thrifty

-module(thrifty@fuzz_cli).
-compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch, inline]).
-define(FILEPATH, "src/thrifty/fuzz_cli.gleam").
-export([main/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.

-file("src/thrifty/fuzz_cli.gleam", 155).
?DOC(" Attempt to save a failing payload and a small metadata file.\n").
-spec maybe_save_failure(
    boolean(),
    binary(),
    integer(),
    integer(),
    bitstring(),
    thrifty@types:decode_error()
) -> {ok, nil} | {error, binary()}.
maybe_save_failure(Enabled, Dir, Seed, Iter, Data, Reason) ->
    case Enabled of
        false ->
            {ok, nil};

        true ->
            thrifty@fuzz_persistence:persist_failure(
                Dir,
                Seed,
                Iter,
                Data,
                Reason
            )
    end.

-file("src/thrifty/fuzz_cli.gleam", 179).
?DOC(
    " Core fuzz loop that mutates a single byte and invokes the reader.\n"
    "\n"
    " Notes\n"
    " - This harness is purposely conservative: it uses `with_options` to limit\n"
    "   resources and discards reader results. Extend to persist failing inputs\n"
    "   when required.\n"
).
-spec normalize_mod(integer(), integer()) -> integer().
normalize_mod(Value, Modulus) ->
    Rem = case Modulus of
        0 -> 0;
        Gleam@denominator -> Value rem Gleam@denominator
    end,
    case Rem < 0 of
        true ->
            Rem + Modulus;

        false ->
            Rem
    end.

-file("src/thrifty/fuzz_cli.gleam", 113).
?DOC(
    " Run deterministic single-byte mutation iterations for a single seed.\n"
    "\n"
    " Inputs\n"
    " - `data`: original payload.\n"
    " - `size`: payload byte size.\n"
    " - `seed`: deterministic seed controlling mutation positions/values.\n"
    " - `iterations`: number of mutations to generate for this seed.\n"
).
-spec fuzz_loop(bitstring(), integer(), integer(), integer(), integer()) -> nil.
fuzz_loop(Data, Size, Seed, Index, Remaining) ->
    case Remaining =:= 0 of
        true ->
            nil;

        false ->
            Position = normalize_mod((Seed * 31) + (Index * 17), Size),
            Value = normalize_mod((Seed * 97) + (Index * 101), 256),
            Mutated = thrifty@fuzz_utils:mutate_byte(Data, Position, Value),
            Reader = thrifty@reader:with_options(
                Mutated,
                {reader_options, 32, 4096, 4194304, accept_canonical_only}
            ),
            case thrifty@reader:read_struct(Reader) of
                {ok, _} ->
                    nil;

                {error, Err} ->
                    _ = maybe_save_failure(
                        false,
                        <<"artifact/fuzz-failures"/utf8>>,
                        Seed,
                        Index,
                        Mutated,
                        Err
                    ),
                    nil
            end,
            fuzz_loop(Data, Size, Seed, Index + 1, Remaining - 1)
    end.

-file("src/thrifty/fuzz_cli.gleam", 102).
?DOC(
    " Prepare fuzzing state for a given payload and spawn seed-based iterations.\n"
    "\n"
    " Inputs\n"
    " - `file`: path to the golden file (used only for logging).\n"
    " - `data`: payload bytes to mutate.\n"
    "\n"
    " Behavior\n"
    " - Skips empty payloads. Logs size and iterates `seeds` invoking `fuzz_with_seed`.\n"
).
-spec fuzz_with_seed(bitstring(), integer(), integer(), integer()) -> nil.
fuzz_with_seed(Data, Size, Seed, Iterations) ->
    fuzz_loop(Data, Size, Seed, 0, Iterations).

-file("src/thrifty/fuzz_cli.gleam", 81).
?DOC(
    " Read a golden file and trigger fuzzing of its payloads.\n"
    "\n"
    " Inputs\n"
    " - `file`: path to a golden binary file.\n"
    "\n"
    " Behavior\n"
    " - On read error prints a message and continues. On success delegates to\n"
    "   `fuzz_payloads/2` to run deterministic mutations.\n"
).
-spec fuzz_payloads(binary(), bitstring()) -> nil.
fuzz_payloads(File, Data) ->
    Size = erlang:byte_size(Data),
    case Size =:= 0 of
        true ->
            gleam_stdlib:println(
                <<"Skipping empty payload: "/utf8, File/binary>>
            );

        false ->
            gleam_stdlib:println(
                <<<<<<<<"Fuzzing "/utf8, File/binary>>/binary, " ("/utf8>>/binary,
                        (erlang:integer_to_binary(Size))/binary>>/binary,
                    " bytes)"/utf8>>
            ),
            gleam@list:each(
                [13, 29, 41, 53, 67, 79, 97, 109],
                fun(Seed) -> fuzz_with_seed(Data, Size, Seed, 200) end
            )
    end.

-file("src/thrifty/fuzz_cli.gleam", 66).
-spec fuzz_file(binary()) -> nil.
fuzz_file(File) ->
    case thrifty@file_io:read_binary(File) of
        {error, Error} ->
            gleam_stdlib:println(
                <<<<<<"Skipping "/utf8, File/binary>>/binary, ": "/utf8>>/binary,
                    Error/binary>>
            );

        {ok, Data} ->
            fuzz_payloads(File, Data)
    end.

-file("src/thrifty/fuzz_cli.gleam", 60).
?DOC(
    " Run a short deterministic fuzz run over the configured golden payloads.\n"
    "\n"
    " Purpose\n"
    " - Convenience entrypoint for manual or CI smoke tests that exercise the\n"
    "   reader against small, mutated variants of canonical golden payloads.\n"
    "\n"
    " Behavior\n"
    " - Iterates the predefined `files` list, reads each binary, and applies a set\n"
    "   of deterministic single-byte mutations controlled by `seeds` and\n"
    "   `iterations_per_seed`.\n"
    " - Each mutated payload is passed to the reader created with conservative\n"
    "   `ReaderOptions` to verify the reader does not crash on malformed inputs.\n"
    "\n"
    " Outputs\n"
    " - Prints progress to stdout. This function is intended as a smoke-test only\n"
    "   and does not return structured results; callers should inspect logs or\n"
    "   extend the harness to persist failing cases.\n"
).
-spec main() -> nil.
main() ->
    gleam_stdlib:println(<<"Starting fuzz run over golden payloads"/utf8>>),
    gleam@list:each(
        [<<"artifact/golden/user_profile.bin"/utf8>>,
            <<"artifact/golden/ping_message.bin"/utf8>>,
            <<"artifact/golden/complex_struct.bin"/utf8>>,
            <<"artifact/golden/bool_list.bin"/utf8>>],
        fun fuzz_file/1
    ),
    gleam_stdlib:println(<<"Fuzz run completed without crashes"/utf8>>).