glidicon

-module(glidicon).
-compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch]).

-export([color/1, hash/1, image/1, create/1]).
-export_type([identicon/0]).

-opaque identicon() :: {identicon,
        bitstring(),
        {integer(), integer(), integer()},
        binary()}.

-spec color(identicon()) -> {integer(), integer(), integer()}.
color(Identicon) ->
    erlang:element(3, Identicon).

-spec hash(identicon()) -> bitstring().
hash(Identicon) ->
    erlang:element(2, Identicon).

-spec image(identicon()) -> binary().
image(Identicon) ->
    erlang:element(4, Identicon).

-spec identicon() -> identicon().
identicon() ->
    {identicon, <<>>, {0, 0, 0}, <<""/utf8>>}.

-spec set_hash(identicon(), binary()) -> identicon().
set_hash(Identicon, Input) ->
    erlang:setelement(
        2,
        Identicon,
        gleam_crypto_ffi:hash(md5, gleam_stdlib:identity(Input))
    ).

-spec set_color(identicon()) -> identicon().
set_color(Identicon) ->
    _assert_subject = erlang:element(2, Identicon),
    <<R, G, B, _/bitstring>> = case _assert_subject of
        <<_, _, _, _/bitstring>> -> _assert_subject;
        _assert_fail ->
            erlang:error(#{gleam_error => let_assert,
                        message => <<"Assertion pattern match failed"/utf8>>,
                        value => _assert_fail,
                        module => <<"glidicon"/utf8>>,
                        function => <<"set_color"/utf8>>,
                        line => 45})
    end,
    erlang:setelement(3, Identicon, {R, G, B}).

-spec chunk(bitstring()) -> list({integer(), integer(), integer()}).
chunk(Bits) ->
    case Bits of
        <<A, B, C, Rest/bitstring>> ->
            [{A, B, C} | chunk(Rest)];

        _ ->
            []
    end.

-spec mirror_chunks(list({integer(), integer(), integer()})) -> list(list(integer())).
mirror_chunks(Chunks) ->
    gleam@list:map(
        Chunks,
        fun(Chunk) ->
            {A, B, C} = Chunk,
            [A, B, C, B, A]
        end
    ).

-spec add_indices(list(integer())) -> list({integer(), integer()}).
add_indices(Bits) ->
    _pipe = Bits,
    gleam@list:index_map(_pipe, fun(Val, Index) -> {Index, Val} end).

-spec remove_odd_values(list({integer(), integer()})) -> list({integer(),
    integer()}).
remove_odd_values(Bits) ->
    gleam@list:filter(
        Bits,
        fun(Bit) -> gleam@int:is_even(erlang:element(2, Bit)) end
    ).

-spec calculate_diagonals(list({integer(), integer()})) -> list({{integer(),
        integer()},
    {integer(), integer()}}).
calculate_diagonals(Bits) ->
    gleam@list:map(
        Bits,
        fun(Bit) ->
            {Index, _} = Bit,
            Horizontal = (Index rem 5) * 50,
            Vertical = (Index div 5) * 50,
            Top_left = {Horizontal, Vertical},
            Bottom_right = {Horizontal + 50, Vertical + 50},
            {Top_left, Bottom_right}
        end
    ).

-spec draw_image(
    list({{integer(), integer()}, {integer(), integer()}}),
    {integer(), integer(), integer()}
) -> binary().
draw_image(Diagonals, Color) ->
    Image = egd:create(250, 250),
    Fill_color = egd:color(Color),
    gleam@list:each(
        Diagonals,
        fun(Diagonal) ->
            {Top_left, Bottom_right} = Diagonal,
            egd:'filledRectangle'(Image, Top_left, Bottom_right, Fill_color)
        end
    ),
    egd:render(Image).

-spec set_image(identicon()) -> identicon().
set_image(Identicon) ->
    erlang:setelement(
        4,
        Identicon,
        begin
            _pipe = erlang:element(2, Identicon),
            _pipe@1 = chunk(_pipe),
            _pipe@2 = mirror_chunks(_pipe@1),
            _pipe@3 = gleam@list:flatten(_pipe@2),
            _pipe@4 = add_indices(_pipe@3),
            _pipe@5 = remove_odd_values(_pipe@4),
            _pipe@6 = calculate_diagonals(_pipe@5),
            draw_image(_pipe@6, erlang:element(3, Identicon))
        end
    ).

-spec create(binary()) -> identicon().
create(Input) ->
    _pipe = identicon(),
    _pipe@1 = set_hash(_pipe, Input),
    _pipe@2 = set_color(_pipe@1),
    set_image(_pipe@2).