package packetio

import (
	"errors"
	"fmt"
	"io"
	"net"
	"testing"
	"time"

	"github.com/stretchr/testify/assert"
)

func TestBuffer(t *testing.T) {
	assert := assert.New(t)

	buffer := NewBuffer()
	packet := make([]byte, 4)

	// Write once
	n, err := buffer.Write([]byte{0, 1})
	assert.NoError(err)
	assert.Equal(2, n)

	// Read once
	n, err = buffer.Read(packet)
	assert.NoError(err)
	assert.Equal(2, n)
	assert.Equal([]byte{0, 1}, packet[:n])

	// Read deadline
	err = buffer.SetReadDeadline(time.Unix(0, 1))
	assert.NoError(err)
	n, err = buffer.Read(packet)
	var e net.Error
	if !errors.As(err, &e) || !e.Timeout() {
		t.Errorf("Unexpected error: %v", err)
	}
	assert.Equal(0, n)

	// Reset deadline
	err = buffer.SetReadDeadline(time.Time{})
	assert.NoError(err)

	// Write twice
	n, err = buffer.Write([]byte{2, 3, 4})
	assert.NoError(err)
	assert.Equal(3, n)

	n, err = buffer.Write([]byte{5, 6, 7})
	assert.NoError(err)
	assert.Equal(3, n)

	// Read twice
	n, err = buffer.Read(packet)
	assert.NoError(err)
	assert.Equal(3, n)
	assert.Equal([]byte{2, 3, 4}, packet[:n])

	n, err = buffer.Read(packet)
	assert.NoError(err)
	assert.Equal(3, n)
	assert.Equal([]byte{5, 6, 7}, packet[:n])

	// Write once prior to close.
	_, err = buffer.Write([]byte{3})
	assert.NoError(err)

	// Close
	err = buffer.Close()
	assert.NoError(err)

	// Future writes will error
	_, err = buffer.Write([]byte{4})
	assert.Error(err)

	// But we can read the remaining data.
	n, err = buffer.Read(packet)
	assert.NoError(err)
	assert.Equal(1, n)
	assert.Equal([]byte{3}, packet[:n])

	// Until EOF
	_, err = buffer.Read(packet)
	assert.Equal(io.EOF, err)
}

func testWraparound(t *testing.T, grow bool) {
	assert := assert.New(t)

	buffer := NewBuffer()
	err := buffer.grow()
	assert.NoError(err)

	buffer.head = len(buffer.data) - 13
	buffer.tail = buffer.head

	p1 := []byte{1, 2, 3}
	p2 := []byte{4, 5, 6}
	p3 := []byte{7, 8, 9}
	p4 := []byte{10, 11, 12}

	_, err = buffer.Write(p1)
	assert.NoError(err)
	_, err = buffer.Write(p2)
	assert.NoError(err)
	_, err = buffer.Write(p3)
	assert.NoError(err)

	p := make([]byte, 10)

	n, err := buffer.Read(p)
	assert.NoError(err)
	assert.Equal(p1, p[:n])

	if grow {
		err = buffer.grow()
		assert.NoError(err)
	}

	n, err = buffer.Read(p)
	assert.NoError(err)
	assert.Equal(p2, p[:n])

	_, err = buffer.Write(p4)
	assert.NoError(err)

	n, err = buffer.Read(p)
	assert.NoError(err)
	assert.Equal(p3, p[:n])
	n, err = buffer.Read(p)
	assert.NoError(err)
	assert.Equal(p4, p[:n])

	if !grow {
		assert.Equal(len(buffer.data), minSize)
	} else {
		assert.Equal(len(buffer.data), 2*minSize)
	}
}

func TestBufferWraparound(t *testing.T) {
	testWraparound(t, false)
}

func TestBufferWraparoundGrow(t *testing.T) {
	testWraparound(t, true)
}

func TestBufferAsync(t *testing.T) {
	assert := assert.New(t)

	buffer := NewBuffer()

	// Start up a goroutine to start a blocking read.
	done := make(chan struct{})
	go func() {
		packet := make([]byte, 4)

		n, err := buffer.Read(packet)
		assert.NoError(err)
		assert.Equal(2, n)
		assert.Equal([]byte{0, 1}, packet[:n])

		_, err = buffer.Read(packet)
		assert.Equal(io.EOF, err)

		close(done)
	}()

	// Wait for the reader to start reading.
	time.Sleep(time.Millisecond)

	// Write once
	n, err := buffer.Write([]byte{0, 1})
	assert.NoError(err)
	assert.Equal(2, n)

	// Wait for the reader to start reading again.
	time.Sleep(time.Millisecond)

	// Close will unblock the reader.
	err = buffer.Close()
	assert.NoError(err)

	<-done
}

func TestBufferLimitCount(t *testing.T) {
	assert := assert.New(t)

	buffer := NewBuffer()
	buffer.SetLimitCount(2)

	assert.Equal(0, buffer.Count())

	// Write twice
	n, err := buffer.Write([]byte{0, 1})
	assert.NoError(err)
	assert.Equal(2, n)
	assert.Equal(1, buffer.Count())

	n, err = buffer.Write([]byte{2, 3})
	assert.NoError(err)
	assert.Equal(2, n)
	assert.Equal(2, buffer.Count())

