// Copyright 2016 Sam Whited.
// Use of this source code is governed by the BSD 2-clause license that can be
// found in the LICENSE file.

// +build !go1.7

package xmpp

import (
	"net"
	"strconv"
	"time"

	"golang.org/x/net/context"
)

func (d *Dialer) dial(
	ctx context.Context, network string, config *Config) (*Conn, error) {
	if ctx == nil {
		panic("xmpp.Dial: nil context")
	}

	// Backwards compatibility with old net.Dialer cancelation methods.
	deadline := d.deadline(ctx, time.Now())
	if !deadline.IsZero() {
		if d, ok := ctx.Deadline(); !ok || deadline.Before(d) {
			subCtx, cancel := context.WithDeadline(ctx, deadline)
			defer cancel()
			ctx = subCtx
		}
	}
	if oldCancel := d.Cancel; oldCancel != nil {
		subCtx, cancel := context.WithCancel(ctx)
		defer cancel()
		go func() {
			select {
			case <-oldCancel:
				cancel()
			case <-subCtx.Done():
			}
		}()
		ctx = subCtx
	}

	c := &Conn{
		config: config,
	}

	if d.NoLookup {
		p, err := lookupPort(network, config.connType())
		if err != nil {
			return nil, err
		}
		conn, err := d.Dialer.Dial(network, net.JoinHostPort(
			config.Location.Domainpart(),
			strconv.FormatUint(uint64(p), 10),
		))
		if err != nil {
			return nil, err
		}
		c.rwc = conn
		return c, nil
	}

	addrs, err := lookupService(config.connType(), network, c.RemoteAddr())
	if err != nil {
		return nil, err
	}

	// Try dialing all of the SRV records we know about, breaking as soon as the
	// connection is established.
	for _, addr := range addrs {
		if conn, e := d.Dialer.Dial(
			network, net.JoinHostPort(
				addr.Target, strconv.FormatUint(uint64(addr.Port), 10),
			),
		); e != nil {
			err = e
			continue
		} else {
			err = nil
			c.rwc = conn
			break
		}
	}
	if err != nil {
		return nil, err
	}

	return c, nil
}