%% Licensed under the Apache License, Version 2.0 (the "License");
%% you may not use this file except in compliance with the License.
%% You may obtain a copy of the License at
%%
%% http://www.apache.org/licenses/LICENSE-2.0
%%
%% Unless required by applicable law or agreed to in writing, software
%% distributed under the License is distributed on an "AS IS" BASIS,
%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
%% See the License for the specific language governing permissions and
%% limitations under the License.
%%
%% @copyright 2000-2003 Richard Carlsson
%% @author Richard Carlsson <[email protected]>
%% @doc Support functions for property lists.
%%
%% <p>Property lists are ordinary lists containing entries in the form
%% of either tuples, whose first elements are keys used for lookup and
%% insertion, or atoms, which work as shorthand for tuples <code>{Atom,
%% true}</code>. (Other terms are allowed in the lists, but are ignored
%% by this module.) If there is more than one entry in a list for a
%% certain key, the first occurrence normally overrides any later
%% (irrespective of the arity of the tuples).</p>
%%
%% <p>Property lists are useful for representing inherited properties,
%% such as options passed to a function where a user may specify options
%% overriding the default settings, object properties, annotations,
%% etc.</p>
%%
%% % @type property() = atom() | tuple()
-module(proplists).
-export([property/1, property/2, unfold/1, compact/1, lookup/2,
lookup_all/2, is_defined/2, get_value/2, get_value/3,
get_all_values/2, append_values/2, get_bool/2, get_keys/1,
delete/2, substitute_aliases/2, substitute_negations/2,
expand/2, normalize/2, split/2]).
%% ---------------------------------------------------------------------
-export_type([property/0, proplist/0]).
-type property() :: atom() | tuple().
-type proplist() :: [property()].
%% ---------------------------------------------------------------------
%% @doc Creates a normal form (minimal) representation of a property. If
%% <code>PropertyIn</code> is <code>{Key, true}</code> where
%% <code>Key</code> is an atom, this returns <code>Key</code>, otherwise
%% the whole term <code>PropertyIn</code> is returned.
%%
%% @see property/2
-spec property(PropertyIn) -> PropertyOut when
PropertyIn :: property(),
PropertyOut :: property().
property({Key, true}) when is_atom(Key) ->
Key;
property(Property) ->
Property.
%% @doc Creates a normal form (minimal) representation of a simple
%% key/value property. Returns <code>Key</code> if <code>Value</code> is
%% <code>true</code> and <code>Key</code> is an atom, otherwise a tuple
%% <code>{Key, Value}</code> is returned.
%%
%% @see property/1
-spec property(Key, Value) -> Property when
Key :: term(),
Value :: term(),
Property :: atom() | {term(), term()}.
property(Key, true) when is_atom(Key) ->
Key;
property(Key, Value) ->
{Key, Value}.
%% ---------------------------------------------------------------------
%% @doc Unfolds all occurences of atoms in <code>ListIn</code> to tuples
%% <code>{Atom, true}</code>.
%%
%% @see compact/1
-spec unfold(ListIn) -> ListOut when
ListIn :: [term()],
ListOut :: [term()].
unfold([P | Ps]) ->
if is_atom(P) ->
[{P, true} | unfold(Ps)];
true ->
[P | unfold(Ps)]
end;
unfold([]) ->
[].
%% @doc Minimizes the representation of all entries in the list. This is
%% equivalent to <code>[property(P) || P <- ListIn]</code>.
%%
%% @see unfold/1
%% @see property/1
-spec compact(ListIn) -> ListOut when
ListIn :: [property()],
ListOut :: [property()].
compact(ListIn) ->
[property(P) || P <- ListIn].
%% ---------------------------------------------------------------------
%% @doc Returns the first entry associated with <code>Key</code> in
%% <code>List</code>, if one exists, otherwise returns
%% <code>none</code>. For an atom <code>A</code> in the list, the tuple
%% <code>{A, true}</code> is the entry associated with <code>A</code>.
%%
%% @see lookup_all/2
%% @see get_value/2
%% @see get_bool/2
-spec lookup(Key, List) -> 'none' | tuple() when
Key :: term(),
List :: [term()].
lookup(Key, [P | Ps]) ->
if is_atom(P), P =:= Key ->
{Key, true};
tuple_size(P) >= 1, element(1, P) =:= Key ->
%% Note that <code>Key</code> does not have to be an atom in this case.
