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

package nfs4

import (
	"testing"

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

// FuzzDecodeCompound feeds arbitrary compound payloads through the
// argument and result walkers: no input may panic, and every malformed
// body must arrive as an error, never as a wrong split.
func FuzzDecodeCompound(f *testing.F) {
	args := AppendCompoundArgs(nil, "seed", MinorVersion, [][]byte{
		AppendSequenceArgs(nil, SessionID{1}, 1, 0, 0, true),
		AppendPutRootfh(nil),
		AppendLookup(nil, "a"),
	})
	f.Add(args)
	res := AppendCompoundRes(nil, ErrOK, "seed", [][]byte{
		append(AppendOpHeader(nil, OpSequence, ErrOK), AppendSequenceRes(nil, SessionID{1}, 1, 0, 0, 0)...),
		AppendOpHeader(nil, OpPutRootfh, ErrOK),
	})
	f.Add(res)
	f.Add([]byte{0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 3, 0, 0, 0, 75, 0, 0, 0, 0})
	f.Add([]byte{0, 0, 0, 9, 0, 0, 0, 1, 0, 0, 0, 1})
	f.Fuzz(func(t *testing.T, data []byte) {
		// The property under test is that none of this panics; a
		// malformed body is an ordinary error and a well formed one
		// decodes with bodies that stay inside the payload.
		_, d, err := DecodeCompoundArgs(data)
		if err == nil {
			for {
				op, oerr := d.Uint32()
				if oerr != nil || walkArgs(op, d) {
					break
				}
			}
		}
		_, _, _ = DecodeCompoundResBodies(data)
		_, _, _ = DecodeCompoundResBodiesCB(data)
	})
}

// walkArgs walks one operation's arguments the way the dispatcher does,
// so the fuzzed stream exercises the real decoders. The boolean reports
// that the stream ended or was refused.
func walkArgs(op uint32, d *xdr.Decoder) bool {
	switch op {
	case OpExchangeID:
		_, err := DecodeExchangeIDArgs(d)
		return err != nil
	case OpCreateSession:
		_, err := DecodeCreateSessionArgs(d)
		return err != nil
	case OpSequence:
		_, err := DecodeSequenceArgs(d)
		return err != nil
	case OpSecinfoNoName:
		_, err := DecodeSecinfoNoNameArgs(d)
		return err != nil
	}
	_, err := d.Uint32()
	return err != nil
}

// TestRegistryValues pins the registry numbers this package speaks
// against the standards: an accidental renumbering of any of these
// breaks interoperation with every conformant peer, so the values
// themselves are the contract.
func TestRegistryValues(t *testing.T) {
	pins := []struct {
		name string
		got  uint32
		want uint32
		rfc  string
	}{
		{"session id size", uint32(len(SessionID{})), 16, "RFC 7863"},
		{"FATTR4_TIME_ACCESS_SET", AttrTimeAccessSet, 48, "RFC 7863"},
		{"FATTR4_TIME_MODIFY_SET", AttrTimeModifySet, 54, "RFC 7863"},
		{"LAYOUT4_FLEX_FILES", LayoutTypeFlexfiles, 4, "RFC 8435"},
		{"LAYOUT4_NFSV4_1_FILES", LayoutTypeFiles, 1, "RFC 7863"},
		{"LAYOUT4_OSD2_OBJECTS", LayoutTypeObjects, 2, "RFC 7863"},
		{"LAYOUT4_BLOCK_VOLUME", LayoutTypeBlock, 3, "RFC 7863"},
		{"layoutiomode4 RW", IoModeRW, 2, "RFC 7863"},
		{"layoutiomode4 ANY", IoModeAny, 3, "RFC 7863"},
		{"SP4_MACH_CRED", StateProtectMachCred, 1, "RFC 8881"},
		{"SP4_SSV", StateProtectSSV, 2, "RFC 8881"},
		{"SECINFO_STYLE4_CURRENT_FH", StyleCurrentFH, 0, "RFC 8881"},
		{"SECINFO_STYLE4_PARENT", StyleParent, 1, "RFC 8881"},
		{"NFS4ERR_NXIO", ErrNXIO, 6, "RFC 8881"},
		{"NFS4ERR_BADOWNER", ErrBadOwner, 10093, "RFC 8881"},
		{"NFS4ERR_NOXATTR", ErrNoXattr, 10095, "RFC 8276"},
		{"NFS4ERR_XATTR2BIG", ErrXattr2Big, 10096, "RFC 8276"},
	}
	for _, p := range pins {
		if p.got != p.want {
			t.Errorf("%s: got %d, want %d per %s", p.name, p.got, p.want, p.rfc)
		}
	}
}