package ackhandler

import (
	"time"

	"github.com/lucas-clemente/quic-go/frames"
	"github.com/lucas-clemente/quic-go/protocol"

	. "github.com/onsi/ginkgo"
	. "github.com/onsi/gomega"
)

var _ = Describe("receivedPacketHandler", func() {
	var (
		handler *receivedPacketHandler
	)

	BeforeEach(func() {
		handler = NewReceivedPacketHandler().(*receivedPacketHandler)
	})

	Context("accepting packets", func() {
		It("handles a packet that arrives late", func() {
			err := handler.ReceivedPacket(protocol.PacketNumber(1))
			Expect(err).ToNot(HaveOccurred())
			err = handler.ReceivedPacket(protocol.PacketNumber(3))
			Expect(err).ToNot(HaveOccurred())
			err = handler.ReceivedPacket(protocol.PacketNumber(2))
			Expect(err).ToNot(HaveOccurred())
		})

		It("rejects packets with packet number 0", func() {
			err := handler.ReceivedPacket(protocol.PacketNumber(0))
			Expect(err).To(MatchError(errInvalidPacketNumber))
		})

		It("rejects a duplicate package", func() {
			for i := 1; i < 5; i++ {
				err := handler.ReceivedPacket(protocol.PacketNumber(i))
				Expect(err).ToNot(HaveOccurred())
			}
			err := handler.ReceivedPacket(4)
			Expect(err).To(MatchError(ErrDuplicatePacket))
		})

		It("ignores a packet with PacketNumber less than the LeastUnacked of a previously received StopWaiting", func() {
			err := handler.ReceivedPacket(5)
			Expect(err).ToNot(HaveOccurred())
			err = handler.ReceivedStopWaiting(&frames.StopWaitingFrame{LeastUnacked: 10})
			Expect(err).ToNot(HaveOccurred())
			err = handler.ReceivedPacket(9)
			Expect(err).To(MatchError(ErrPacketSmallerThanLastStopWaiting))
		})

		It("does not ignore a packet with PacketNumber equal to LeastUnacked of a previously received StopWaiting", func() {
			err := handler.ReceivedPacket(5)
			Expect(err).ToNot(HaveOccurred())
			err = handler.ReceivedStopWaiting(&frames.StopWaitingFrame{LeastUnacked: 10})
			Expect(err).ToNot(HaveOccurred())
			err = handler.ReceivedPacket(10)
			Expect(err).ToNot(HaveOccurred())
		})

		It("saves the time when each packet arrived", func() {
			err := handler.ReceivedPacket(protocol.PacketNumber(3))
			Expect(err).ToNot(HaveOccurred())
			Expect(handler.largestObservedReceivedTime).To(BeTemporally("~", time.Now(), 10*time.Millisecond))
		})

		It("updates the largestObserved and the largestObservedReceivedTime", func() {
			handler.largestObserved = 3
			handler.largestObservedReceivedTime = time.Now().Add(-1 * time.Second)
			err := handler.ReceivedPacket(5)
			Expect(err).ToNot(HaveOccurred())
			Expect(handler.largestObserved).To(Equal(protocol.PacketNumber(5)))
			Expect(handler.largestObservedReceivedTime).To(BeTemporally("~", time.Now(), 10*time.Millisecond))
		})

		It("doesn't update the largestObserved and the largestObservedReceivedTime for a belated packet", func() {
			timestamp := time.Now().Add(-1 * time.Second)
			handler.largestObserved = 5
			handler.largestObservedReceivedTime = timestamp
			err := handler.ReceivedPacket(4)
			Expect(err).ToNot(HaveOccurred())
			Expect(handler.largestObserved).To(Equal(protocol.PacketNumber(5)))
			Expect(handler.largestObservedReceivedTime).To(Equal(timestamp))
		})

		It("doesn't store more than MaxTrackedReceivedPackets packets", func() {
			err := handler.ReceivedPacket(1)
			Expect(err).ToNot(HaveOccurred())
			for i := protocol.PacketNumber(3); i < 3+protocol.MaxTrackedReceivedPackets-1; i++ {
				err := handler.ReceivedPacket(protocol.PacketNumber(i))
				Expect(err).ToNot(HaveOccurred())
			}
			err = handler.ReceivedPacket(protocol.PacketNumber(protocol.MaxTrackedReceivedPackets) + 10)
			Expect(err).To(MatchError(errTooManyOutstandingReceivedPackets))
		})

