package main

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

	"github.com/VictoriaMetrics/VictoriaMetrics/app/vmalert/config"
	"github.com/VictoriaMetrics/VictoriaMetrics/app/vmalert/datasource"
	"github.com/VictoriaMetrics/VictoriaMetrics/app/vmalert/notifier"
	"github.com/VictoriaMetrics/VictoriaMetrics/app/vmalert/remoteread"
	"github.com/VictoriaMetrics/VictoriaMetrics/app/vmalert/remotewrite"
	"github.com/VictoriaMetrics/VictoriaMetrics/app/vmalert/templates"
	"github.com/VictoriaMetrics/VictoriaMetrics/lib/buildinfo"
	"github.com/VictoriaMetrics/VictoriaMetrics/lib/envflag"
	"github.com/VictoriaMetrics/VictoriaMetrics/lib/fasttime"
	"github.com/VictoriaMetrics/VictoriaMetrics/lib/flagutil"
	"github.com/VictoriaMetrics/VictoriaMetrics/lib/httpserver"
	"github.com/VictoriaMetrics/VictoriaMetrics/lib/logger"
	"github.com/VictoriaMetrics/VictoriaMetrics/lib/procutil"
	"github.com/VictoriaMetrics/VictoriaMetrics/lib/pushmetrics"
	"github.com/VictoriaMetrics/metrics"
)

var (
	rulePath = flagutil.NewArrayString("rule", `Path to the files with alert rules.
Example: gs://bucket/path/to/rules, s3://bucket/path/to/rules, or fs:///path/to/local/rules/dir
If scheme remote storage scheme is omitted, local file system is used.
Local file system supports hierarchical patterns and regexes. 
Remote file system supports only matching by prefix, e.g. s3://bucket/dir/rule_ will match all files with prefix
rule_ in folder dir.
This flag can be specified multiple times.
Examples:
 -rule="/path/to/file". Path to a single file with alerting rules
 -rule="dir/*.yaml" -rule="/*.yaml" -rule="gcs://vmalert-rules/tenant_%{TENANT_ID}/prod". 
Rule files may contain %{ENV_VAR} placeholders, which are substituted by the corresponding env vars
`)

	ruleTemplatesPath = flagutil.NewArrayString("rule.templates", `Path or glob pattern to location with go template definitions
	for rules annotations templating. Flag can be specified multiple times.
Examples:
 -rule.templates="/path/to/file". Path to a single file with go templates
 -rule.templates="dir/*.tpl" -rule.templates="/*.tpl". Relative path to all .tpl files in "dir" folder,
absolute path to all .tpl files in root.`)

	rulesCheckInterval = flag.Duration("rule.configCheckInterval", 0, "Interval for checking for changes in '-rule' files. "+
		"By default the checking is disabled. Send SIGHUP signal in order to force config check for changes. DEPRECATED - see '-configCheckInterval' instead")

	configCheckInterval = flag.Duration("configCheckInterval", 0, "Interval for checking for changes in '-rule' or '-notifier.config' files. "+
		"By default the checking is disabled. Send SIGHUP signal in order to force config check for changes.")

	httpListenAddr   = flag.String("httpListenAddr", ":8880", "Address to listen for http connections. See also -httpListenAddr.useProxyProtocol")
	useProxyProtocol = flag.Bool("httpListenAddr.useProxyProtocol", false, "Whether to use proxy protocol for connections accepted at -httpListenAddr . "+
		"See https://www.haproxy.org/download/1.8/doc/proxy-protocol.txt")
	evaluationInterval = flag.Duration("evaluationInterval", time.Minute, "How often to evaluate the rules")

	validateTemplates   = flag.Bool("rule.validateTemplates", true, "Whether to validate annotation and label templates")
	validateExpressions = flag.Bool("rule.validateExpressions", true, "Whether to validate rules expressions via MetricsQL engine")
	maxResolveDuration  = flag.Duration("rule.maxResolveDuration", 0, "Limits the maximum duration for automatic alert expiration, "+
		"which is by default equal to 3 evaluation intervals of the parent group.")
	resendDelay            = flag.Duration("rule.resendDelay", 0, "Minimum amount of time to wait before resending an alert to notifier")
	ruleUpdateEntriesLimit = flag.Int("rule.updateEntriesLimit", 20, "Defines the max number of rule's state updates stored in-memory. "+
		"Rule's updates are available on rule's Details page and are used for debugging purposes. The number of stored updates can be overriden per rule via update_entries_limit param.")

