package net

import (
	"fmt"
	"net"
	"net/http"
	"sync"
)

type DualStackHTTPServer struct {
    Handler http.Handler
}

func (s *DualStackHTTPServer) ListenAndServe(ipv4 string, ipv6 string, port int) error {
    v4Listener, err := net.Listen("tcp4", fmt.Sprintf("%s:%d", ipv4, port))
    if err != nil {
        return fmt.Errorf("IPv4 listen: %v", err)
    }

    v6Listener, err := net.Listen("tcp6", fmt.Sprintf("[%s]:%d", ipv6, port))
    if err != nil {
        v4Listener.Close()
        return fmt.Errorf("IPv6 listen: %v", err)
    }

    srv := &http.Server{ Handler: s.Handler }

    var wg sync.WaitGroup
    errs := make(chan error, 2)

    for _, listener := range []net.Listener{v4Listener, v6Listener} {
        wg.Add(1)
        go func(l net.Listener) {
            defer wg.Done()
            errs <- srv.Serve(l)
        }(listener)
    }

    return <-errs
}