// serviceConfig constructs the config for all good instances of a single service.
func serviceConfig(client *api.Client, name string, passing map[string]bool, tagPrefix string) (config []string) {
	if name == "" || len(passing) == 0 {
		return nil
	}

	q := &api.QueryOptions{RequireConsistent: true}
	svcs, _, err := client.Catalog().Service(name, "", q)
	if err != nil {
		log.Printf("[WARN] [%s] Error getting catalog service %s. %v", name, err)
		return nil
	}

	for _, svc := range svcs {
		// check if the instance is in the list of instances
		// which passed the health check
		if _, ok := passing[svc.ServiceID]; !ok {
			continue
		}

		for _, tag := range svc.ServiceTags {
			if host, path, ok := parseURLPrefixTag(tag, tagPrefix); ok {
				name, addr, port := svc.ServiceName, svc.ServiceAddress, svc.ServicePort
				if runtime.GOOS == "darwin" && !strings.Contains(addr, ".") {
					addr += ".local"
				}
				config = append(config, fmt.Sprintf("route add %s %s%s http://%s:%d/ tags %q", name, host, path, addr, port, strings.Join(svc.ServiceTags, ",")))
			}
		}
	}
	return config
}

func putKV(client *api.Client, key, value string, index uint64) (bool, error) {
	p := &api.KVPair{Key: key[1:], Value: []byte(value), ModifyIndex: index}
	ok, _, err := client.KV().CAS(p, nil)
	if err != nil {
		return false, err
	}
	return ok, nil
}

func getKV(client *api.Client, key string, waitIndex uint64) (string, uint64, error) {
	q := &api.QueryOptions{RequireConsistent: true, WaitIndex: waitIndex}
	kvpair, meta, err := client.KV().Get(key, q)
	if err != nil {
		return "", 0, err
	}
	if kvpair == nil {
		return "", meta.LastIndex, nil
	}
	return strings.TrimSpace(string(kvpair.Value)), meta.LastIndex, nil
}

// datacenter returns the datacenter of the local agent
func datacenter(c *api.Client) (string, error) {
	self, err := c.Agent().Self()
	if err != nil {
		return "", err
	}

	cfg, ok := self["Config"]
	if !ok {
		return "", errors.New("consul: self.Config not found")
	}
	dc, ok := cfg["Datacenter"].(string)
	if !ok {
		return "", errors.New("consul: self.Datacenter not found")
	}
	return dc, nil
}

// watchAutoConfig monitors the consul health checks and creates a new configuration
// on every change.
func watchAutoConfig(client *api.Client, tagPrefix string, config chan []string) {
	var lastIndex uint64

	for {
		q := &api.QueryOptions{RequireConsistent: true, WaitIndex: lastIndex}
		checks, meta, err := client.Health().State("passing", q)
		if err != nil {
			log.Printf("[WARN] Error fetching health state. %v", err)
			time.Sleep(time.Second)
			continue
		}

		log.Printf("[INFO] Health changed to #%d", meta.LastIndex)
		config <- servicesConfig(client, checks, tagPrefix)
		lastIndex = meta.LastIndex
	}
}

func nextValue(client *api.Client, path string, lastIndex uint64) (string, uint64) {
	for {
		q := &api.QueryOptions{RequireConsistent: true, WaitIndex: lastIndex}
		kvpair, meta, err := client.KV().Get(path, q)
		if err != nil {
			log.Printf("[WARN] Error fetching config from %s. %v", path, err)
			time.Sleep(time.Second)
			continue
		}

		if kvpair == nil {
			return "", meta.LastIndex
		}

		return strings.TrimSpace(string(kvpair.Value)), meta.LastIndex
	}
}