-module(fswalk).
-compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch]).

-export([builder/0, with_path/2, with_traversal_filter/2, walk/1]).
-export_type([non/0, som/0, walk_builder/2, stat/0, entry/0]).

-type non() :: any().

-type som() :: any().

-opaque walk_builder(FYP, FYQ) :: {walk_builder,
        gleam@option:option(list(fun((entry()) -> boolean()))),
        gleam@option:option(binary())} |
    {gleam_phantom, FYP, FYQ}.

-type stat() :: {stat, boolean()}.

-type entry() :: {entry, binary(), stat()}.

-spec builder() -> walk_builder(non(), non()).
builder() ->
    {walk_builder, none, none}.

-spec with_path(walk_builder(FYT, any()), binary()) -> walk_builder(FYT, som()).
with_path(Builder, Path) ->
    {walk_builder, erlang:element(2, Builder), {some, Path}}.

-spec with_traversal_filter(
    walk_builder(any(), FZA),
    fun((entry()) -> boolean())
) -> walk_builder(som(), FZA).
with_traversal_filter(Builder, Traversal_filter) ->
    {walk_builder,
        {some,
            gleam@list:append(
                gleam@option:unwrap(erlang:element(2, Builder), []),
                [Traversal_filter]
            )},
        erlang:element(3, Builder)}.

-spec to_entry(gleam_community@path:path()) -> entry().
to_entry(Path) ->
    Filename = gleam_community@path:to_string(Path),
    {entry,
        Filename,
        {stat,
            begin
                _pipe = simplifile_erl:is_directory(Filename),
                gleam@result:unwrap(_pipe, false)
            end}}.

-spec filter_many(list(GAT), list(fun((GAT) -> boolean()))) -> list(GAT).
filter_many(Xs, Filters) ->
    _pipe = Xs,
    gleam@list:filter(
        _pipe,
        fun(Entry) -> gleam@list:all(Filters, fun(F) -> F(Entry) end) end
    ).

-spec walk_path(gleam_community@path:path(), list(fun((entry()) -> boolean()))) -> gleam@iterator:iterator({ok,
        entry()} |
    {error, simplifile:file_error()}).
walk_path(Pth, Traversal_filters) ->
    _pipe = gleam@iterator:once(
        fun() ->
            simplifile_erl:read_directory(gleam_community@path:to_string(Pth))
        end
    ),
    gleam@iterator:flat_map(
        _pipe,
        fun(Readdir_result) -> _pipe@1 = Readdir_result,
            _pipe@2 = gleam@result:map_error(
                _pipe@1,
                fun(E) -> gleam@iterator:once(fun() -> {error, E} end) end
            ),
            _pipe@4 = gleam@result:map(
                _pipe@2,
                fun(Basenames) ->
                    Paths = gleam@list:map(
                        Basenames,
                        fun(Basename) ->
                            gleam_community@path:append_string(Pth, Basename)
                        end
                    ),
                    {All_entries, Dir_entries} = gleam@list:fold(
                        Paths,
                        {[], []},
                        fun(Acc, It) ->
                            Entry = to_entry(It),
                            Is_dir = begin
                                _pipe@3 = simplifile_erl:is_directory(
                                    gleam_community@path:to_string(It)
                                ),
                                gleam@result:unwrap(_pipe@3, false)
                            end,
                            {[Entry | erlang:element(1, Acc)], case Is_dir of
                                    true ->
                                        [Entry | erlang:element(2, Acc)];

                                    false ->
                                        erlang:element(2, Acc)
                                end}
                        end
                    ),
                    Traverse_dirs = filter_many(Dir_entries, Traversal_filters),
                    gleam@iterator:concat(
                        [gleam@iterator:from_list(
                                gleam@list:map(
                                    All_entries,
                                    fun(It@1) -> {ok, It@1} end
                                )
                            ) |
                            gleam@list:map(
                                Traverse_dirs,
                                fun(Ent) ->
                                    walk_path(
                                        gleam_community@path:from_string(
                                            erlang:element(2, Ent)
                                        ),
                                        Traversal_filters
                                    )
                                end
                            )]
                    )
                end
            ),
            gleam@result:unwrap_both(_pipe@4) end
    ).

-spec walk(walk_builder(any(), som())) -> gleam@iterator:iterator({ok, entry()} |
    {error, simplifile:file_error()}).
walk(Builder) ->
    {walk_builder, Traversal_filter_opt, Path_opt} = Builder,
    {some, Root_path} = case Path_opt of
        {some, _} -> Path_opt;
        _assert_fail ->
            erlang:error(#{gleam_error => let_assert,
                        message => <<"Assertion pattern match failed"/utf8>>,
                        value => _assert_fail,
                        module => <<"fswalk"/utf8>>,
                        function => <<"walk"/utf8>>,
                        line => 56})
    end,
    Traversal_filters = case Traversal_filter_opt of
        {some, Xs} ->
            Xs;

        _ ->
            []
    end,
    walk_path(gleam_community@path:from_string(Root_path), Traversal_filters).