-module(handles@internal@parser).
-compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch]).

-export([run/1]).
-export_type([ast/0, parse_result/0]).

-type ast() :: {constant, integer(), binary()} |
    {property, integer(), list(binary())} |
    {partial, integer(), binary(), list(binary())} |
    {block,
        integer(),
        integer(),
        handles@internal@block:kind(),
        list(binary()),
        list(ast())}.

-type parse_result() :: {eof, list(ast())} |
    {block_end,
        integer(),
        handles@internal@block:kind(),
        list(ast()),
        list(handles@internal@tokenizer:token())}.

-spec parse(list(handles@internal@tokenizer:token()), list(ast())) -> {ok,
        parse_result()} |
    {error, handles@error:tokenizer_error()}.
parse(Tokens, Ast) ->
    case Tokens of
        [] ->
            {ok, {eof, lists:reverse(Ast)}};

        [{block_end, Index, Kind} | Tail] ->
            {ok, {block_end, Index, Kind, lists:reverse(Ast), Tail}};

        [{constant, Index@1, Value} | Tail@1] ->
            parse(Tail@1, [{constant, Index@1, Value} | Ast]);

        [{property, Index@2, Path} | Tail@2] ->
            parse(Tail@2, [{property, Index@2, Path} | Ast]);

        [{partial, Index@3, Id, Value@1} | Tail@3] ->
            parse(Tail@3, [{partial, Index@3, Id, Value@1} | Ast]);

        [{block_start, Start_index, Start_kind, Path@1} | Tail@4] ->
            case parse(Tail@4, []) of
                {error, Err} ->
                    {error, Err};

                {ok, {eof, _}} ->
                    {error, {unbalanced_block, Start_index}};

                {ok, {block_end, End_index, End_kind, Children, Rest}} when End_kind =:= Start_kind ->
                    parse(
                        Rest,
                        [{block,
                                Start_index,
                                End_index,
                                Start_kind,
                                Path@1,
                                Children} |
                            Ast]
                    );

                {ok, {block_end, Index@4, _, _, _}} ->
                    {error, {unexpected_block_end, Index@4}}
            end
    end.

-spec run(list(handles@internal@tokenizer:token())) -> {ok, list(ast())} |
    {error, handles@error:tokenizer_error()}.
run(Tokens) ->
    _pipe = parse(Tokens, []),
    gleam@result:'try'(_pipe, fun(It) -> case It of
                {eof, Ast} ->
                    {ok, Ast};

                {block_end, Index, _, _, _} ->
                    {error, {unexpected_block_end, Index}}
            end end).