package imapserver

import (
	"net"
	"time"
)

// IdleTimeoutListener wraps a listener so every accepted connection gets a rolling
// deadline extended by d on each read/write. Unlike SMTP (go-smtp's Server.ReadTimeout/
// WriteTimeout), go-imap/v2's imapserver.Options has no timeout knob at all, so an idle
// or slow-drip connection can otherwise hold a goroutine (and a file descriptor) open
// indefinitely. 30 minutes (the caller's chosen d) matches RFC 2177's guidance that an
// IDLE-capable client re-issue IDLE at least that often, so a real IDLE session renews
// its own deadline in time and is never cut off by this.
func IdleTimeoutListener(inner net.Listener, d time.Duration) net.Listener {
	return &idleTimeoutListener{Listener: inner, d: d}
}

type idleTimeoutListener struct {
	net.Listener
	d time.Duration
}

func (l *idleTimeoutListener) Accept() (net.Conn, error) {
	conn, err := l.Listener.Accept()
	if err != nil {
		return nil, err
	}
	conn.SetDeadline(time.Now().Add(l.d))
	return &idleTimeoutConn{Conn: conn, d: l.d}, nil
}

type idleTimeoutConn struct {
	net.Conn
	d time.Duration
}

func (c *idleTimeoutConn) Read(b []byte) (int, error) {
	n, err := c.Conn.Read(b)
	c.Conn.SetDeadline(time.Now().Add(c.d))
	return n, err
}

func (c *idleTimeoutConn) Write(b []byte) (int, error) {
	n, err := c.Conn.Write(b)
	c.Conn.SetDeadline(time.Now().Add(c.d))
	return n, err
}