package wire

import (
	"bytes"
	"crypto/rand"
	"fmt"
	"math"
	mrand "math/rand/v2"
	"net/netip"
	"testing"
	"time"

	"github.com/quic-go/quic-go/internal/protocol"
	"github.com/quic-go/quic-go/internal/qerr"
	"github.com/quic-go/quic-go/quicvarint"

	"github.com/stretchr/testify/require"
)

func getRandomValueUpTo(max uint64) uint64 {
	maxVals := []uint64{math.MaxUint8 / 4, math.MaxUint16 / 4, math.MaxUint32 / 4, math.MaxUint64 / 4}
	return mrand.Uint64N(min(max, maxVals[mrand.IntN(4)]))
}

func getRandomValue() uint64 { return getRandomValueUpTo(quicvarint.Max) }

func appendInitialSourceConnectionID(b []byte) []byte {
	b = quicvarint.Append(b, uint64(initialSourceConnectionIDParameterID))
	b = quicvarint.Append(b, 6)
	return append(b, []byte("foobar")...)
}

func TestTransportParametersStringRepresentation(t *testing.T) {
	rcid := protocol.ParseConnectionID([]byte{0xde, 0xad, 0xc0, 0xde})
	minAckDelay := 42 * time.Millisecond
	p := &TransportParameters{
		InitialMaxStreamDataBidiLocal:   1234,
		InitialMaxStreamDataBidiRemote:  2345,
		InitialMaxStreamDataUni:         3456,
		InitialMaxData:                  4567,
		MaxBidiStreamNum:                1337,
		MaxUniStreamNum:                 7331,
		MaxIdleTimeout:                  42 * time.Second,
		OriginalDestinationConnectionID: protocol.ParseConnectionID([]byte{0xde, 0xad, 0xbe, 0xef}),
		InitialSourceConnectionID:       protocol.ParseConnectionID([]byte{0xde, 0xca, 0xfb, 0xad}),
		RetrySourceConnectionID:         &rcid,
		AckDelayExponent:                14,
		MaxAckDelay:                     37 * time.Millisecond,
		StatelessResetToken:             &protocol.StatelessResetToken{0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77, 0x88, 0x99, 0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff, 0x00},
		ActiveConnectionIDLimit:         123,
		MaxDatagramFrameSize:            876,
		EnableResetStreamAt:             true,
		MinAckDelay:                     &minAckDelay,
	}
	expected := "&wire.TransportParameters{OriginalDestinationConnectionID: deadbeef, InitialSourceConnectionID: decafbad, RetrySourceConnectionID: deadc0de, InitialMaxStreamDataBidiLocal: 1234, InitialMaxStreamDataBidiRemote: 2345, InitialMaxStreamDataUni: 3456, InitialMaxData: 4567, MaxBidiStreamNum: 1337, MaxUniStreamNum: 7331, MaxIdleTimeout: 42s, AckDelayExponent: 14, MaxAckDelay: 37ms, ActiveConnectionIDLimit: 123, StatelessResetToken: 0x112233445566778899aabbccddeeff00, MaxDatagramFrameSize: 876, EnableResetStreamAt: true, MinAckDelay: 42ms}"
	require.Equal(t, expected, p.String())
}

func TestTransportParametersStringRepresentationWithoutOptionalFields(t *testing.T) {
	p := &TransportParameters{
		InitialMaxStreamDataBidiLocal:   1234,
		InitialMaxStreamDataBidiRemote:  2345,
		InitialMaxStreamDataUni:         3456,
		InitialMaxData:                  4567,
		MaxBidiStreamNum:                1337,
		MaxUniStreamNum:                 7331,
		MaxIdleTimeout:                  42 * time.Second,
		OriginalDestinationConnectionID: protocol.ParseConnectionID([]byte{0xde, 0xad, 0xbe, 0xef}),
		InitialSourceConnectionID:       protocol.ParseConnectionID([]byte{}),
		AckDelayExponent:                14,
		MaxAckDelay:                     37 * time.Second,
		ActiveConnectionIDLimit:         89,
		MaxDatagramFrameSize:            protocol.InvalidByteCount,
	}
	expected := "&wire.TransportParameters{OriginalDestinationConnectionID: deadbeef, InitialSourceConnectionID: (empty), InitialMaxStreamDataBidiLocal: 1234, InitialMaxStreamDataBidiRemote: 2345, InitialMaxStreamDataUni: 3456, InitialMaxData: 4567, MaxBidiStreamNum: 1337, MaxUniStreamNum: 7331, MaxIdleTimeout: 42s, AckDelayExponent: 14, MaxAckDelay: 37s, ActiveConnectionIDLimit: 89, EnableResetStreamAt: false}"
	require.Equal(t, expected, p.String())
}

