client.go

package main

import (
	"context"
	"net"
	"net/textproto"
	"time"
)

// Client is
type Client struct {
	baseConn net.Conn
	conn     *textproto.Conn
}

// New is
func New(ctx context.Context, addr string) (*Client, error) {
	var dialer net.Dialer
	baseConn, err := dialer.DialContext(ctx, "tcp", addr)
	if err != nil {
		return nil, err
	}
	conn := textproto.NewConn(baseConn)
	return &Client{
		baseConn: baseConn,
		conn:     conn,
	}, nil
}

// Close is
func (c *Client) Close() error {
	return c.baseConn.Close()
}

var reset = time.Time{}
var immediately = time.Unix(1, 0)

func (c *Client) wrapReadFunc(ctx context.Context, f func()) {
	c.baseConn.SetReadDeadline(reset)
	stop := make(chan struct{})
	done := make(chan struct{})
	go func() {
		select {
		case <-ctx.Done():
			c.baseConn.SetReadDeadline(immediately)
		case <-stop:
		}
		close(done)
	}()

	f()
	close(stop)
	<-done
	c.baseConn.SetReadDeadline(reset)
}

func (c *Client) wrapWriteFunc(ctx context.Context, f func()) {
	c.baseConn.SetWriteDeadline(reset)
	stop := make(chan struct{})
	done := make(chan struct{})
	go func() {
		select {
		case <-ctx.Done():
			c.baseConn.SetWriteDeadline(immediately)
		case <-stop:
		}
		close(done)
	}()

	f()
	close(stop)
	<-done
	c.baseConn.SetWriteDeadline(reset)
}

// ReadCodeLine is
func (c *Client) ReadCodeLine(ctx context.Context, code int) (outCode int, outMsg string, outErr error) {
	c.wrapReadFunc(ctx, func() {
		outCode, outMsg, outErr = c.conn.ReadCodeLine(code)
	})
	return
}

func main() {
}