package quic

import (
	"bytes"

	"golang.org/x/exp/rand"

	"github.com/refraction-networking/uquic/internal/ackhandler"
	"github.com/refraction-networking/uquic/internal/protocol"
	"github.com/refraction-networking/uquic/internal/wire"

	. "github.com/onsi/ginkgo/v2"
	. "github.com/onsi/gomega"
	"go.uber.org/mock/gomock"
)

var _ = Describe("Framer", func() {
	const (
		id1 = protocol.StreamID(10)
		id2 = protocol.StreamID(11)
	)

	var (
		framer           framer
		stream1, stream2 *MockSendStreamI
		streamGetter     *MockStreamGetter
		version          protocol.Version
	)

	BeforeEach(func() {
		streamGetter = NewMockStreamGetter(mockCtrl)
		stream1 = NewMockSendStreamI(mockCtrl)
		stream1.EXPECT().StreamID().Return(protocol.StreamID(5)).AnyTimes()
		stream2 = NewMockSendStreamI(mockCtrl)
		stream2.EXPECT().StreamID().Return(protocol.StreamID(6)).AnyTimes()
		framer = newFramer(streamGetter)
	})

	Context("handling control frames", func() {
		It("adds control frames", func() {
			mdf := &wire.MaxDataFrame{MaximumData: 0x42}
			msf := &wire.MaxStreamsFrame{MaxStreamNum: 0x1337}
			framer.QueueControlFrame(mdf)
			framer.QueueControlFrame(msf)
			frames, length := framer.AppendControlFrames(nil, 1000, protocol.Version1)
			Expect(frames).To(HaveLen(2))
			fs := []wire.Frame{frames[0].Frame, frames[1].Frame}
			Expect(fs).To(ContainElement(mdf))
			Expect(fs).To(ContainElement(msf))
			Expect(length).To(Equal(mdf.Length(version) + msf.Length(version)))
		})

		It("says if it has data", func() {
			Expect(framer.HasData()).To(BeFalse())
			f := &wire.MaxDataFrame{MaximumData: 0x42}
			framer.QueueControlFrame(f)
			Expect(framer.HasData()).To(BeTrue())
			frames, _ := framer.AppendControlFrames(nil, 1000, protocol.Version1)
			Expect(frames).To(HaveLen(1))
			Expect(framer.HasData()).To(BeFalse())
		})

		It("appends to the slice given", func() {
			ping := &wire.PingFrame{}
			mdf := &wire.MaxDataFrame{MaximumData: 0x42}
			framer.QueueControlFrame(mdf)
			frames, length := framer.AppendControlFrames([]ackhandler.Frame{{Frame: ping}}, 1000, protocol.Version1)
			Expect(frames).To(HaveLen(2))
			Expect(frames[0].Frame).To(Equal(ping))
			Expect(frames[1].Frame).To(Equal(mdf))
			Expect(length).To(Equal(mdf.Length(version)))
		})

		It("adds the right number of frames", func() {
			maxSize := protocol.ByteCount(1000)
			bf := &wire.DataBlockedFrame{MaximumData: 0x1337}
			bfLen := bf.Length(version)
			numFrames := int(maxSize / bfLen) // max number of frames that fit into maxSize
			for i := 0; i < numFrames+1; i++ {
				framer.QueueControlFrame(bf)
			}
			frames, length := framer.AppendControlFrames(nil, maxSize, protocol.Version1)
			Expect(frames).To(HaveLen(numFrames))
			Expect(length).To(BeNumerically(">", maxSize-bfLen))
			frames, length = framer.AppendControlFrames(nil, maxSize, protocol.Version1)
			Expect(frames).To(HaveLen(1))
			Expect(length).To(Equal(bfLen))
		})