	externalURL         = flag.String("external.url", "", "External URL is used as alert's source for sent alerts to the notifier")
	externalAlertSource = flag.String("external.alert.source", "", `External Alert Source allows to override the Source link for alerts sent to AlertManager `+
		`for cases where you want to build a custom link to Grafana, Prometheus or any other service. `+
		`Supports templating - see https://docs.victoriametrics.com/vmalert.html#templating . `+
		`For example, link to Grafana: -external.alert.source='explore?orgId=1&left=["now-1h","now","VictoriaMetrics",{"expr":{{$expr|jsonEscape|queryEscape}} },{"mode":"Metrics"},{"ui":[true,true,true,"none"]}]' . `+
		`If empty 'vmalert/alert?group_id={{.GroupID}}&alert_id={{.AlertID}}' is used.`)
	externalLabels = flagutil.NewArrayString("external.label", "Optional label in the form 'Name=value' to add to all generated recording rules and alerts. "+
		"Pass multiple -label flags in order to add multiple label sets.")

	remoteReadLookBack = flag.Duration("remoteRead.lookback", time.Hour, "Lookback defines how far to look into past for alerts timeseries."+
		" For example, if lookback=1h then range from now() to now()-1h will be scanned.")
	remoteReadIgnoreRestoreErrors = flag.Bool("remoteRead.ignoreRestoreErrors", true, "Whether to ignore errors from remote storage when restoring alerts state on startup. DEPRECATED - this flag has no effect and will be removed in the next releases.")

	disableAlertGroupLabel = flag.Bool("disableAlertgroupLabel", false, "Whether to disable adding group's Name as label to generated alerts and time series.")

	dryRun = flag.Bool("dryRun", false, "Whether to check only config files without running vmalert. The rules file are validated. The -rule flag must be specified.")
)

var alertURLGeneratorFn notifier.AlertURLGenerator

func main() {
	// Write flags and help message to stdout, since it is easier to grep or pipe.
	flag.CommandLine.SetOutput(os.Stdout)
	flag.Usage = usage
	envflag.Parse()
	remoteread.InitSecretFlags()
	remotewrite.InitSecretFlags()
	datasource.InitSecretFlags()
	buildinfo.Init()
	logger.Init()
	pushmetrics.Init()

	if !*remoteReadIgnoreRestoreErrors {
		logger.Warnf("flag `remoteRead.ignoreRestoreErrors` is deprecated and will be removed in next releases.")
	}

	err := templates.Load(*ruleTemplatesPath, true)
	if err != nil {
		logger.Fatalf("failed to parse %q: %s", *ruleTemplatesPath, err)
	}

	if *dryRun {
		groups, err := config.Parse(*rulePath, notifier.ValidateTemplates, true)
		if err != nil {
			logger.Fatalf("failed to parse %q: %s", *rulePath, err)
		}
		if len(groups) == 0 {
			logger.Fatalf("No rules for validation. Please specify path to file(s) with alerting and/or recording rules using `-rule` flag")
		}
		return
	}

	eu, err := getExternalURL(*externalURL, *httpListenAddr, httpserver.IsTLS())
	if err != nil {
		logger.Fatalf("failed to init `external.url`: %s", err)
	}

	alertURLGeneratorFn, err = getAlertURLGenerator(eu, *externalAlertSource, *validateTemplates)
	if err != nil {
		logger.Fatalf("failed to init `external.alert.source`: %s", err)
	}

