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%% Copyright (c) 2012, Magnus Klaar <klaar@ninenines.eu>
%%
%% Permission to use, copy, modify, and/or distribute this software for any
%% purpose with or without fee is hereby granted, provided that the above
%% copyright notice and this permission notice appear in all copies.
%%
%% THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
%% WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
%% MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
%% ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
%% WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
%% ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
%% OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
%% @doc Accessor function for goldrush event terms.
-module(gre).
-export([
make/2,
has/2,
fetch/2,
append/2,
merge/2,
find/2,
keys/1,
pairs/1
]).
-type event() :: {list, [{atom(), term()}]}.
-export_type([event/0]).
%% @doc Construct an event term.
-spec make(term(), [list]) -> event().
make(Term, [Type]) ->
{Type, Term}.
%% @doc Check if a field exists in an event.
-spec has(atom(), event()) -> boolean().
has(Key, {list, List}) ->
lists:keymember(Key, 1, List).
-spec append(term(), event()) -> event().
append(KeyVal, {list, List}) ->
{list, [KeyVal|List]}.
-spec merge(event(), event()) -> event().
merge({list, AList}, {list, BList}) ->
{list, lists:merge(AList, BList)}.
%% @doc Get the value of a field in an event.
%% The field is expected to exist in the event.
-spec fetch(atom(), event()) -> term().
fetch(Key, {list, List}=Event) ->
case lists:keyfind(Key, 1, List) of
{_, Value} -> Value;
false -> erlang:error(badarg, [Key, Event])
end.
%% @doc Find the value of a field in an event.
%% This is equivalent to testing if a field exists using {@link has/2}
%% before accessing the value of the field using {@link fetch/2}.
-spec find(atom(), event()) -> {true, term()} | false.
find(Key, {list, List}) ->
case lists:keyfind(Key, 1, List) of
{_, Value} -> {true, Value};
false -> false
end.
%% @doc Get the names of all fields in an event.
-spec keys(event()) -> [atom()].
keys({list, List}) ->
kv_keys_(List).
%% @private Get the names of all fields in a key-value list.
-spec kv_keys_([{atom(), term()}]) -> [atom()].
kv_keys_([{Key, _}|T]) ->
[Key|kv_keys_(T)];
kv_keys_([]) ->
[].
%% @doc Get the name and value of all fields in an event.
-spec pairs(event()) -> [{atom(), term()}].
pairs({list, List}) ->
lists:sort(List).
-ifdef(TEST).
-include_lib("eunit/include/eunit.hrl").
gre_test_() ->
[?_assert(gre:has(a, gre:make([{a,1}], [list]))),
?_assertNot(gre:has(b, gre:make([{a,1}], [list]))),
?_assertEqual(1, gre:fetch(a, gre:make([{a,1}], [list]))),
?_assertError(badarg, gre:fetch(a, gre:make([], [list]))),
?_assertEqual([], gre:keys(gre:make([], [list]))),
?_assertEqual([a], gre:keys(gre:make([{a,1}], [list]))),
?_assertEqual([a,b], gre:keys(gre:make([{a,1},{b,2}], [list]))),
?_assertEqual([{a,1},{b,2}], gre:pairs(gre:make([{b,2},{a,1}], [list])))
].
-endif.
|
