Add src/hk_browser_registry.erl

src/hk_browser_registry.erl

@@ -0,0 +1,70 @@
+%%%-------------------------------------------------------------------
+%%% @doc HK-BROWSER :: session_id -> pid directory.
+%%%
+%%% `hk_browser_session' processes are anonymous (started under
+%%% `simple_one_for_one', so they can't be `{local, Name}' registered
+%%% by session id -- ids are runtime data, not compile-time atoms).
+%%% This registry is the lookup table the API and agent runtime use
+%%% instead. A session registers itself once Chromium is confirmed
+%%% ready; the registry monitors it and removes the entry on exit
+%%% (including the gap between a crash and `hk_browser_sup' bringing
+%%% a replacement back up under the same session id, which
+%%% re-registers when *it* becomes ready).
+%%% @end
+%%%-------------------------------------------------------------------
+-module(hk_browser_registry).
+-behaviour(gen_server).
+
+-export([start_link/0, register/2, unregister/1, lookup/1, list_sessions/0]).
+-export([init/1, handle_call/3, handle_cast/2, handle_info/2]).
+
+-define(TAB, hk_browser_registry_tab).
+
+start_link() ->
+    hk_sup_util:start_link_retry(
+        fun() -> gen_server:start_link({local, ?MODULE}, ?MODULE, [], []) end).
+
+-spec register(binary(), pid()) -> ok.
+register(SessionId, Pid) ->
+    gen_server:call(?MODULE, {register, SessionId, Pid}).
+
+-spec unregister(binary()) -> ok.
+unregister(SessionId) ->
+    gen_server:call(?MODULE, {unregister, SessionId}).
+
+-spec lookup(binary()) -> {ok, pid()} | {error, not_found}.
+lookup(SessionId) ->
+    case ets:lookup(?TAB, SessionId) of
+        [{SessionId, Pid}] -> {ok, Pid};
+        [] -> {error, not_found}
+    end.
+
+-spec list_sessions() -> [{binary(), pid()}].
+list_sessions() ->
+    ets:tab2list(?TAB).
+
+init([]) ->
+    ets:new(?TAB, [set, named_table, protected]),
+    {ok, #{monitors => #{}}}.
+
+handle_call({register, SessionId, Pid}, _From, State = #{monitors := Mons}) ->
+    ets:insert(?TAB, {SessionId, Pid}),
+    MonRef = erlang:monitor(process, Pid),
+    {reply, ok, State#{monitors := Mons#{MonRef => SessionId}}};
+handle_call({unregister, SessionId}, _From, State) ->
+    ets:delete(?TAB, SessionId),
+    {reply, ok, State}.
+
+handle_cast(_Msg, State) ->
+    {noreply, State}.
+
+handle_info({'DOWN', MonRef, process, _Pid, _Reason}, State = #{monitors := Mons}) ->
+    case maps:take(MonRef, Mons) of
+        {SessionId, Mons2} ->
+            ets:delete(?TAB, SessionId),
+            {noreply, State#{monitors := Mons2}};
+        error ->
+            {noreply, State}
+    end;
+handle_info(_Info, State) ->
+    {noreply, State}.