func TestMarshalAndUnmarshalTransportParameters(t *testing.T) {
	var token protocol.StatelessResetToken
	rand.Read(token[:])
	rcid := protocol.ParseConnectionID([]byte{0xde, 0xad, 0xc0, 0xde})
	minAckDelay := 42 * time.Millisecond
	params := &TransportParameters{
		InitialMaxStreamDataBidiLocal:   protocol.ByteCount(getRandomValue()),
		InitialMaxStreamDataBidiRemote:  protocol.ByteCount(getRandomValue()),
		InitialMaxStreamDataUni:         protocol.ByteCount(getRandomValue()),
		InitialMaxData:                  protocol.ByteCount(getRandomValue()),
		MaxIdleTimeout:                  0xcafe * time.Second,
		MaxBidiStreamNum:                protocol.StreamNum(getRandomValueUpTo(uint64(protocol.MaxStreamCount))),
		MaxUniStreamNum:                 protocol.StreamNum(getRandomValueUpTo(uint64(protocol.MaxStreamCount))),
		DisableActiveMigration:          true,
		StatelessResetToken:             &token,
		OriginalDestinationConnectionID: protocol.ParseConnectionID([]byte{0xde, 0xad, 0xbe, 0xef}),
		InitialSourceConnectionID:       protocol.ParseConnectionID([]byte{0xde, 0xca, 0xfb, 0xad}),
		RetrySourceConnectionID:         &rcid,
		AckDelayExponent:                13,
		MaxAckDelay:                     42 * time.Millisecond,
		ActiveConnectionIDLimit:         2 + getRandomValueUpTo(quicvarint.Max-2),
		MaxUDPPayloadSize:               1200 + protocol.ByteCount(getRandomValueUpTo(quicvarint.Max-1200)),
		MaxDatagramFrameSize:            protocol.ByteCount(getRandomValue()),
		EnableResetStreamAt:             getRandomValue()%2 == 0,
		MinAckDelay:                     &minAckDelay,
	}
	data := params.Marshal(protocol.PerspectiveServer)

	p := &TransportParameters{}
	require.NoError(t, p.Unmarshal(data, protocol.PerspectiveServer))
	require.Equal(t, params.InitialMaxStreamDataBidiLocal, p.InitialMaxStreamDataBidiLocal)
	require.Equal(t, params.InitialMaxStreamDataBidiRemote, p.InitialMaxStreamDataBidiRemote)
	require.Equal(t, params.InitialMaxStreamDataUni, p.InitialMaxStreamDataUni)
	require.Equal(t, params.InitialMaxData, p.InitialMaxData)
	require.Equal(t, params.MaxUniStreamNum, p.MaxUniStreamNum)
	require.Equal(t, params.MaxBidiStreamNum, p.MaxBidiStreamNum)
	require.Equal(t, params.MaxIdleTimeout, p.MaxIdleTimeout)
	require.Equal(t, params.DisableActiveMigration, p.DisableActiveMigration)
	require.Equal(t, params.StatelessResetToken, p.StatelessResetToken)
	require.Equal(t, protocol.ParseConnectionID([]byte{0xde, 0xad, 0xbe, 0xef}), p.OriginalDestinationConnectionID)
	require.Equal(t, protocol.ParseConnectionID([]byte{0xde, 0xca, 0xfb, 0xad}), p.InitialSourceConnectionID)
	require.Equal(t, &rcid, p.RetrySourceConnectionID)
	require.Equal(t, uint8(13), p.AckDelayExponent)
	require.Equal(t, 42*time.Millisecond, p.MaxAckDelay)
	require.Equal(t, params.ActiveConnectionIDLimit, p.ActiveConnectionIDLimit)
	require.Equal(t, params.MaxUDPPayloadSize, p.MaxUDPPayloadSize)
	require.Equal(t, params.MaxDatagramFrameSize, p.MaxDatagramFrameSize)
	require.Equal(t, params.EnableResetStreamAt, p.EnableResetStreamAt)
	require.NotNil(t, p.MinAckDelay)
	require.Equal(t, minAckDelay, *p.MinAckDelay)
}

func TestMarshalAdditionalTransportParameters(t *testing.T) {
	origAdditionalTransportParametersClient := AdditionalTransportParametersClient
	t.Cleanup(func() {
		AdditionalTransportParametersClient = origAdditionalTransportParametersClient
	})
	AdditionalTransportParametersClient = map[uint64][]byte{1337: []byte("foobar")}

	result := quicvarint.Append([]byte{}, 1337)
	result = quicvarint.Append(result, 6)
	result = append(result, []byte("foobar")...)

	params := &TransportParameters{}
	require.True(t, bytes.Contains(params.Marshal(protocol.PerspectiveClient), result))
	require.False(t, bytes.Contains(params.Marshal(protocol.PerspectiveServer), result))
}

func TestMarshalRetrySourceConnectionID(t *testing.T) {
	// no retry source connection ID
	data := (&TransportParameters{
		StatelessResetToken:     &protocol.StatelessResetToken{},
		ActiveConnectionIDLimit: 2,
	}).Marshal(protocol.PerspectiveServer)
	var p TransportParameters
	require.NoError(t, p.Unmarshal(data, protocol.PerspectiveServer))
	require.Nil(t, p.RetrySourceConnectionID)

	// zero-length retry source connection ID
	rcid := protocol.ParseConnectionID([]byte{})
	data = (&TransportParameters{
		RetrySourceConnectionID: &rcid,
		StatelessResetToken:     &protocol.StatelessResetToken{},
		ActiveConnectionIDLimit: 2,
	}).Marshal(protocol.PerspectiveServer)
	p = TransportParameters{}
	require.NoError(t, p.Unmarshal(data, protocol.PerspectiveServer))
	require.NotNil(t, p.RetrySourceConnectionID)
	require.Zero(t, p.RetrySourceConnectionID.Len())
}

func TestTransportParameterNoMaxAckDelayIfDefault(t *testing.T) {
	const num = 1000
	var defaultLen, dataLen int
	maxAckDelay := protocol.DefaultMaxAckDelay + time.Millisecond
	for range num {
		dataDefault := (&TransportParameters{
			MaxAckDelay:         protocol.DefaultMaxAckDelay,
			StatelessResetToken: &protocol.StatelessResetToken{},
		}).Marshal(protocol.PerspectiveServer)
		defaultLen += len(dataDefault)
		data := (&TransportParameters{
			MaxAckDelay:         maxAckDelay,
			StatelessResetToken: &protocol.StatelessResetToken{},
		}).Marshal(protocol.PerspectiveServer)
		dataLen += len(data)
	}
	entryLen := quicvarint.Len(uint64(ackDelayExponentParameterID)) +
		quicvarint.Len(uint64(quicvarint.Len(uint64(maxAckDelay.Milliseconds())))) +
		quicvarint.Len(uint64(maxAckDelay.Milliseconds()))
	require.InDelta(t, float32(defaultLen)/num+float32(entryLen), float32(dataLen)/num, 1)
}

