package frames

import (
	"bytes"

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

var _ = Describe("StreamFrame", func() {
	Context("when parsing", func() {
		It("accepts sample frame", func() {
			b := bytes.NewReader([]byte{0xa0, 0x1, 0x06, 0x00, 'f', 'o', 'o', 'b', 'a', 'r'})
			frame, err := ParseStreamFrame(b)
			Expect(err).ToNot(HaveOccurred())
			Expect(frame.FinBit).To(BeFalse())
			Expect(frame.StreamID).To(Equal(protocol.StreamID(1)))
			Expect(frame.Offset).To(BeZero())
			Expect(frame.DataLenPresent).To(BeTrue())
			Expect(frame.Data).To(Equal([]byte("foobar")))
		})

		It("accepts frame without data length", func() {
			b := bytes.NewReader([]byte{0x80, 0x1, 'f', 'o', 'o', 'b', 'a', 'r'})
			frame, err := ParseStreamFrame(b)
			Expect(err).ToNot(HaveOccurred())
			Expect(frame.FinBit).To(BeFalse())
			Expect(frame.StreamID).To(Equal(protocol.StreamID(1)))
			Expect(frame.Offset).To(BeZero())
			Expect(frame.DataLenPresent).To(BeFalse())
			Expect(frame.Data).To(Equal([]byte("foobar")))
		})
	})

	Context("when writing", func() {
		It("writes sample frame", func() {
			b := &bytes.Buffer{}
			(&StreamFrame{
				StreamID:       1,
				Data:           []byte("foobar"),
				DataLenPresent: true,
			}).Write(b, 0)
			Expect(b.Bytes()).To(Equal([]byte{0xa0, 0x1, 0x06, 0x00, 'f', 'o', 'o', 'b', 'a', 'r'}))
		})

		It("has proper min length for a short StreamID and a short offset", func() {
			b := &bytes.Buffer{}
			f := &StreamFrame{
				StreamID: 1,
				Data:     []byte("f"),
				Offset:   0,
			}
			f.Write(b, 0)
			Expect(f.MinLength()).To(Equal(protocol.ByteCount(b.Len())))
		})

		It("has proper min length for a long StreamID and a big offset", func() {
			b := &bytes.Buffer{}
			f := &StreamFrame{
				StreamID: 0xDECAFBAD,
				Data:     []byte("f"),
				Offset:   0xDEADBEEFCAFE,
			}
			f.Write(b, 0)
			Expect(f.MinLength()).To(Equal(protocol.ByteCount(b.Len())))
		})

		Context("data length field", func() {
			It("writes the data length", func() {
				dataLen := 0x1337
				b := &bytes.Buffer{}
				f := &StreamFrame{
					StreamID:       1,
					Data:           bytes.Repeat([]byte{'f'}, dataLen),
					DataLenPresent: true,
					Offset:         0,
				}
				f.Write(b, 0)
				minLength, _ := f.MinLength()
				headerLength := minLength - 1
				Expect(b.Bytes()[0] & 0x20).To(Equal(uint8(0x20)))
				Expect(b.Bytes()[headerLength-2 : headerLength]).To(Equal([]byte{0x37, 0x13}))
			})

			It("omits the data length field", func() {
				dataLen := 0x1337
				b := &bytes.Buffer{}
				f := &StreamFrame{
					StreamID:       1,
					Data:           bytes.Repeat([]byte{'f'}, dataLen),
					DataLenPresent: false,
					Offset:         0,
				}
				f.Write(b, 0)
				Expect(b.Bytes()[0] & 0x20).To(Equal(uint8(0)))
				Expect(b.Bytes()[1 : b.Len()-dataLen]).ToNot(ContainSubstring(string([]byte{0x37, 0x13})))
				minLength, _ := f.MinLength()
				f.DataLenPresent = true
				minLengthWithoutDataLen, _ := f.MinLength()
				Expect(minLength).To(Equal(minLengthWithoutDataLen - 2))
			})

			It("calculates the correcct min-length", func() {
				f := &StreamFrame{
					StreamID:       0xCAFE,
					Data:           []byte("foobar"),
					DataLenPresent: false,
					Offset:         0xDEADBEEF,
				}
				minLengthWithoutDataLen, _ := f.MinLength()
				f.DataLenPresent = true
				Expect(f.MinLength()).To(Equal(minLengthWithoutDataLen + 2))
			})
		})

		Context("offset lengths", func() {
			It("does not write an offset if the offset is 0", func() {
				b := &bytes.Buffer{}
				(&StreamFrame{
					StreamID: 1,
					Data:     []byte("foobar"),
					Offset:   0,
				}).Write(b, 0)
				Expect(b.Bytes()[0] & 0x1c).To(Equal(uint8(0x0)))
			})

			It("writes a 2-byte offset if the offset is larger than 0", func() {
				b := &bytes.Buffer{}
				(&StreamFrame{
					StreamID: 1,
					Data:     []byte("foobar"),
					Offset:   0x1337,
				}).Write(b, 0)
				Expect(b.Bytes()[0] & 0x1c).To(Equal(uint8(0x1 << 2)))
				Expect(b.Bytes()[2:4]).To(Equal([]byte{0x37, 0x13}))
			})

