// Copyright 2021 Martin Dosch.
// Use of this source code is governed by the BSD-2-clause
// license that can be found in the LICENSE file.package main

package main

import (
	"fmt"
	"net"
	"sort"
	"strings"

	"github.com/mattn/go-xmpp" // BSD-3-Clause
)

type srv struct {
	host     string
	xmpps    bool
	port     uint16
	priority uint16
	weight   uint16
}
type srvMixed []srv

type byPriority []srv

func (o byPriority) Len() int      { return len(o) }
func (o byPriority) Swap(i, j int) { o[i], o[j] = o[j], o[i] }
func (o byPriority) Less(i, j int) bool {
	if o[i].priority == o[j].priority {
		return o[i].weight > o[j].weight
	}
	return o[i].priority < o[j].priority
}

func connect(options xmpp.Options, directTLS bool) (*xmpp.Client, error) {

	// Look up SRV records if server is not specified manually.
	srvMixed := srvMixed{}
	if options.Host == "" {
		server := options.User[strings.Index(options.User, "@")+1:]
		// Look up xmpp-client SRV records.
		if _, addrs, err := net.LookupSRV("xmpp-client", "tcp", server); err == nil {
			if len(addrs) > 0 {
				for _, adr := range addrs {
					srvMixed = append(srvMixed, srv{strings.TrimSuffix(adr.Target, "."),
						false, adr.Port, adr.Priority, adr.Weight})
				}
			}
		}
		// Look up xmpps-client SRV records.
		if _, addrs, err := net.LookupSRV("xmpps-client", "tcp", server); err == nil {
			if len(addrs) > 0 {
				if addrs[0].Target != "." {
					for _, adr := range addrs {
						srvMixed = append(srvMixed,
							srv{strings.TrimSuffix(adr.Target, "."), true, adr.Port,
								adr.Priority, adr.Weight})
					}
				}
			}
		}
		if len(srvMixed) > 0 {
			// Sort xmpp- and xmpps-client SRV records according to the priority
			// and wight.
			sort.Sort(byPriority(srvMixed))
			for _, adr := range srvMixed {
				if !directTLS && !adr.xmpps {
					// Use StartTLS
					options.NoTLS = true
					options.StartTLS = true
					options.Host = net.JoinHostPort(adr.host, fmt.Sprint(adr.port))
					// Connect to server
					client, err := options.NewClient()
					if err == nil {
						return client, err
					}
				} else if adr.xmpps {
					// Use direct TLS
					options.NoTLS = false
					options.StartTLS = false
					options.Host = net.JoinHostPort(adr.host, fmt.Sprint(adr.port))
					// Connect to server
					client, err := options.NewClient()
					if err == nil {
						return client, err
					}

				}
			}
		}
		// Try port 5222 if no xmpp-client SRV records are provided.
		options.NoTLS = true
		options.StartTLS = true
		options.Host = net.JoinHostPort(server, "5222")
		// Connect to server
		client, err := options.NewClient()
		return client, err
	}
	// Connect to server
	client, err := options.NewClient()
	return client, err
}