package flowcontrol

import (
	"time"

	"github.com/lucas-clemente/quic-go/congestion"
	"github.com/lucas-clemente/quic-go/handshake"
	"github.com/lucas-clemente/quic-go/protocol"
	. "github.com/onsi/ginkgo"
	. "github.com/onsi/gomega"
)

type mockConnectionParametersManager struct {
	sendStreamFlowControlWindow        protocol.ByteCount
	sendConnectionFlowControlWindow    protocol.ByteCount
	receiveStreamFlowControlWindow     protocol.ByteCount
	receiveConnectionFlowControlWindow protocol.ByteCount
}

func (m *mockConnectionParametersManager) SetFromMap(map[handshake.Tag][]byte) error {
	panic("not implemented")
}
func (m *mockConnectionParametersManager) GetSHLOMap() (map[handshake.Tag][]byte, error) {
	panic("not implemented")
}
func (m *mockConnectionParametersManager) GetCHLOMap() (map[handshake.Tag][]byte, error) {
	panic("not implemented")
}
func (m *mockConnectionParametersManager) GetSendStreamFlowControlWindow() protocol.ByteCount {
	return m.sendStreamFlowControlWindow
}
func (m *mockConnectionParametersManager) GetSendConnectionFlowControlWindow() protocol.ByteCount {
	return m.sendConnectionFlowControlWindow
}
func (m *mockConnectionParametersManager) GetReceiveStreamFlowControlWindow() protocol.ByteCount {
	return m.receiveStreamFlowControlWindow
}
func (m *mockConnectionParametersManager) GetReceiveConnectionFlowControlWindow() protocol.ByteCount {
	return m.receiveConnectionFlowControlWindow
}
func (m *mockConnectionParametersManager) GetMaxOutgoingStreams() uint32 { panic("not implemented") }
func (m *mockConnectionParametersManager) GetMaxIncomingStreams() uint32 { panic("not implemented") }
func (m *mockConnectionParametersManager) GetIdleConnectionStateLifetime() time.Duration {
	panic("not implemented")
}
func (m *mockConnectionParametersManager) TruncateConnectionID() bool { panic("not implemented") }

var _ handshake.ConnectionParametersManager = &mockConnectionParametersManager{}

var _ = Describe("Flow controller", func() {
	var controller *flowController

	BeforeEach(func() {
		controller = &flowController{}
		controller.rttStats = &congestion.RTTStats{}
	})

	Context("Constructor", func() {
		var cpm *mockConnectionParametersManager
		var rttStats *congestion.RTTStats

		BeforeEach(func() {
			cpm = &mockConnectionParametersManager{
				sendStreamFlowControlWindow:        1000,
				receiveStreamFlowControlWindow:     2000,
				sendConnectionFlowControlWindow:    3000,
				receiveConnectionFlowControlWindow: 4000,
			}
			rttStats = &congestion.RTTStats{}
		})

		It("reads the stream send and receive windows when acting as stream-level flow controller", func() {
			fc := newFlowController(5, cpm, rttStats)
			Expect(fc.streamID).To(Equal(protocol.StreamID(5)))
			Expect(fc.receiveFlowControlWindow).To(Equal(protocol.ByteCount(2000)))
			Expect(fc.maxReceiveFlowControlWindowIncrement).To(Equal(protocol.MaxReceiveStreamFlowControlWindow))
		})

		It("reads the stream send and receive windows when acting as connection-level flow controller", func() {
			fc := newFlowController(0, cpm, rttStats)
			Expect(fc.streamID).To(Equal(protocol.StreamID(0)))
			Expect(fc.receiveFlowControlWindow).To(Equal(protocol.ByteCount(4000)))
			Expect(fc.maxReceiveFlowControlWindowIncrement).To(Equal(protocol.MaxReceiveConnectionFlowControlWindow))
		})

		It("does not set the stream flow control windows for sending", func() {
			fc := newFlowController(5, cpm, rttStats)
			Expect(fc.sendFlowControlWindow).To(BeZero())
		})

		It("does not set the connection flow control windows for sending", func() {
			fc := newFlowController(0, cpm, rttStats)
			Expect(fc.sendFlowControlWindow).To(BeZero())
		})
	})

	Context("send flow control", func() {
		var cpm *mockConnectionParametersManager

		BeforeEach(func() {
			cpm = &mockConnectionParametersManager{
				sendStreamFlowControlWindow:     1000,
				sendConnectionFlowControlWindow: 3000,
			}
			controller.connectionParameters = cpm
		})

		It("adds bytes sent", func() {
			controller.bytesSent = 5
			controller.AddBytesSent(6)
			Expect(controller.bytesSent).To(Equal(protocol.ByteCount(5 + 6)))
		})

