package rules

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"math"
	"net/url"
	"regexp"
	"sort"
	"sync"
	"text/template"
	"time"
	"unicode"

	"go.uber.org/zap"

	"github.com/ClickHouse/clickhouse-go/v2"
	"github.com/ClickHouse/clickhouse-go/v2/lib/driver"
	"go.signoz.io/signoz/pkg/query-service/common"
	"go.signoz.io/signoz/pkg/query-service/converter"
	"go.signoz.io/signoz/pkg/query-service/postprocess"

	"go.signoz.io/signoz/pkg/query-service/app/querier"
	querierV2 "go.signoz.io/signoz/pkg/query-service/app/querier/v2"
	"go.signoz.io/signoz/pkg/query-service/app/queryBuilder"
	"go.signoz.io/signoz/pkg/query-service/constants"
	"go.signoz.io/signoz/pkg/query-service/interfaces"
	v3 "go.signoz.io/signoz/pkg/query-service/model/v3"
	"go.signoz.io/signoz/pkg/query-service/utils/labels"
	querytemplate "go.signoz.io/signoz/pkg/query-service/utils/queryTemplate"
	"go.signoz.io/signoz/pkg/query-service/utils/times"
	"go.signoz.io/signoz/pkg/query-service/utils/timestamp"

	logsv3 "go.signoz.io/signoz/pkg/query-service/app/logs/v3"
	"go.signoz.io/signoz/pkg/query-service/formatter"

	yaml "gopkg.in/yaml.v2"
)

type ThresholdRule struct {
	id            string
	name          string
	source        string
	ruleCondition *RuleCondition
	evalWindow    time.Duration
	holdDuration  time.Duration
	labels        labels.Labels
	annotations   labels.Labels

	preferredChannels   []string
	mtx                 sync.Mutex
	evaluationDuration  time.Duration
	evaluationTimestamp time.Time

	health RuleHealth

	lastError error

	// map of active alerts
	active map[uint64]*Alert

	version string
	// temporalityMap is a map of metric name to temporality
	// to avoid fetching temporality for the same metric multiple times
	// querying the v4 table on low cardinal temporality column
	// should be fast but we can still avoid the query if we have the data in memory
	temporalityMap map[string]map[v3.Temporality]bool

	opts ThresholdRuleOpts

	lastTimestampWithDatapoints time.Time
	typ                         string

	querier   interfaces.Querier
	querierV2 interfaces.Querier
}

type ThresholdRuleOpts struct {
	// sendUnmatched sends observed metric values
	// even if they dont match the rule condition. this is
	// useful in testing the rule
	SendUnmatched bool

	// sendAlways will send alert irresepective of resendDelay
	// or other params
	SendAlways bool
}

func NewThresholdRule(
	id string,
	p *PostableRule,
	opts ThresholdRuleOpts,
	featureFlags interfaces.FeatureLookup,
	reader interfaces.Reader,
) (*ThresholdRule, error) {

	if p.RuleCondition == nil {
		return nil, fmt.Errorf("no rule condition")
	} else if !p.RuleCondition.IsValid() {
		return nil, fmt.Errorf("invalid rule condition")
	}

	t := ThresholdRule{
		id:                id,
		name:              p.AlertName,
		source:            p.Source,
		ruleCondition:     p.RuleCondition,
		evalWindow:        time.Duration(p.EvalWindow),
		labels:            labels.FromMap(p.Labels),
		annotations:       labels.FromMap(p.Annotations),
		preferredChannels: p.PreferredChannels,
		health:            HealthUnknown,
		active:            map[uint64]*Alert{},
		opts:              opts,
		typ:               p.AlertType,
		version:           p.Version,
		temporalityMap:    make(map[string]map[v3.Temporality]bool),
	}

	if int64(t.evalWindow) == 0 {
		t.evalWindow = 5 * time.Minute
	}

	querierOption := querier.QuerierOptions{
		Reader:        reader,
		Cache:         nil,
		KeyGenerator:  queryBuilder.NewKeyGenerator(),
		FeatureLookup: featureFlags,
	}

	querierOptsV2 := querierV2.QuerierOptions{
		Reader:        reader,
		Cache:         nil,
		KeyGenerator:  queryBuilder.NewKeyGenerator(),
		FeatureLookup: featureFlags,
	}

