package utils

import (
	"bytes"
	"io"

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

var _ = Describe("Big Endian encoding / decoding", func() {
	Context("ReadUint16", func() {
		It("reads a big endian", func() {
			b := []byte{0x13, 0xEF}
			val, err := BigEndian.ReadUint16(bytes.NewReader(b))
			Expect(err).ToNot(HaveOccurred())
			Expect(val).To(Equal(uint16(0x13EF)))
		})

		It("throws an error if less than 2 bytes are passed", func() {
			b := []byte{0x13, 0xEF}
			for i := 0; i < len(b); i++ {
				_, err := BigEndian.ReadUint16(bytes.NewReader(b[:i]))
				Expect(err).To(MatchError(io.EOF))
			}
		})
	})

	Context("ReadUint32", func() {
		It("reads a big endian", func() {
			b := []byte{0x12, 0x35, 0xAB, 0xFF}
			val, err := BigEndian.ReadUint32(bytes.NewReader(b))
			Expect(err).ToNot(HaveOccurred())
			Expect(val).To(Equal(uint32(0x1235ABFF)))
		})

		It("throws an error if less than 4 bytes are passed", func() {
			b := []byte{0x12, 0x35, 0xAB, 0xFF}
			for i := 0; i < len(b); i++ {
				_, err := BigEndian.ReadUint32(bytes.NewReader(b[:i]))
				Expect(err).To(MatchError(io.EOF))
			}
		})
	})

	Context("ReadUint64", func() {
		It("reads a big endian", func() {
			b := []byte{0x12, 0x35, 0xAB, 0xFF, 0xEF, 0xBE, 0xAD, 0xDE}
			val, err := BigEndian.ReadUint64(bytes.NewReader(b))
			Expect(err).ToNot(HaveOccurred())
			Expect(val).To(Equal(uint64(0x1235ABFFEFBEADDE)))
		})

		It("throws an error if less than 8 bytes are passed", func() {
			b := []byte{0x12, 0x35, 0xAB, 0xFF, 0xEF, 0xBE, 0xAD, 0xDE}
			for i := 0; i < len(b); i++ {
				_, err := BigEndian.ReadUint64(bytes.NewReader(b[:i]))
				Expect(err).To(MatchError(io.EOF))
			}
		})
	})

	Context("WriteUint16", func() {
		It("outputs 2 bytes", func() {
			b := &bytes.Buffer{}
			BigEndian.WriteUint16(b, uint16(1))
			Expect(b.Len()).To(Equal(2))
		})

		It("outputs a big endian", func() {
			num := uint16(0xFF11)
			b := &bytes.Buffer{}
			BigEndian.WriteUint16(b, num)
			Expect(b.Bytes()).To(Equal([]byte{0xFF, 0x11}))
		})
	})

	Context("WriteUint24", func() {
		It("outputs 3 bytes", func() {
			b := &bytes.Buffer{}
			BigEndian.WriteUint24(b, uint32(1))
			Expect(b.Len()).To(Equal(3))
		})

		It("outputs a big endian", func() {
			num := uint32(0x010203)
			b := &bytes.Buffer{}
			BigEndian.WriteUint24(b, num)
			Expect(b.Bytes()).To(Equal([]byte{0x01, 0x02, 0x03}))
		})

		It("panics if the value doesn't fit into 24 bits", func() {
			num := uint32(0x01020304)
			b := &bytes.Buffer{}
			Expect(func() { BigEndian.WriteUint24(b, num) }).Should(Panic())
		})
	})

	Context("WriteUint32", func() {
		It("outputs 4 bytes", func() {
			b := &bytes.Buffer{}
			BigEndian.WriteUint32(b, uint32(1))
			Expect(b.Len()).To(Equal(4))
		})

		It("outputs a big endian", func() {
			num := uint32(0xEFAC3512)
			b := &bytes.Buffer{}
			BigEndian.WriteUint32(b, num)
			Expect(b.Bytes()).To(Equal([]byte{0xEF, 0xAC, 0x35, 0x12}))
		})
	})

