package protocol

import (
	"bytes"
	"crypto/rand"
	"io"

	. "github.com/onsi/ginkgo/v2"
	. "github.com/onsi/gomega"
)

var _ = Describe("Connection ID generation", func() {
	It("generates random connection IDs", func() {
		c1, err := GenerateConnectionID(8)
		Expect(err).ToNot(HaveOccurred())
		Expect(c1).ToNot(BeZero())
		c2, err := GenerateConnectionID(8)
		Expect(err).ToNot(HaveOccurred())
		Expect(c1).ToNot(Equal(c2))
	})

	It("generates connection IDs with the requested length", func() {
		c, err := GenerateConnectionID(5)
		Expect(err).ToNot(HaveOccurred())
		Expect(c.Len()).To(Equal(5))
	})

	It("generates random length destination connection IDs", func() {
		var has8ByteConnID, has20ByteConnID bool
		for i := 0; i < 1000; i++ {
			c, err := GenerateConnectionIDForInitial()
			Expect(err).ToNot(HaveOccurred())
			Expect(c.Len()).To(BeNumerically(">=", 8))
			Expect(c.Len()).To(BeNumerically("<=", 20))
			if c.Len() == 8 {
				has8ByteConnID = true
			}
			if c.Len() == 20 {
				has20ByteConnID = true
			}
		}
		Expect(has8ByteConnID).To(BeTrue())
		Expect(has20ByteConnID).To(BeTrue())
	})

	It("reads the connection ID", func() {
		buf := bytes.NewBuffer([]byte{1, 2, 3, 4, 5, 6, 7, 8, 9})
		c, err := ReadConnectionID(buf, 9)
		Expect(err).ToNot(HaveOccurred())
		Expect(c.Bytes()).To(Equal([]byte{1, 2, 3, 4, 5, 6, 7, 8, 9}))
	})

	It("returns io.EOF if there's not enough data to read", func() {
		buf := bytes.NewBuffer([]byte{1, 2, 3, 4})
		_, err := ReadConnectionID(buf, 5)
		Expect(err).To(MatchError(io.EOF))
	})

	It("returns a 0 length connection ID", func() {
		buf := bytes.NewBuffer([]byte{1, 2, 3, 4})
		c, err := ReadConnectionID(buf, 0)
		Expect(err).ToNot(HaveOccurred())
		Expect(c.Len()).To(BeZero())
	})

	It("errors when trying to read a too long connection ID", func() {
		buf := bytes.NewBuffer(make([]byte, 21))
		_, err := ReadConnectionID(buf, 21)
		Expect(err).To(MatchError(ErrInvalidConnectionIDLen))
	})

	It("returns the length", func() {
		c := ParseConnectionID([]byte{1, 2, 3, 4, 5, 6, 7})
		Expect(c.Len()).To(Equal(7))
	})

	It("has 0 length for the default value", func() {
		var c ConnectionID
		Expect(c.Len()).To(BeZero())
	})

	It("returns the bytes", func() {
		c := ParseConnectionID([]byte{1, 2, 3, 4, 5, 6, 7})
		Expect(c.Bytes()).To(Equal([]byte{1, 2, 3, 4, 5, 6, 7}))
	})

	It("returns a nil byte slice for the default value", func() {
		var c ConnectionID
		Expect(c.Bytes()).To(HaveLen(0))
	})

	It("has a string representation", func() {
		c := ParseConnectionID([]byte{0xde, 0xad, 0xbe, 0xef, 0x42})
		Expect(c.String()).To(Equal("deadbeef42"))
	})

	It("has a long string representation", func() {
		c := ParseConnectionID([]byte{0x13, 0x37, 0, 0, 0xde, 0xca, 0xfb, 0xad})
		Expect(c.String()).To(Equal("13370000decafbad"))
	})

	It("has a string representation for the default value", func() {
		var c ConnectionID
		Expect(c.String()).To(Equal("(empty)"))
	})

	Context("arbitrary length connection IDs", func() {
		It("returns the bytes", func() {
			b := make([]byte, 30)
			rand.Read(b)
			c := ArbitraryLenConnectionID(b)
			Expect(c.Bytes()).To(Equal(b))
		})

		It("returns the length", func() {
			c := ArbitraryLenConnectionID(make([]byte, 156))
			Expect(c.Len()).To(Equal(156))
		})

		It("has a string representation", func() {
			c := ArbitraryLenConnectionID([]byte{0xde, 0xad, 0xbe, 0xef, 0x42})
			Expect(c.String()).To(Equal("deadbeef42"))
		})

		It("has a string representation for the default value", func() {
			var c ArbitraryLenConnectionID
			Expect(c.String()).To(Equal("(empty)"))
		})
	})
})