// Copyright (c) 2023 The Gnet Authors. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package gnet

import (
	"net"
	"runtime"
)

func (eng *engine) listen() (err error) {
	if eng.opts.LockOSThread {
		runtime.LockOSThread()
		defer runtime.UnlockOSThread()
	}

	defer func() { eng.shutdown(err) }()

	var buffer [0x10000]byte
	for {
		if eng.ln.pc != nil {
			// Read data from UDP socket.
			n, addr, e := eng.ln.pc.ReadFrom(buffer[:])
			if e != nil {
				err = e
				eng.opts.Logger.Errorf("failed to receive data from UDP fd due to error:%v", err)
				return
			}

			el := eng.lb.next(addr)
			c := newUDPConn(el, eng.ln.addr, addr)
			el.ch <- packUDPConn(c, buffer[:n])
		} else {
			// Accept TCP socket.
			tc, e := eng.ln.ln.Accept()
			if e != nil {
				err = e
				eng.opts.Logger.Errorf("Accept() fails due to error: %v", err)
				return
			}
			el := eng.lb.next(tc.RemoteAddr())
			c := newTCPConn(tc, el)
			el.ch <- c
			go func(c *conn, tc net.Conn, el *eventloop) {
				var buffer [0x10000]byte
				for {
					n, err := tc.Read(buffer[:])
					if err != nil {
						el.ch <- &netErr{c, err}
						return
					}
					el.ch <- packTCPConn(c, buffer[:n])
				}
			}(c, tc, el)
		}
	}
}