	Context("WriteUint40", func() {
		It("outputs 5 bytes", func() {
			b := &bytes.Buffer{}
			BigEndian.WriteUint40(b, uint64(1))
			Expect(b.Len()).To(Equal(5))
		})

		It("outputs a big endian", func() {
			num := uint64(0xDECAFBAD42)
			b := &bytes.Buffer{}
			BigEndian.WriteUint40(b, num)
			Expect(b.Bytes()).To(Equal([]byte{0xDE, 0xCA, 0xFB, 0xAD, 0x42}))
		})

		It("panics if the value doesn't fit into 40 bits", func() {
			num := uint64(0x010203040506)
			b := &bytes.Buffer{}
			Expect(func() { BigEndian.WriteUint40(b, num) }).Should(Panic())
		})
	})

	Context("WriteUint48", func() {
		It("outputs 6 bytes", func() {
			b := &bytes.Buffer{}
			BigEndian.WriteUint48(b, uint64(1))
			Expect(b.Len()).To(Equal(6))
		})

		It("outputs a big endian", func() {
			num := uint64(0xDEADBEEFCAFE)
			b := &bytes.Buffer{}
			BigEndian.WriteUint48(b, num)
			Expect(b.Bytes()).To(Equal([]byte{0xDE, 0xAD, 0xBE, 0xEF, 0xCA, 0xFE}))
		})

		It("panics if the value doesn't fit into 48 bits", func() {
			num := uint64(0xDEADBEEFCAFE01)
			b := &bytes.Buffer{}
			Expect(func() { BigEndian.WriteUint48(b, num) }).Should(Panic())
		})
	})

	Context("WriteUint56", func() {
		It("outputs 7 bytes", func() {
			b := &bytes.Buffer{}
			BigEndian.WriteUint56(b, uint64(1))
			Expect(b.Len()).To(Equal(7))
		})

		It("outputs a big endian", func() {
			num := uint64(0xEEDDCCBBAA9988)
			b := &bytes.Buffer{}
			BigEndian.WriteUint56(b, num)
			Expect(b.Bytes()).To(Equal([]byte{0xEE, 0xDD, 0xCC, 0xBB, 0xAA, 0x99, 0x88}))
		})

		It("panics if the value doesn't fit into 56 bits", func() {
			num := uint64(0xEEDDCCBBAA998801)
			b := &bytes.Buffer{}
			Expect(func() { BigEndian.WriteUint56(b, num) }).Should(Panic())
		})
	})

	Context("WriteUint64", func() {
		It("outputs 8 bytes", func() {
			b := &bytes.Buffer{}
			BigEndian.WriteUint64(b, uint64(1))
			Expect(b.Len()).To(Equal(8))
		})

		It("outputs a big endian", func() {
			num := uint64(0xFFEEDDCCBBAA9988)
			b := &bytes.Buffer{}
			BigEndian.WriteUint64(b, num)
			Expect(b.Bytes()).To(Equal([]byte{0xFF, 0xEE, 0xDD, 0xCC, 0xBB, 0xAA, 0x99, 0x88}))
		})
	})

	Context("ReadUintN", func() {

		It("reads n bytes", func() {
			m := map[uint8]uint64{
				0: 0x0,
				1: 0x01,
				2: 0x0102,
				3: 0x010203,
				4: 0x01020304,
				5: 0x0102030405,
				6: 0x010203040506,
				7: 0x01020304050607,
				8: 0x0102030405060708,
			}
			for n, expected := range m {
				b := bytes.NewReader([]byte{0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8})
				i, err := BigEndian.ReadUintN(b, n)
				Expect(err).ToNot(HaveOccurred())
				Expect(i).To(Equal(expected))
			}
		})

		It("errors", func() {
			b := bytes.NewReader([]byte{0x1, 0x2})
			_, err := BigEndian.ReadUintN(b, 3)
			Expect(err).To(HaveOccurred())
		})
	})
})