P;
true ->
lookup(Key, Ps)
end;
lookup(_Key, []) ->
none.
%% @doc Returns the list of all entries associated with <code>Key</code>
%% in <code>List</code>. If no such entry exists, the result is the
%% empty list.
%%
%% @see lookup/2
-spec lookup_all(Key, List) -> [tuple()] when
Key :: term(),
List :: [term()].
lookup_all(Key, [P | Ps]) ->
if is_atom(P), P =:= Key ->
[{Key, true} | lookup_all(Key, Ps)];
tuple_size(P) >= 1, element(1, P) =:= Key ->
[P | lookup_all(Key, Ps)];
true ->
lookup_all(Key, Ps)
end;
lookup_all(_Key, []) ->
[].
%% ---------------------------------------------------------------------
%% @doc Returns <code>true</code> if <code>List</code> contains at least
%% one entry associated with <code>Key</code>, otherwise
%% <code>false</code> is returned.
-spec is_defined(Key, List) -> boolean() when
Key :: term(),
List :: [term()].
is_defined(Key, [P | Ps]) ->
if is_atom(P), P =:= Key ->
true;
tuple_size(P) >= 1, element(1, P) =:= Key ->
true;
true ->
is_defined(Key, Ps)
end;
is_defined(_Key, []) ->
false.
%% ---------------------------------------------------------------------
%% @equiv get_value(Key, List, undefined)
-spec get_value(Key, List) -> term() when
Key :: term(),
List :: [term()].
get_value(Key, List) ->
get_value(Key, List, undefined).
%% @doc Returns the value of a simple key/value property in
%% <code>List</code>. If <code>lookup(Key, List)</code> would yield
%% <code>{Key, Value}</code>, this function returns the corresponding
%% <code>Value</code>, otherwise <code>Default</code> is returned.
%%
%% @see lookup/2
%% @see get_value/2
%% @see get_all_values/2
%% @see get_bool/2
-spec get_value(Key, List, Default) -> term() when
Key :: term(),
List :: [term()],
Default :: term().
get_value(Key, [P | Ps], Default) ->
if is_atom(P), P =:= Key ->
true;
tuple_size(P) >= 1, element(1, P) =:= Key ->
case P of
{_, Value} ->
Value;
_ ->
%% Don</code>t continue the search!
Default
end;
true ->
get_value(Key, Ps, Default)
end;
get_value(_Key, [], Default) ->
Default.
%% @doc Similar to <code>get_value/2</code>, but returns the list of
%% values for <em>all</em> entries <code>{Key, Value}</code> in
%% <code>List</code>. If no such entry exists, the result is the empty
%% list.
%%
%% @see get_value/2
-spec get_all_values(Key, List) -> [term()] when
Key :: term(),
List :: [term()].
get_all_values(Key, [P | Ps]) ->
if is_atom(P), P =:= Key ->
[true | get_all_values(Key, Ps)];
tuple_size(P) >= 1, element(1, P) =:= Key ->
case P of
{_, Value} ->
[Value | get_all_values(Key, Ps)];
_ ->
get_all_values(Key, Ps)
end;
true ->
get_all_values(Key, Ps)
end;
get_all_values(_Key, []) ->
[].
%% @doc Similar to <code>get_all_values/2</code>, but each value is
%% wrapped in a list unless it is already itself a list, and the
%% resulting list of lists is concatenated. This is often useful for
%% "incremental" options; e.g., <code>append_values(a, [{a, [1,2]}, {b,
%% 0}, {a, 3}, {c, -1}, {a, [4]}])</code> will return the list
%% <code>[1,2,3,4]</code>.
%%
%% @see get_all_values/2
-spec append_values(Key, ListIn) -> ListOut when
Key :: term(),
ListIn :: [term()],
ListOut :: [term()].
append_values(Key, [P | Ps]) ->
if is_atom(P), P =:= Key ->
[true | append_values(Key, Ps)];
tuple_size(P) >= 1, element(1, P) =:= Key ->
case P of
{_, Value} when is_list(Value) ->
Value ++ append_values(Key, Ps);
{_, Value} ->
[Value | append_values(Key, Ps)];
_ ->
append_values(Key, Ps)
end;
true ->
append_values(Key, Ps)
end;
append_values(_Key, []) ->
[].
