package frames

import (
	"bytes"

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

var _ = Describe("StopWaitingFrame", func() {
	Context("stop waiting frames", func() {
		Context("when parsing", func() {
			It("accepts sample frame", func() {
				b := bytes.NewReader([]byte{0x06, 0xA4, 0x03})
				frame, err := ParseStopWaitingFrame(b, 5, 1)
				Expect(err).ToNot(HaveOccurred())
				Expect(frame.Entropy).To(Equal(byte(0xA4)))
				Expect(frame.LeastUnacked).To(Equal(protocol.PacketNumber(2)))
			})

			It("rejects frames with an invalid LeastUnackedDelta", func() {
				b := bytes.NewReader([]byte{0x06, 0xA4, 0xD})
				_, err := ParseStopWaitingFrame(b, 10, 1)
				Expect(err).To(HaveOccurred())
			})
		})

		Context("when writing", func() {
			It("writes a sample frame", func() {
				b := &bytes.Buffer{}
				packetNumber := protocol.PacketNumber(13)
				frame := &StopWaitingFrame{
					LeastUnacked:    10,
					Entropy:         0xAD,
					PacketNumberLen: protocol.PacketNumberLen6,
				}
				frame.Write(b, packetNumber, 0)
				Expect(b.Bytes()[0]).To(Equal(uint8(0x06)))
				Expect(b.Bytes()[1]).To(Equal(uint8(frame.Entropy)))
				Expect(b.Bytes()[2:8]).To(Equal([]byte{3, 0, 0, 0, 0, 0}))
			})

			It("errors when PacketNumberLen was not set", func() {
				b := &bytes.Buffer{}
				frame := &StopWaitingFrame{
					LeastUnacked: 10,
					Entropy:      0xAD,
				}
				err := frame.Write(b, 13, 0)
				Expect(err).To(HaveOccurred())
				Expect(err).To(Equal(errPacketNumberLenNotSet))
			})

			It("errors when the LeastUnackedDelta would be negative", func() {
				b := &bytes.Buffer{}
				frame := &StopWaitingFrame{
					LeastUnacked:    10,
					PacketNumberLen: protocol.PacketNumberLen1,
				}
				err := frame.Write(b, 5, 0)
				Expect(err).To(HaveOccurred())
				Expect(err).To(Equal(errLeastUnackedHigherThanPacketNumber))
			})

			Context("LeastUnackedDelta length", func() {
				It("writes a 1-byte LeastUnackedDelta", func() {
					b := &bytes.Buffer{}
					frame := &StopWaitingFrame{
						LeastUnacked:    10,
						PacketNumberLen: protocol.PacketNumberLen1,
					}
					frame.Write(b, 13, 0)
					Expect(b.Len()).To(Equal(3))
					Expect(b.Bytes()[2]).To(Equal(uint8(3)))
				})

				It("writes a 2-byte LeastUnackedDelta", func() {
					b := &bytes.Buffer{}
					frame := &StopWaitingFrame{
						LeastUnacked:    0x10,
						PacketNumberLen: protocol.PacketNumberLen2,
					}
					frame.Write(b, 0x1300, 0)
					Expect(b.Len()).To(Equal(4))
					Expect(b.Bytes()[2:4]).To(Equal([]byte{0xF0, 0x12}))
				})

				It("writes a 4-byte LeastUnackedDelta", func() {
					b := &bytes.Buffer{}
					frame := &StopWaitingFrame{
						LeastUnacked:    0x1000,
						PacketNumberLen: protocol.PacketNumberLen4,
					}
					frame.Write(b, 0x12345678, 0)
					Expect(b.Len()).To(Equal(6))
					Expect(b.Bytes()[2:6]).To(Equal([]byte{0x78, 0x46, 0x34, 0x12}))
				})

				It("writes a 6-byte LeastUnackedDelta", func() {
					b := &bytes.Buffer{}
					frame := &StopWaitingFrame{
						LeastUnacked:    0x10,
						PacketNumberLen: protocol.PacketNumberLen6,
					}
					frame.Write(b, 0x123456789ABC, 0)
					Expect(b.Len()).To(Equal(8))
					Expect(b.Bytes()[2:8]).To(Equal([]byte{0xAC, 0x9A, 0x78, 0x56, 0x34, 0x12}))
				})
			})
		})

		Context("minLength", func() {
			It("calculates the right minLength", func() {
				for _, length := range []protocol.PacketNumberLen{protocol.PacketNumberLen1, protocol.PacketNumberLen2, protocol.PacketNumberLen4, protocol.PacketNumberLen6} {
					frame := &StopWaitingFrame{
						LeastUnacked:    10,
						PacketNumberLen: length,
					}
					Expect(frame.MinLength()).To(Equal(protocol.ByteCount(length + 2)))
				}
			})

			It("errors when packetNumberLen is not set", func() {
				frame := &StopWaitingFrame{
					LeastUnacked: 10,
				}
				_, err := frame.MinLength()
				Expect(err).To(HaveOccurred())
				Expect(err).To(Equal(errPacketNumberLenNotSet))
			})
		})

		Context("self consistency", func() {
			It("reads a stop waiting frame that it wrote", func() {
				packetNumber := protocol.PacketNumber(13)
				frame := &StopWaitingFrame{
					LeastUnacked:    10,
					Entropy:         0xAC,
					PacketNumberLen: protocol.PacketNumberLen4,
				}
				b := &bytes.Buffer{}
				frame.Write(b, packetNumber, 0)
				readframe, err := ParseStopWaitingFrame(bytes.NewReader(b.Bytes()), packetNumber, protocol.PacketNumberLen4)
				Expect(err).ToNot(HaveOccurred())
				Expect(readframe.Entropy).To(Equal(frame.Entropy))
				Expect(readframe.LeastUnacked).To(Equal(frame.LeastUnacked))
			})
		})
	})
})