	var validateTplFn config.ValidateTplFn
	if *validateTemplates {
		validateTplFn = notifier.ValidateTemplates
	}

	if *replayFrom != "" || *replayTo != "" {
		rw, err := remotewrite.Init(context.Background())
		if err != nil {
			logger.Fatalf("failed to init remoteWrite: %s", err)
		}
		if rw == nil {
			logger.Fatalf("remoteWrite.url can't be empty in replay mode")
		}
		groupsCfg, err := config.Parse(*rulePath, validateTplFn, *validateExpressions)
		if err != nil {
			logger.Fatalf("cannot parse configuration file: %s", err)
		}
		// prevent queries from caching and boundaries aligning
		// when querying VictoriaMetrics datasource.
		q, err := datasource.Init(url.Values{"nocache": {"1"}})
		if err != nil {
			logger.Fatalf("failed to init datasource: %s", err)
		}
		if err := replay(groupsCfg, q, rw); err != nil {
			logger.Fatalf("replay failed: %s", err)
		}
		return
	}

	ctx, cancel := context.WithCancel(context.Background())
	manager, err := newManager(ctx)
	if err != nil {
		logger.Fatalf("failed to init: %s", err)
	}
	logger.Infof("reading rules configuration file from %q", strings.Join(*rulePath, ";"))
	groupsCfg, err := config.Parse(*rulePath, validateTplFn, *validateExpressions)
	if err != nil {
		logger.Fatalf("cannot parse configuration file: %s", err)
	}

	// Register SIGHUP handler for config re-read just before manager.start call.
	// This guarantees that the config will be re-read if the signal arrives during manager.start call.
	// See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/1240
	sighupCh := procutil.NewSighupChan()

	if err := manager.start(ctx, groupsCfg); err != nil {
		logger.Fatalf("failed to start: %s", err)
	}

	go configReload(ctx, manager, groupsCfg, sighupCh)

	rh := &requestHandler{m: manager}
	go httpserver.Serve(*httpListenAddr, *useProxyProtocol, rh.handler)

	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()
	manager.close()
}

var (
	configReloads      = metrics.NewCounter(`vmalert_config_last_reload_total`)
	configReloadErrors = metrics.NewCounter(`vmalert_config_last_reload_errors_total`)
	configSuccess      = metrics.NewCounter(`vmalert_config_last_reload_successful`)
	configTimestamp    = metrics.NewCounter(`vmalert_config_last_reload_success_timestamp_seconds`)
)

func newManager(ctx context.Context) (*manager, error) {
	q, err := datasource.Init(nil)
	if err != nil {
		return nil, fmt.Errorf("failed to init datasource: %w", err)
	}

	labels := make(map[string]string)
	for _, s := range *externalLabels {
		if len(s) == 0 {
			continue
		}
		n := strings.IndexByte(s, '=')
		if n < 0 {
			return nil, fmt.Errorf("missing '=' in `-label`. It must contain label in the form `Name=value`; got %q", s)
		}
		labels[s[:n]] = s[n+1:]
	}

	nts, err := notifier.Init(alertURLGeneratorFn, labels, *externalURL)
	if err != nil {
		return nil, fmt.Errorf("failed to init notifier: %w", err)
	}
	manager := &manager{
		groups:         make(map[uint64]*Group),
		querierBuilder: q,
		notifiers:      nts,
		labels:         labels,
	}
	rw, err := remotewrite.Init(ctx)
	if err != nil {
		return nil, fmt.Errorf("failed to init remoteWrite: %w", err)
	}
	manager.rw = rw

	rr, err := remoteread.Init()
	if err != nil {
		return nil, fmt.Errorf("failed to init remoteRead: %w", err)
	}
	manager.rr = rr

