(** Fuzz tests for the rpmsg library (wire codec and endpoint transport). *)

open Crowbar

let truncate s = String.sub s 0 (min (String.length s) 512)

(* ── Wire codec ────────────────────────────────────────────────────────── *)

let test_codec_roundtrip name src dst =
  let info = Rpmsg.{ name; src; dst } in
  let buf = Bytes.create Rpmsg.endpoint_info_size in
  Wire.Codec.encode Rpmsg.endpoint_info_codec info buf 0;
  let decoded = Wire.Codec.decode Rpmsg.endpoint_info_codec buf 0 in
  if decoded.src <> src then fail "src mismatch";
  if decoded.dst <> dst then fail "dst mismatch"

let test_decode_crash_safety buf =
  if String.length buf < Rpmsg.endpoint_info_size then ()
  else
    let b = Bytes.of_string buf in
    let _ = Wire.Codec.decode Rpmsg.endpoint_info_codec b 0 in
    ()

(* ── Endpoint transport ────────────────────────────────────────────────── *)

let test_pipe_roundtrip buf =
  let buf = truncate buf in
  if String.length buf = 0 then ()
  else
    Eio_main.run @@ fun env ->
    Eio.Switch.run @@ fun sw ->
    let source, sink = Eio.Process.pipe ~sw (Eio.Stdenv.process_mgr env) in
    let ep = Rpmsg.Endpoint.of_source_sink ~source ~sink in
    Rpmsg.Endpoint.send ep buf;
    match Rpmsg.Endpoint.recv ep ~max_size:512 with
    | None -> fail "expected message"
    | Some received -> if received <> buf then fail "roundtrip mismatch"

let test_max_size_message buf =
  let max = Rpmsg.Endpoint.max_message_size in
  let buf = String.sub buf 0 (min (String.length buf) max) in
  if String.length buf = 0 then ()
  else
    Eio_main.run @@ fun env ->
    Eio.Switch.run @@ fun sw ->
    let source, sink = Eio.Process.pipe ~sw (Eio.Stdenv.process_mgr env) in
    let ep = Rpmsg.Endpoint.of_source_sink ~source ~sink in
    Rpmsg.Endpoint.send ep buf;
    match Rpmsg.Endpoint.recv ep ~max_size:max with
    | None -> fail "expected message"
    | Some received ->
        if received <> buf then fail "max size roundtrip mismatch"

let test_binary_payload b1 b2 b3 b4 =
  let buf =
    String.init 4 (fun i ->
        Char.chr ((match i with 0 -> b1 | 1 -> b2 | 2 -> b3 | _ -> b4) mod 256))
  in
  Eio_main.run @@ fun env ->
  Eio.Switch.run @@ fun sw ->
  let source, sink = Eio.Process.pipe ~sw (Eio.Stdenv.process_mgr env) in
  let ep = Rpmsg.Endpoint.of_source_sink ~source ~sink in
  Rpmsg.Endpoint.send ep buf;
  match Rpmsg.Endpoint.recv ep ~max_size:4 with
  | None -> fail "expected message"
  | Some received -> if received <> buf then fail "binary roundtrip mismatch"

(* ── Suite ─────────────────────────────────────────────────────────────── *)

let suite =
  ( "rpmsg",
    [
      (* Wire codec *)
      test_case "codec roundtrip"
        [ bytes; range 65536; range 65536 ]
        test_codec_roundtrip;
      test_case "decode crash safety" [ bytes ] test_decode_crash_safety;
      (* Endpoint transport *)
      test_case "pipe roundtrip" [ bytes ] test_pipe_roundtrip;
      test_case "max size message" [ bytes ] test_max_size_message;
      test_case "binary payload"
        [ uint8; uint8; uint8; uint8 ]
        test_binary_payload;
    ] )