	t.querier = querier.NewQuerier(querierOption)
	t.querierV2 = querierV2.NewQuerier(querierOptsV2)

	zap.L().Info("creating new ThresholdRule", zap.String("name", t.name), zap.String("id", t.id))

	return &t, nil
}

func (r *ThresholdRule) Name() string {
	return r.name
}

func (r *ThresholdRule) ID() string {
	return r.id
}

func (r *ThresholdRule) Condition() *RuleCondition {
	return r.ruleCondition
}

func (r *ThresholdRule) GeneratorURL() string {
	return prepareRuleGeneratorURL(r.ID(), r.source)
}

func (r *ThresholdRule) PreferredChannels() []string {
	return r.preferredChannels
}

// targetVal returns the target value for the rule condition
// when the y-axis and target units are non-empty, it
// converts the target value to the y-axis unit
func (r *ThresholdRule) targetVal() float64 {
	if r.ruleCondition == nil || r.ruleCondition.Target == nil {
		return 0
	}

	// get the converter for the target unit
	unitConverter := converter.FromUnit(converter.Unit(r.ruleCondition.TargetUnit))
	// convert the target value to the y-axis unit
	value := unitConverter.Convert(converter.Value{
		F: *r.ruleCondition.Target,
		U: converter.Unit(r.ruleCondition.TargetUnit),
	}, converter.Unit(r.Unit()))

	return value.F
}

func (r *ThresholdRule) matchType() MatchType {
	if r.ruleCondition == nil {
		return AtleastOnce
	}
	return r.ruleCondition.MatchType
}

func (r *ThresholdRule) compareOp() CompareOp {
	if r.ruleCondition == nil {
		return ValueIsEq
	}
	return r.ruleCondition.CompareOp
}

func (r *ThresholdRule) Type() RuleType {
	return RuleTypeThreshold
}

func (r *ThresholdRule) SetLastError(err error) {
	r.mtx.Lock()
	defer r.mtx.Unlock()
	r.lastError = err
}

func (r *ThresholdRule) LastError() error {
	r.mtx.Lock()
	defer r.mtx.Unlock()
	return r.lastError
}

func (r *ThresholdRule) SetHealth(health RuleHealth) {
	r.mtx.Lock()
	defer r.mtx.Unlock()
	r.health = health
}

func (r *ThresholdRule) Health() RuleHealth {
	r.mtx.Lock()
	defer r.mtx.Unlock()
	return r.health
}

// SetEvaluationDuration updates evaluationDuration to the duration it took to evaluate the rule on its last evaluation.
func (r *ThresholdRule) SetEvaluationDuration(dur time.Duration) {
	r.mtx.Lock()
	defer r.mtx.Unlock()
	r.evaluationDuration = dur
}

func (r *ThresholdRule) HoldDuration() time.Duration {
	return r.holdDuration
}

func (r *ThresholdRule) EvalWindow() time.Duration {
	return r.evalWindow
}

// Labels returns the labels of the alerting rule.
func (r *ThresholdRule) Labels() labels.BaseLabels {
	return r.labels
}

// Annotations returns the annotations of the alerting rule.
func (r *ThresholdRule) Annotations() labels.BaseLabels {
	return r.annotations
}

// GetEvaluationDuration returns the time in seconds it took to evaluate the alerting rule.
func (r *ThresholdRule) GetEvaluationDuration() time.Duration {
	r.mtx.Lock()
	defer r.mtx.Unlock()
	return r.evaluationDuration
}

// SetEvaluationTimestamp updates evaluationTimestamp to the timestamp of when the rule was last evaluated.
func (r *ThresholdRule) SetEvaluationTimestamp(ts time.Time) {
	r.mtx.Lock()
	defer r.mtx.Unlock()
	r.evaluationTimestamp = ts
}

// GetEvaluationTimestamp returns the time the evaluation took place.
func (r *ThresholdRule) GetEvaluationTimestamp() time.Time {
	r.mtx.Lock()
	defer r.mtx.Unlock()
	return r.evaluationTimestamp
}

