import (
	"io"
	"net"
)

type Mux struct {
	ops chan func(map[net.Addr]net.Conn)
}

func (m *Mux) Add(conn net.Conn) {
	m.ops <- func(m map[net.Addr]net.Conn) {
		m[conn.RemoteAddr()] = conn
	}
}

func (m *Mux) Remove(addr net.Addr) {
	m.ops <- func(m map[net.Addr]net.Conn) {
		delete(m, addr)
	}
}

func (m *Mux) SendMessage(msg string) error {
	result := make(chan error, 1)
	m.ops <- func(m map[net.Addr]net.Conn) {
		for _, conn := range m {
			_, err := io.WriteString(conn, msg)
			if err != nil {
				result <- err
				return
			}
		}
		result <- nil
	}
	return <-result
}

func (m *Mux) loop() {
	var conns map[net.Addr]net.Conn
	for op := range m.ops {
		op(conns)
	}
}