// The MIT License (MIT)
//
// Copyright (c) 2015 xtaci
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

package kcp

import (
	"net"
	"sync/atomic"

	"github.com/pkg/errors"
)

func sameUDPAddr(a, b *net.UDPAddr) bool {
	if a == nil || b == nil {
		return false
	}
	if a.Port != b.Port || a.Zone != b.Zone {
		return false
	}
	return a.IP.Equal(b.IP)
}

// defaultReadLoop is the standard procedure for reading from a connection
func (s *UDPSession) defaultReadLoop() {
	buf := make([]byte, mtuLimit)

	var src *net.UDPAddr
	var srcStr string
	if s.remote != nil {
		if udp, ok := s.remote.(*net.UDPAddr); ok {
			src = udp
		} else {
			srcStr = s.remote.String()
		}
	}
	for {
		n, addr, err := s.conn.ReadFrom(buf)
		if err != nil {
			s.notifyReadError(errors.WithStack(err))
			return
		}

		if s.isClosed() {
			return
		}

		// make sure the packet is from the same source
		if src == nil && srcStr == "" { // set source address if nil
			if udp, ok := addr.(*net.UDPAddr); ok {
				src = udp
			} else {
				srcStr = addr.String()
			}
		} else if src != nil {
			udp, ok := addr.(*net.UDPAddr)
			if !ok || !sameUDPAddr(src, udp) {
				atomic.AddUint64(&DefaultSnmp.InErrs, 1)
				continue
			}
		} else if addr.String() != srcStr {
			atomic.AddUint64(&DefaultSnmp.InErrs, 1)
			continue
		}

		s.packetInput(buf[:n])
	}
}

// defaultReadLoop is the standard procedure for reading and accepting connections on a listener
func (l *Listener) defaultMonitor() {
	buf := make([]byte, mtuLimit)
	for {
		n, from, err := l.conn.ReadFrom(buf)
		if err != nil {
			l.notifyReadError(errors.WithStack(err))
			return
		}

		l.packetInput(buf[:n], from)
	}
}