// State returns the maximum state of alert instances for this rule.
// StateFiring > StatePending > StateInactive
func (r *ThresholdRule) State() AlertState {

	r.mtx.Lock()
	defer r.mtx.Unlock()
	maxState := StateInactive
	for _, a := range r.active {
		if a.State > maxState {
			maxState = a.State
		}
	}
	return maxState
}

func (r *ThresholdRule) currentAlerts() []*Alert {
	r.mtx.Lock()
	defer r.mtx.Unlock()

	alerts := make([]*Alert, 0, len(r.active))

	for _, a := range r.active {
		anew := *a
		alerts = append(alerts, &anew)
	}
	return alerts
}

func (r *ThresholdRule) ActiveAlerts() []*Alert {
	var res []*Alert
	for _, a := range r.currentAlerts() {
		if a.ResolvedAt.IsZero() {
			res = append(res, a)
		}
	}
	return res
}

func (r *ThresholdRule) FetchTemporality(ctx context.Context, metricNames []string, ch driver.Conn) (map[string]map[v3.Temporality]bool, error) {

	metricNameToTemporality := make(map[string]map[v3.Temporality]bool)

	query := fmt.Sprintf(`SELECT DISTINCT metric_name, temporality FROM %s.%s WHERE metric_name IN $1`, constants.SIGNOZ_METRIC_DBNAME, constants.SIGNOZ_TIMESERIES_v4_1DAY_TABLENAME)

	rows, err := ch.Query(ctx, query, metricNames)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	for rows.Next() {
		var metricName, temporality string
		err := rows.Scan(&metricName, &temporality)
		if err != nil {
			return nil, err
		}
		if _, ok := metricNameToTemporality[metricName]; !ok {
			metricNameToTemporality[metricName] = make(map[v3.Temporality]bool)
		}
		metricNameToTemporality[metricName][v3.Temporality(temporality)] = true
	}
	return metricNameToTemporality, nil
}

// populateTemporality same as addTemporality but for v4 and better
func (r *ThresholdRule) populateTemporality(ctx context.Context, qp *v3.QueryRangeParamsV3, ch driver.Conn) error {

	missingTemporality := make([]string, 0)
	metricNameToTemporality := make(map[string]map[v3.Temporality]bool)
	if qp.CompositeQuery != nil && len(qp.CompositeQuery.BuilderQueries) > 0 {
		for _, query := range qp.CompositeQuery.BuilderQueries {
			// if there is no temporality specified in the query but we have it in the map
			// then use the value from the map
			if query.Temporality == "" && r.temporalityMap[query.AggregateAttribute.Key] != nil {
				// We prefer delta if it is available
				if r.temporalityMap[query.AggregateAttribute.Key][v3.Delta] {
					query.Temporality = v3.Delta
				} else if r.temporalityMap[query.AggregateAttribute.Key][v3.Cumulative] {
					query.Temporality = v3.Cumulative
				} else {
					query.Temporality = v3.Unspecified
				}
			}
			// we don't have temporality for this metric
			if query.DataSource == v3.DataSourceMetrics && query.Temporality == "" {
				missingTemporality = append(missingTemporality, query.AggregateAttribute.Key)
			}
			if _, ok := metricNameToTemporality[query.AggregateAttribute.Key]; !ok {
				metricNameToTemporality[query.AggregateAttribute.Key] = make(map[v3.Temporality]bool)
			}
		}
	}

	nameToTemporality, err := r.FetchTemporality(ctx, missingTemporality, ch)
	if err != nil {
		return err
	}

	if qp.CompositeQuery != nil && len(qp.CompositeQuery.BuilderQueries) > 0 {
		for name := range qp.CompositeQuery.BuilderQueries {
			query := qp.CompositeQuery.BuilderQueries[name]
			if query.DataSource == v3.DataSourceMetrics && query.Temporality == "" {
				if nameToTemporality[query.AggregateAttribute.Key][v3.Delta] {
					query.Temporality = v3.Delta
				} else if nameToTemporality[query.AggregateAttribute.Key][v3.Cumulative] {
					query.Temporality = v3.Cumulative
				} else {
					query.Temporality = v3.Unspecified
				}
				r.temporalityMap[query.AggregateAttribute.Key] = nameToTemporality[query.AggregateAttribute.Key]
			}
		}
	}
	return nil
}

