package main

import (
	"context"
	"flag"
	"fmt"
	"net/http"
	"net/url"
	"os"
	"strings"
	"time"

	"github.com/VictoriaMetrics/VictoriaMetrics/app/vmalert/common"
	"github.com/VictoriaMetrics/VictoriaMetrics/app/vmalert/config"
	"github.com/VictoriaMetrics/VictoriaMetrics/app/vmalert/datasource"
	"github.com/VictoriaMetrics/VictoriaMetrics/app/vmalert/provider"
	"github.com/VictoriaMetrics/VictoriaMetrics/lib/buildinfo"
	"github.com/VictoriaMetrics/VictoriaMetrics/lib/envflag"
	"github.com/VictoriaMetrics/VictoriaMetrics/lib/flagutil"
	"github.com/VictoriaMetrics/VictoriaMetrics/lib/httpserver"
	"github.com/VictoriaMetrics/VictoriaMetrics/lib/logger"
	"github.com/VictoriaMetrics/VictoriaMetrics/lib/procutil"
)

var (
	rulePath = flagutil.NewArray("rule", `Path to file with alert rules, accepts patterns. 
Flag can be specified multiple time. 
Examples:
 -rule /path/to/file. Path to single file with alerting rules
 -rule dir/*.yaml -rule /*.yaml. Paths to all yaml files in relative dir folder and absolute yaml file in a root.`)
	validateAlertAnnotations = flag.Bool("rule.validateAnnotations", true, "Indicates to validate annotation templates")
	httpListenAddr           = flag.String("httpListenAddr", ":8880", "Address to listen for http connections")
	datasourceURL            = flag.String("datasource.url", "", "Victoria Metrics or VMSelect url. Required parameter. e.g. http://127.0.0.1:8428")
	basicAuthUsername        = flag.String("datasource.basicAuth.username", "", "Optional basic auth username to use for -datasource.url")
	basicAuthPassword        = flag.String("datasource.basicAuth.password", "", "Optional basic auth password to use for -datasource.url")
	evaluationInterval       = flag.Duration("evaluationInterval", 1*time.Minute, "How often to evaluate the rules. Default 1m")
	providerURL              = flag.String("provider.url", "", "Prometheus alertmanager url. Required parameter. e.g. http://127.0.0.1:9093")
	externalURL              = flag.String("external.url", "", "Reachable external url. URL is used to generate sharable alert url and in annotation templates")
)

func main() {
	envflag.Parse()
	buildinfo.Init()
	logger.Init()
	checkFlags()
	ctx, cancel := context.WithCancel(context.Background())
	eu, err := getExternalURL(*externalURL, *httpListenAddr, httpserver.IsTLS())
	if err != nil {
		logger.Fatalf("can not get external url:%s ", err)
	}
	common.InitTemplateFunc(eu)

	logger.Infof("reading alert rules configuration file from %s", strings.Join(*rulePath, ";"))
	alertGroups, err := config.Parse(*rulePath, *validateAlertAnnotations)
	if err != nil {
		logger.Fatalf("Cannot parse configuration file: %s", err)
	}

	w := &watchdog{
		storage: datasource.NewVMStorage(*datasourceURL, *basicAuthUsername, *basicAuthPassword, &http.Client{}),
		alertProvider: provider.NewAlertManager(*providerURL, func(group, name string) string {
			return strings.Replace(fmt.Sprintf("%s/%s/%s/status", eu, group, name), "//", "/", -1)
		}, &http.Client{}),
	}
	for id := range alertGroups {
		go func(group common.Group) {
			w.run(ctx, group, *evaluationInterval)
		}(alertGroups[id])
	}
	go func() {
		httpserver.Serve(*httpListenAddr, func(w http.ResponseWriter, r *http.Request) bool {
			panic("not implemented")
		})
	}()
	sig := procutil.WaitForSigterm()
	logger.Infof("service received signal %s", sig)
	if err := httpserver.Stop(*httpListenAddr); err != nil {
		logger.Fatalf("cannot stop the webservice: %s", err)
	}
	cancel()
	w.stop()
}

type watchdog struct {
	storage       *datasource.VMStorage
	alertProvider provider.AlertProvider
}

func (w *watchdog) run(ctx context.Context, a common.Group, evaluationInterval time.Duration) {
	logger.Infof("watchdog for %s has been run", a.Name)
	t := time.NewTicker(evaluationInterval)
	var metrics []datasource.Metric
	var err error
	var alerts []common.Alert
	defer t.Stop()
	for {
		select {
		case <-t.C:
			start := time.Now()
			for _, r := range a.Rules {
				if metrics, err = w.storage.Query(ctx, r.Expr); err != nil {
					logger.Errorf("error reading metrics %s", err)
					continue
				}
				// todo check for and calculate alert states
				if len(metrics) < 1 {
					continue
				}
				// todo define alert end time
				alerts = common.AlertsFromMetrics(metrics, a.Name, r, start, time.Time{})
				// todo save to storage
				if err := w.alertProvider.Send(alerts); err != nil {
					logger.Errorf("error sending alerts %s", err)
					continue
				}
				// todo is alert still active/pending?
			}

		case <-ctx.Done():
			logger.Infof("%s receive stop signal", a.Name)
			return
		}
	}
}

func getExternalURL(externalURL, httpListenAddr string, isSecure bool) (*url.URL, error) {
	if externalURL != "" {
		return url.Parse(externalURL)
	}
	hname, err := os.Hostname()
	if err != nil {
		return nil, err
	}
	port := ""
	if ipport := strings.Split(httpListenAddr, ":"); len(ipport) > 1 {
		port = ":" + ipport[1]
	}
	schema := "http://"
	if isSecure {
		schema = "https://"
	}
	return url.Parse(fmt.Sprintf("%s%s%s", schema, hname, port))
}

func (w *watchdog) stop() {
	panic("not implemented")
}

func checkFlags() {
	if *providerURL == "" {
		flag.PrintDefaults()
		logger.Fatalf("provider.url is empty")
	}
	if *datasourceURL == "" {
		flag.PrintDefaults()
		logger.Fatalf("datasource.url is empty")
	}
}