%% Copyright (c) 2017-2024 Guilherme Andrade
%%
%% Permission is hereby granted, free of charge, to any person obtaining a
%% copy of this software and associated documentation files (the "Software"),
%% to deal in the Software without restriction, including without limitation
%% the rights to use, copy, modify, merge, publish, distribute, sublicense,
%% and/or sell copies of the Software, and to permit persons to whom the
%% Software is furnished to do so, subject to the following conditions:
%%
%% The above copyright notice and this permission notice shall be included in
%% all copies or substantial portions of the Software.
%%
%% THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
%% IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
%% FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
%% AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
%% LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
%% FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
%% DEALINGS IN THE SOFTWARE.
%%
%% locus is an independent project and has not been authorized, sponsored,
%% or otherwise approved by MaxMind.
%% @doc Loads a file from the filesystem without blocking the caller
-module(locus_filesystem_load).
-behaviour(gen_server).
-include_lib("kernel/include/file.hrl").
%% ------------------------------------------------------------------
%% API Function Exports
%% ------------------------------------------------------------------
-export(
[start_link/2
]).
-ignore_xref(
[start_link/2
]).
%% ------------------------------------------------------------------
%% gen_server Function Exports
%% ------------------------------------------------------------------
-export(
[init/1,
handle_call/3,
handle_cast/2,
handle_info/2,
terminate/2,
code_change/3
]).
%% ------------------------------------------------------------------
%% Record and Type Definitions
%% ------------------------------------------------------------------
-type msg() ::
{event, event()} |
{finished, {success, success()}} |
{finished, dismissed} |
{finished, {error, not_found}} |
{finished, {error, term()}}.
-export_type([msg/0]).
-type event() ::
event_load_attempt_started() |
event_load_attempt_dismissed().
-export_type([event/0]).
-type event_load_attempt_started() :: {load_attempt_started, source()}.
-export_type([event_load_attempt_started/0]).
-type event_load_attempt_dismissed() :: {load_attempt_dismissed, source()}.
-export_type([event_load_attempt_dismissed/0]).
-type source() :: {cache | filesystem, path()}.
-export_type([source/0]).
-type success() ::
#{ modified_on := calendar:datetime(),
content := binary()
}.
-export_type([success/0]).
-type path() :: file:filename_all().
-export_type([path/0]).
-record(state, {
owner_pid :: pid(),
source :: source(),
previously_modified_on :: calendar:datetime() | unknown
}).
-opaque state() :: #state{}.
-export_type([state/0]).
%% ------------------------------------------------------------------
%% API Function Definitions
%% ------------------------------------------------------------------
-spec start_link(source(), calendar:datetime() | unknown) -> {ok, pid()}.
%% @private
start_link(Source, PrevModificationDT) ->
gen_server:start_link(?MODULE, [self(), Source, PrevModificationDT], []).
%% ------------------------------------------------------------------
%% gen_server Function Definitions
%% ------------------------------------------------------------------
-spec init([InitArg, ...]) -> {ok, state()}
when InitArg :: OwnerPid | Source | PrevModificationDT,
OwnerPid :: pid(),
Source :: source(),
PrevModificationDT :: calendar:datetime() | unknown.
%% @private
init([OwnerPid, Source, PrevModificationDT]) ->
_ = process_flag(trap_exit, true),
self() ! read,
{ok, #state{
owner_pid = OwnerPid,
source = Source,
previously_modified_on = PrevModificationDT
}}.
-spec handle_call(term(), {pid(), reference()}, state())
-> {stop, unexpected_call, state()}.
%% @private
handle_call(_Call, _From, State) ->
{stop, unexpected_call, State}.
-spec handle_cast(term(), state())
-> {stop, unexpected_cast, state()}.
%% @private
handle_cast(_Cast, State) ->
{stop, unexpected_cast, State}.
-spec handle_info(term(), state())
-> {stop, normal, state()} |
{stop, unexpected_info, state()}.
%% @private
handle_info(read, State) ->
handle_read(State);
handle_info(_Info, State) ->
{stop, unexpected_info, State}.
-spec terminate(term(), state()) -> ok.
%% @private
terminate(_Reason, _State) ->
ok.
-spec code_change(term(), state(), term()) -> {ok, state()}.
%% @private
code_change(_OldVsn, #state{} = State, _Extra) ->
{ok, State}.
%% ------------------------------------------------------------------
%% Internal Function Definitions
%% ------------------------------------------------------------------
-spec handle_read(state()) -> {stop, normal, state()}.
handle_read(State) ->
#state{source = Source, previously_modified_on = PrevModificationDT} = State,
{_, Path} = Source,
report_event({load_attempt_started, Source}, State),
case file:read_file_info(Path, [{time, universal}]) of
{ok, #file_info{ mtime = ModificationDT }}
when ModificationDT =:= PrevModificationDT ->
report_event({load_attempt_dismissed, Source}, State),
notify_owner({finished, dismissed}, State),
{stop, normal, State};
{ok, #file_info{ mtime = ModificationDT }} ->
handle_new_read(Path, ModificationDT, State);
{error, enoent} ->
notify_owner({finished, {error, not_found}}, State),
{stop, normal, State};
{error, Reason} ->
notify_owner({finished, {error, {read_file_info, Reason}}}, State),
{stop, normal, State}
end.
-spec handle_new_read(path(), calendar:datetime(), state()) -> {stop, normal, state()}.
handle_new_read(Path, ModificationDT, State) ->
case file:read_file(Path) of
{ok, Content} ->
Success =
#{ modified_on => ModificationDT,
content => Content
},
notify_owner({finished, {success, Success}}, State),
{stop, normal, State};
{error, enoent} ->
notify_owner({finished, {error, not_found}}, State),
{stop, normal, State};
{error, Reason} ->
notify_owner({finished, {error, {read_file, Reason}}}, State),
{stop, normal, State}
end.
%% ------------------------------------------------------------------
%% Internal Function Definitions - Events
%% ------------------------------------------------------------------
-spec report_event(event(), state()) -> ok.
report_event(Event, State) ->
notify_owner({event, Event}, State).
-spec notify_owner(msg(), state()) -> ok.
notify_owner(Msg, State) ->
#state{owner_pid = OwnerPid} = State,
_ = erlang:send(OwnerPid, {self(), Msg}, [noconnect]),
ok.