		It("gets the bytesSent", func() {
			controller.bytesSent = 8
			Expect(controller.GetBytesSent()).To(Equal(protocol.ByteCount(8)))
		})

		It("gets the size of the remaining flow control window", func() {
			controller.bytesSent = 5
			controller.sendFlowControlWindow = 12
			Expect(controller.SendWindowSize()).To(Equal(protocol.ByteCount(12 - 5)))
		})

		It("gets the offset of the flow control window", func() {
			controller.bytesSent = 5
			controller.sendFlowControlWindow = 12
			Expect(controller.SendWindowOffset()).To(Equal(protocol.ByteCount(12)))
		})

		It("updates the size of the flow control window", func() {
			controller.bytesSent = 5
			updateSuccessful := controller.UpdateSendWindow(15)
			Expect(updateSuccessful).To(BeTrue())
			Expect(controller.SendWindowOffset()).To(Equal(protocol.ByteCount(15)))
			Expect(controller.SendWindowSize()).To(Equal(protocol.ByteCount(15 - 5)))
		})

		It("does not decrease the flow control window", func() {
			updateSuccessful := controller.UpdateSendWindow(20)
			Expect(updateSuccessful).To(BeTrue())
			Expect(controller.SendWindowSize()).To(Equal(protocol.ByteCount(20)))
			updateSuccessful = controller.UpdateSendWindow(10)
			Expect(updateSuccessful).To(BeFalse())
			Expect(controller.SendWindowSize()).To(Equal(protocol.ByteCount(20)))
		})

		It("asks the ConnectionParametersManager for the stream flow control window size", func() {
			controller.streamID = 5
			Expect(controller.getSendFlowControlWindow()).To(Equal(protocol.ByteCount(1000)))
			// make sure the value is not cached
			cpm.sendStreamFlowControlWindow = 2000
			Expect(controller.getSendFlowControlWindow()).To(Equal(protocol.ByteCount(2000)))
		})

		It("stops asking the ConnectionParametersManager for the flow control stream window size once a window update has arrived", func() {
			controller.streamID = 5
			Expect(controller.UpdateSendWindow(8000))
			cpm.sendStreamFlowControlWindow = 9000
			Expect(controller.getSendFlowControlWindow()).To(Equal(protocol.ByteCount(8000)))
		})

		It("asks the ConnectionParametersManager for the connection flow control window size", func() {
			controller.streamID = 0
			Expect(controller.getSendFlowControlWindow()).To(Equal(protocol.ByteCount(3000)))
			// make sure the value is not cached
			cpm.sendConnectionFlowControlWindow = 5000
			Expect(controller.getSendFlowControlWindow()).To(Equal(protocol.ByteCount(5000)))
		})

		It("stops asking the ConnectionParametersManager for the connection flow control window size once a window update has arrived", func() {
			controller.streamID = 0
			Expect(controller.UpdateSendWindow(7000))
			cpm.sendConnectionFlowControlWindow = 9000
			Expect(controller.getSendFlowControlWindow()).To(Equal(protocol.ByteCount(7000)))
		})
	})

	Context("receive flow control", func() {
		var receiveFlowControlWindow protocol.ByteCount = 10000
		var receiveFlowControlWindowIncrement protocol.ByteCount = 600

		BeforeEach(func() {
			controller.receiveFlowControlWindow = receiveFlowControlWindow
			controller.receiveFlowControlWindowIncrement = receiveFlowControlWindowIncrement
		})

		It("adds bytes read", func() {
			controller.bytesRead = 5
			controller.AddBytesRead(6)
			Expect(controller.bytesRead).To(Equal(protocol.ByteCount(5 + 6)))
		})

		It("triggers a window update when necessary", func() {
			controller.lastWindowUpdateTime = time.Now().Add(-time.Hour)
			readPosition := receiveFlowControlWindow - receiveFlowControlWindowIncrement/2 + 1
			controller.bytesRead = readPosition
			updateNecessary, offset := controller.MaybeTriggerWindowUpdate()
			Expect(updateNecessary).To(BeTrue())
			Expect(offset).To(Equal(readPosition + receiveFlowControlWindowIncrement))
			Expect(controller.receiveFlowControlWindow).To(Equal(readPosition + receiveFlowControlWindowIncrement))
			Expect(controller.lastWindowUpdateTime).To(BeTemporally("~", time.Now(), 5*time.Millisecond))
		})

		It("doesn't trigger a window update when not necessary", func() {
			lastWindowUpdateTime := time.Now().Add(-time.Hour)
			controller.lastWindowUpdateTime = lastWindowUpdateTime
			readPosition := receiveFlowControlWindow - receiveFlowControlWindow/2 - 1
			controller.bytesRead = readPosition
			updateNecessary, _ := controller.MaybeTriggerWindowUpdate()
			Expect(updateNecessary).To(BeFalse())
			Expect(controller.lastWindowUpdateTime).To(Equal(lastWindowUpdateTime))
		})

