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

package rpc

import (
	"bytes"
	"errors"
	"testing"

	"sourcedock.dev/petrbalvin/nfs/internal/xdr"
)

func TestCallRoundTrip(t *testing.T) {
	cred := Auth{Flavor: FlavorSys, Body: []byte{1, 2, 3}}
	c := Call{XID: 0xfeedface, Program: 100003, Version: 4, Procedure: 1, Cred: cred}

	rec, err := AppendCall(nil, c)
	if err != nil {
		t.Fatalf("encode: %v", err)
	}
	rec = append(rec, xdr.AppendString(nil, "tag")...)

	got, args, err := DecodeCall(rec)
	if err != nil {
		t.Fatalf("decode: %v", err)
	}
	if got.XID != c.XID || got.Program != c.Program || got.Version != c.Version ||
		got.Procedure != c.Procedure ||
		got.Cred.Flavor != c.Cred.Flavor || !bytes.Equal(got.Cred.Body, c.Cred.Body) {
		t.Fatalf("round trip: got %+v, want %+v", got, c)
	}
	tag, err := xdr.NewDecoder(args).String()
	if err != nil || tag != "tag" {
		t.Fatalf("arguments after the header: %q, %v", tag, err)
	}
}

func TestDecodeCallRejectsReplies(t *testing.T) {
	rec := xdr.AppendUint32(xdr.AppendUint32(nil, 1), MsgReply)
	if _, _, err := DecodeCall(rec); err == nil {
		t.Fatal("a reply record decoded as a call")
	}
}

func TestOversizedAuthBody(t *testing.T) {
	c := Call{XID: 1, Program: 100003, Version: Version, Procedure: 0,
		Cred: Auth{Flavor: FlavorSys, Body: make([]byte, maxAuthBody+1)}}
	if _, err := AppendCall(nil, c); err == nil {
		t.Fatal("an oversized credential encoded without error")
	}
}

func TestAcceptedReplyRoundTrip(t *testing.T) {
	rec, err := AppendAcceptedReply(nil, 7, AuthNull, AcceptSuccess, Mismatch{})
	if err != nil {
		t.Fatalf("encode: %v", err)
	}
	rec = append(rec, xdr.AppendUint32(nil, 42)...)

	r, err := DecodeReply(rec)
	if err != nil {
		t.Fatalf("decode: %v", err)
	}
	if r.XID != 7 || r.Status != AcceptSuccess {
		t.Fatalf("got xid %d status %d", r.XID, r.Status)
	}
	body, err := xdr.NewDecoder(r.Body).Uint32()
	if err != nil || body != 42 {
		t.Fatalf("result body: %d, %v", body, err)
	}
}

func TestProgMismatchReply(t *testing.T) {
	rec, err := AppendAcceptedReply(nil, 9, AuthNull, AcceptProgMismatch, Mismatch{Low: 4, High: 4})
	if err != nil {
		t.Fatalf("encode: %v", err)
	}
	r, err := DecodeReply(rec)
	if err != nil {
		t.Fatalf("decode: %v", err)
	}
	if r.Status != AcceptProgMismatch || r.Mismatch != (Mismatch{4, 4}) {
		t.Fatalf("got status %d mismatch %+v", r.Status, r.Mismatch)
	}
}

func TestUnknownAcceptStatus(t *testing.T) {
	if _, err := AppendAcceptedReply(nil, 1, AuthNull, 99, Mismatch{}); err == nil {
		t.Fatal("an unknown accept status encoded without error")
	}
}

func TestAuthSysRoundTrip(t *testing.T) {
	a := AuthSys{Stamp: 12, Machine: "client", UID: 1000, GID: 100, GIDs: []uint32{100, 5, 27}}
	body, err := a.Body()
	if err != nil {
		t.Fatalf("encode: %v", err)
	}
	got, err := DecodeAuthSysBody(body)
	if err != nil {
		t.Fatalf("decode: %v", err)
	}
	if got.Stamp != a.Stamp || got.Machine != a.Machine || got.UID != a.UID ||
		got.GID != a.GID || !equalU32(got.GIDs, a.GIDs) {
		t.Fatalf("round trip: got %+v, want %+v", got, a)
	}
}

