-module(gurka_parser).

-include("gurka.hrl").

-export([parse/1, tokens/1]).

-spec parse(File) -> {ok, Feature} | {error, Reason} when
    File :: file:name(),
    Feature :: feature(),
    Reason :: file:posix() | badarg | terminated | system_limit.
parse(File) ->
    case file:read_file(File) of
        {ok, Binary} ->
            {_, Lines} = lists:foldl(fun(Line, {Row, AccIn}) ->
                {Row + 1, [{Row, Line, tokens(Line)} | AccIn]}
            end, {1, []}, binary:split(Binary, [<<$\n>>, <<$\r>>], [global, trim])),
            {ok, inherit_tags(compact(process(undefined, undefined, lists:reverse(Lines))))};
        {error, Reason} ->
            {error, Reason}
    end.

-spec process(Phase, Action, Lines) -> Feature when
    Phase :: phase(),
    Action :: action(),
    Lines :: lines(),
    Feature :: feature().
process(_Phase, _Action, []) ->
    [];
process(Phase, Action, [{_Row, _Line, []} | Lines]) ->
    process(Phase, Action, Lines);
process(Phase, Action, [{Row, _Line, Tags = [<<$@, _/binary>> | _]} | Lines]) ->
    [#step{phase = Phase, action = tags, tokens = Tags, row = Row} | process(Phase, Action, Lines)];
process(Phase, Action, [{Row, Line, [<<"|">> | Tokens]} | Lines]) ->
    {Lines2, Table} = build_table([{Row, Line, [<<"|">> | Tokens]} | Lines], []),
    [#step{phase = Phase, action = table, tokens = Table, row = Row} | process(Phase, Action, Lines2)];
process(Phase, Action, [{Row, _Line, [<<"\"\"\"">> | _Tokens]} | Lines]) ->
    {Lines2, Docstring} = build_docstring(Lines, []),
    [#step{phase = Phase, action = docstring, tokens = Docstring, row = Row} | process(Phase, Action, Lines2)];
process(Phase, Action, [{Row, _Line, [FirstToken | Tokens]} | Lines]) ->
    case normalize_token(FirstToken) of
        "and" ->
            [#step{phase = Phase, action = Action, tokens = Tokens, row = Row} | process(Phase, Action, Lines)];
        "but" ->
            [#step{phase = Phase, action = Action, tokens = Tokens, row = Row} | process(Phase, Action, Lines)];
        "given" ->
            [#step{phase = Phase, action = given, tokens = Tokens, row = Row} | process(Phase, given, Lines)];
        "when" ->
            [#step{phase = Phase, action = 'when', tokens = Tokens, row = Row} | process(Phase, 'when', Lines)];
        "then" ->
            [#step{phase = Phase, action = then, tokens = Tokens, row = Row} | process(Phase, then, Lines)];
        "examples" ->
            [#step{phase = Phase, action = examples, tokens = Tokens, row = Row} | process(Phase, examples, Lines)];
        "feature" ->
            [#step{phase = feature, action = start, tokens = Tokens, row = Row} | process(feature, undefined, Lines)];
        "background" ->
            [#step{phase = background, action = start, tokens = Tokens, row = Row} | process(background, undefined, Lines)];
        "scenario" ->
            case normalize_token(hd(Tokens)) of
                "outline" ->
                    [#step{phase = scenario_outline, action = start, tokens = tl(Tokens), row = Row} | process(scenario_outline, undefined, Lines)];
                _ ->
                    [#step{phase = scenario, action = start, tokens = Tokens, row = Row} | process(scenario, undefined, Lines)]
            end;
        _ ->
            [#step{phase = Phase, action = desc, tokens = [FirstToken | Tokens], row = Row} | process(Phase, Action, Lines)]
    end.

compact(Feature) ->
    compact(lists:reverse(Feature), []).

compact([], Acc) ->
    Acc;
compact([#step{action = docstring, tokens = Docstring} | [Step | Steps]], Acc) ->
    compact([Step#step{tokens = Step#step.tokens ++ [{docstring, Docstring}]} | Steps], Acc);
compact([#step{action = table, tokens = Table} | [Step = #step{action = examples} | Steps]], Acc) ->
    compact([Step#step{tokens = Table} | Steps], Acc);
compact([#step{action = table, tokens = Table} | [Step | Steps]], Acc) ->
    compact([Step#step{tokens = Step#step.tokens ++ [{table, Table}]} | Steps], Acc);
compact([Step = #step{phase = Phase, action = start} | [#step{action = tags, tokens = Tags} | Steps]], Acc) when Phase == feature; Phase == scenario; Phase == scenario_outline ->
    compact([Step#step{meta = [{tags, [Tag || <<$@, Tag/binary>> <- Tags]}]} | Steps], Acc);
compact([Step = #step{phase = scenario_outline, action = examples} | [#step{action = tags, tokens = Tags} | Steps]], Acc) ->
    compact([Step#step{meta = [{tags, [Tag || <<$@, Tag/binary>> <- Tags]}]} | Steps], Acc);
compact([#step{action = tags} | Steps], Acc) ->
    compact(Steps, Acc);
compact([Step | Steps], Acc) ->
    compact(Steps, [Step | Acc]).