		It("updates the highestReceived", func() {
			controller.highestReceived = 1337
			increment, err := controller.UpdateHighestReceived(1338)
			Expect(err).ToNot(HaveOccurred())
			Expect(increment).To(Equal(protocol.ByteCount(1338 - 1337)))
			Expect(controller.highestReceived).To(Equal(protocol.ByteCount(1338)))
		})

		It("does not decrease the highestReceived", func() {
			controller.highestReceived = 1337
			increment, err := controller.UpdateHighestReceived(1000)
			Expect(err).To(MatchError(ErrReceivedSmallerByteOffset))
			Expect(increment).To(BeZero())
			Expect(controller.highestReceived).To(Equal(protocol.ByteCount(1337)))
		})

		It("does not error when setting the same byte offset", func() {
			controller.highestReceived = 1337
			increment, err := controller.UpdateHighestReceived(1337)
			Expect(err).ToNot(HaveOccurred())
			Expect(increment).To(BeZero())
		})

		It("increases the highestReceived by a given increment", func() {
			controller.highestReceived = 1337
			controller.IncrementHighestReceived(123)
			Expect(controller.highestReceived).To(Equal(protocol.ByteCount(1337 + 123)))
		})

		It("detects a flow control violation", func() {
			controller.UpdateHighestReceived(receiveFlowControlWindow + 1)
			Expect(controller.CheckFlowControlViolation()).To(BeTrue())
		})

		It("does not give a flow control violation when using the window completely", func() {
			controller.UpdateHighestReceived(receiveFlowControlWindow)
			Expect(controller.CheckFlowControlViolation()).To(BeFalse())
		})

		Context("receive window increment auto-tuning", func() {
			var oldIncrement protocol.ByteCount

			BeforeEach(func() {
				oldIncrement = controller.receiveFlowControlWindowIncrement
				controller.maxReceiveFlowControlWindowIncrement = 3000
			})

			// update the congestion such that it returns a given value for the smoothed RTT
			setRtt := func(t time.Duration) {
				controller.rttStats.UpdateRTT(t, 0, time.Now())
				Expect(controller.rttStats.SmoothedRTT()).To(Equal(t)) // make sure it worked
			}

			It("doesn't increase the increment for a new stream", func() {
				controller.maybeAdjustWindowIncrement()
				Expect(controller.receiveFlowControlWindowIncrement).To(Equal(oldIncrement))
			})

			It("doesn't increase the increment when no RTT estimate is available", func() {
				setRtt(0)
				controller.lastWindowUpdateTime = time.Now()
				controller.maybeAdjustWindowIncrement()
				Expect(controller.receiveFlowControlWindowIncrement).To(Equal(oldIncrement))
			})

			It("increases the increment when the last WindowUpdate was sent less than two RTTs ago", func() {
				setRtt(10 * time.Millisecond)
				controller.lastWindowUpdateTime = time.Now().Add(-19 * time.Millisecond)
				controller.maybeAdjustWindowIncrement()
				Expect(controller.receiveFlowControlWindowIncrement).To(Equal(2 * oldIncrement))
			})

			It("doesn't increase the increase increment when the last WindowUpdate was sent more than two RTTs ago", func() {
				setRtt(10 * time.Millisecond)
				controller.lastWindowUpdateTime = time.Now().Add(-21 * time.Millisecond)
				controller.maybeAdjustWindowIncrement()
				Expect(controller.receiveFlowControlWindowIncrement).To(Equal(oldIncrement))
			})

			It("doesn't increase the increment to a value higher than the maxReceiveFlowControlWindowIncrement", func() {
				setRtt(10 * time.Millisecond)
				controller.lastWindowUpdateTime = time.Now().Add(-19 * time.Millisecond)
				controller.maybeAdjustWindowIncrement()
				Expect(controller.receiveFlowControlWindowIncrement).To(Equal(2 * oldIncrement)) // 1200
				// because the lastWindowUpdateTime is updated by MaybeTriggerWindowUpdate(), we can just call maybeAdjustWindowIncrement() multiple times and get an increase of the increment every time
				controller.maybeAdjustWindowIncrement()
				Expect(controller.receiveFlowControlWindowIncrement).To(Equal(2 * 2 * oldIncrement)) // 2400
				controller.maybeAdjustWindowIncrement()
				Expect(controller.receiveFlowControlWindowIncrement).To(Equal(controller.maxReceiveFlowControlWindowIncrement)) // 3000
				controller.maybeAdjustWindowIncrement()
				Expect(controller.receiveFlowControlWindowIncrement).To(Equal(controller.maxReceiveFlowControlWindowIncrement)) // 3000
			})
		})
	})
})