	// Over capacity
	_, err = buffer.Write([]byte{4, 5})
	assert.Equal(ErrFull, err)
	assert.Equal(2, buffer.Count())

	// Read once
	packet := make([]byte, 4)
	n, err = buffer.Read(packet)
	assert.NoError(err)
	assert.Equal(2, n)
	assert.Equal([]byte{0, 1}, packet[:n])
	assert.Equal(1, buffer.Count())

	// Write once
	n, err = buffer.Write([]byte{6, 7})
	assert.NoError(err)
	assert.Equal(2, n)
	assert.Equal(2, buffer.Count())

	// Over capacity
	_, err = buffer.Write([]byte{8, 9})
	assert.Equal(ErrFull, err)
	assert.Equal(2, buffer.Count())

	// Read twice
	n, err = buffer.Read(packet)
	assert.NoError(err)
	assert.Equal(2, n)
	assert.Equal([]byte{2, 3}, packet[:n])
	assert.Equal(1, buffer.Count())

	n, err = buffer.Read(packet)
	assert.NoError(err)
	assert.Equal(2, n)
	assert.Equal([]byte{6, 7}, packet[:n])
	assert.Equal(0, buffer.Count())

	// Nothing left.
	err = buffer.Close()
	assert.NoError(err)
}

func TestBufferLimitSize(t *testing.T) {
	assert := assert.New(t)

	buffer := NewBuffer()
	buffer.SetLimitSize(11)

	assert.Equal(0, buffer.Size())

	// Write twice
	n, err := buffer.Write([]byte{0, 1})
	assert.NoError(err)
	assert.Equal(2, n)
	assert.Equal(4, buffer.Size())

	n, err = buffer.Write([]byte{2, 3})
	assert.NoError(err)
	assert.Equal(2, n)
	assert.Equal(8, buffer.Size())

	// Over capacity
	_, err = buffer.Write([]byte{4, 5})
	assert.Equal(ErrFull, err)
	assert.Equal(8, buffer.Size())

	// Cheeky write at exact size.
	n, err = buffer.Write([]byte{6})
	assert.NoError(err)
	assert.Equal(1, n)
	assert.Equal(11, buffer.Size())

	// Read once
	packet := make([]byte, 4)
	n, err = buffer.Read(packet)
	assert.NoError(err)
	assert.Equal(2, n)
	assert.Equal([]byte{0, 1}, packet[:n])
	assert.Equal(7, buffer.Size())

	// Write once
	n, err = buffer.Write([]byte{7, 8})
	assert.NoError(err)
	assert.Equal(2, n)
	assert.Equal(11, buffer.Size())

	// Over capacity
	_, err = buffer.Write([]byte{9, 10})
	assert.Equal(ErrFull, err)
	assert.Equal(11, buffer.Size())

	// Read everything
	n, err = buffer.Read(packet)
	assert.NoError(err)
	assert.Equal(2, n)
	assert.Equal([]byte{2, 3}, packet[:n])
	assert.Equal(7, buffer.Size())

	n, err = buffer.Read(packet)
	assert.NoError(err)
	assert.Equal(1, n)
	assert.Equal([]byte{6}, packet[:n])
	assert.Equal(4, buffer.Size())

	n, err = buffer.Read(packet)
	assert.NoError(err)
	assert.Equal(2, n)
	assert.Equal([]byte{7, 8}, packet[:n])
	assert.Equal(0, buffer.Size())

	// Nothing left.
	err = buffer.Close()
	assert.NoError(err)
}

func TestBufferLimitSizes(t *testing.T) {
	if sizeHardLimit {
		t.Skip("skipping since packetioSizeHardLimit is enabled")
	}
	sizes := []int{
		128 * 1024,
		1024 * 1024,
		8 * 1024 * 1024,
		0, // default
	}
	const headerSize = 2
	const packetSize = 0x8000

	for _, size := range sizes {
		size := size
		name := "default"
		if size > 0 {
			name = fmt.Sprintf("%dkBytes", size/1024)
		}

		t.Run(name, func(t *testing.T) {
			assert := assert.New(t)

			buffer := NewBuffer()
			if size == 0 {
				size = maxSize
			} else {
				buffer.SetLimitSize(size + headerSize)
			}
			now := time.Now()
			assert.NoError(buffer.SetReadDeadline(now.Add(5 * time.Second))) // Set deadline to avoid test deadlock

			nPackets := size / (packetSize + headerSize)

			for i := 0; i < nPackets; i++ {
				_, err := buffer.Write(make([]byte, packetSize))
				assert.NoError(err)
			}

			// Next write is expected to be errored.
			_, err := buffer.Write(make([]byte, packetSize))
			assert.Error(err, ErrFull)

			packet := make([]byte, size)
			for i := 0; i < nPackets; i++ {
				n, err := buffer.Read(packet)
				assert.NoError(err)
				assert.Equal(packetSize, n)
				if err != nil {
					t.FailNow()
				}
			}
		})
	}
}

func TestBufferMisc(t *testing.T) {
	assert := assert.New(t)

	buffer := NewBuffer()