			It("writes a 3-byte offset if the offset", func() {
				b := &bytes.Buffer{}
				(&StreamFrame{
					StreamID: 1,
					Data:     []byte("foobar"),
					Offset:   0x13CAFE,
				}).Write(b, 0)
				Expect(b.Bytes()[0] & 0x1c).To(Equal(uint8(0x2 << 2)))
				Expect(b.Bytes()[2:5]).To(Equal([]byte{0xFE, 0xCA, 0x13}))
			})

			It("writes a 4-byte offset if the offset", func() {
				b := &bytes.Buffer{}
				(&StreamFrame{
					StreamID: 1,
					Data:     []byte("foobar"),
					Offset:   0xDEADBEEF,
				}).Write(b, 0)
				Expect(b.Bytes()[0] & 0x1c).To(Equal(uint8(0x3 << 2)))
				Expect(b.Bytes()[2:6]).To(Equal([]byte{0xEF, 0xBE, 0xAD, 0xDE}))
			})

			It("writes a 5-byte offset if the offset", func() {
				b := &bytes.Buffer{}
				(&StreamFrame{
					StreamID: 1,
					Data:     []byte("foobar"),
					Offset:   0x13DEADBEEF,
				}).Write(b, 0)
				Expect(b.Bytes()[0] & 0x1c).To(Equal(uint8(0x4 << 2)))
				Expect(b.Bytes()[2:7]).To(Equal([]byte{0xEF, 0xBE, 0xAD, 0xDE, 0x13}))
			})

			It("writes a 6-byte offset if the offset", func() {
				b := &bytes.Buffer{}
				(&StreamFrame{
					StreamID: 1,
					Data:     []byte("foobar"),
					Offset:   0xDEADBEEFCAFE,
				}).Write(b, 0)
				Expect(b.Bytes()[0] & 0x1c).To(Equal(uint8(0x5 << 2)))
				Expect(b.Bytes()[2:8]).To(Equal([]byte{0xFE, 0xCA, 0xEF, 0xBE, 0xAD, 0xDE}))
			})

			It("writes a 7-byte offset if the offset", func() {
				b := &bytes.Buffer{}
				(&StreamFrame{
					StreamID: 1,
					Data:     []byte("foobar"),
					Offset:   0x13DEADBEEFCAFE,
				}).Write(b, 0)
				Expect(b.Bytes()[0] & 0x1c).To(Equal(uint8(0x6 << 2)))
				Expect(b.Bytes()[2:9]).To(Equal([]byte{0xFE, 0xCA, 0xEF, 0xBE, 0xAD, 0xDE, 0x13}))
			})

			It("writes a 8-byte offset if the offset", func() {
				b := &bytes.Buffer{}
				(&StreamFrame{
					StreamID: 1,
					Data:     []byte("foobar"),
					Offset:   0x1337DEADBEEFCAFE,
				}).Write(b, 0)
				Expect(b.Bytes()[0] & 0x1c).To(Equal(uint8(0x7 << 2)))
				Expect(b.Bytes()[2:10]).To(Equal([]byte{0xFE, 0xCA, 0xEF, 0xBE, 0xAD, 0xDE, 0x37, 0x13}))
			})
		})

		Context("lengths of StreamIDs", func() {
			It("returns an error for a non-valid StreamID length", func() {
				b := &bytes.Buffer{}
				err := (&StreamFrame{
					StreamID:    1,
					streamIDLen: 13,
					Data:        []byte("foobar"),
				}).Write(b, 0)
				Expect(err).To(HaveOccurred())
				Expect(err).To(Equal(errInvalidStreamIDLen))
			})

			It("writes a 1 byte StreamID", func() {
				b := &bytes.Buffer{}
				(&StreamFrame{
					StreamID: 13,
					Data:     []byte("foobar"),
				}).Write(b, 0)
				Expect(b.Bytes()[0] & 0x3).To(Equal(uint8(0x0)))
				Expect(b.Bytes()[1]).To(Equal(uint8(13)))
			})

			It("writes a 2 byte StreamID", func() {
				b := &bytes.Buffer{}
				(&StreamFrame{
					StreamID: 0xCAFE,
					Data:     []byte("foobar"),
				}).Write(b, 0)
				Expect(b.Bytes()[0] & 0x3).To(Equal(uint8(0x1)))
				Expect(b.Bytes()[1:3]).To(Equal([]byte{0xFE, 0xCA}))
			})

			It("writes a 3 byte StreamID", func() {
				b := &bytes.Buffer{}
				(&StreamFrame{
					StreamID: 0x13BEEF,
					Data:     []byte("foobar"),
				}).Write(b, 0)
				Expect(b.Bytes()[0] & 0x3).To(Equal(uint8(0x2)))
				Expect(b.Bytes()[1:4]).To(Equal([]byte{0xEF, 0xBE, 0x13}))
			})