		It("drops *_BLOCKED frames when 0-RTT is rejected", func() {
			ping := &wire.PingFrame{}
			ncid := &wire.NewConnectionIDFrame{
				SequenceNumber: 10,
				ConnectionID:   protocol.ParseConnectionID([]byte{0xde, 0xad, 0xbe, 0xef}),
			}
			frames := []wire.Frame{
				&wire.DataBlockedFrame{MaximumData: 1337},
				&wire.StreamDataBlockedFrame{StreamID: 42, MaximumStreamData: 1337},
				&wire.StreamsBlockedFrame{StreamLimit: 13},
				ping,
				ncid,
			}
			rand.Shuffle(len(frames), func(i, j int) { frames[i], frames[j] = frames[j], frames[i] })
			for _, f := range frames {
				framer.QueueControlFrame(f)
			}
			Expect(framer.Handle0RTTRejection()).To(Succeed())
			fs, length := framer.AppendControlFrames(nil, protocol.MaxByteCount, protocol.Version1)
			Expect(fs).To(HaveLen(2))
			Expect(length).To(Equal(ping.Length(version) + ncid.Length(version)))
		})

		It("detects when too many frames are queued", func() {
			for i := 0; i < maxControlFrames-1; i++ {
				framer.QueueControlFrame(&wire.PingFrame{})
				framer.QueueControlFrame(&wire.PingFrame{})
				Expect(framer.QueuedTooManyControlFrames()).To(BeFalse())
				frames, _ := framer.AppendControlFrames([]ackhandler.Frame{}, 1, protocol.Version1)
				Expect(frames).To(HaveLen(1))
				Expect(framer.(*framerI).controlFrames).To(HaveLen(i + 1))
			}
			framer.QueueControlFrame(&wire.PingFrame{})
			Expect(framer.QueuedTooManyControlFrames()).To(BeFalse())
			Expect(framer.(*framerI).controlFrames).To(HaveLen(maxControlFrames))
			framer.QueueControlFrame(&wire.PingFrame{})
			Expect(framer.QueuedTooManyControlFrames()).To(BeTrue())
			Expect(framer.(*framerI).controlFrames).To(HaveLen(maxControlFrames))
		})
	})

	Context("handling PATH_RESPONSE frames", func() {
		It("packs a single PATH_RESPONSE per packet", func() {
			f1 := &wire.PathResponseFrame{Data: [8]byte{1, 2, 3, 4, 5, 6, 7, 8}}
			f2 := &wire.PathResponseFrame{Data: [8]byte{2, 3, 4, 5, 6, 7, 8, 9}}
			cf1 := &wire.DataBlockedFrame{MaximumData: 1337}
			cf2 := &wire.HandshakeDoneFrame{}
			framer.QueueControlFrame(f1)
			framer.QueueControlFrame(f2)
			framer.QueueControlFrame(cf1)
			framer.QueueControlFrame(cf2)
			// the first packet should contain a single PATH_RESPONSE frame, but all the other control frames
			Expect(framer.HasData()).To(BeTrue())
			frames, length := framer.AppendControlFrames(nil, protocol.MaxByteCount, protocol.Version1)
			Expect(frames).To(HaveLen(3))
			Expect(frames[0].Frame).To(Equal(f1))
			Expect([]wire.Frame{frames[1].Frame, frames[2].Frame}).To(ContainElement(cf1))
			Expect([]wire.Frame{frames[1].Frame, frames[2].Frame}).To(ContainElement(cf2))
			Expect(length).To(Equal(f1.Length(protocol.Version1) + cf1.Length(protocol.Version1) + cf2.Length(protocol.Version1)))
			// the second packet should contain the other PATH_RESPONSE frame
			Expect(framer.HasData()).To(BeTrue())
			frames, length = framer.AppendControlFrames(nil, protocol.MaxByteCount, protocol.Version1)
			Expect(frames).To(HaveLen(1))
			Expect(frames[0].Frame).To(Equal(f2))
			Expect(length).To(Equal(f2.Length(protocol.Version1)))
			Expect(framer.HasData()).To(BeFalse())
		})

		It("limits the number of queued PATH_RESPONSE frames", func() {
			var pathResponses []*wire.PathResponseFrame
			for i := 0; i < 2*maxPathResponses; i++ {
				var f wire.PathResponseFrame
				rand.Read(f.Data[:])
				pathResponses = append(pathResponses, &f)
				framer.QueueControlFrame(&f)
			}
			for i := 0; i < maxPathResponses; i++ {
				Expect(framer.HasData()).To(BeTrue())
				frames, length := framer.AppendControlFrames(nil, protocol.MaxByteCount, protocol.Version1)
				Expect(frames).To(HaveLen(1))
				Expect(frames[0].Frame).To(Equal(pathResponses[i]))
				Expect(length).To(Equal(pathResponses[i].Length(protocol.Version1)))
			}
			Expect(framer.HasData()).To(BeFalse())
			frames, length := framer.AppendControlFrames(nil, protocol.MaxByteCount, protocol.Version1)
			Expect(frames).To(BeEmpty())
			Expect(length).To(BeZero())
		})
	})