// ForEachActiveAlert runs the given function on each alert.
// This should be used when you want to use the actual alerts from the ThresholdRule
// and not on its copy.
// If you want to run on a copy of alerts then don't use this, get the alerts from 'ActiveAlerts()'.
func (r *ThresholdRule) ForEachActiveAlert(f func(*Alert)) {
	r.mtx.Lock()
	defer r.mtx.Unlock()

	for _, a := range r.active {
		f(a)
	}
}

func (r *ThresholdRule) SendAlerts(ctx context.Context, ts time.Time, resendDelay time.Duration, interval time.Duration, notifyFunc NotifyFunc) {
	zap.L().Info("sending alerts", zap.String("rule", r.Name()))
	alerts := []*Alert{}
	r.ForEachActiveAlert(func(alert *Alert) {
		if r.opts.SendAlways || alert.needsSending(ts, resendDelay) {
			alert.LastSentAt = ts
			// Allow for two Eval or Alertmanager send failures.
			delta := resendDelay
			if interval > resendDelay {
				delta = interval
			}
			alert.ValidUntil = ts.Add(4 * delta)
			anew := *alert
			alerts = append(alerts, &anew)
		} else {
			zap.L().Debug("skipping send alert due to resend delay", zap.String("rule", r.Name()), zap.Any("alert", alert.Labels))
		}
	})
	notifyFunc(ctx, "", alerts...)
}

func (r *ThresholdRule) Unit() string {
	if r.ruleCondition != nil && r.ruleCondition.CompositeQuery != nil {
		return r.ruleCondition.CompositeQuery.Unit
	}
	return ""
}

func (r *ThresholdRule) prepareQueryRange(ts time.Time) *v3.QueryRangeParamsV3 {

	// todo(srikanthccv): make this configurable
	// 2 minutes is reasonable time to wait for data to be available
	// 60 seconds (SDK) + 10 seconds (batch) + rest for n/w + serialization + write to disk etc..
	start := ts.Add(-time.Duration(r.evalWindow)).UnixMilli() - 2*60*1000
	end := ts.UnixMilli() - 2*60*1000
	// round to minute otherwise we could potentially miss data
	start = start - (start % (60 * 1000))
	end = end - (end % (60 * 1000))

	if r.ruleCondition.QueryType() == v3.QueryTypeClickHouseSQL {
		params := &v3.QueryRangeParamsV3{
			Start: start,
			End:   end,
			Step:  int64(math.Max(float64(common.MinAllowedStepInterval(start, end)), 60)),
			CompositeQuery: &v3.CompositeQuery{
				QueryType:         r.ruleCondition.CompositeQuery.QueryType,
				PanelType:         r.ruleCondition.CompositeQuery.PanelType,
				BuilderQueries:    make(map[string]*v3.BuilderQuery),
				ClickHouseQueries: make(map[string]*v3.ClickHouseQuery),
				PromQueries:       make(map[string]*v3.PromQuery),
				Unit:              r.ruleCondition.CompositeQuery.Unit,
			},
			Variables: make(map[string]interface{}, 0),
			NoCache:   true,
		}
		querytemplate.AssignReservedVarsV3(params)
		for name, chQuery := range r.ruleCondition.CompositeQuery.ClickHouseQueries {
			if chQuery.Disabled {
				continue
			}
			tmpl := template.New("clickhouse-query")
			tmpl, err := tmpl.Parse(chQuery.Query)
			if err != nil {
				zap.L().Error("failed to parse clickhouse query to populate vars", zap.String("ruleid", r.ID()), zap.Error(err))
				r.SetHealth(HealthBad)
				return params
			}
			var query bytes.Buffer
			err = tmpl.Execute(&query, params.Variables)
			if err != nil {
				zap.L().Error("failed to populate clickhouse query", zap.String("ruleid", r.ID()), zap.Error(err))
				r.SetHealth(HealthBad)
				return params
			}
			params.CompositeQuery.ClickHouseQueries[name] = &v3.ClickHouseQuery{
				Query:    query.String(),
				Disabled: chQuery.Disabled,
				Legend:   chQuery.Legend,
			}
		}
		return params
	}

	if r.ruleCondition.CompositeQuery != nil && r.ruleCondition.CompositeQuery.BuilderQueries != nil {
		for _, q := range r.ruleCondition.CompositeQuery.BuilderQueries {
			// If the step interval is less than the minimum allowed step interval, set it to the minimum allowed step interval
			if minStep := common.MinAllowedStepInterval(start, end); q.StepInterval < minStep {
				q.StepInterval = minStep
			}
		}
	}

	if r.ruleCondition.CompositeQuery.PanelType != v3.PanelTypeGraph {
		r.ruleCondition.CompositeQuery.PanelType = v3.PanelTypeGraph
	}