			It("writes a 4 byte StreamID", func() {
				b := &bytes.Buffer{}
				(&StreamFrame{
					StreamID: 0xDECAFBAD,
					Data:     []byte("foobar"),
				}).Write(b, 0)
				Expect(b.Bytes()[0] & 0x3).To(Equal(uint8(0x3)))
				Expect(b.Bytes()[1:5]).To(Equal([]byte{0xAD, 0xFB, 0xCA, 0xDE}))
			})
		})
	})

	Context("shortening of StreamIDs", func() {
		It("determines the length of a 1 byte StreamID", func() {
			f := &StreamFrame{StreamID: 0xFF}
			f.calculateStreamIDLength()
			Expect(f.streamIDLen).To(Equal(protocol.ByteCount(1)))
		})

		It("determines the length of a 2 byte StreamID", func() {
			f := &StreamFrame{StreamID: 0xFFFF}
			f.calculateStreamIDLength()
			Expect(f.streamIDLen).To(Equal(protocol.ByteCount(2)))
		})

		It("determines the length of a 1 byte StreamID", func() {
			f := &StreamFrame{StreamID: 0xFFFFFF}
			f.calculateStreamIDLength()
			Expect(f.streamIDLen).To(Equal(protocol.ByteCount(3)))
		})

		It("determines the length of a 1 byte StreamID", func() {
			f := &StreamFrame{StreamID: 0xFFFFFFFF}
			f.calculateStreamIDLength()
			Expect(f.streamIDLen).To(Equal(protocol.ByteCount(4)))
		})
	})

	Context("shortening of Offsets", func() {
		It("determines length 0 of offset 0", func() {
			f := &StreamFrame{Offset: 0}
			Expect(f.getOffsetLength()).To(Equal(protocol.ByteCount(0)))
		})

		It("determines the length of a 2 byte offset", func() {
			f := &StreamFrame{Offset: 0xFFFF}
			Expect(f.getOffsetLength()).To(Equal(protocol.ByteCount(2)))
		})

		It("determines the length of a 2 byte offset, even if it would fit into 1 byte", func() {
			f := &StreamFrame{Offset: 0x1}
			Expect(f.getOffsetLength()).To(Equal(protocol.ByteCount(2)))
		})

		It("determines the length of a 3 byte offset", func() {
			f := &StreamFrame{Offset: 0xFFFFFF}
			Expect(f.getOffsetLength()).To(Equal(protocol.ByteCount(3)))
		})

		It("determines the length of a 4 byte offset", func() {
			f := &StreamFrame{Offset: 0xFFFFFFFF}
			Expect(f.getOffsetLength()).To(Equal(protocol.ByteCount(4)))
		})

		It("determines the length of a 5 byte offset", func() {
			f := &StreamFrame{Offset: 0xFFFFFFFFFF}
			Expect(f.getOffsetLength()).To(Equal(protocol.ByteCount(5)))
		})

		It("determines the length of a 6 byte offset", func() {
			f := &StreamFrame{Offset: 0xFFFFFFFFFFFF}
			Expect(f.getOffsetLength()).To(Equal(protocol.ByteCount(6)))
		})

		It("determines the length of a 7 byte offset", func() {
			f := &StreamFrame{Offset: 0xFFFFFFFFFFFFFF}
			Expect(f.getOffsetLength()).To(Equal(protocol.ByteCount(7)))
		})

		It("determines the length of an 8 byte offset", func() {
			f := &StreamFrame{Offset: 0xFFFFFFFFFFFFFFFF}
			Expect(f.getOffsetLength()).To(Equal(protocol.ByteCount(8)))
		})
	})

	Context("splitting off earlier stream frames", func() {
		It("splits off nothing", func() {
			f := &StreamFrame{
				StreamID: 1,
				Data:     []byte("bar"),
				Offset:   3,
			}
			Expect(f.MaybeSplitOffFrame(1000)).To(BeNil())
			Expect(f.Offset).To(Equal(protocol.ByteCount(3)))
		})

		It("splits off initial frame", func() {
			f := &StreamFrame{
				StreamID: 1,
				Data:     []byte("foobar"),
				Offset:   3,
				FinBit:   true,
			}
			minLength, _ := f.MinLength()
			previous := f.MaybeSplitOffFrame(minLength - 1 + 3)
			Expect(previous).ToNot(BeNil())
			Expect(previous.StreamID).To(Equal(protocol.StreamID(1)))
			Expect(previous.Data).To(Equal([]byte("foo")))
			Expect(previous.Offset).To(Equal(protocol.ByteCount(3)))
			Expect(previous.FinBit).To(BeFalse())
			Expect(f.StreamID).To(Equal(protocol.StreamID(1)))
			Expect(f.Data).To(Equal([]byte("bar")))
			Expect(f.Offset).To(Equal(protocol.ByteCount(6)))
			Expect(f.FinBit).To(BeTrue())
		})
	})
})