		It("passes on errors from receivedPacketHistory", func() {
			var err error
			for i := protocol.PacketNumber(0); i < 5*protocol.MaxTrackedReceivedAckRanges; i++ {
				err = handler.ReceivedPacket(2*i + 1)
				// this will eventually return an error
				// details about when exactly the receivedPacketHistory errors are tested there
				if err != nil {
					break
				}
			}
			Expect(err).To(MatchError(errTooManyOutstandingReceivedAckRanges))
		})
	})

	Context("handling STOP_WAITING frames", func() {
		It("increases the ignorePacketsBelow number", func() {
			err := handler.ReceivedStopWaiting(&frames.StopWaitingFrame{LeastUnacked: protocol.PacketNumber(12)})
			Expect(err).ToNot(HaveOccurred())
			Expect(handler.ignorePacketsBelow).To(Equal(protocol.PacketNumber(11)))
		})

		It("increase the ignorePacketsBelow number, even if all packets below the LeastUnacked were already acked", func() {
			for i := 1; i < 20; i++ {
				err := handler.ReceivedPacket(protocol.PacketNumber(i))
				Expect(err).ToNot(HaveOccurred())
			}
			err := handler.ReceivedStopWaiting(&frames.StopWaitingFrame{LeastUnacked: protocol.PacketNumber(12)})
			Expect(err).ToNot(HaveOccurred())
			Expect(handler.ignorePacketsBelow).To(Equal(protocol.PacketNumber(11)))
		})

		It("does not decrease the ignorePacketsBelow number when an out-of-order StopWaiting arrives", func() {
			err := handler.ReceivedStopWaiting(&frames.StopWaitingFrame{LeastUnacked: protocol.PacketNumber(12)})
			Expect(err).ToNot(HaveOccurred())
			Expect(handler.ignorePacketsBelow).To(Equal(protocol.PacketNumber(11)))
			err = handler.ReceivedStopWaiting(&frames.StopWaitingFrame{LeastUnacked: protocol.PacketNumber(6)})
			Expect(err).ToNot(HaveOccurred())
			Expect(handler.ignorePacketsBelow).To(Equal(protocol.PacketNumber(11)))
		})
	})

	Context("ACK package generation", func() {
		It("generates a simple ACK frame", func() {
			err := handler.ReceivedPacket(protocol.PacketNumber(1))
			Expect(err).ToNot(HaveOccurred())
			err = handler.ReceivedPacket(protocol.PacketNumber(2))
			Expect(err).ToNot(HaveOccurred())
			ack, err := handler.GetAckFrame(true)
			Expect(err).ToNot(HaveOccurred())
			Expect(ack.LargestAcked).To(Equal(protocol.PacketNumber(2)))
			Expect(ack.LowestAcked).To(Equal(protocol.PacketNumber(1)))
			Expect(ack.AckRanges).To(BeEmpty())
		})

		It("generates an ACK frame with missing packets", func() {
			err := handler.ReceivedPacket(protocol.PacketNumber(1))
			Expect(err).ToNot(HaveOccurred())
			err = handler.ReceivedPacket(protocol.PacketNumber(4))
			Expect(err).ToNot(HaveOccurred())
			ack, err := handler.GetAckFrame(true)
			Expect(err).ToNot(HaveOccurred())
			Expect(ack.LargestAcked).To(Equal(protocol.PacketNumber(4)))
			Expect(ack.LowestAcked).To(Equal(protocol.PacketNumber(1)))
			Expect(ack.AckRanges).To(HaveLen(2))
			Expect(ack.AckRanges[0]).To(Equal(frames.AckRange{FirstPacketNumber: 4, LastPacketNumber: 4}))
			Expect(ack.AckRanges[1]).To(Equal(frames.AckRange{FirstPacketNumber: 1, LastPacketNumber: 1}))
		})

		It("does not generate an ACK if an ACK has already been sent for the largest Packet", func() {
			err := handler.ReceivedPacket(protocol.PacketNumber(1))
			Expect(err).ToNot(HaveOccurred())
			err = handler.ReceivedPacket(protocol.PacketNumber(2))
			Expect(err).ToNot(HaveOccurred())
			ack, err := handler.GetAckFrame(true)
			Expect(err).ToNot(HaveOccurred())
			Expect(ack).ToNot(BeNil())
			ack, err = handler.GetAckFrame(true)
			Expect(err).ToNot(HaveOccurred())
			Expect(ack).To(BeNil())
		})