	// default mode
	return &v3.QueryRangeParamsV3{
		Start:          start,
		End:            end,
		Step:           int64(math.Max(float64(common.MinAllowedStepInterval(start, end)), 60)),
		CompositeQuery: r.ruleCondition.CompositeQuery,
		Variables:      make(map[string]interface{}, 0),
		NoCache:        true,
	}
}

// The following function is used to prepare the where clause for the query
// `lbls` contains the key value pairs of the labels from the result of the query
// We iterate over the where clause and replace the labels with the actual values
// There are two cases:
// 1. The label is present in the where clause
// 2. The label is not present in the where clause
//
// Example for case 2:
// Latency by serviceName without any filter
// In this case, for each service with latency > threshold we send a notification
// The expectation will be that clicking on the related traces for service A, will
// take us to the traces page with the filter serviceName=A
// So for all the missing labels in the where clause, we add them as key = value
//
// Example for case 1:
// Severity text IN (WARN, ERROR)
// In this case, the Severity text will appear in the `lbls` if it were part of the group
// by clause, in which case we replace it with the actual value for the notification
// i.e Severity text = WARN
// If the Severity text is not part of the group by clause, then we add it as it is
func (r *ThresholdRule) fetchFilters(selectedQuery string, lbls labels.Labels) []v3.FilterItem {
	var filterItems []v3.FilterItem

	added := make(map[string]struct{})

	if r.ruleCondition.CompositeQuery.QueryType == v3.QueryTypeBuilder &&
		r.ruleCondition.CompositeQuery.BuilderQueries[selectedQuery] != nil &&
		r.ruleCondition.CompositeQuery.BuilderQueries[selectedQuery].Filters != nil {

		for _, item := range r.ruleCondition.CompositeQuery.BuilderQueries[selectedQuery].Filters.Items {
			exists := false
			for _, label := range lbls {
				if item.Key.Key == label.Name {
					// if the label is present in the where clause, replace it with key = value
					filterItems = append(filterItems, v3.FilterItem{
						Key:      item.Key,
						Operator: v3.FilterOperatorEqual,
						Value:    label.Value,
					})
					exists = true
					added[label.Name] = struct{}{}
					break
				}
			}

			if !exists {
				// if the label is not present in the where clause, add it as it is
				filterItems = append(filterItems, item)
			}
		}
	}

	// add the labels which are not present in the where clause
	for _, label := range lbls {
		if _, ok := added[label.Name]; !ok {
			filterItems = append(filterItems, v3.FilterItem{
				Key:      v3.AttributeKey{Key: label.Name},
				Operator: v3.FilterOperatorEqual,
				Value:    label.Value,
			})
		}
	}

	return filterItems
}

func (r *ThresholdRule) prepareLinksToLogs(ts time.Time, lbls labels.Labels) string {
	selectedQuery := r.GetSelectedQuery()

	// TODO(srikanthccv): handle formula queries
	if selectedQuery < "A" || selectedQuery > "Z" {
		return ""
	}

	q := r.prepareQueryRange(ts)
	// Logs list view expects time in milliseconds
	tr := timeRange{
		Start:    q.Start,
		End:      q.End,
		PageSize: 100,
	}

	options := Options{
		MaxLines:      2,
		Format:        "list",
		SelectColumns: []v3.AttributeKey{},
	}

	period, _ := json.Marshal(tr)
	urlEncodedTimeRange := url.QueryEscape(string(period))