%% ---------------------------------------------------------------------
%% @doc Returns the value of a boolean key/value option. If
%% <code>lookup(Key, List)</code> would yield <code>{Key, true}</code>,
%% this function returns <code>true</code>; otherwise <code>false</code>
%% is returned.
%%
%% @see lookup/2
%% @see get_value/2
-spec get_bool(Key, List) -> boolean() when
Key :: term(),
List :: [term()].
get_bool(Key, [P | Ps]) ->
if is_atom(P), P =:= Key ->
true;
tuple_size(P) >= 1, element(1, P) =:= Key ->
case P of
{_, true} ->
true;
_ ->
%% Don't continue the search!
false
end;
true ->
get_bool(Key, Ps)
end;
get_bool(_Key, []) ->
false.
%% ---------------------------------------------------------------------
%% @doc Returns an unordered list of the keys used in <code>List</code>,
%% not containing duplicates.
-spec get_keys(List) -> [term()] when
List :: [term()].
get_keys(Ps) ->
sets:to_list(get_keys(Ps, sets:new())).
get_keys([P | Ps], Keys) ->
if is_atom(P) ->
get_keys(Ps, sets:add_element(P, Keys));
tuple_size(P) >= 1 ->
get_keys(Ps, sets:add_element(element(1, P), Keys));
true ->
get_keys(Ps, Keys)
end;
get_keys([], Keys) ->
Keys.
%% ---------------------------------------------------------------------
%% @doc Deletes all entries associated with <code>Key</code> from
%% <code>List</code>.
-spec delete(Key, List) -> List when
Key :: term(),
List :: [term()].
delete(Key, [P | Ps]) ->
if is_atom(P), P =:= Key ->
delete(Key, Ps);
tuple_size(P) >= 1, element(1, P) =:= Key ->
delete(Key, Ps);
true ->
[P | delete(Key, Ps)]
end;
delete(_, []) ->
[].
%% ---------------------------------------------------------------------
%% @doc Substitutes keys of properties. For each entry in
%% <code>ListIn</code>, if it is associated with some key <code>K1</code>
%% such that <code>{K1, K2}</code> occurs in <code>Aliases</code>, the
%% key of the entry is changed to <code>Key2</code>. If the same
%% <code>K1</code> occurs more than once in <code>Aliases</code>, only
%% the first occurrence is used.
%%
%% <p>Example: <code>substitute_aliases([{color, colour}], L)</code>
%% will replace all tuples <code>{color, ...}</code> in <code>L</code>
%% with <code>{colour, ...}</code>, and all atoms <code>color</code>
%% with <code>colour</code>.</p>
%%
%% @see substitute_negations/2
%% @see normalize/2
-spec substitute_aliases(Aliases, ListIn) -> ListOut when
Aliases :: [{Key, Key}],
Key :: term(),
ListIn :: [term()],
ListOut :: [term()].
substitute_aliases(As, Props) ->
[substitute_aliases_1(As, P) || P <- Props].
substitute_aliases_1([{Key, Key1} | As], P) ->
if is_atom(P), P =:= Key ->
property(Key1, true);
tuple_size(P) >= 1, element(1, P) =:= Key ->
property(setelement(1, P, Key1));
true ->
substitute_aliases_1(As, P)
end;
substitute_aliases_1([], P) ->
P.
%% ---------------------------------------------------------------------
%% @doc Substitutes keys of boolean-valued properties and simultaneously
%% negates their values. For each entry in <code>ListIn</code>, if it is
%% associated with some key <code>K1</code> such that <code>{K1,
%% K2}</code> occurs in <code>Negations</code>, then if the entry was
%% <code>{K1, true}</code> it will be replaced with <code>{K2,
%% false}</code>, otherwise it will be replaced with <code>{K2,
%% true}</code>, thus changing the name of the option and simultaneously
%% negating the value given by <code>get_bool(ListIn)</code>. If the same
%% <code>K1</code> occurs more than once in <code>Negations</code>, only
%% the first occurrence is used.