	// Write once
	n, err := buffer.Write([]byte{0, 1, 2, 3})
	assert.NoError(err)
	assert.Equal(4, n)

	// Try to read with a short buffer
	packet := make([]byte, 3)
	_, err = buffer.Read(packet)
	assert.Equal(io.ErrShortBuffer, err)

	// Close
	err = buffer.Close()
	assert.NoError(err)

	// Make sure you can Close twice
	err = buffer.Close()
	assert.NoError(err)
}

func TestBufferAlloc(t *testing.T) {
	packet := make([]byte, 1024)

	test := func(f func(count int) func(), count int, max float64) func(t *testing.T) {
		return func(t *testing.T) {
			allocs := testing.AllocsPerRun(3, f(count))
			if allocs > max {
				t.Errorf("count=%v, max=%v, got %v",
					count, max, allocs,
				)
			}
		}
	}

	w := func(count int) func() {
		return func() {
			buffer := NewBuffer()
			for i := 0; i < count; i++ {
				_, err := buffer.Write(packet)
				if err != nil {
					t.Errorf("Write: %v", err)
					break
				}
			}
		}
	}

	t.Run("100 writes", test(w, 100, 13))
	t.Run("200 writes", test(w, 200, 17))
	t.Run("400 writes", test(w, 400, 19))
	t.Run("1000 writes", test(w, 1000, 23))

	wr := func(count int) func() {
		return func() {
			buffer := NewBuffer()
			for i := 0; i < count; i++ {
				_, err := buffer.Write(packet)
				if err != nil {
					t.Fatalf("Write: %v", err)
				}
				_, err = buffer.Read(packet)
				if err != nil {
					t.Fatalf("Read: %v", err)
				}
			}
		}
	}

	t.Run("100 writes and reads", test(wr, 100, 7))
	t.Run("1000 writes and reads", test(wr, 1000, 7))
	t.Run("10000 writes and reads", test(wr, 10000, 7))
}

func benchmarkBufferWR(b *testing.B, size int64, write bool, grow int) { // nolint:unparam
	buffer := NewBuffer()
	packet := make([]byte, size)

	// Grow the buffer first
	pad := make([]byte, 1022)
	for buffer.Size() < grow {
		_, err := buffer.Write(pad)
		if err != nil {
			b.Fatalf("Write: %v", err)
		}
	}
	for buffer.Size() > 0 {
		_, err := buffer.Read(pad)
		if err != nil {
			b.Fatalf("Write: %v", err)
		}
	}

	if write {
		_, err := buffer.Write(packet)
		if err != nil {
			b.Fatalf("Write: %v", err)
		}
	}

	b.SetBytes(size)
	b.ResetTimer()

	for i := 0; i < b.N; i++ {
		_, err := buffer.Write(packet)
		if err != nil {
			b.Fatalf("Write: %v", err)
		}
		_, err = buffer.Read(packet)
		if err != nil {
			b.Fatalf("Read: %v", err)
		}
	}
}

// In this benchmark, the buffer is often empty, which is hopefully
// typical of real usage.
func BenchmarkBufferWR14(b *testing.B) {
	benchmarkBufferWR(b, 14, false, 128000)
}

func BenchmarkBufferWR140(b *testing.B) {
	benchmarkBufferWR(b, 140, false, 128000)
}

func BenchmarkBufferWR1400(b *testing.B) {
	benchmarkBufferWR(b, 1400, false, 128000)
}

// Here, the buffer never becomes empty, which forces wraparound
func BenchmarkBufferWWR14(b *testing.B) {
	benchmarkBufferWR(b, 14, true, 128000)
}

func BenchmarkBufferWWR140(b *testing.B) {
	benchmarkBufferWR(b, 140, true, 128000)
}

func BenchmarkBufferWWR1400(b *testing.B) {
	benchmarkBufferWR(b, 1400, true, 128000)
}

func benchmarkBuffer(b *testing.B, size int64) {
	buffer := NewBuffer()
	b.SetBytes(size)

	done := make(chan struct{})
	go func() {
		packet := make([]byte, size)

		for {
			_, err := buffer.Read(packet)
			if errors.Is(err, io.EOF) {
				break
			} else if err != nil {
				b.Error(err)
				break
			}
		}

		close(done)
	}()

	packet := make([]byte, size)

	b.ResetTimer()

	for i := 0; i < b.N; i++ {
		var err error
		for {
			_, err = buffer.Write(packet)
			if !errors.Is(err, ErrFull) {
				break
			}
			time.Sleep(time.Microsecond)
		}
		if err != nil {
			b.Fatal(err)
		}
	}

	err := buffer.Close()
	if err != nil {
		b.Fatal(err)
	}

	<-done
}

func BenchmarkBuffer14(b *testing.B) {
	benchmarkBuffer(b, 14)
}

func BenchmarkBuffer140(b *testing.B) {
	benchmarkBuffer(b, 140)
}

func BenchmarkBuffer1400(b *testing.B) {
	benchmarkBuffer(b, 1400)
}