rememo_erlang

-module(rememo@memo).
-compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch, inline]).
-define(FILEPATH, "src/rememo/memo.gleam").
-export([create/1, set/3, get/2, memoize/3]).

-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 cache is a [Erlang Term Storage database](https://www.erlang.org/doc/apps/erts/persistent_term.html).\n").

-file("src/rememo/memo.gleam", 20).
?DOC(
    " Make a new memoization cache that will be used for the rest of the inner scope\n"
    " of the provided function.\n"
    " Pass this cache to the function you want to memoize.\n"
    " \n"
    " This is best used with a `use` expression:\n"
    " ```gleam\n"
    " use cache <- create()\n"
    " f(a, b, c, cache)\n"
    " ```\n"
).
-spec create(fun((internal@carpenter@table:set(any(), any())) -> IDL)) -> IDL.
create(Fun) ->
    Table_name = begin
        _pipe = tempo@instant:now(),
        gleam@string:inspect(_pipe)
    end,
    Cache_table@1 = case begin
        _pipe@1 = internal@carpenter@table:build(Table_name),
        _pipe@2 = internal@carpenter@table:privacy(_pipe@1, private),
        _pipe@3 = internal@carpenter@table:write_concurrency(
            _pipe@2,
            auto_write_concurrency
        ),
        _pipe@4 = internal@carpenter@table:read_concurrency(_pipe@3, true),
        _pipe@5 = internal@carpenter@table:decentralized_counters(_pipe@4, true),
        _pipe@6 = internal@carpenter@table:compression(_pipe@5, false),
        internal@carpenter@table:set(_pipe@6)
    end of
        {ok, Cache_table} -> Cache_table;
        _assert_fail ->
            erlang:error(#{gleam_error => let_assert,
                        message => <<"Pattern match failed, no pattern matched the value."/utf8>>,
                        file => <<?FILEPATH/utf8>>,
                        module => <<"rememo/memo"/utf8>>,
                        function => <<"create"/utf8>>,
                        line => 23,
                        value => _assert_fail,
                        start => 659,
                        'end' => 927,
                        pattern_start => 670,
                        pattern_end => 685})
    end,
    Result = Fun(Cache_table@1),
    internal@carpenter@table:drop(Cache_table@1),
    Result.

-file("src/rememo/memo.gleam", 39).
?DOC(
    " Manually add a key-value pair to the memoization cache.\n"
    " Useful if you need to pre-seed the cache with a starting value, for example.\n"
).
-spec set(internal@carpenter@table:set(IDN, IDO), IDN, IDO) -> nil.
set(Cache, Key, Value) ->
    internal@carpenter@table:insert(Cache, [{Key, Value}]).

-file("src/rememo/memo.gleam", 45).
?DOC(
    " Manually look up a value from the memoization cache for a given key.\n"
    " Useful if you want to also return intermediate results as well as a final result, for example.\n"
).
-spec get(internal@carpenter@table:set(IDR, IDS), IDR) -> {ok, IDS} |
    {error, nil}.
get(Cache, Key) ->
    case internal@carpenter@table:lookup(Cache, Key) of
        [] ->
            {error, nil};

        [{_, V} | _] ->
            {ok, V}
    end.

-file("src/rememo/memo.gleam", 65).
?DOC(
    " Look up the value associated with the given key in the memoization cache,\n"
    " and return it if it exists.  If it doesn't exist, evaluate the callback function\n"
    " update the cache with the key and the corresponding value the callback returned, \n"
    " and return that value.\n"
    " \n"
    " This works well with a `use` expression:\n"
    " ```gleam\n"
    " fn f(a, b, c, cache) {\n"
    "   use <- memoize(cache, #(a, b, c))\n"
    "   // function body goes here\n"
    " }\n"
    " ```\n"
).
-spec memoize(internal@carpenter@table:set(IDX, IDY), IDX, fun(() -> IDY)) -> IDY.
memoize(Cache, Key, Fun) ->
    case get(Cache, Key) of
        {ok, Value} ->
            Value;

        {error, nil} ->
            Result = Fun(),
            set(Cache, Key, Result),
            Result
    end.