-module(gsc_test_ytree).

-export([main/0]).
-include("$gsc_include/gsc.hrl").

main() ->
    Src =
        """
        contract Foo =
            type foo = bar
        """,
    handle_src_str(Src).

-type syntax_target() :: signal
                       | file
                       | {block_of, syntax_target()}
                       | top_decl
                           | contract
                           | interface
                           | namespace
                           | '@compiler'
                           | include
                       | using
                       .

-record(ct, {payable  = none :: none | false | true,
             main     = none :: none | false | true,
             contract = none :: none | tk(),
             con      = none :: none | tk(),
             impls    = none :: none | false | {true, [tk()]},
             '='      = none :: none | tk()}).

%% @doc This is all the stuff needed to be consumed before parsin
%% anything in the contract
-type contract_meta() :: #ct{}.


%% @doc
%% This is all the stuff that has to be parsed before actual parsing
%% can begin.
-type stem_meta() :: none
                   | contract_meta().

% @doc ys = syntax stem
-record(ys, {target    = signal  :: syntax_target(),
             signal              :: [tk()],
             stem_meta           :: stem_meta(),
             forest              :: [#ys{}]}).

-type syntax_stem() :: #ys{}.


handle_src_str(SrcStr) ->
    Sig = gsc:unsafe_signal_from_string(SrcStr),
    Result = gulp(file, Sig),
    io:format("~tp~n", [Result]).


-spec gulp(Target, Signal) -> Result when
        Target :: syntax_target(),
        Signal :: [tk()],
        Result :: {gulp, syntax_stem()} | {error, any()}.

gulp(file, Sig) ->
    gulp({block_of, top_decl}, Sig);
gulp({block_of, X}, Sig) ->
    {gulp, BlockItems} = gsc_signal:gulp_block_items(Sig),
    #ys{target    = {block_of, X},
        signal    = Sig,
        stem_meta = none,
        forest    = [gulp(X, Item) || Item <- BlockItems]};
gulp(top_decl, Sig) ->
    % TopDecl ::= ['payable'] ['main'] 'contract' Con [Implement] '=' Block(Decl)
    %           | 'contract' 'interface' Con [Implement] '=' Block(Decl)
    %           | 'namespace' Con '=' Block(Decl)
    %           | '@compiler' PragmaOp Version
    %           | 'include' String
    %           | Using
    NewTarget =
        case gsc_tokens:strings(3, Sig) of
            ["namespace", _,           _]           -> namespace;
            ["@compiler", _,           _]           -> '@compiler';
            ["include",   _,           _]           -> include;
            ["using",     _,           _]           -> using;
            ["payable",   "main",      "contract"]  -> contract;
            ["payable",   "contract",  "interface"] -> interface;
            ["payable",   "contract",  _]           -> contract;
            ["contract",  "interface", _]           -> interface;
            ["contract",  _,           _]           -> contract;
            ["main",      "contract",  _]           -> contract;
            ["main",      "payable",   "contract"]  -> contract
        end,
    gulp(NewTarget, Sig);
gulp(contract, Sig) ->
    {slurp, CtMeta, BlockSignal} = slurp(#ct{}, Sig),
    {gulp, BlockItems} = gsc_signal:gulp_block_items(BlockSignal),
    Forest = [gulp(decl, Item) || Item <- BlockItems],
    #ys{target = contract,
        signal = Sig,
        stem_meta = CtMeta,
        forest = Forest};
% Decl ::= 'type'     Id ['(' TVar* ')'] '=' TypeAlias
%        | 'record'   Id ['(' TVar* ')'] '=' RecordType
%        | 'datatype' Id ['(' TVar* ')'] '=' DataType
%        | 'let'      Id [':' Type]      '=' Expr
%        | (EModifier* 'entrypoint' | FModifier* 'function') Block(FunDecl)
%        | Using
gulp(decl, Sig) ->
    NewTarget =
        case strings(1, Sig) of
            ["type"]     -> type;
            ["record"]   -> record;
            ["datatype"] -> datatype;
            ["let"]      -> 'let';
            ["using"]    -> using;
            _            -> fn
        end,
    gulp(NewTarget, Sig);
gulp(NyiTarget, Sig) ->
    error({nyi, [?MODULE, gulp, NyiTarget, Sig]}).


%% ['payable'] ['main'] 'contract' Con [Implement] '=' Block(Decl)
slurp(Meta = #ct{payable = none, main = none}, Sig) ->
    %% nato phonetic alphabet
    {Pa, Mi, No} =
        case gsc_tokens:strings(2, Sig) of
            ["payable", "main"] -> {true, true, 2};
            ["main", "payable"] -> {true, true, 2};
            ["payable", _]      -> {true, false, 1};
            ["main", _]         -> {false, true, 1};
            _                   -> {false, false, 0}
        end,
    NewMeta = Meta#ct{payable = Pa, main = Mi},
    NewSig = take(No, Sig),
    slurp(NewMeta, NewSig);
slurp(M = #ct{contract = none}, Sig) ->
    case Sig of
        [Tk = #tk{str = "contract"} | Rest] ->
            slurp(M#ct{contract = Tk}, Rest);
        _ ->
            error(no_keyword_contract)
    end;
slurp(M = #ct{con = none}, Sig) ->
    case Sig of
        [Tk = #tk{shape = con} | Rest] ->
            slurp(M#ct{con = Tk}, Rest);
        [#tk{str = Irregar} | _] ->
            error(illegal_contract_name, Irregar);
        [] ->
            error(no_contract_name)
    end;
slurp(M = #ct{impls = none}, Sig) ->
    case Sig of
        [#tk{str = ":"} | Rest] ->
            {slurp, Impls, NewRest} = slurp({sep1, con, ","}, Rest),
            NewM = M#ct{impls = {true, Impls}},
            slurp(NewM, NewRest);
        _ ->
            slurp(M#ct{impls = false}, Sig)
    end;
slurp(M = #ct{'=' = none}, Sig) ->
    case Sig of
        [Tk = #tk{str = "="} | Rest] ->
            {slurp, M#ct{'=' = Tk}, Rest};
        _ ->
            error("where the fuck my = be at nigga")
    end;
slurp({sep1, TkShape, SepByStr}, Tks) ->
    case Tks of
        [Tk = #tk{shape = TkShape} | Rest] ->
            slurp_sep1_ii([Tk], TkShape, SepByStr, Rest);
        _ ->
            error(irregar)
    end;
slurp(BadMeta, BadTokens) ->
    error({nyi, [?MODULE, slurp, BadMeta, BadTokens]}).


slurp_sep1_ii(Stk, TkShape, SepByStr, Sig) ->
    case Sig of
        [#tk{str = SepByStr}, T = #tk{shape = TkShape} | Rest] ->
            slurp_sep1_ii([T | Stk], TkShape, SepByStr, Rest);
        _ ->
            {slurp, lists:reverse(Stk), Sig}
    end.

strings(N, Tks) ->
    gsc_tokens:strings(N, Tks).


take(N, [_ | Rest]) when N >= 1 -> take(N-1, Rest);
take(0, List)                   -> List;
take(_, [])                     -> [].