package vnet

import (
	"context"
	"sync"
	"testing"
	"time"

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

func TestTokenBucketFilter(t *testing.T) {
	t.Run("bitrateBelowCapacity", func(t *testing.T) {
		mnic := newMockNIC(t)

		tbf, err := NewTokenBucketFilter(mnic, TBFRate(10*MBit), TBFMaxBurst(10*MBit))
		assert.NoError(t, err, "should succeed")

		received := 0
		mnic.mockOnInboundChunk = func(Chunk) {
			received++
		}

		time.Sleep(1 * time.Second)

		sent := 100
		for i := 0; i < sent; i++ {
			tbf.onInboundChunk(&chunkUDP{
				userData: make([]byte, 1200),
			})
		}

		assert.NoError(t, tbf.Close())

		assert.Equal(t, sent, received)
	})

	subTest := func(t *testing.T, capacity int, duration time.Duration) {
		log := logging.NewDefaultLoggerFactory().NewLogger("test")

		mnic := newMockNIC(t)

		tbf, err := NewTokenBucketFilter(mnic, TBFRate(capacity))
		assert.NoError(t, err, "should succeed")

		chunkChan := make(chan Chunk)
		mnic.mockOnInboundChunk = func(c Chunk) {
			chunkChan <- c
		}

		var wg sync.WaitGroup
		wg.Add(1)

		ctx, cancel := context.WithCancel(context.Background())

		go func() {
			defer wg.Done()

			bytesReceived := 0
			packetsReceived := 0
			start := time.Now()
			for {
				select {
				case <-ctx.Done():
					bits := float64(bytesReceived) * 8.0
					rate := bits / time.Since(start).Seconds()
					mBitPerSecond := rate / float64(MBit)

					// Allow 5% more than capacity due to max bursts
					assert.Less(t, rate, 1.05*float64(capacity))
					assert.Greater(t, rate, float64(0))

					log.Infof("duration=%v, bytesReceived=%v, packetsReceived=%v throughput=%.2f Mb/s", time.Since(start), bytesReceived, packetsReceived, mBitPerSecond)
					return

				case c := <-chunkChan:
					bytesReceived += len(c.UserData())
					packetsReceived++
				}
			}
		}()

		go func() {
			defer cancel()
			bytesSent := 0
			packetsSent := 0
			var start time.Time
			for start = time.Now(); time.Since(start) < duration; {
				c := &chunkUDP{
					userData: make([]byte, 1200),
				}
				tbf.onInboundChunk(c)
				bytesSent += len(c.UserData())
				packetsSent++
				time.Sleep(1 * time.Millisecond)
			}
			bits := float64(bytesSent) * 8.0
			rate := bits / time.Since(start).Seconds()
			mBitPerSecond := rate / float64(MBit)
			log.Infof("duration=%v, bytesSent=%v, packetsSent=%v throughput=%.2f Mb/s", time.Since(start), bytesSent, packetsSent, mBitPerSecond)

			assert.NoError(t, tbf.Close())
		}()

		wg.Wait()
	}

	t.Run("500Kbit-s", func(t *testing.T) {
		subTest(t, 500*KBit, 10*time.Second)
	})

	t.Run("1Mbit-s", func(t *testing.T) {
		subTest(t, 1*MBit, 10*time.Second)
	})

	t.Run("2Mbit-s", func(t *testing.T) {
		subTest(t, 2*MBit, 10*time.Second)
	})
}