	Context("popping STREAM frames", func() {
		It("returns nil when popping an empty framer", func() {
			Expect(framer.AppendStreamFrames(nil, 1000, protocol.Version1)).To(BeEmpty())
		})

		It("returns STREAM frames", func() {
			streamGetter.EXPECT().GetOrOpenSendStream(id1).Return(stream1, nil)
			f := &wire.StreamFrame{
				StreamID:       id1,
				Data:           []byte("foobar"),
				Offset:         42,
				DataLenPresent: true,
			}
			stream1.EXPECT().popStreamFrame(gomock.Any(), protocol.Version1).Return(ackhandler.StreamFrame{Frame: f}, true, false)
			framer.AddActiveStream(id1)
			fs, length := framer.AppendStreamFrames(nil, 1000, protocol.Version1)
			Expect(fs).To(HaveLen(1))
			Expect(fs[0].Frame.DataLenPresent).To(BeFalse())
			Expect(length).To(Equal(f.Length(version)))
		})

		It("says if it has data", func() {
			streamGetter.EXPECT().GetOrOpenSendStream(id1).Return(stream1, nil).Times(2)
			Expect(framer.HasData()).To(BeFalse())
			framer.AddActiveStream(id1)
			Expect(framer.HasData()).To(BeTrue())
			f1 := &wire.StreamFrame{StreamID: id1, Data: []byte("foo")}
			f2 := &wire.StreamFrame{StreamID: id1, Data: []byte("bar")}
			stream1.EXPECT().popStreamFrame(gomock.Any(), protocol.Version1).Return(ackhandler.StreamFrame{Frame: f1}, true, true)
			stream1.EXPECT().popStreamFrame(gomock.Any(), protocol.Version1).Return(ackhandler.StreamFrame{Frame: f2}, true, false)
			frames, _ := framer.AppendStreamFrames(nil, protocol.MaxByteCount, protocol.Version1)
			Expect(frames).To(HaveLen(1))
			Expect(frames[0].Frame).To(Equal(f1))
			Expect(framer.HasData()).To(BeTrue())
			frames, _ = framer.AppendStreamFrames(nil, protocol.MaxByteCount, protocol.Version1)
			Expect(frames).To(HaveLen(1))
			Expect(frames[0].Frame).To(Equal(f2))
			Expect(framer.HasData()).To(BeFalse())
		})

		It("appends to a frame slice", func() {
			streamGetter.EXPECT().GetOrOpenSendStream(id1).Return(stream1, nil)
			f := &wire.StreamFrame{
				StreamID:       id1,
				Data:           []byte("foobar"),
				DataLenPresent: true,
			}
			stream1.EXPECT().popStreamFrame(gomock.Any(), protocol.Version1).Return(ackhandler.StreamFrame{Frame: f}, true, false)
			framer.AddActiveStream(id1)
			f0 := ackhandler.StreamFrame{Frame: &wire.StreamFrame{StreamID: 9999}}
			frames := []ackhandler.StreamFrame{f0}
			fs, length := framer.AppendStreamFrames(frames, 1000, protocol.Version1)
			Expect(fs).To(HaveLen(2))
			Expect(fs[0]).To(Equal(f0))
			Expect(fs[1].Frame.Data).To(Equal([]byte("foobar")))
			Expect(fs[1].Frame.DataLenPresent).To(BeFalse())
			Expect(length).To(Equal(f.Length(version)))
		})

		It("skips a stream that was reported active, but was completed shortly after", func() {
			streamGetter.EXPECT().GetOrOpenSendStream(id1).Return(nil, nil)
			streamGetter.EXPECT().GetOrOpenSendStream(id2).Return(stream2, nil)
			f := &wire.StreamFrame{
				StreamID:       id2,
				Data:           []byte("foobar"),
				DataLenPresent: true,
			}
			stream2.EXPECT().popStreamFrame(gomock.Any(), protocol.Version1).Return(ackhandler.StreamFrame{Frame: f}, true, false)
			framer.AddActiveStream(id1)
			framer.AddActiveStream(id2)
			frames, _ := framer.AppendStreamFrames(nil, 1000, protocol.Version1)
			Expect(frames).To(HaveLen(1))
			Expect(frames[0].Frame).To(Equal(f))
		})

