package network

import (
	"fmt"
	"git.sxidc.com/go-tools/utils/syncutils"
	"io"
	"net"
	"time"
)

const (
	tcpServerReceiveBufferSize = 1024
)

// TCPServerRequestCallback 请求回调
// 参数：
// dataReader: 请求数据DataReader
// 返回值:
// 响应数据DataReader: 可以使用DataWriter构造，然后使用ToReader转换成DataReader，返回nil代表还要继续接收数据，不做响应
type TCPServerRequestCallback func(dataReader *DataReader) *DataReader

type TCPServerOption func(opt *TCPServerOptions)

func WithTCPServerReceiveBufferSize(receiveBufferSize int) TCPServerOption {
	return func(opt *TCPServerOptions) {
		opt.receiveBufferSize = receiveBufferSize
	}
}

func WithTCPServerWriteTimeout(timeout time.Duration) TCPServerOption {
	return func(opt *TCPServerOptions) {
		opt.writeTimeout = timeout
	}
}

func WithTCPServerReadTimeout(timeout time.Duration) TCPServerOption {
	return func(opt *TCPServerOptions) {
		opt.readTimeout = timeout
	}
}

func WithTCPServerRequestCallback(requestCallback TCPServerRequestCallback) TCPServerOption {
	return func(opt *TCPServerOptions) {
		opt.requestCallback = requestCallback
	}
}

type TCPServerOptions struct {
	// 默认1024字节，一般保证足够收取一个数据包
	receiveBufferSize int

	// 写超时，不设置就是阻塞写
	writeTimeout time.Duration

	// 读超时，不设置就是阻塞读
	readTimeout time.Duration

	// 请求数据回调
	requestCallback TCPServerRequestCallback
}

func NewTCPServerOptions(opts ...TCPServerOption) *TCPServerOptions {
	options := new(TCPServerOptions)

	for _, opt := range opts {
		opt(options)
	}

	if options.receiveBufferSize == 0 {
		options.receiveBufferSize = tcpServerReceiveBufferSize
	}

	return options
}

type TCPServer struct {
	options  *TCPServerOptions
	listener *net.TCPListener
	doneChan chan any
}

// Connect 建立连接
func (server *TCPServer) Connect(address string, options *TCPServerOptions) error {
	addr, err := net.ResolveTCPAddr("tcp", address)
	if err != nil {
		return err
	}

	listener, err := net.ListenTCP("tcp", addr)
	if err != nil {
		return err
	}

	server.options = options
	server.listener = listener
	server.doneChan = make(chan any)

	// 启动读取请求协程
	go server.accept()

	return nil
}

// Disconnect 断开连接
func (server *TCPServer) Disconnect() error {
	err := server.listener.Close()
	if err != nil {
		return err
	}
	server.listener = nil

	server.doneChan <- nil
	close(server.doneChan)
	server.doneChan = nil

	return nil
}

func (server *TCPServer) accept() {
	readRequestDoneChannels := syncutils.NewSyncVar(make([]chan any, 0), false)

	for {
		select {
		case <-server.doneChan:
			readRequestDoneChannels.ForWrite(func(channels []chan any) []chan any {
				for _, channel := range channels {
					channel <- nil
					close(channel)
				}

				return make([]chan any, 0)
			})

			return
		default:
			conn, err := server.listener.AcceptTCP()
			if err != nil {
				fmt.Println(err)
				continue
			}

			readRequestDoneChan := make(chan any)
			readRequestDoneChannels.ForWrite(func(channels []chan any) []chan any {
				channels = append(channels, readRequestDoneChan)
				return channels
			})

			go server.readRequest(conn, readRequestDoneChan, func(doneChan chan any, err error) {
				readRequestDoneChannels.ForWrite(func(channels []chan any) []chan any {
					for i, toRemoveDoneChan := range channels {
						if doneChan == toRemoveDoneChan {
							close(toRemoveDoneChan)
							channels = append(channels[:i], channels[i+1:]...)
							break
						}
					}

					return channels
				})
			})
		}
	}
}

func (server *TCPServer) readRequest(conn *net.TCPConn, doneChan chan any, errCloseCallback func(doneChan chan any, err error)) {
	for {
		select {
		case <-doneChan:
			if conn != nil {
				closeConnection(conn)
			}

			return
		default:
			err := readTCP(conn, server.options.receiveBufferSize, func(data []byte) (bool, error) {
				// 没有提供请求响应函数
				if server.options.requestCallback == nil {
					return false, nil
				}

				// 交给上层回调处理，返回处理结果和响应数据
				responseDataReader := server.options.requestCallback(NewDataReader(data))
				if responseDataReader != nil {
					server.response(conn, responseDataReader.GetBytes())
					return true, nil
				}

				return true, nil
			}, withReadDeadline(server.options.readTimeout))
			if err != nil {
				// 对端关闭
				if err == io.EOF {
					closeConnection(conn)
					errCloseCallback(doneChan, err)
					return
				}

				fmt.Println(err)
				continue
			}
		}
	}
}

func (server *TCPServer) response(conn net.Conn, data []byte) {
	err := writeTCP(conn, data, withWriteDeadline(server.options.writeTimeout))
	if err != nil {
		fmt.Println("Response Error:", err)
		return
	}
}