inherit_tags(Feature) ->
    inherit_tags(Feature, {[], []}).

inherit_tags([], _) ->
    [];
inherit_tags([Step = #step{phase = feature, action = start} | Steps], _) ->
    FeatureTags = proplists:get_value(tags, Step#step.meta, []),
    NewMeta = [{merged_tags, FeatureTags} | Step#step.meta],
    [Step#step{meta = NewMeta} | inherit_tags(Steps, {FeatureTags, []})];
inherit_tags([Step = #step{phase = Phase, action = start} | Steps], {FeatureTags, _}) when Phase == scenario; Phase == scenario_outline ->
    ScenarioTags = proplists:get_value(tags, Step#step.meta, []),
    NewMeta = [{merged_tags, FeatureTags ++ ScenarioTags} | Step#step.meta],
    [Step#step{meta = NewMeta} | inherit_tags(Steps, {FeatureTags, ScenarioTags})];
inherit_tags([Step = #step{phase = scenario_outline, action = examples} | Steps], {FeatureTags, ScenarioTags}) ->
    ExamplesTags = proplists:get_value(tags, Step#step.meta, []),
    NewMeta = [{merged_tags, FeatureTags ++ ScenarioTags ++ ExamplesTags} | Step#step.meta],
    [Step#step{meta = NewMeta} | inherit_tags(Steps, {FeatureTags, ScenarioTags})];
inherit_tags([Step | Steps], Tags) ->
    [Step | inherit_tags(Steps, Tags)].

build_table([], Table) ->
    {[], lists:reverse(Table)};
build_table([{_Row, Line, [<<"|">> | _Tokens]} | Lines], Table) ->
    Cells = [list_to_binary(string:strip(Field)) || Field <- string:tokens(string:strip(binary_to_list(Line)), "|")],
    build_table(Lines, [Cells | Table]);
build_table(Lines, Table) ->
    {Lines, lists:reverse(Table)}.

build_docstring([], Docstring) ->
    {[], Docstring};
build_docstring([{_Row, _Line, [<<"\"\"\"">> | _Tokens]} | Lines], Docstring) ->
    {Lines, list_to_binary(Docstring)};
build_docstring([{_Row, Line, _Tokens} | Lines], []) ->
    build_docstring(Lines, string:strip(binary_to_list(Line)));
build_docstring([{_Row, Line, _Tokens} | Lines], Docstring) ->
    build_docstring(Lines, Docstring ++ "\n" ++ string:strip(binary_to_list(Line))).

normalize_token(Token) ->
    hd(string:tokens(string:to_lower(binary_to_list(Token)), ":")).

tokens(Line) ->
    [strip_quotes(Token) || Token <- tokens(Line, [], <<>>)].

tokens(<<>>, Tokens, <<>>) ->
    Tokens;
tokens(<<>>, [<<$", $">>], <<$">>) ->
    [<<$", $", $">>];
tokens(<<>>, Tokens, Buffer) ->
    Tokens ++ [Buffer];
tokens(<<$\s, Line/binary>>, Tokens, <<>>) ->
    tokens(Line, Tokens, <<>>);
tokens(<<$\s, Line/binary>>, Tokens, <<$", Buffer/binary>>) ->
    tokens(Line, Tokens, <<$", Buffer/binary, $\s>>);
tokens(<<$\s, Line/binary>>, Tokens, Buffer) ->
    tokens(<<$\s, Line/binary>>, Tokens ++ [Buffer], <<>>);
tokens(<<$\", Line/binary>>, Tokens, <<>>) ->
    tokens(Line, Tokens, <<$">>);
tokens(<<$\", Line/binary>>, Tokens, <<$", Buffer/binary>>) ->
    tokens(Line, Tokens ++ [<<$", Buffer/binary, $">>], <<>>);
tokens(<<$\", Line/binary>>, Tokens, Buffer) ->
    tokens(Line, Tokens ++ [Buffer], <<$">>);
tokens(<<Character, Line/binary>>, Tokens, Buffer) ->
    tokens(Line, Tokens, <<Buffer/binary, Character>>).

strip_quotes(<<>>) ->
    <<>>;
strip_quotes(<<$", $", $">>) ->
    <<$", $", $">>;
strip_quotes(<<$", Token/binary>>) ->
    case binary:last(Token) of
        $" ->
            binary:part(Token, {0, byte_size(Token) - 1});
        _ ->
            Token
    end;
strip_quotes(Token) ->
    Token.