func TestTransportParameterNoAckDelayExponentIfDefault(t *testing.T) {
	const num = 1000
	var defaultLen, dataLen int
	for range num {
		dataDefault := (&TransportParameters{
			AckDelayExponent:    protocol.DefaultAckDelayExponent,
			StatelessResetToken: &protocol.StatelessResetToken{},
		}).Marshal(protocol.PerspectiveServer)
		defaultLen += len(dataDefault)
		data := (&TransportParameters{
			AckDelayExponent:    protocol.DefaultAckDelayExponent + 1,
			StatelessResetToken: &protocol.StatelessResetToken{},
		}).Marshal(protocol.PerspectiveServer)
		dataLen += len(data)
	}
	entryLen := quicvarint.Len(uint64(ackDelayExponentParameterID)) +
		quicvarint.Len(uint64(quicvarint.Len(protocol.DefaultAckDelayExponent+1))) +
		quicvarint.Len(protocol.DefaultAckDelayExponent+1)
	require.InDelta(t, float32(defaultLen)/num+float32(entryLen), float32(dataLen)/num, 1)
}

func TestTransportParameterSetsDefaultValuesWhenNotSent(t *testing.T) {
	data := (&TransportParameters{
		AckDelayExponent:        protocol.DefaultAckDelayExponent,
		StatelessResetToken:     &protocol.StatelessResetToken{},
		ActiveConnectionIDLimit: protocol.DefaultActiveConnectionIDLimit,
	}).Marshal(protocol.PerspectiveServer)
	p := &TransportParameters{}
	require.NoError(t, p.Unmarshal(data, protocol.PerspectiveServer))
	require.EqualValues(t, protocol.DefaultAckDelayExponent, p.AckDelayExponent)
	require.EqualValues(t, protocol.DefaultActiveConnectionIDLimit, p.ActiveConnectionIDLimit)
}

