-module(olive@watcher).
-compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch]).

-export([start/2]).
-export_type([watcher_error/0, message/0, state/0, internal_msg/0, watch_events/0]).

-if(?OTP_RELEASE >= 27).
-define(MODULEDOC(Str), -moduledoc(Str)).
-define(DOC(Str), -doc(Str)).
-else.
-define(MODULEDOC(Str), -compile([])).
-define(DOC(Str), -compile([])).
-endif.

?MODULEDOC(
    " The `watcher` module watches a list of dir and triggers a `FilesChanged` message\n"
    " to be handled by calling code.\n"
).

-type watcher_error() :: no_file_watcher_supported_for_os |
    {no_file_watcher_installed, gleam@dynamic:dynamic_()}.

-type message() :: {files_changed, binary()}.

-type state() :: {state,
        gleam@option:option(gleam@erlang@process:timer()),
        gleam@erlang@process:subject(message())}.

-opaque internal_msg() :: {trigger_files_changed, binary()} | ignore_changes.

-type watch_events() :: event_needing_rebuild | other_events.

-file("src/olive/watcher.gleam", 57).
-spec check_watcher_install() -> {ok, nil} | {error, binary()}.
check_watcher_install() ->
    case olive_ffi:check_watcher_installed() of
        {error, no_file_watcher_supported_for_os} ->
            {error, <<"No file watcher supported for your OS"/utf8>>};

        {error, {no_file_watcher_installed, Watcher}} ->
            {error,
                <<"No file watcher installed, please install: "/utf8,
                    (gleam@string:inspect(Watcher))/binary>>};

        {ok, _} ->
            {ok, nil}
    end.

-file("src/olive/watcher.gleam", 94).
-spec maybe_cancel_timer(gleam@option:option(gleam@erlang@process:timer())) -> nil.
maybe_cancel_timer(Timer) ->
    case Timer of
        none ->
            nil;

        {some, Timer@1} ->
            gleam@erlang@process:cancel_timer(Timer@1),
            nil
    end.

-file("src/olive/watcher.gleam", 75).
-spec do_loop(internal_msg(), state()) -> gleam@otp@actor:next(any(), state()).
do_loop(Msg, State) ->
    case Msg of
        ignore_changes ->
            gleam@otp@actor:continue(State);

        {trigger_files_changed, File_name} ->
            maybe_cancel_timer(erlang:element(2, State)),
            Timer = gleam@erlang@process:send_after(
                erlang:element(3, State),
                50,
                {files_changed, File_name}
            ),
            gleam@otp@actor:continue(
                begin
                    _record = State,
                    {state, {some, Timer}, erlang:element(3, _record)}
                end
            )
    end.

-file("src/olive/watcher.gleam", 146).
-spec erlang_string_to_string_decoder() -> gleam@dynamic@decode:decoder(binary()).
erlang_string_to_string_decoder() ->
    gleam@dynamic@decode:new_primitive_decoder(
        <<"ErlangString"/utf8>>,
        fun(Data) -> _pipe = olive_ffi:coerce(Data),
            _pipe@1 = unicode:characters_to_binary(_pipe),
            {ok, _pipe@1} end
    ).

-file("src/olive/watcher.gleam", 153).
?DOC(" Converts an atom to an event\n").
-spec atom_to_watch_events() -> gleam@dynamic@decode:decoder(watch_events()).
atom_to_watch_events() ->
    Modified = erlang:binary_to_atom(<<"modified"/utf8>>),
    Renamed = erlang:binary_to_atom(<<"renamed"/utf8>>),
    gleam@dynamic@decode:new_primitive_decoder(
        <<"Atom"/utf8>>,
        fun(Data) -> case gleam_erlang_ffi:atom_from_dynamic(Data) of
                {ok, Ev} when Ev =:= Modified ->
                    {ok, event_needing_rebuild};

                {ok, Ev@1} when Ev@1 =:= Renamed ->
                    {ok, event_needing_rebuild};

                _ ->
                    {ok, other_events}
            end end
    ).

-file("src/olive/watcher.gleam", 115).
-spec watch_decoder(gleam@dynamic:dynamic_()) -> internal_msg().
watch_decoder(Msg) ->
    Decoder = begin
        gleam@dynamic@decode:subfield(
            [2, 0],
            erlang_string_to_string_decoder(),
            fun(File_name) ->
                gleam@dynamic@decode:subfield(
                    [2, 1],
                    gleam@dynamic@decode:list(atom_to_watch_events()),
                    fun(Events) ->
                        gleam@dynamic@decode:success({File_name, Events})
                    end
                )
            end
        )
    end,
    case gleam@dynamic@decode:run(Msg, Decoder) of
        {ok, {File_name@1, Events@1}} ->
            case {filepath:extension(File_name@1),
                gleam@list:contains(Events@1, event_needing_rebuild)} of
                {{ok, <<"gleam"/utf8>>}, true} ->
                    {trigger_files_changed, File_name@1};

                {_, _} ->
                    ignore_changes
            end;

        {error, _} ->
            olive@logging:error(<<"Error occured while watching files"/utf8>>),
            ignore_changes
    end.

-file("src/olive/watcher.gleam", 104).
-spec watch_folder(binary()) -> gleam@erlang@process:selector(internal_msg()).
watch_folder(Dir) ->
    Atom = erlang:binary_to_atom(<<"fs_watcher_"/utf8, Dir/binary>>),
    _assert_subject = fs:start_link(Atom, Dir),
    {ok, _} = case _assert_subject of
        {ok, _} -> _assert_subject;
        _assert_fail ->
            erlang:error(#{gleam_error => let_assert,
                        message => <<"Pattern match failed, no pattern matched the value."/utf8>>,
                        value => _assert_fail,
                        module => <<"olive/watcher"/utf8>>,
                        function => <<"watch_folder"/utf8>>,
                        line => 107})
    end,
    fs:subscribe(Atom),
    Selectors = begin
        _pipe = gleam_erlang_ffi:new_selector(),
        gleam@erlang@process:selecting_anything(_pipe, fun watch_decoder/1)
    end,
    Selectors.

-file("src/olive/watcher.gleam", 69).
-spec start_watchers(list(binary())) -> gleam@erlang@process:selector(internal_msg()).
start_watchers(Dirs) ->
    _pipe = Dirs,
    _pipe@1 = gleam@list:map(_pipe, fun watch_folder/1),
    gleam@list:fold(
        _pipe@1,
        gleam_erlang_ffi:new_selector(),
        fun gleam_erlang_ffi:merge_selector/2
    ).

-file("src/olive/watcher.gleam", 47).
-spec init_watcher(
    olive@config:config(),
    gleam@erlang@process:subject(message())
) -> gleam@otp@actor:init_result(state(), internal_msg()).
init_watcher(Config, Watch_subject) ->
    case check_watcher_install() of
        {error, Err} ->
            {failed, Err};

        {ok, _} ->
            Selectors = start_watchers(erlang:element(7, Config)),
            {ready, {state, none, Watch_subject}, Selectors}
    end.

-file("src/olive/watcher.gleam", 39).
-spec start(olive@config:config(), gleam@erlang@process:subject(message())) -> {ok,
        gleam@erlang@process:subject(internal_msg())} |
    {error, gleam@otp@actor:start_error()}.
start(Config, Watch_subject) ->
    gleam@otp@actor:start_spec(
        {spec,
            fun() -> init_watcher(Config, Watch_subject) end,
            5000,
            fun do_loop/2}
    ).