%%--------------------------------------------------------------------
%% Copyright (c) 2020-2021 EMQ Technologies Co., Ltd. All Rights Reserved.
%%
%% 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.
%%--------------------------------------------------------------------

-module(emqx_authz_rule).

-include("emqx_authz.hrl").
-include_lib("emqx/include/logger.hrl").

-ifdef(TEST).
-compile(export_all).
-compile(nowarn_export_all).
-endif.

%% APIs
-export([ match/4
        , matches/4
        , compile/1
        ]).

-export_type([rule/0]).

compile({Permission, all}) when ?ALLOW_DENY(Permission) -> {Permission, all, all, [compile_topic(<<"#">>)]};
compile({Permission, Who, Action, TopicFilters}) when ?ALLOW_DENY(Permission), ?PUBSUB(Action), is_list(TopicFilters) ->
    {atom(Permission), compile_who(Who), atom(Action), [compile_topic(Topic) || Topic <- TopicFilters]}.

compile_who(all) -> all;
compile_who({user, Username}) -> compile_who({username, Username});
compile_who({username, {re, Username}}) ->
    {ok, MP} = re:compile(bin(Username)),
    {username, MP};
compile_who({username, Username}) -> {username, {eq, bin(Username)}};
compile_who({client, Clientid}) -> compile_who({clientid, Clientid});
compile_who({clientid, {re, Clientid}}) ->
    {ok, MP} = re:compile(bin(Clientid)),
    {clientid, MP};
compile_who({clientid, Clientid}) -> {clientid, {eq, bin(Clientid)}};
compile_who({ipaddr, CIDR}) ->
    {ipaddr, esockd_cidr:parse(CIDR, true)};
compile_who({ipaddrs, CIDRs}) ->
    {ipaddrs, lists:map(fun(CIDR) -> esockd_cidr:parse(CIDR, true) end, CIDRs)};
compile_who({'and', L}) when is_list(L) ->
    {'and', [compile_who(Who) || Who <- L]};
compile_who({'or', L}) when is_list(L) ->
    {'or', [compile_who(Who) || Who <- L]}.

compile_topic(<<"eq ", Topic/binary>>) ->
    {eq, emqx_topic:words(Topic)};
compile_topic({eq, Topic}) ->
    {eq, emqx_topic:words(bin(Topic))};
compile_topic(Topic) ->
    Words = emqx_topic:words(bin(Topic)),
    case pattern(Words) of
        true  -> {pattern, Words};
        false -> Words
    end.

pattern(Words) ->
    lists:member(<<"%u">>, Words) orelse lists:member(<<"%c">>, Words).

atom(B) when is_binary(B) ->
    try binary_to_existing_atom(B, utf8)
    catch
        _ -> binary_to_atom(B)
    end;
atom(A) when is_atom(A) -> A.

bin(L) when is_list(L) ->
    list_to_binary(L);
bin(B) when is_binary(B) ->
    B.

-spec(matches(emqx_types:clientinfo(), emqx_types:pubsub(), emqx_types:topic(), [rule()])
      -> {matched, allow} | {matched, deny} | nomatch).
matches(_Client, _PubSub, _Topic, []) -> nomatch;
matches(Client, PubSub, Topic, [{Permission, Who, Action, TopicFilters} | Tail]) ->
    case match(Client, PubSub, Topic, {Permission, Who, Action, TopicFilters}) of
        nomatch -> matches(Client, PubSub, Topic, Tail);
        Matched -> Matched
    end.

-spec(match(emqx_types:clientinfo(), emqx_types:pubsub(), emqx_types:topic(), rule())
      -> {matched, allow} | {matched, deny} | nomatch).
match(Client, PubSub, Topic, {Permission, Who, Action, TopicFilters}) ->
    case match_action(PubSub, Action) andalso
         match_who(Client, Who) andalso
         match_topics(Client, Topic, TopicFilters) of
        true -> {matched, Permission};
        _ -> nomatch
    end.

match_action(publish, publish) -> true;
match_action(subscribe, subscribe) -> true;
match_action(_, all) -> true;
match_action(_, _) -> false.

match_who(_, all) -> true;
match_who(#{username := undefined}, {username, _}) ->
    false;
match_who(#{username := Username}, {username, {eq, Username}}) -> true;
match_who(#{username := Username}, {username, {re_pattern, _, _, _, _} = MP}) ->
    case re:run(Username, MP) of
        {match, _} -> true;
        _ -> false
    end;
match_who(#{clientid := Clientid}, {clientid, {eq, Clientid}}) -> true;
match_who(#{clientid := Clientid}, {clientid, {re_pattern, _, _, _, _} = MP}) ->
    case re:run(Clientid, MP) of
        {match, _} -> true;
        _ -> false
    end;
match_who(#{peerhost := undefined}, {ipaddr, _CIDR}) ->
    false;
match_who(#{peerhost := IpAddress}, {ipaddr, CIDR}) ->
    esockd_cidr:match(IpAddress, CIDR);
match_who(#{peerhost := undefined}, {ipaddrs, _CIDR}) ->
    false;
match_who(#{peerhost := IpAddress}, {ipaddrs, CIDRs}) ->
    lists:any(fun(CIDR) ->
        esockd_cidr:match(IpAddress, CIDR)
    end, CIDRs);
match_who(ClientInfo, {'and', Principals}) when is_list(Principals) ->
    lists:foldl(fun(Principal, Permission) ->
                  match_who(ClientInfo, Principal) andalso Permission
                end, true, Principals);
match_who(ClientInfo, {'or', Principals}) when is_list(Principals) ->
    lists:foldl(fun(Principal, Permission) ->
                  match_who(ClientInfo, Principal) orelse Permission
                end, false, Principals);
match_who(_, _) -> false.

match_topics(_ClientInfo, _Topic, []) ->
    false;
match_topics(ClientInfo, Topic, [{pattern, PatternFilter}|Filters]) ->
    TopicFilter = feed_var(ClientInfo, PatternFilter),
    match_topic(emqx_topic:words(Topic), TopicFilter)
        orelse match_topics(ClientInfo, Topic, Filters);
match_topics(ClientInfo, Topic, [TopicFilter|Filters]) ->
   match_topic(emqx_topic:words(Topic), TopicFilter)
       orelse match_topics(ClientInfo, Topic, Filters).

match_topic(Topic, {'eq', TopicFilter}) ->
    Topic =:= TopicFilter;
match_topic(Topic, TopicFilter) ->
    emqx_topic:match(Topic, TopicFilter).

feed_var(ClientInfo, Pattern) ->
    feed_var(ClientInfo, Pattern, []).
feed_var(_ClientInfo, [], Acc) ->
    lists:reverse(Acc);
feed_var(ClientInfo = #{clientid := undefined}, [<<"%c">>|Words], Acc) ->
    feed_var(ClientInfo, Words, [<<"%c">>|Acc]);
feed_var(ClientInfo = #{clientid := ClientId}, [<<"%c">>|Words], Acc) ->
    feed_var(ClientInfo, Words, [ClientId |Acc]);
feed_var(ClientInfo = #{username := undefined}, [<<"%u">>|Words], Acc) ->
    feed_var(ClientInfo, Words, [<<"%u">>|Acc]);
feed_var(ClientInfo = #{username := Username}, [<<"%u">>|Words], Acc) ->
    feed_var(ClientInfo, Words, [Username|Acc]);
feed_var(ClientInfo, [W|Words], Acc) ->
    feed_var(ClientInfo, Words, [W|Acc]).