// Copyright 2013 Prometheus Team
// 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 main

import (
	"flag"
	"fmt"
	"net"
	"os"
	"strings"
	"time"

	"github.com/prometheus/log"

	"github.com/prometheus/alertmanager/config"
	"github.com/prometheus/alertmanager/manager"
	"github.com/prometheus/alertmanager/web"
	"github.com/prometheus/alertmanager/web/api"
)

var (
	configFile       = flag.String("config.file", "alertmanager.conf", "Alert Manager configuration file name.")
	silencesFile     = flag.String("silences.file", "silences.json", "Silence storage file name.")
	minRefreshPeriod = flag.Duration("alerts.min-refresh-period", 5*time.Minute, "Minimum required alert refresh period before an alert is purged.")
	listenAddress    = flag.String("web.listen-address", ":9093", "Address to listen on for the web interface and API.")
	pathPrefix       = flag.String("web.path-prefix", "/", "Prefix for all web paths.")
	hostname         = flag.String("web.hostname", "", "Hostname on which the Alertmanager is available to the outside world.")
	externalURL      = flag.String("web.external-url", "", "The URL under which Alertmanager is externally reachable (for example, if Alertmanager is served via a reverse proxy). Used for generating relative and absolute links back to Alertmanager itself. If omitted, relevant URL components will be derived automatically.")
)

func alertmanagerURL(hostname, pathPrefix, addr, externalURL string) (string, error) {
	if externalURL != "" {
		return externalURL, nil
	}

	var err error
	if hostname == "" {
		hostname, err = os.Hostname()
		if err != nil {
			return "", err
		}
	}

	_, port, err := net.SplitHostPort(addr)
	if err != nil {
		return "", err
	}
	return fmt.Sprintf("http://%s:%s%s", hostname, port, pathPrefix), nil
}

func main() {
	flag.Parse()

	if !strings.HasPrefix(*pathPrefix, "/") {
		*pathPrefix = "/" + *pathPrefix
	}
	if !strings.HasSuffix(*pathPrefix, "/") {
		*pathPrefix = *pathPrefix + "/"
	}

	versionInfoTmpl.Execute(os.Stdout, BuildInfo)

	conf := config.MustLoadFromFile(*configFile)

	silencer := manager.NewSilencer()
	defer silencer.Close()

	err := silencer.LoadFromFile(*silencesFile)
	if err != nil {
		log.Warn("Couldn't load silences, starting up with empty silence list: ", err)
	}
	saveSilencesTicker := time.NewTicker(10 * time.Second)
	go func() {
		for range saveSilencesTicker.C {
			if err := silencer.SaveToFile(*silencesFile); err != nil {
				log.Error("Error saving silences to file: ", err)
			}
		}
	}()
	defer saveSilencesTicker.Stop()

	amURL, err := alertmanagerURL(*hostname, *pathPrefix, *listenAddress, *externalURL)
	if err != nil {
		log.Fatalln("Error building Alertmanager URL:", err)
	}
	notifier := manager.NewNotifier(conf.NotificationConfig, amURL)
	defer notifier.Close()

	inhibitor := new(manager.Inhibitor)
	inhibitor.SetInhibitRules(conf.InhibitRules())

	options := &manager.MemoryAlertManagerOptions{
		Inhibitor:          inhibitor,
		Silencer:           silencer,
		Notifier:           notifier,
		MinRefreshInterval: *minRefreshPeriod,
	}
	alertManager := manager.NewMemoryAlertManager(options)
	alertManager.SetAggregationRules(conf.AggregationRules())
	go alertManager.Run()

	// Web initialization.
	flags := map[string]string{}
	flag.VisitAll(func(f *flag.Flag) {
		flags[f.Name] = f.Value.String()
	})

	statusHandler := &web.StatusHandler{
		Config:     conf.String(),
		Flags:      flags,
		BuildInfo:  BuildInfo,
		Birth:      time.Now(),
		PathPrefix: *pathPrefix,
	}

	webService := &web.WebService{
		// REST API Service.
		AlertManagerService: &api.AlertManagerService{
			Manager:    alertManager,
			Silencer:   silencer,
			PathPrefix: *pathPrefix,
		},

		// Template-based page handlers.
		AlertsHandler: &web.AlertsHandler{
			Manager:                alertManager,
			IsSilencedInterrogator: silencer,
		},
		SilencesHandler: &web.SilencesHandler{
			Silencer: silencer,
		},
		StatusHandler: statusHandler,
	}
	go webService.ServeForever(*listenAddress, *pathPrefix)

	// React to configuration changes.
	watcher := config.NewFileWatcher(*configFile)
	go watcher.Watch(func(conf *config.Config) {
		inhibitor.SetInhibitRules(conf.InhibitRules())
		notifier.SetNotificationConfigs(conf.NotificationConfig)
		alertManager.SetAggregationRules(conf.AggregationRules())
		statusHandler.UpdateConfig(conf.String())
	})

	log.Info("Running notification dispatcher...")
	notifier.Dispatch()
}