%%
%% <p>Example: <code>substitute_negations([{no_foo, foo}], L)</code>
%% will replace any atom <code>no_foo</code> or tuple <code>{no_foo,
%% true}</code> in <code>L</code> with <code>{foo, false}</code>, and
%% any other tuple <code>{no_foo, ...}</code> with <code>{foo,
%% true}</code>.</p>
%%
%% @see get_bool/2
%% @see substitute_aliases/2
%% @see normalize/2
-spec substitute_negations(Negations, ListIn) -> ListOut when
Negations :: [{Key1, Key2}],
Key1 :: term(),
Key2 :: term(),
ListIn :: [term()],
ListOut :: [term()].
substitute_negations(As, Props) ->
[substitute_negations_1(As, P) || P <- Props].
substitute_negations_1([{Key, Key1} | As], P) ->
if is_atom(P), P =:= Key ->
property(Key1, false);
tuple_size(P) >= 1, element(1, P) =:= Key ->
case P of
{_, true} ->
property(Key1, false);
{_, false} ->
property(Key1, true);
_ ->
%% The property is supposed to be a boolean, so any
%% other tuple is interpreted as `false', as done in
%% `get_bool'.
property(Key1, true)
end;
true ->
substitute_negations_1(As, P)
end;
substitute_negations_1([], P) ->
P.
%% ---------------------------------------------------------------------
%% @doc Expands particular properties to corresponding sets of
%% properties (or other terms). For each pair <code>{Property,
%% Expansion}</code> in <code>Expansions</code>, if <code>E</code> is
%% the first entry in <code>ListIn</code> with the same key as
%% <code>Property</code>, and <code>E</code> and <code>Property</code>
%% have equivalent normal forms, then <code>E</code> is replaced with
%% the terms in <code>Expansion</code>, and any following entries with
%% the same key are deleted from <code>ListIn</code>.
%%
%% <p>For example, the following expressions all return <code>[fie, bar,
%% baz, fum]</code>:
%% <ul>
%% <li><code>expand([{foo, [bar, baz]}],
%% [fie, foo, fum])</code></li>
%% <li><code>expand([{{foo, true}, [bar, baz]}],
%% [fie, foo, fum])</code></li>
%% <li><code>expand([{{foo, false}, [bar, baz]}],
%% [fie, {foo, false}, fum])</code></li>
%% </ul>
%% However, no expansion is done in the following call:
%% <ul>
%% <li><code>expand([{{foo, true}, [bar, baz]}],
%% [{foo, false}, fie, foo, fum])</code></li>
%% </ul>
%% because <code>{foo, false}</code> shadows <code>foo</code>.</p>
%%
%% <p>Note that if the original property term is to be preserved in the
%% result when expanded, it must be included in the expansion list. The
%% inserted terms are not expanded recursively. If
%% <code>Expansions</code> contains more than one property with the same
%% key, only the first occurrance is used.</p>
%%
%% @see normalize/2
-spec expand(Expansions, ListIn) -> ListOut when
Expansions :: [{Property :: property(), Expansion :: [term()]}],
ListIn :: [term()],
ListOut :: [term()].
expand(Es, Ps) when is_list(Ps) ->
Es1 = [{property(P), V} || {P, V} <- Es],
flatten(expand_0(key_uniq(Es1), Ps)).
%% Here, all key properties are normalized and there are no multiple
%% entries in the list of expansions for any specific key property. We
%% insert the expansions one at a time - this is quadratic, but gives
%% the desired behaviour in a simple way.
expand_0([{P, L} | Es], Ps) ->
expand_0(Es, expand_1(P, L, Ps));
expand_0([], Ps) ->
Ps.
expand_1(P, L, Ps) ->
%% First, we must find out what key to look for.
%% P has a minimal representation here.
if is_atom(P) ->
expand_2(P, P, L, Ps);
tuple_size(P) >= 1 ->
expand_2(element(1, P), P, L, Ps);
true ->
Ps % refuse to expand non-property
end.
expand_2(Key, P1, L, [P | Ps]) ->
if is_atom(P), P =:= Key ->
expand_3(Key, P1, P, L, Ps);
tuple_size(P) >= 1, element(1, P) =:= Key ->
expand_3(Key, P1, property(P), L, Ps);
true ->
%% This case handles non-property entries, and thus
%% any already inserted expansions (lists), by simply
%% ignoring them.
[P | expand_2(Key, P1, L, Ps)]
end;
expand_2(_, _, _, []) ->
[].
expand_3(Key, P1, P, L, Ps) ->
%% Here, we have found the first entry with a matching key. Both P
%% and P1 have minimal representations here. The inserted list will
%% be flattened afterwards. If the expansion is done, we drop the
%% found entry and alao delete any later entries with the same key.
if P1 =:= P ->
[L | delete(Key, Ps)];
true ->
%% The existing entry does not match - keep it.
