/*
   Copyright 2014 CoreOS, Inc.

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
*/

package discovery

import (
	"fmt"
	"log"
	"net"
	"strings"

	"github.com/coreos/etcd/pkg/types"
)

var (
	// indirection for testing
	lookupSRV = net.LookupSRV
)

// TODO(barakmich): Currently ignores priority and weight (as they don't make as much sense for a bootstrap)
// Also doesn't do any lookups for the token (though it could)
// Also sees each entry as a separate instance.
func SRVGetCluster(name, dns string, defaultToken string, apurls types.URLs) (string, string, error) {
	stringParts := make([]string, 0)
	tempName := int(0)
	tcpAPUrls := make([]string, 0)

	// First, resolve the apurls
	for _, url := range apurls {
		tcpAddr, err := net.ResolveTCPAddr("tcp", url.Host)
		if err != nil {
			log.Printf("discovery: Couldn't resolve host %s during SRV discovery", url.Host)
			return "", "", err
		}
		tcpAPUrls = append(tcpAPUrls, tcpAddr.String())
	}

	updateNodeMap := func(service, prefix string) error {
		_, addrs, err := lookupSRV(service, "tcp", dns)
		if err != nil {
			return err
		}
		for _, srv := range addrs {
			host := net.JoinHostPort(srv.Target, fmt.Sprintf("%d", srv.Port))
			tcpAddr, err := net.ResolveTCPAddr("tcp", host)
			if err != nil {
				log.Printf("discovery: Couldn't resolve host %s during SRV discovery", host)
				continue
			}
			n := ""
			for _, url := range tcpAPUrls {
				if url == tcpAddr.String() {
					n = name
				}
			}
			if n == "" {
				n = fmt.Sprintf("%d", tempName)
				tempName += 1
			}
			stringParts = append(stringParts, fmt.Sprintf("%s=%s%s", n, prefix, tcpAddr.String()))
			log.Printf("discovery: Got bootstrap from DNS for %s at host %s to %s%s", service, host, prefix, tcpAddr.String())
		}
		return nil
	}

	failCount := 0
	err := updateNodeMap("etcd-server-ssl", "https://")
	if err != nil {
		log.Printf("discovery: Error querying DNS SRV records for _etcd-server-ssl %s", err)
		failCount += 1
	}
	err = updateNodeMap("etcd-server", "http://")
	if err != nil {
		log.Printf("discovery: Error querying DNS SRV records for _etcd-server %s", err)
		failCount += 1
	}
	if failCount == 2 {
		log.Printf("discovery: SRV discovery failed: too many errors querying DNS SRV records")
		return "", "", err
	}
	return strings.Join(stringParts, ","), defaultToken, nil
}