func equalU32(a, b []uint32) bool {
	if len(a) != len(b) {
		return false
	}
	for i := range a {
		if a[i] != b[i] {
			return false
		}
	}
	return true
}

func TestAuthSysTooManyGroups(t *testing.T) {
	a := AuthSys{GIDs: make([]uint32, 17)}
	if _, err := a.Body(); err == nil {
		t.Fatal("17 supplementary groups encoded without error")
	}
	if _, err := DecodeAuthSysBody(xdr.AppendUint32(xdr.AppendUint32(nil, 0), 17)); err == nil {
		t.Fatal("a credential claiming 17 groups decoded without error")
	}
}

func TestDecodeRejectedReply(t *testing.T) {
	// RPC_MISMATCH carries the version range.
	rec := xdr.AppendUint32(nil, 5)
	rec = xdr.AppendUint32(rec, MsgReply)
	rec = xdr.AppendUint32(rec, 1) // rejected
	rec = xdr.AppendUint32(rec, RejectRPCMismatch)
	rec = xdr.AppendUint32(rec, 2)
	rec = xdr.AppendUint32(rec, 4)
	r, err := DecodeReply(rec)
	if err != nil || r.XID != 5 || !r.Rejected || r.Mismatch != (Mismatch{2, 4}) {
		t.Fatalf("rpc mismatch: %+v, %v", r, err)
	}
	if r.Status != 0 || r.Body != nil {
		t.Fatalf("a rejected reply carries no result: %+v", r)
	}

	// An auth error carries one status word.
	rec = xdr.AppendUint32(nil, 6)
	rec = xdr.AppendUint32(rec, MsgReply)
	rec = xdr.AppendUint32(rec, 1)
	rec = xdr.AppendUint32(rec, RejectAuthError)
	rec = xdr.AppendUint32(rec, AuthBadVerf)
	if r, err = DecodeReply(rec); err != nil || r.XID != 6 || !r.Rejected || r.AuthStat != AuthBadVerf {
		t.Fatalf("auth error: %+v, %v", r, err)
	}
}

func TestDecodeAuthOversizeBody(t *testing.T) {
	// A credential body beyond 400 bytes is refused, not buffered.
	huge := xdr.AppendUint32(nil, FlavorSys)
	huge = xdr.AppendUint32(huge, maxAuthBody+1)
	huge = append(huge, make([]byte, 8)...)
	rec := xdr.AppendUint32(nil, 1)
	rec = xdr.AppendUint32(rec, MsgCall)
	rec = xdr.AppendUint32(rec, Version)
	rec = xdr.AppendUint32(rec, 100003)
	rec = xdr.AppendUint32(rec, 4)
	rec = xdr.AppendUint32(rec, 0)
	rec = append(rec, huge...)
	if _, _, err := DecodeCall(rec); !errors.Is(err, ErrBadMessage) {
		t.Fatalf("an oversized credential decoded as %v", err)
	}
}

func TestDecodeReplyGarbage(t *testing.T) {
	for _, rec := range [][]byte{
		nil,
		{0, 0, 0},                // short
		xdr.AppendUint32(nil, 1), // no type
		{0, 0, 0, 1, 0, 0, 0, 9}, // unknown reply stat 9
	} {
		if _, err := DecodeReply(rec); !errors.Is(err, ErrBadMessage) {
			t.Fatalf("record %x decoded with %v, want ErrBadMessage", rec, err)
		}
	}
}

func TestPeekHeader(t *testing.T) {
	// A minimal call record: xid and the call type.
	b := xdr.AppendUint32(xdr.AppendUint32(nil, 0x55), MsgCall)
	xid, mtype, err := PeekHeader(b)
	if err != nil || xid != 0x55 || mtype != MsgCall {
		t.Fatalf("call peek: %x %d, %v", xid, mtype, err)
	}
	if _, _, err := PeekHeader(nil); !errors.Is(err, ErrBadMessage) {
		t.Fatalf("an empty record: %v", err)
	}
}