func TestTransportParameterErrors(t *testing.T) {
	tests := []struct {
		name           string
		params         *TransportParameters
		perspective    protocol.Perspective
		data           []byte
		expectedErrMsg string
	}{
		{
			name: "invalid stateless reset token length",
			data: func() []byte {
				b := quicvarint.Append(nil, uint64(statelessResetTokenParameterID))
				b = quicvarint.Append(b, 15)
				return append(b, make([]byte, 15)...)
			}(),
			perspective:    protocol.PerspectiveServer,
			expectedErrMsg: "wrong length for stateless_reset_token: 15 (expected 16)",
		},
		{
			name: "small max UDP payload size",
			data: func() []byte {
				b := quicvarint.Append(nil, uint64(maxUDPPayloadSizeParameterID))
				b = quicvarint.Append(b, uint64(quicvarint.Len(1199)))
				return quicvarint.Append(b, 1199)
			}(),
			perspective:    protocol.PerspectiveServer,
			expectedErrMsg: "invalid value for max_udp_payload_size: 1199 (minimum 1200)",
		},
		{
			name: "active connection ID limit too small",
			params: &TransportParameters{
				ActiveConnectionIDLimit: 1,
				StatelessResetToken:     &protocol.StatelessResetToken{},
			},
			perspective:    protocol.PerspectiveServer,
			expectedErrMsg: "invalid value for active_connection_id_limit: 1 (minimum 2)",
		},
		{
			name: "ack delay exponent too large",
			params: &TransportParameters{
				AckDelayExponent:    21,
				StatelessResetToken: &protocol.StatelessResetToken{},
			},
			perspective:    protocol.PerspectiveServer,
			expectedErrMsg: "invalid value for ack_delay_exponent: 21 (maximum 20)",
		},
		{
			name: "disable active migration has content",
			data: func() []byte {
				b := quicvarint.Append(nil, uint64(disableActiveMigrationParameterID))
				b = quicvarint.Append(b, 6)
				return append(b, []byte("foobar")...)
			}(),
			perspective:    protocol.PerspectiveServer,
			expectedErrMsg: "wrong length for disable_active_migration: 6 (expected empty)",
		},
		{
			name: "server doesn't set original destination connection ID",
			data: func() []byte {
				b := quicvarint.Append(nil, uint64(statelessResetTokenParameterID))
				b = quicvarint.Append(b, 16)
				b = append(b, make([]byte, 16)...)
				return appendInitialSourceConnectionID(b)
			}(),
			perspective:    protocol.PerspectiveServer,
			expectedErrMsg: "missing original_destination_connection_id",
		},
		{
			name:           "initial source connection ID is missing",
			data:           []byte{},
			perspective:    protocol.PerspectiveClient,
			expectedErrMsg: "missing initial_source_connection_id",
		},
		{
			name: "max ack delay is too large",
			params: &TransportParameters{
				MaxAckDelay:         1 << 14 * time.Millisecond,
				StatelessResetToken: &protocol.StatelessResetToken{},
			},
			perspective:    protocol.PerspectiveServer,
			expectedErrMsg: "invalid value for max_ack_delay: 16384ms (maximum 16383ms)",
		},
		{
			name: "varint value has wrong length",
			data: func() []byte {
				b := quicvarint.Append(nil, uint64(initialMaxStreamDataBidiLocalParameterID))
				b = quicvarint.Append(b, 2)
				val := uint64(0xdeadbeef)
				b = quicvarint.Append(b, val)
				return appendInitialSourceConnectionID(b)
			}(),
			perspective:    protocol.PerspectiveServer,
			expectedErrMsg: fmt.Sprintf("inconsistent transport parameter length for transport parameter %#x", initialMaxStreamDataBidiLocalParameterID),
		},
		{
			name: "initial max streams bidi is too large",
			data: func() []byte {
				b := quicvarint.Append(nil, uint64(initialMaxStreamsBidiParameterID))
				b = quicvarint.Append(b, uint64(quicvarint.Len(uint64(protocol.MaxStreamCount+1))))
				b = quicvarint.Append(b, uint64(protocol.MaxStreamCount+1))
				return appendInitialSourceConnectionID(b)
			}(),
			perspective:    protocol.PerspectiveServer,
			expectedErrMsg: "initial_max_streams_bidi too large: 1152921504606846977 (maximum 1152921504606846976)",
		},
		{
			name: "initial max streams uni is too large",
			data: func() []byte {
				b := quicvarint.Append(nil, uint64(initialMaxStreamsUniParameterID))
				b = quicvarint.Append(b, uint64(quicvarint.Len(uint64(protocol.MaxStreamCount+1))))
				b = quicvarint.Append(b, uint64(protocol.MaxStreamCount+1))
				return appendInitialSourceConnectionID(b)
			}(),
			perspective:    protocol.PerspectiveServer,
			expectedErrMsg: "initial_max_streams_uni too large: 1152921504606846977 (maximum 1152921504606846976)",
		},
		{
			name: "not enough data to read",
			data: func() []byte {
				b := quicvarint.Append(nil, 0x42)
				b = quicvarint.Append(b, 7)
				return append(b, []byte("foobar")...)
			}(),
			perspective:    protocol.PerspectiveServer,
			expectedErrMsg: "remaining length (6) smaller than parameter length (7)",
		},
		{
			name: "client sent stateless reset token",
			data: func() []byte {
				b := quicvarint.Append(nil, uint64(statelessResetTokenParameterID))
				b = quicvarint.Append(b, uint64(quicvarint.Len(16)))
				return append(b, make([]byte, 16)...)
			}(),
			perspective:    protocol.PerspectiveClient,
			expectedErrMsg: "client sent a stateless_reset_token",
		},
		{
			name: "client sent original destination connection ID",
			data: func() []byte {
				b := quicvarint.Append(nil, uint64(originalDestinationConnectionIDParameterID))
				b = quicvarint.Append(b, 6)
				return append(b, []byte("foobar")...)
			}(),
			perspective:    protocol.PerspectiveClient,
			expectedErrMsg: "client sent an original_destination_connection_id",
		},
		{
			name: "huge max ack delay value",
			data: func() []byte {
				val := uint64(math.MaxUint64) / 5
				b := quicvarint.Append(nil, uint64(maxAckDelayParameterID))
				b = quicvarint.Append(b, uint64(quicvarint.Len(val)))
				b = quicvarint.Append(b, val)
				return appendInitialSourceConnectionID(b)
			}(),
			perspective:    protocol.PerspectiveClient,
			expectedErrMsg: "invalid value for max_ack_delay: 3689348814741910323ms (maximum 16383ms)",
		},
		{
			name: "invalid value for reset_stream_at",
			data: func() []byte {
				b := quicvarint.Append(nil, uint64(resetStreamAtParameterID))
				b = quicvarint.Append(b, 1)
				b = quicvarint.Append(b, 1)
				return appendInitialSourceConnectionID(b)
			}(),
			perspective:    protocol.PerspectiveClient,
			expectedErrMsg: "wrong length for reset_stream_at: 1 (expected empty)",
		},
		{
			name: "min ack delay is greater than max ack delay",
			data: func() []byte {
				b := quicvarint.Append(nil, uint64(minAckDelayParameterID))
				b = quicvarint.Append(b, uint64(quicvarint.Len(42001)))
				b = quicvarint.Append(b, 42001) // 42001 microseconds
				b = quicvarint.Append(b, uint64(maxAckDelayParameterID))
				b = quicvarint.Append(b, uint64(quicvarint.Len(42)))
				b = quicvarint.Append(b, 42) // 42 microseconds
				return appendInitialSourceConnectionID(b)
			}(),
			perspective:    protocol.PerspectiveClient,
			expectedErrMsg: "min_ack_delay (42.001ms) is greater than max_ack_delay (42ms)",
		},
		{
			name: "huge min ack delay value",
			data: func() []byte {
				b := quicvarint.Append(nil, uint64(minAckDelayParameterID))
				b = quicvarint.Append(b, uint64(quicvarint.Len(quicvarint.Max)))
				b = quicvarint.Append(b, quicvarint.Max)
				b = quicvarint.Append(b, uint64(maxAckDelayParameterID))
				b = quicvarint.Append(b, uint64(quicvarint.Len(42)))
				b = quicvarint.Append(b, 42) // 42 microseconds
				return appendInitialSourceConnectionID(b)
			}(),
			perspective:    protocol.PerspectiveClient,
			expectedErrMsg: "min_ack_delay (2562047h47m16.854775807s) is greater than max_ack_delay (42ms)",
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			var err error
			if tt.params != nil {
				data := tt.params.Marshal(tt.perspective)
				err = (&TransportParameters{}).Unmarshal(data, tt.perspective)
			} else {
				err = (&TransportParameters{}).Unmarshal(tt.data, tt.perspective)
			}
			require.Error(t, err)
			transportErr, ok := err.(*qerr.TransportError)
			require.True(t, ok)
			require.Equal(t, qerr.TransportParameterError, transportErr.ErrorCode)
			require.Equal(t, tt.expectedErrMsg, transportErr.ErrorMessage)
		})
	}
}