	return manager, nil
}

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 getAlertURLGenerator(externalURL *url.URL, externalAlertSource string, validateTemplate bool) (notifier.AlertURLGenerator, error) {
	if externalAlertSource == "" {
		return func(a notifier.Alert) string {
			gID, aID := strconv.FormatUint(a.GroupID, 10), strconv.FormatUint(a.ID, 10)
			return fmt.Sprintf("%s/vmalert/alert?%s=%s&%s=%s", externalURL, paramGroupID, gID, paramAlertID, aID)
		}, nil
	}
	if validateTemplate {
		if err := notifier.ValidateTemplates(map[string]string{
			"tpl": externalAlertSource,
		}); err != nil {
			return nil, fmt.Errorf("error validating source template %s: %w", externalAlertSource, err)
		}
	}
	m := map[string]string{
		"tpl": externalAlertSource,
	}
	return func(alert notifier.Alert) string {
		templated, err := alert.ExecTemplate(nil, alert.Labels, m)
		if err != nil {
			logger.Errorf("can not exec source template %s", err)
		}
		return fmt.Sprintf("%s/%s", externalURL, templated["tpl"])
	}, nil
}

func usage() {
	const s = `
vmalert processes alerts and recording rules.

See the docs at https://docs.victoriametrics.com/vmalert.html .
`
	flagutil.Usage(s)
}

func configReload(ctx context.Context, m *manager, groupsCfg []config.Group, sighupCh <-chan os.Signal) {
	var configCheckCh <-chan time.Time
	checkInterval := *configCheckInterval
	if checkInterval == 0 && *rulesCheckInterval > 0 {
		logger.Warnf("flag `rule.configCheckInterval` is deprecated - use `configCheckInterval` instead")
		checkInterval = *rulesCheckInterval
	}
	if checkInterval > 0 {
		ticker := time.NewTicker(checkInterval)
		configCheckCh = ticker.C
		defer ticker.Stop()
	}

	var validateTplFn config.ValidateTplFn
	if *validateTemplates {
		validateTplFn = notifier.ValidateTemplates
	}

	// init reload metrics with positive values to improve alerting conditions
	configSuccess.Set(1)
	configTimestamp.Set(fasttime.UnixTimestamp())
	for {
		select {
		case <-ctx.Done():
			return
		case <-sighupCh:
			tmplMsg := ""
			if len(*ruleTemplatesPath) > 0 {
				tmplMsg = fmt.Sprintf("and templates %q ", *ruleTemplatesPath)
			}
			logger.Infof("SIGHUP received. Going to reload rules %q %s...", *rulePath, tmplMsg)
			configReloads.Inc()
		case <-configCheckCh:
		}
		if err := notifier.Reload(); err != nil {
			configReloadErrors.Inc()
			configSuccess.Set(0)
			logger.Errorf("failed to reload notifier config: %s", err)
			continue
		}
		err := templates.Load(*ruleTemplatesPath, false)
		if err != nil {
			configReloadErrors.Inc()
			configSuccess.Set(0)
			logger.Errorf("failed to load new templates: %s", err)
			continue
		}
		newGroupsCfg, err := config.Parse(*rulePath, validateTplFn, *validateExpressions)
		if err != nil {
			configReloadErrors.Inc()
			configSuccess.Set(0)
			logger.Errorf("cannot parse configuration file: %s", err)
			continue
		}
		if configsEqual(newGroupsCfg, groupsCfg) {
			templates.Reload()
			// set success to 1 since previous reload
			// could have been unsuccessful
			configSuccess.Set(1)
			// config didn't change - skip it
			continue
		}
		if err := m.update(ctx, newGroupsCfg, false); err != nil {
			configReloadErrors.Inc()
			configSuccess.Set(0)
			logger.Errorf("error while reloading rules: %s", err)
			continue
		}
		templates.Reload()
		groupsCfg = newGroupsCfg
		configSuccess.Set(1)
		configTimestamp.Set(fasttime.UnixTimestamp())
		logger.Infof("Rules reloaded successfully from %q", *rulePath)
	}
}

func configsEqual(a, b []config.Group) bool {
	if len(a) != len(b) {
		return false
	}
	for i := range a {
		if a[i].Checksum != b[i].Checksum {
			return false
		}
	}
	return true
}