[P | Ps]
end.
key_uniq([{K, V} | Ps]) ->
[{K, V} | key_uniq_1(K, Ps)];
key_uniq([]) ->
[].
key_uniq_1(K, [{K1, V} | Ps]) ->
if K =:= K1 ->
key_uniq_1(K, Ps);
true ->
[{K1, V} | key_uniq_1(K1, Ps)]
end;
key_uniq_1(_, []) ->
[].
%% This does top-level flattening only.
flatten([E | Es]) when is_list(E) ->
E ++ flatten(Es);
flatten([E | Es]) ->
[E | flatten(Es)];
flatten([]) ->
[].
%% ---------------------------------------------------------------------
%% @doc Passes <code>List</code> through a sequence of
%% substitution/expansion stages. For an <code>aliases</code> operation,
%% the function <code>substitute_aliases/2</code> is applied using the
%% given list of aliases; for a <code>negations</code> operation,
%% <code>substitute_negations/2</code> is applied using the given
%% negation list; for an <code>expand</code> operation, the function
%% <code>expand/2</code> is applied using the given list of expansions.
%% The final result is automatically compacted (cf.
%% <code>compact/1</code>).
%%
%% <p>Typically you want to substitute negations first, then aliases,
%% then perform one or more expansions (sometimes you want to pre-expand
%% particular entries before doing the main expansion). You might want
%% to substitute negations and/or aliases repeatedly, to allow such
%% forms in the right-hand side of aliases and expansion lists.</p>
%%
%% @see substitute_aliases/2
%% @see substitute_negations/2
%% @see expand/2
%% @see compact/1
-spec normalize(ListIn, Stages) -> ListOut when
ListIn :: [term()],
Stages :: [Operation],
Operation :: {'aliases', Aliases}
| {'negations', Negations}
| {'expand', Expansions},
Aliases :: [{Key, Key}],
Negations :: [{Key, Key}],
Expansions :: [{Property :: property(), Expansion :: [term()]}],
ListOut :: [term()].
normalize(L, [{aliases, As} | Xs]) ->
normalize(substitute_aliases(As, L), Xs);
normalize(L, [{expand, Es} | Xs]) ->
normalize(expand(Es, L), Xs);
normalize(L, [{negations, Ns} | Xs]) ->
normalize(substitute_negations(Ns, L), Xs);
normalize(L, []) ->
compact(L).
%% ---------------------------------------------------------------------
%% @doc Partitions <code>List</code> into a list of sublists and a
%% remainder. <code>Lists</code> contains one sublist for each key in
%% <code>Keys</code>, in the corresponding order. The relative order of
%% the elements in each sublist is preserved from the original
%% <code>List</code>. <code>Rest</code> contains the elements in
%% <code>List</code> that are not associated with any of the given keys,
%% also with their original relative order preserved.
%%
%% <p>Example:<pre>
%% split([{c, 2}, {e, 1}, a, {c, 3, 4}, d, {b, 5}, b], [a, b, c])</pre>
%% returns<pre>
%% {[[a], [{b, 5}, b],[{c, 2}, {c, 3, 4}]], [{e, 1}, d]}</pre>
%% </p>
-spec split(List, Keys) -> {Lists, Rest} when
List :: [term()],
Keys :: [term()],
Lists :: [[term()]],
Rest :: [term()].
split(List, Keys) ->
{Store, Rest} = split(List, dict:from_list([{K, []} || K <- Keys]), []),
{[lists:reverse(dict:fetch(K, Store)) || K <- Keys],
lists:reverse(Rest)}.
split([P | Ps], Store, Rest) ->
if is_atom(P) ->
case dict:is_key(P, Store) of
true ->
split(Ps, dict_prepend(P, P, Store), Rest);
false ->
split(Ps, Store, [P | Rest])
end;
tuple_size(P) >= 1 ->
%% Note that Key does not have to be an atom in this case.
Key = element(1, P),
case dict:is_key(Key, Store) of
true ->
split(Ps, dict_prepend(Key, P, Store), Rest);
false ->
split(Ps, Store, [P | Rest])
end;
true ->
split(Ps, Store, [P | Rest])
end;
split([], Store, Rest) ->
{Store, Rest}.
dict_prepend(Key, Val, Dict) ->
dict:store(Key, [Val | dict:fetch(Key, Dict)], Dict).