func TestTransportParameterUnknownParameters(t *testing.T) {
	// write a known parameter
	b := quicvarint.Append(nil, uint64(initialMaxStreamDataBidiLocalParameterID))
	b = quicvarint.Append(b, uint64(quicvarint.Len(0x1337)))
	b = quicvarint.Append(b, 0x1337)
	// write an unknown parameter
	b = quicvarint.Append(b, 0x42)
	b = quicvarint.Append(b, 6)
	b = append(b, []byte("foobar")...)
	// write a known parameter
	b = quicvarint.Append(b, uint64(initialMaxStreamDataBidiRemoteParameterID))
	b = quicvarint.Append(b, uint64(quicvarint.Len(0x42)))
	b = quicvarint.Append(b, 0x42)
	b = appendInitialSourceConnectionID(b)
	p := &TransportParameters{}
	err := p.Unmarshal(b, protocol.PerspectiveClient)
	require.NoError(t, err)
	require.Equal(t, protocol.ByteCount(0x1337), p.InitialMaxStreamDataBidiLocal)
	require.Equal(t, protocol.ByteCount(0x42), p.InitialMaxStreamDataBidiRemote)
}

func TestTransportParameterRejectsDuplicateParameters(t *testing.T) {
	// write first parameter
	b := quicvarint.Append(nil, uint64(initialMaxStreamDataBidiLocalParameterID))
	b = quicvarint.Append(b, uint64(quicvarint.Len(0x1337)))
	b = quicvarint.Append(b, 0x1337)
	// write a second parameter
	b = quicvarint.Append(b, uint64(initialMaxStreamDataBidiRemoteParameterID))
	b = quicvarint.Append(b, uint64(quicvarint.Len(0x42)))
	b = quicvarint.Append(b, 0x42)
	// write first parameter again
	b = quicvarint.Append(b, uint64(initialMaxStreamDataBidiLocalParameterID))
	b = quicvarint.Append(b, uint64(quicvarint.Len(0x1337)))
	b = quicvarint.Append(b, 0x1337)
	b = appendInitialSourceConnectionID(b)
	err := (&TransportParameters{}).Unmarshal(b, protocol.PerspectiveClient)
	require.Error(t, err)
	transportErr, ok := err.(*qerr.TransportError)
	require.True(t, ok)
	require.Equal(t, qerr.TransportParameterError, transportErr.ErrorCode)
	require.Equal(t, fmt.Sprintf("received duplicate transport parameter %#x", initialMaxStreamDataBidiLocalParameterID), transportErr.ErrorMessage)
}

func TestTransportParameterPreferredAddress(t *testing.T) {
	testCases := []struct {
		name    string
		hasIPv4 bool
		hasIPv6 bool
	}{
		{"IPv4 and IPv6", true, true},
		{"IPv4 only", true, false},
		{"IPv6 only", false, true},
		{"neither IPv4 nor IPv6", false, false},
	}

	for _, tc := range testCases {
		t.Run(tc.name, func(t *testing.T) {
			testTransportParameterPreferredAddress(t, tc.hasIPv4, tc.hasIPv6)
		})
	}
}

func testTransportParameterPreferredAddress(t *testing.T, hasIPv4, hasIPv6 bool) {
	addr4 := netip.AddrPortFrom(netip.AddrFrom4([4]byte{127, 0, 0, 1}), 42)
	addr6 := netip.AddrPortFrom(netip.AddrFrom16([16]byte{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16}), 13)
	pa := &PreferredAddress{
		ConnectionID:        protocol.ParseConnectionID([]byte{0xde, 0xad, 0xbe, 0xef}),
		StatelessResetToken: protocol.StatelessResetToken{16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1},
	}
	if hasIPv4 {
		pa.IPv4 = addr4
	}
	if hasIPv6 {
		pa.IPv6 = addr6
	}

	data := (&TransportParameters{
		PreferredAddress:        pa,
		StatelessResetToken:     &protocol.StatelessResetToken{},
		ActiveConnectionIDLimit: 2,
	}).Marshal(protocol.PerspectiveServer)
	p := &TransportParameters{}
	require.NoError(t, p.Unmarshal(data, protocol.PerspectiveServer))
	if hasIPv4 {
		require.True(t, p.PreferredAddress.IPv4.IsValid())
		require.Equal(t, addr4, p.PreferredAddress.IPv4)
	} else {
		require.False(t, p.PreferredAddress.IPv4.IsValid())
	}
	if hasIPv6 {
		require.True(t, p.PreferredAddress.IPv6.IsValid())
		require.Equal(t, addr6, p.PreferredAddress.IPv6)
	} else {
		require.False(t, p.PreferredAddress.IPv6.IsValid())
	}
	require.Equal(t, pa.ConnectionID, p.PreferredAddress.ConnectionID)
	require.Equal(t, pa.StatelessResetToken, p.PreferredAddress.StatelessResetToken)
}

func TestTransportParameterPreferredAddressFromClient(t *testing.T) {
	b := quicvarint.Append(nil, uint64(preferredAddressParameterID))
	b = quicvarint.Append(b, 6)
	b = append(b, []byte("foobar")...)
	p := &TransportParameters{}
	err := p.Unmarshal(b, protocol.PerspectiveClient)
	require.Error(t, err)
	require.IsType(t, &qerr.TransportError{}, err)
	transportErr := err.(*qerr.TransportError)
	require.Equal(t, qerr.TransportParameterError, transportErr.ErrorCode)
	require.Equal(t, "client sent a preferred_address", transportErr.ErrorMessage)
}

