// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
// SPDX-License-Identifier: MIT

package rdma

import (
	"bytes"
	"testing"
)

// The inline frame round trips: the fixed fields, the chunk lists and
// the payload survive the encode-decode pair. A frame whose payload is
// nil decodes as RDMA_NOMSG.
func TestFrameRoundTrip(t *testing.T) {
	h := Header{
		XID: 42, Credit: 16, Proc: ProcMsg,
		Reads: []ReadChunk{{Position: 8, Segment: Segment{Handle: 1, Length: 64, Offset: 512}}},
		Writes: []WriteChunk{{Segments: []Segment{
			{Handle: 2, Length: 128, Offset: 1024},
		}}},
		Reply:   &WriteChunk{Segments: []Segment{{Handle: 3, Length: 256, Offset: 2048}}},
		Payload: []byte("the rpc call bytes"),
	}
	frame := AppendFrame(nil, h)
	got, err := DecodeFrame(frame)
	if err != nil {
		t.Fatalf("decode: %v", err)
	}
	if got.XID != 42 || got.Credit != 16 || got.Proc != ProcMsg {
		t.Fatalf("header %+v", got)
	}
	if len(got.Reads) != 1 || got.Reads[0].Position != 8 ||
		got.Reads[0].Segment.Length != 64 || got.Reads[0].Segment.Offset != 512 {
		t.Fatalf("reads %+v", got.Reads)
	}
	if len(got.Writes) != 1 || len(got.Writes[0].Segments) != 1 ||
		got.Writes[0].Segments[0].Length != 128 {
		t.Fatalf("writes %+v", got.Writes)
	}
	if got.Reply == nil || len(got.Reply.Segments) != 1 || got.Reply.Segments[0].Length != 256 {
		t.Fatalf("reply %+v", got.Reply)
	}
	if !bytes.Equal(got.Payload, h.Payload) {
		t.Fatalf("payload %q", got.Payload)
	}

	nomsg := AppendFrame(nil, Header{XID: 7, Credit: 4, Proc: ProcNomsg})
	got, err = DecodeFrame(nomsg)
	if err != nil {
		t.Fatal(err)
	}
	if got.Proc != ProcNomsg || got.Payload != nil {
		t.Fatalf("nomsg %+v", got)
	}
}

// The stream framing splits frames off a buffer and detects a torn or
// corrupted stream.
func TestStreamFraming(t *testing.T) {
	h := Header{XID: 9, Credit: 4, Proc: ProcMsg, Payload: []byte("abc")}
	frame := AppendStreamFrame(nil, h)
	got, consumed, ok, err := ReadStreamFrame(frame)
	if err != nil || !ok {
		t.Fatalf("read: ok %v err %v", ok, err)
	}
	if consumed != len(frame) {
		t.Fatalf("consumed %d of %d", consumed, len(frame))
	}
	if hdr, derr := DecodeFrame(got); derr != nil || hdr.XID != 9 || string(hdr.Payload) != "abc" {
		t.Fatalf("frame %+v %v", hdr, derr)
	}

	// A torn frame: not a whole frame yet.
	if _, _, ok, _ := ReadStreamFrame(frame[:len(frame)-1]); ok {
		t.Fatal("a torn frame read as whole")
	}
	// A corrupted magic.
	broken := append([]byte{}, frame...)
	broken[0] ^= 0xff
	if _, _, _, err := ReadStreamFrame(broken); err != ErrFrame {
		t.Fatalf("broken magic: %v", err)
	}
}