package telegram

import (
	"io"
	"math/rand"

	"github.com/juju/errors"
)

// Telegram defines an interface to connect to Telegram. This
// encapsulates logic of working with middleproxies or direct
// connections.
type Telegram interface {
	Dial(int16) (io.ReadWriteCloser, error)
	Init(io.ReadWriteCloser) (io.ReadWriteCloser, error)
}

type baseTelegram struct {
	dialer *tgDialer

	v4Addresses map[int16][]string
	v6Addresses map[int16][]string
}

func (b *baseTelegram) Dial(dcIdx int16) (io.ReadWriteCloser, error) {
	addrs := make([]string, 2)
	if addr, ok := b.v6Addresses[dcIdx]; ok && len(addr) > 0 {
		addrs = append(addrs, addr[rand.Intn(len(addr))])
	}
	if addr, ok := b.v4Addresses[dcIdx]; ok && len(addr) > 0 {
		addrs = append(addrs, addr[rand.Intn(len(addr))])
	}

	for _, addr := range addrs {
		if conn, err := b.dialer.dialRWC(addr); err == nil {
			return conn, err
		}
	}

	return nil, errors.New("Cannot connect to Telegram")
}