "t": Transfer (spend) on Host
%%%     The same as "spend" above, but in this context the host field of the URL is
%%%     interpreted as host[:port] information and the network chain ID that will be used
%%%     will be derived from whatever chain the given host reports.
%%%   "d": Dead-drop signature request
%%%     This instructs the wallet to retrieve a signature data blob from an HTTP or HTTPS
%%%     URL that can be reconstructed by replacing "grids" with "https" or "grid" with
%%%     "http", omitting the "/1/d" path component and then recnstructing the URL.
%%%     This provides a lightweight method for services to enable contract calls from
%%%     wallets that are not capable of compiling contract source.
%%% @end

-module(gd_grids).
-vsn("0.6.5").
-author("Craig Everett <craigeverett@qpq.swiss>").
-copyright("QPQ AG <info@qpq.swiss>").
-license("GPL-3.0-or-later").

-export([parse/1]).
-include("$zx_include/zx_logger.hrl").


-spec parse(URL) -> {ok, Instruction} | {error, Reason}
    when URL         :: string(),
         Instruction :: {{spend, chain | node}, {Location, Recipient, Amount, Payload}}
                      | {{sign | mess, http | https}, URL},
         Location    :: Node  :: {inet:ip_address() | inet:hostname(), inet:port_number()}
                      | Chain :: binary(),
         Recipient   :: gajudesk:id(),
         Amount      :: non_neg_integer(),
         Payload     :: binary(),
         URL         :: string(),
         Reason      :: bad_url.

parse(URL) ->
    case uri_string:parse(URL) of
        #{path := "/1/s/" ++ R, host := H, query := Q, scheme := "grids"} ->
            spend(R, chain, list_to_binary(H), Q);
        #{path := "/1/s/" ++ R, host := H, query := Q, scheme := "grid"} ->
            spend(R, chain, list_to_binary(H), Q);
        #{path := "/1/t/" ++ R, host := H, port := P, query := Q, scheme := "grids"} ->
            spend(R, node, {H, P}, Q);
        #{path := "/1/t/" ++ R, host := H, port := P, query := Q, scheme := "grid"} ->
            spend(R, node, {H, P}, Q);
        #{path := "/1/t/" ++ R, host := H, query := Q, scheme := "grids"} ->
            spend(R, node, {H, 3013}, Q);
        #{path := "/1/t/" ++ R, host := H, query := Q, scheme := "grid"} ->
            spend(R, node, {H, 3013}, Q);
        U = #{path := "/1/d/" ++ L, scheme := "grids"} ->
            NewURL = uri_string:recompose(U#{scheme := "https", path := L}),
            {ok ,{{sign, https}, NewURL}};
        U = #{path := "/1/d/" ++ L, scheme := "grid"} ->
            NewURL = uri_string:recompose(U#{scheme := "http", path := L}),
            {ok, {{sign, http}, NewURL}};
        {error, Reason, Info} ->
            ok = tell("URL parsing failed with ~w: ~p", [Reason, Info]),
           {error, bad_url};
        U ->
            ok = tell("GRIDS cannot proceed with this result: ~p", [U]),
            {error, bad_url}
    end.

spend(Recipient, Context, Location, Qwargs) ->
    case dissect_query(Qwargs) of
        {ok, Amount, Payload} ->
            {ok, {{spend, Context}, {Location, Recipient, Amount, Payload}}};
        Error ->
            Error
    end.


dissect_query(Qwargs) ->
    case uri_string:dissect_query(Qwargs) of
        {error, Reason, Info} ->
            ok = tell("URL parsing failed with ~w: ~p", [Reason, Info]),
            {error, bad_url};
        ArgList ->
            case l_to_i(proplists:get_value("a", ArgList, "0")) of
                {ok, Amount} ->
                    Payload = list_to_binary(proplists:get_value("p", ArgList, "")),
                    {ok, Amount, Payload};
                Error ->
                    Error
            end
    end.

l_to_i(S) ->
    try
        {ok, list_to_integer(S)}
    catch
        error:badarg -> {error, bad_url}
    end.