		It("skips a stream that was reported active, but doesn't have any data", func() {
			streamGetter.EXPECT().GetOrOpenSendStream(id1).Return(stream1, nil)
			streamGetter.EXPECT().GetOrOpenSendStream(id2).Return(stream2, nil)
			f := &wire.StreamFrame{
				StreamID:       id2,
				Data:           []byte("foobar"),
				DataLenPresent: true,
			}
			stream1.EXPECT().popStreamFrame(gomock.Any(), protocol.Version1).Return(ackhandler.StreamFrame{}, false, false)
			stream2.EXPECT().popStreamFrame(gomock.Any(), protocol.Version1).Return(ackhandler.StreamFrame{Frame: f}, true, false)
			framer.AddActiveStream(id1)
			framer.AddActiveStream(id2)
			frames, _ := framer.AppendStreamFrames(nil, 1000, protocol.Version1)
			Expect(frames).To(HaveLen(1))
			Expect(frames[0].Frame).To(Equal(f))
		})

		It("pops from a stream multiple times, if it has enough data", func() {
			streamGetter.EXPECT().GetOrOpenSendStream(id1).Return(stream1, nil).Times(2)
			f1 := &wire.StreamFrame{StreamID: id1, Data: []byte("foobar")}
			f2 := &wire.StreamFrame{StreamID: id1, Data: []byte("foobaz")}
			stream1.EXPECT().popStreamFrame(gomock.Any(), protocol.Version1).Return(ackhandler.StreamFrame{Frame: f1}, true, true)
			stream1.EXPECT().popStreamFrame(gomock.Any(), protocol.Version1).Return(ackhandler.StreamFrame{Frame: f2}, true, false)
			framer.AddActiveStream(id1) // only add it once
			frames, _ := framer.AppendStreamFrames(nil, protocol.MinStreamFrameSize, protocol.Version1)
			Expect(frames).To(HaveLen(1))
			Expect(frames[0].Frame).To(Equal(f1))
			frames, _ = framer.AppendStreamFrames(nil, protocol.MinStreamFrameSize, protocol.Version1)
			Expect(frames).To(HaveLen(1))
			Expect(frames[0].Frame).To(Equal(f2))
			// no further calls to popStreamFrame, after popStreamFrame said there's no more data
			frames, _ = framer.AppendStreamFrames(nil, protocol.MinStreamFrameSize, protocol.Version1)
			Expect(frames).To(BeNil())
		})

		It("re-queues a stream at the end, if it has enough data", func() {
			streamGetter.EXPECT().GetOrOpenSendStream(id1).Return(stream1, nil).Times(2)
			streamGetter.EXPECT().GetOrOpenSendStream(id2).Return(stream2, nil)
			f11 := &wire.StreamFrame{StreamID: id1, Data: []byte("foobar")}
			f12 := &wire.StreamFrame{StreamID: id1, Data: []byte("foobaz")}
			f2 := &wire.StreamFrame{StreamID: id2, Data: []byte("raboof")}
			stream1.EXPECT().popStreamFrame(gomock.Any(), protocol.Version1).Return(ackhandler.StreamFrame{Frame: f11}, true, true)
			stream1.EXPECT().popStreamFrame(gomock.Any(), protocol.Version1).Return(ackhandler.StreamFrame{Frame: f12}, true, false)
			stream2.EXPECT().popStreamFrame(gomock.Any(), protocol.Version1).Return(ackhandler.StreamFrame{Frame: f2}, true, false)
			framer.AddActiveStream(id1) // only add it once
			framer.AddActiveStream(id2)
			// first a frame from stream 1
			frames, _ := framer.AppendStreamFrames(nil, protocol.MinStreamFrameSize, protocol.Version1)
			Expect(frames).To(HaveLen(1))
			Expect(frames[0].Frame).To(Equal(f11))
			// then a frame from stream 2
			frames, _ = framer.AppendStreamFrames(nil, protocol.MinStreamFrameSize, protocol.Version1)
			Expect(frames).To(HaveLen(1))
			Expect(frames[0].Frame).To(Equal(f2))
			// then another frame from stream 1
			frames, _ = framer.AppendStreamFrames(nil, protocol.MinStreamFrameSize, protocol.Version1)
			Expect(frames).To(HaveLen(1))
			Expect(frames[0].Frame).To(Equal(f12))
		})