func TestTransportParameterPreferredAddressZeroLengthConnectionID(t *testing.T) {
	pa := &PreferredAddress{
		IPv4:                netip.AddrPortFrom(netip.AddrFrom4([4]byte{127, 0, 0, 1}), 42),
		IPv6:                netip.AddrPortFrom(netip.AddrFrom16([16]byte{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16}), 13),
		ConnectionID:        protocol.ParseConnectionID([]byte{}),
		StatelessResetToken: protocol.StatelessResetToken{16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1},
	}
	data := (&TransportParameters{
		PreferredAddress:    pa,
		StatelessResetToken: &protocol.StatelessResetToken{},
	}).Marshal(protocol.PerspectiveServer)
	p := &TransportParameters{}
	err := p.Unmarshal(data, protocol.PerspectiveServer)
	require.Error(t, err)
	require.IsType(t, &qerr.TransportError{}, err)
	transportErr := err.(*qerr.TransportError)
	require.Equal(t, qerr.TransportParameterError, transportErr.ErrorCode)
	require.Equal(t, "invalid connection ID length: 0", transportErr.ErrorMessage)
}

func TestPreferredAddressErrorOnEOF(t *testing.T) {
	raw := []byte{
		127, 0, 0, 1, // IPv4
		0, 42, // IPv4 Port
		1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, // IPv6
		13, 37, // IPv6 Port,
		4, // conn ID len
		0xde, 0xad, 0xbe, 0xef,
		16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, // stateless reset token
	}
	for i := 1; i < len(raw); i++ {
		b := quicvarint.Append(nil, uint64(preferredAddressParameterID))
		b = append(b, raw[:i]...)
		p := &TransportParameters{}
		err := p.Unmarshal(b, protocol.PerspectiveServer)
		require.Error(t, err)
	}
}

func TestTransportParametersFromSessionTicket(t *testing.T) {
	params := &TransportParameters{
		InitialMaxStreamDataBidiLocal:  protocol.ByteCount(getRandomValue()),
		InitialMaxStreamDataBidiRemote: protocol.ByteCount(getRandomValue()),
		InitialMaxStreamDataUni:        protocol.ByteCount(getRandomValue()),
		InitialMaxData:                 protocol.ByteCount(getRandomValue()),
		MaxBidiStreamNum:               protocol.StreamNum(getRandomValueUpTo(uint64(protocol.MaxStreamCount))),
		MaxUniStreamNum:                protocol.StreamNum(getRandomValueUpTo(uint64(protocol.MaxStreamCount))),
		ActiveConnectionIDLimit:        2 + getRandomValueUpTo(quicvarint.Max-2),
		MaxDatagramFrameSize:           protocol.ByteCount(getRandomValueUpTo(uint64(MaxDatagramSize))),
		EnableResetStreamAt:            getRandomValue()%2 == 0,
	}
	require.True(t, params.ValidFor0RTT(params))
	b := params.MarshalForSessionTicket(nil)
	var tp TransportParameters
	require.NoError(t, tp.UnmarshalFromSessionTicket(b))
	require.Equal(t, params.InitialMaxStreamDataBidiLocal, tp.InitialMaxStreamDataBidiLocal)
	require.Equal(t, params.InitialMaxStreamDataBidiRemote, tp.InitialMaxStreamDataBidiRemote)
	require.Equal(t, params.InitialMaxStreamDataUni, tp.InitialMaxStreamDataUni)
	require.Equal(t, params.InitialMaxData, tp.InitialMaxData)
	require.Equal(t, params.MaxBidiStreamNum, tp.MaxBidiStreamNum)
	require.Equal(t, params.MaxUniStreamNum, tp.MaxUniStreamNum)
	require.Equal(t, params.ActiveConnectionIDLimit, tp.ActiveConnectionIDLimit)
	require.Equal(t, params.MaxDatagramFrameSize, tp.MaxDatagramFrameSize)
	require.Equal(t, params.EnableResetStreamAt, tp.EnableResetStreamAt)
}

func TestSessionTicketInvalidTransportParameters(t *testing.T) {
	var p TransportParameters
	require.Error(t, p.UnmarshalFromSessionTicket([]byte("foobar")))
}

func TestSessionTicketTransportParameterVersionMismatch(t *testing.T) {
	var p TransportParameters
	data := p.MarshalForSessionTicket(nil)
	b := quicvarint.Append(nil, transportParameterMarshalingVersion+1)
	b = append(b, data[quicvarint.Len(transportParameterMarshalingVersion):]...)
	err := p.UnmarshalFromSessionTicket(b)
	require.EqualError(t, err, fmt.Sprintf("unknown transport parameter marshaling version: %d", transportParameterMarshalingVersion+1))
}

func TestTransportParametersValidFor0RTT(t *testing.T) {
	saved := &TransportParameters{
		InitialMaxStreamDataBidiLocal:  1,
		InitialMaxStreamDataBidiRemote: 2,
		InitialMaxStreamDataUni:        3,
		InitialMaxData:                 4,
		MaxBidiStreamNum:               5,
		MaxUniStreamNum:                6,
		ActiveConnectionIDLimit:        7,
		MaxDatagramFrameSize:           1000,
	}

