// Package graceful provides a graceful tcp handling library
package graceful

import (
	"errors"
	"net"
	"time"
)

const network = "tcp"

var ErrInterfaceConversion = errors.New("interface conversion failed")

// Listener is a wrapper for net.TCPListener
type Listener struct {
	*net.TCPListener

	keepAlive time.Duration
}

// New wraps Listener around net.TCPListener
func New(laddr string, keepAlive time.Duration) (*Listener, error) {
	l, err := net.Listen(network, laddr)
	if err != nil {
		return nil, err
	}
	tcpl, ok := l.(*net.TCPListener)
	if !ok {
		return nil, ErrInterfaceConversion
	}
	return &Listener{
		TCPListener: tcpl,
		keepAlive:   keepAlive,
	}, nil
}

// Accept wraps net.TCPListener.AcceptTCP method
func (l *Listener) Accept() (net.Conn, error) {
	conn, err := l.AcceptTCP()
	if err != nil {
		return conn, err
	}
	if l.keepAlive > 0 {
		conn.SetKeepAlive(true)
		conn.SetKeepAlivePeriod(l.keepAlive)
	}
	return conn, nil
}

// Stop stops the listener
func (l *Listener) Stop() {
	l.TCPListener.Close()
}