%% -*- erlang-indent-level: 2 -*-
%%-------------------------------------------------------------------------
-module(maps_has_map_fields).
-export([test/0]).
test() ->
false = has_a_field(#{}),
false = has_a_field(#{b => 2}),
true = has_a_field(#{a => 3}),
true = has_a_field(#{b => c, a => false}),
false = has_a_b_field(#{a => true}),
false = has_a_b_field(#{b => a}),
true = has_a_b_field(#{a => 1, b => 2}),
true = has_a_b_field(#{b => 3, a => 4}),
false = has_binary_field(#{}),
false = has_binary_field(#{#{} => yay}),
true = has_binary_field(#{<<"true">> => false}),
false = has_binary_but_no_map_field(#{}),
false = has_map_but_no_binary_field(#{}),
false = has_binary_but_no_map_field(#{#{} => 1}),
false = has_map_but_no_binary_field(#{<<"true">> => true}),
true = has_binary_but_no_map_field(#{<<"true">> => false}),
true = has_map_but_no_binary_field(#{#{} => 1}),
false = has_binary_but_no_map_field(#{<<"true">> => true, #{} => 1}),
false = has_map_but_no_binary_field(#{<<"true">> => true, #{} => 1}),
ok.
has_a_field(#{a := _}) -> true;
has_a_field(#{}) -> false.
has_a_b_field(#{a := _, b := _}) -> true;
has_a_b_field(#{}) -> false.
has_binary_field(#{<<"true">> := _}) -> true;
has_binary_field(#{}) -> false.
has_map_but_no_binary_field(#{<<"true">> := _}) -> false;
has_map_but_no_binary_field(#{} = M) -> maps:is_key(#{}, M).
has_binary_but_no_map_field(#{<<"true">> := _} = M) ->
not maps:is_key(#{}, M);
has_binary_but_no_map_field(#{}) -> false.