		It("only dequeues data from each stream once per packet", func() {
			streamGetter.EXPECT().GetOrOpenSendStream(id1).Return(stream1, nil)
			streamGetter.EXPECT().GetOrOpenSendStream(id2).Return(stream2, nil)
			f1 := &wire.StreamFrame{StreamID: id1, Data: []byte("foobar")}
			f2 := &wire.StreamFrame{StreamID: id2, Data: []byte("raboof")}
			// both streams have more data, and will be re-queued
			stream1.EXPECT().popStreamFrame(gomock.Any(), protocol.Version1).Return(ackhandler.StreamFrame{Frame: f1}, true, true)
			stream2.EXPECT().popStreamFrame(gomock.Any(), protocol.Version1).Return(ackhandler.StreamFrame{Frame: f2}, true, true)
			framer.AddActiveStream(id1)
			framer.AddActiveStream(id2)
			frames, length := framer.AppendStreamFrames(nil, 1000, protocol.Version1)
			Expect(frames).To(HaveLen(2))
			Expect(frames[0].Frame).To(Equal(f1))
			Expect(frames[1].Frame).To(Equal(f2))
			Expect(length).To(Equal(f1.Length(version) + f2.Length(version)))
		})

		It("returns multiple normal frames in the order they were reported active", func() {
			streamGetter.EXPECT().GetOrOpenSendStream(id1).Return(stream1, nil)
			streamGetter.EXPECT().GetOrOpenSendStream(id2).Return(stream2, nil)
			f1 := &wire.StreamFrame{Data: []byte("foobar")}
			f2 := &wire.StreamFrame{Data: []byte("foobaz")}
			stream1.EXPECT().popStreamFrame(gomock.Any(), protocol.Version1).Return(ackhandler.StreamFrame{Frame: f1}, true, false)
			stream2.EXPECT().popStreamFrame(gomock.Any(), protocol.Version1).Return(ackhandler.StreamFrame{Frame: f2}, true, false)
			framer.AddActiveStream(id2)
			framer.AddActiveStream(id1)
			frames, _ := framer.AppendStreamFrames(nil, 1000, protocol.Version1)
			Expect(frames).To(HaveLen(2))
			Expect(frames[0].Frame).To(Equal(f2))
			Expect(frames[1].Frame).To(Equal(f1))
		})

		It("only asks a stream for data once, even if it was reported active multiple times", func() {
			streamGetter.EXPECT().GetOrOpenSendStream(id1).Return(stream1, nil)
			f := &wire.StreamFrame{Data: []byte("foobar")}
			stream1.EXPECT().popStreamFrame(gomock.Any(), protocol.Version1).Return(ackhandler.StreamFrame{Frame: f}, true, false) // only one call to this function
			framer.AddActiveStream(id1)
			framer.AddActiveStream(id1)
			frames, _ := framer.AppendStreamFrames(nil, 1000, protocol.Version1)
			Expect(frames).To(HaveLen(1))
		})

		It("does not pop empty frames", func() {
			fs, length := framer.AppendStreamFrames(nil, 500, protocol.Version1)
			Expect(fs).To(BeEmpty())
			Expect(length).To(BeZero())
		})

		It("pops maximum size STREAM frames", func() {
			for i := protocol.MinStreamFrameSize; i < 2000; i++ {
				streamGetter.EXPECT().GetOrOpenSendStream(id1).Return(stream1, nil)
				stream1.EXPECT().popStreamFrame(gomock.Any(), protocol.Version1).DoAndReturn(func(size protocol.ByteCount, v protocol.Version) (ackhandler.StreamFrame, bool, bool) {
					f := &wire.StreamFrame{
						StreamID:       id1,
						DataLenPresent: true,
					}
					f.Data = make([]byte, f.MaxDataLen(size, v))
					Expect(f.Length(version)).To(Equal(size))
					return ackhandler.StreamFrame{Frame: f}, true, false
				})
				framer.AddActiveStream(id1)
				frames, _ := framer.AppendStreamFrames(nil, i, protocol.Version1)
				Expect(frames).To(HaveLen(1))
				f := frames[0].Frame
				Expect(f.DataLenPresent).To(BeFalse())
				Expect(f.Length(version)).To(Equal(i))
			}
		})