		It("does not dequeue an ACK frame if told so", func() {
			err := handler.ReceivedPacket(protocol.PacketNumber(2))
			Expect(err).ToNot(HaveOccurred())
			ack, err := handler.GetAckFrame(false)
			Expect(err).ToNot(HaveOccurred())
			Expect(ack).ToNot(BeNil())
			ack, err = handler.GetAckFrame(false)
			Expect(err).ToNot(HaveOccurred())
			Expect(ack).ToNot(BeNil())
			ack, err = handler.GetAckFrame(false)
			Expect(err).ToNot(HaveOccurred())
			Expect(ack).ToNot(BeNil())
		})

		It("returns a cached ACK frame if the ACK was not dequeued", func() {
			err := handler.ReceivedPacket(protocol.PacketNumber(2))
			Expect(err).ToNot(HaveOccurred())
			ack, err := handler.GetAckFrame(false)
			Expect(err).ToNot(HaveOccurred())
			Expect(ack).ToNot(BeNil())
			ack2, err := handler.GetAckFrame(false)
			Expect(err).ToNot(HaveOccurred())
			Expect(ack2).ToNot(BeNil())
			Expect(&ack).To(Equal(&ack2))
		})

		It("generates a new ACK (and deletes the cached one) when a new packet arrives", func() {
			err := handler.ReceivedPacket(protocol.PacketNumber(1))
			Expect(err).ToNot(HaveOccurred())
			ack, _ := handler.GetAckFrame(true)
			Expect(ack).ToNot(BeNil())
			Expect(ack.LargestAcked).To(Equal(protocol.PacketNumber(1)))
			err = handler.ReceivedPacket(protocol.PacketNumber(3))
			Expect(err).ToNot(HaveOccurred())
			ack, _ = handler.GetAckFrame(true)
			Expect(ack).ToNot(BeNil())
			Expect(ack.LargestAcked).To(Equal(protocol.PacketNumber(3)))
		})

		It("generates a new ACK when an out-of-order packet arrives", func() {
			err := handler.ReceivedPacket(protocol.PacketNumber(1))
			Expect(err).ToNot(HaveOccurred())
			err = handler.ReceivedPacket(protocol.PacketNumber(3))
			Expect(err).ToNot(HaveOccurred())
			ack, _ := handler.GetAckFrame(true)
			Expect(ack).ToNot(BeNil())
			Expect(ack.AckRanges).To(HaveLen(2))
			err = handler.ReceivedPacket(protocol.PacketNumber(2))
			Expect(err).ToNot(HaveOccurred())
			ack, _ = handler.GetAckFrame(true)
			Expect(ack).ToNot(BeNil())
			Expect(ack.AckRanges).To(BeEmpty())
		})

		It("doesn't send old ACK ranges after receiving a StopWaiting", func() {
			err := handler.ReceivedPacket(5)
			Expect(err).ToNot(HaveOccurred())
			err = handler.ReceivedPacket(10)
			Expect(err).ToNot(HaveOccurred())
			err = handler.ReceivedPacket(11)
			Expect(err).ToNot(HaveOccurred())
			err = handler.ReceivedPacket(12)
			Expect(err).ToNot(HaveOccurred())
			err = handler.ReceivedStopWaiting(&frames.StopWaitingFrame{LeastUnacked: protocol.PacketNumber(11)})
			Expect(err).ToNot(HaveOccurred())
			ack, err := handler.GetAckFrame(true)
			Expect(err).ToNot(HaveOccurred())
			Expect(ack).ToNot(BeNil())
			Expect(ack.LargestAcked).To(Equal(protocol.PacketNumber(12)))
			Expect(ack.LowestAcked).To(Equal(protocol.PacketNumber(11)))
			Expect(ack.HasMissingRanges()).To(BeFalse())
		})

		It("deletes packets from the packetHistory after receiving a StopWaiting, after continuously received packets", func() {
			for i := 1; i <= 12; i++ {
				err := handler.ReceivedPacket(protocol.PacketNumber(i))
				Expect(err).ToNot(HaveOccurred())
			}
			err := handler.ReceivedStopWaiting(&frames.StopWaitingFrame{LeastUnacked: protocol.PacketNumber(6)})
			Expect(err).ToNot(HaveOccurred())
			// check that the packets were deleted from the receivedPacketHistory by checking the values in an ACK frame
			ack, err := handler.GetAckFrame(true)
			Expect(err).ToNot(HaveOccurred())
			Expect(ack).ToNot(BeNil())
			Expect(ack.LargestAcked).To(Equal(protocol.PacketNumber(12)))
			Expect(ack.LowestAcked).To(Equal(protocol.PacketNumber(6)))
			Expect(ack.HasMissingRanges()).To(BeFalse())
		})
	})
})