package net_test

import (
    "fmt"
    "math/rand"
    "net"
    "sync"
    "testing"
)

const (
    ndialers = 100
    nlisteners = 100
    nconn = 100000
)

func TestAccept(t *testing.T) {
    listeners := []net.Listener{}
    for k := 0; k < nlisteners; k++ {
        l, err := net.ListenTCP("tcp", &net.TCPAddr{})
        if err != nil {
            panic("Listen failed: " + err.Error())
        }
        listeners = append(listeners, l)
    }

    // start dialers
    var dialWg sync.WaitGroup
    for k := 0; k < ndialers; k++ {
        dialWg.Add(1)
        go func() {
            rng := rand.New(rand.NewSource(int64(k)))
            defer dialWg.Done()
            for j := 0; j < nconn; j++ {
                l := listeners[rng.Intn(len(listeners))]
                fmt.Printf("Dialing %v\n", l.Addr())
                c, err := net.Dial("tcp", l.Addr().String())
                if err != nil {
                    panic("Dial failed: " + err.Error())
                }
                tc := c.(*net.TCPConn)
                if err := tc.SetLinger(0); err != nil {
                    panic(err)
                }
                if err := c.Close(); err != nil {
                    panic(err)
                }
            }
        }()
    }

    // accept on listeners
    var listenWg sync.WaitGroup
    for _, listener := range listeners {
        listenWg.Add(1)
        l := listener
        go func() {
            defer listenWg.Done()
            for {
                fmt.Printf("Accepting on %v\n", l.Addr())
                c, err := l.Accept()
                if err != nil {
                    break
                }
                tc := c.(*net.TCPConn)
                if err := tc.SetLinger(0); err != nil {
                    panic(err)
                }
                if err := c.Close(); err != nil {
                    panic(err)
                }
            }
        }()
    }

    dialWg.Wait()

    for _, l := range listeners {
        if err := l.Close(); err != nil {
            panic("listener close failed: " + err.Error())
        }
    }

    listenWg.Wait()
}