	tests := []struct {
		name   string
		modify func(*TransportParameters)
		valid  bool
	}{
		{
			name:   "No Changes",
			modify: func(p *TransportParameters) {},
			valid:  true,
		},
		{
			name: "InitialMaxStreamDataBidiLocal reduced",
			modify: func(p *TransportParameters) {
				p.InitialMaxStreamDataBidiLocal = saved.InitialMaxStreamDataBidiLocal - 1
			},
			valid: false,
		},
		{
			name: "InitialMaxStreamDataBidiLocal increased",
			modify: func(p *TransportParameters) {
				p.InitialMaxStreamDataBidiLocal = saved.InitialMaxStreamDataBidiLocal + 1
			},
			valid: true,
		},
		{
			name: "InitialMaxStreamDataBidiRemote reduced",
			modify: func(p *TransportParameters) {
				p.InitialMaxStreamDataBidiRemote = saved.InitialMaxStreamDataBidiRemote - 1
			},
			valid: false,
		},
		{
			name: "InitialMaxStreamDataBidiRemote increased",
			modify: func(p *TransportParameters) {
				p.InitialMaxStreamDataBidiRemote = saved.InitialMaxStreamDataBidiRemote + 1
			},
			valid: true,
		},
		{
			name:   "InitialMaxStreamDataUni reduced",
			modify: func(p *TransportParameters) { p.InitialMaxStreamDataUni = saved.InitialMaxStreamDataUni - 1 },
			valid:  false,
		},
		{
			name:   "InitialMaxStreamDataUni increased",
			modify: func(p *TransportParameters) { p.InitialMaxStreamDataUni = saved.InitialMaxStreamDataUni + 1 },
			valid:  true,
		},
		{
			name:   "InitialMaxData reduced",
			modify: func(p *TransportParameters) { p.InitialMaxData = saved.InitialMaxData - 1 },
			valid:  false,
		},
		{
			name:   "InitialMaxData increased",
			modify: func(p *TransportParameters) { p.InitialMaxData = saved.InitialMaxData + 1 },
			valid:  true,
		},
		{
			name:   "MaxBidiStreamNum reduced",
			modify: func(p *TransportParameters) { p.MaxBidiStreamNum = saved.MaxBidiStreamNum - 1 },
			valid:  false,
		},
		{
			name:   "MaxBidiStreamNum increased",
			modify: func(p *TransportParameters) { p.MaxBidiStreamNum = saved.MaxBidiStreamNum + 1 },
			valid:  true,
		},
		{
			name:   "MaxUniStreamNum reduced",
			modify: func(p *TransportParameters) { p.MaxUniStreamNum = saved.MaxUniStreamNum - 1 },
			valid:  false,
		},
		{
			name:   "MaxUniStreamNum increased",
			modify: func(p *TransportParameters) { p.MaxUniStreamNum = saved.MaxUniStreamNum + 1 },
			valid:  true,
		},
		{
			name:   "ActiveConnectionIDLimit changed",
			modify: func(p *TransportParameters) { p.ActiveConnectionIDLimit = 0 },
			valid:  false,
		},
		{
			name:   "MaxDatagramFrameSize increased",
			modify: func(p *TransportParameters) { p.MaxDatagramFrameSize = saved.MaxDatagramFrameSize + 1 },
			valid:  true,
		},
		{
			name:   "MaxDatagramFrameSize reduced",
			modify: func(p *TransportParameters) { p.MaxDatagramFrameSize = saved.MaxDatagramFrameSize - 1 },
			valid:  false,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			p := *saved
			tt.modify(&p)
			require.Equal(t, tt.valid, p.ValidFor0RTT(saved))
		})
	}
}

func TestTransportParametersValidAfter0RTT(t *testing.T) {
	saved := &TransportParameters{
		InitialMaxStreamDataBidiLocal:  1,
		InitialMaxStreamDataBidiRemote: 2,
		InitialMaxStreamDataUni:        3,
		InitialMaxData:                 4,
		MaxBidiStreamNum:               5,
		MaxUniStreamNum:                6,
		ActiveConnectionIDLimit:        7,
		MaxDatagramFrameSize:           1000,
	}