		It("pops multiple STREAM frames", func() {
			for i := 2 * protocol.MinStreamFrameSize; i < 2000; i++ {
				streamGetter.EXPECT().GetOrOpenSendStream(id1).Return(stream1, nil)
				streamGetter.EXPECT().GetOrOpenSendStream(id2).Return(stream2, nil)
				stream1.EXPECT().popStreamFrame(gomock.Any(), protocol.Version1).DoAndReturn(func(size protocol.ByteCount, v protocol.Version) (ackhandler.StreamFrame, bool, bool) {
					f := &wire.StreamFrame{
						StreamID:       id2,
						DataLenPresent: true,
					}
					f.Data = make([]byte, f.MaxDataLen(protocol.MinStreamFrameSize, v))
					return ackhandler.StreamFrame{Frame: f}, true, false
				})
				stream2.EXPECT().popStreamFrame(gomock.Any(), protocol.Version1).DoAndReturn(func(size protocol.ByteCount, v protocol.Version) (ackhandler.StreamFrame, bool, bool) {
					f := &wire.StreamFrame{
						StreamID:       id2,
						DataLenPresent: true,
					}
					f.Data = make([]byte, f.MaxDataLen(size, v))
					Expect(f.Length(version)).To(Equal(size))
					return ackhandler.StreamFrame{Frame: f}, true, false
				})
				framer.AddActiveStream(id1)
				framer.AddActiveStream(id2)
				frames, _ := framer.AppendStreamFrames(nil, i, protocol.Version1)
				Expect(frames).To(HaveLen(2))
				f1 := frames[0].Frame
				f2 := frames[1].Frame
				Expect(f1.DataLenPresent).To(BeTrue())
				Expect(f2.DataLenPresent).To(BeFalse())
				Expect(f1.Length(version) + f2.Length(version)).To(Equal(i))
			}
		})

		It("pops frames that when asked for the the minimum STREAM frame size", func() {
			streamGetter.EXPECT().GetOrOpenSendStream(id1).Return(stream1, nil)
			f := &wire.StreamFrame{Data: []byte("foobar")}
			stream1.EXPECT().popStreamFrame(gomock.Any(), protocol.Version1).Return(ackhandler.StreamFrame{Frame: f}, true, false)
			framer.AddActiveStream(id1)
			framer.AppendStreamFrames(nil, protocol.MinStreamFrameSize, protocol.Version1)
		})

		It("does not pop frames smaller than the minimum size", func() {
			// don't expect a call to PopStreamFrame()
			framer.AppendStreamFrames(nil, protocol.MinStreamFrameSize-1, protocol.Version1)
		})

		It("stops iterating when the remaining size is smaller than the minimum STREAM frame size", func() {
			streamGetter.EXPECT().GetOrOpenSendStream(id1).Return(stream1, nil)
			// pop a frame such that the remaining size is one byte less than the minimum STREAM frame size
			f := &wire.StreamFrame{
				StreamID:       id1,
				Data:           bytes.Repeat([]byte("f"), int(500-protocol.MinStreamFrameSize)),
				DataLenPresent: true,
			}
			stream1.EXPECT().popStreamFrame(gomock.Any(), protocol.Version1).Return(ackhandler.StreamFrame{Frame: f}, true, false)
			framer.AddActiveStream(id1)
			fs, length := framer.AppendStreamFrames(nil, 500, protocol.Version1)
			Expect(fs).To(HaveLen(1))
			Expect(fs[0].Frame).To(Equal(f))
			Expect(length).To(Equal(f.Length(version)))
		})

		It("drops all STREAM frames when 0-RTT is rejected", func() {
			framer.AddActiveStream(id1)
			Expect(framer.Handle0RTTRejection()).To(Succeed())
			fs, length := framer.AppendStreamFrames(nil, protocol.MaxByteCount, protocol.Version1)
			Expect(fs).To(BeEmpty())
			Expect(length).To(BeZero())
		})
	})
})