	tests := []struct {
		name   string
		modify func(*TransportParameters)
		reject bool
	}{
		{
			name:   "no changes",
			modify: func(p *TransportParameters) {},
			reject: false,
		},
		{
			name: "InitialMaxStreamDataBidiLocal reduced",
			modify: func(p *TransportParameters) {
				p.InitialMaxStreamDataBidiLocal = saved.InitialMaxStreamDataBidiLocal - 1
			},
			reject: true,
		},
		{
			name: "InitialMaxStreamDataBidiLocal increased",
			modify: func(p *TransportParameters) {
				p.InitialMaxStreamDataBidiLocal = saved.InitialMaxStreamDataBidiLocal + 1
			},
			reject: false,
		},
		{
			name: "InitialMaxStreamDataBidiRemote reduced",
			modify: func(p *TransportParameters) {
				p.InitialMaxStreamDataBidiRemote = saved.InitialMaxStreamDataBidiRemote - 1
			},
			reject: true,
		},
		{
			name: "InitialMaxStreamDataBidiRemote increased",
			modify: func(p *TransportParameters) {
				p.InitialMaxStreamDataBidiRemote = saved.InitialMaxStreamDataBidiRemote + 1
			},
			reject: false,
		},
		{
			name:   "InitialMaxStreamDataUni reduced",
			modify: func(p *TransportParameters) { p.InitialMaxStreamDataUni = saved.InitialMaxStreamDataUni - 1 },
			reject: true,
		},
		{
			name:   "InitialMaxStreamDataUni increased",
			modify: func(p *TransportParameters) { p.InitialMaxStreamDataUni = saved.InitialMaxStreamDataUni + 1 },
			reject: false,
		},
		{
			name:   "InitialMaxData reduced",
			modify: func(p *TransportParameters) { p.InitialMaxData = saved.InitialMaxData - 1 },
			reject: true,
		},
		{
			name:   "InitialMaxData increased",
			modify: func(p *TransportParameters) { p.InitialMaxData = saved.InitialMaxData + 1 },
			reject: false,
		},
		{
			name:   "MaxBidiStreamNum reduced",
			modify: func(p *TransportParameters) { p.MaxBidiStreamNum = saved.MaxBidiStreamNum - 1 },
			reject: true,
		},
		{
			name:   "MaxBidiStreamNum increased",
			modify: func(p *TransportParameters) { p.MaxBidiStreamNum = saved.MaxBidiStreamNum + 1 },
			reject: false,
		},
		{
			name:   "MaxUniStreamNum reduced",
			modify: func(p *TransportParameters) { p.MaxUniStreamNum = saved.MaxUniStreamNum - 1 },
			reject: true,
		},
		{
			name:   "MaxUniStreamNum increased",
			modify: func(p *TransportParameters) { p.MaxUniStreamNum = saved.MaxUniStreamNum + 1 },
			reject: false,
		},
		{
			name:   "ActiveConnectionIDLimit reduced",
			modify: func(p *TransportParameters) { p.ActiveConnectionIDLimit = saved.ActiveConnectionIDLimit - 1 },
			reject: true,
		},
		{
			name:   "ActiveConnectionIDLimit increased",
			modify: func(p *TransportParameters) { p.ActiveConnectionIDLimit = saved.ActiveConnectionIDLimit + 1 },
			reject: false,
		},
		{
			name:   "MaxDatagramFrameSize reduced",
			modify: func(p *TransportParameters) { p.MaxDatagramFrameSize = saved.MaxDatagramFrameSize - 1 },
			reject: true,
		},
		{
			name:   "MaxDatagramFrameSize increased",
			modify: func(p *TransportParameters) { p.MaxDatagramFrameSize = saved.MaxDatagramFrameSize + 1 },
			reject: false,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			p := *saved
			tt.modify(&p)
			if tt.reject {
				require.False(t, p.ValidForUpdate(saved))
			} else {
				require.True(t, p.ValidForUpdate(saved))
			}
		})
	}
}

func BenchmarkTransportParameters(b *testing.B) {
	b.Run("without preferred address", func(b *testing.B) { benchmarkTransportParameters(b, false) })
	b.Run("with preferred address", func(b *testing.B) { benchmarkTransportParameters(b, true) })
}

func benchmarkTransportParameters(b *testing.B, withPreferredAddress bool) {
	b.ReportAllocs()

	var token protocol.StatelessResetToken
	rand.Read(token[:])
	rcid := protocol.ParseConnectionID([]byte{0xde, 0xad, 0xc0, 0xde})
	params := &TransportParameters{
		InitialMaxStreamDataBidiLocal:   protocol.ByteCount(getRandomValue()),
		InitialMaxStreamDataBidiRemote:  protocol.ByteCount(getRandomValue()),
		InitialMaxStreamDataUni:         protocol.ByteCount(getRandomValue()),
		InitialMaxData:                  protocol.ByteCount(getRandomValue()),
		MaxIdleTimeout:                  0xcafe * time.Second,
		MaxBidiStreamNum:                protocol.StreamNum(getRandomValueUpTo(uint64(protocol.MaxStreamCount))),
		MaxUniStreamNum:                 protocol.StreamNum(getRandomValueUpTo(uint64(protocol.MaxStreamCount))),
		DisableActiveMigration:          true,
		StatelessResetToken:             &token,
		OriginalDestinationConnectionID: protocol.ParseConnectionID([]byte{0xde, 0xad, 0xbe, 0xef}),
		InitialSourceConnectionID:       protocol.ParseConnectionID([]byte{0xde, 0xca, 0xfb, 0xad}),
		RetrySourceConnectionID:         &rcid,
		AckDelayExponent:                13,
		MaxAckDelay:                     42 * time.Millisecond,
		ActiveConnectionIDLimit:         2 + getRandomValueUpTo(quicvarint.Max-2),
		MaxDatagramFrameSize:            protocol.ByteCount(getRandomValue()),
	}
	var token2 protocol.StatelessResetToken
	rand.Read(token2[:])
	if withPreferredAddress {
		var ip4 [4]byte
		var ip6 [16]byte
		rand.Read(ip4[:])
		rand.Read(ip6[:])
		params.PreferredAddress = &PreferredAddress{
			IPv4:                netip.AddrPortFrom(netip.AddrFrom4(ip4), 1234),
			IPv6:                netip.AddrPortFrom(netip.AddrFrom16(ip6), 4321),
			ConnectionID:        protocol.ParseConnectionID([]byte{0xde, 0xad, 0xbe, 0xef}),
			StatelessResetToken: token2,
		}
	}
	data := params.Marshal(protocol.PerspectiveServer)

	var p TransportParameters
	for b.Loop() {
		if err := p.Unmarshal(data, protocol.PerspectiveServer); err != nil {
			b.Fatal(err)
		}
		// check a few fields
		if p.DisableActiveMigration != params.DisableActiveMigration ||
			p.InitialMaxStreamDataBidiLocal != params.InitialMaxStreamDataBidiLocal ||
			*p.StatelessResetToken != *params.StatelessResetToken ||
			p.AckDelayExponent != params.AckDelayExponent {
			b.Fatalf("params mismatch: %v vs %v", p, params)
		}
		if withPreferredAddress && *p.PreferredAddress != *params.PreferredAddress {
			b.Fatalf("preferred address mismatch: %v vs %v", p.PreferredAddress, params.PreferredAddress)
		}
	}
}