	filterItems := r.fetchFilters(selectedQuery, lbls)
	urlData := urlShareableCompositeQuery{
		QueryType: string(v3.QueryTypeBuilder),
		Builder: builderQuery{
			QueryData: []v3.BuilderQuery{
				{
					DataSource:         v3.DataSourceLogs,
					QueryName:          "A",
					AggregateOperator:  v3.AggregateOperatorNoOp,
					AggregateAttribute: v3.AttributeKey{},
					Filters: &v3.FilterSet{
						Items:    filterItems,
						Operator: "AND",
					},
					Expression:   "A",
					Disabled:     false,
					Having:       []v3.Having{},
					StepInterval: 60,
					OrderBy: []v3.OrderBy{
						{
							ColumnName: "timestamp",
							Order:      "desc",
						},
					},
				},
			},
			QueryFormulas: make([]string, 0),
		},
	}

	data, _ := json.Marshal(urlData)
	compositeQuery := url.QueryEscape(string(data))

	optionsData, _ := json.Marshal(options)
	urlEncodedOptions := url.QueryEscape(string(optionsData))

	return fmt.Sprintf("compositeQuery=%s&timeRange=%s&startTime=%d&endTime=%d&options=%s", compositeQuery, urlEncodedTimeRange, tr.Start, tr.End, urlEncodedOptions)
}

func (r *ThresholdRule) prepareLinksToTraces(ts time.Time, lbls labels.Labels) string {
	selectedQuery := r.GetSelectedQuery()

	// TODO(srikanthccv): handle formula queries
	if selectedQuery < "A" || selectedQuery > "Z" {
		return ""
	}

	q := r.prepareQueryRange(ts)
	// Traces list view expects time in nanoseconds
	tr := timeRange{
		Start:    q.Start * time.Second.Microseconds(),
		End:      q.End * time.Second.Microseconds(),
		PageSize: 100,
	}

	options := Options{
		MaxLines:      2,
		Format:        "list",
		SelectColumns: constants.TracesListViewDefaultSelectedColumns,
	}

	period, _ := json.Marshal(tr)
	urlEncodedTimeRange := url.QueryEscape(string(period))

	filterItems := r.fetchFilters(selectedQuery, lbls)
	urlData := urlShareableCompositeQuery{
		QueryType: string(v3.QueryTypeBuilder),
		Builder: builderQuery{
			QueryData: []v3.BuilderQuery{
				{
					DataSource:         v3.DataSourceTraces,
					QueryName:          "A",
					AggregateOperator:  v3.AggregateOperatorNoOp,
					AggregateAttribute: v3.AttributeKey{},
					Filters: &v3.FilterSet{
						Items:    filterItems,
						Operator: "AND",
					},
					Expression:   "A",
					Disabled:     false,
					Having:       []v3.Having{},
					StepInterval: 60,
					OrderBy: []v3.OrderBy{
						{
							ColumnName: "timestamp",
							Order:      "desc",
						},
					},
				},
			},
			QueryFormulas: make([]string, 0),
		},
	}

	data, _ := json.Marshal(urlData)
	compositeQuery := url.QueryEscape(string(data))

	optionsData, _ := json.Marshal(options)
	urlEncodedOptions := url.QueryEscape(string(optionsData))

	return fmt.Sprintf("compositeQuery=%s&timeRange=%s&startTime=%d&endTime=%d&options=%s", compositeQuery, urlEncodedTimeRange, tr.Start, tr.End, urlEncodedOptions)
}

func (r *ThresholdRule) hostFromSource() string {
	parsedUrl, err := url.Parse(r.source)
	if err != nil {
		return ""
	}
	if parsedUrl.Port() != "" {
		return fmt.Sprintf("%s://%s:%s", parsedUrl.Scheme, parsedUrl.Hostname(), parsedUrl.Port())
	}
	return fmt.Sprintf("%s://%s", parsedUrl.Scheme, parsedUrl.Hostname())
}

func (r *ThresholdRule) GetSelectedQuery() string {
	if r.ruleCondition != nil {
		if r.ruleCondition.SelectedQuery != "" {
			return r.ruleCondition.SelectedQuery
		}

		queryNames := map[string]struct{}{}

		if r.ruleCondition.CompositeQuery != nil {
			if r.ruleCondition.QueryType() == v3.QueryTypeBuilder {
				for name := range r.ruleCondition.CompositeQuery.BuilderQueries {
					queryNames[name] = struct{}{}
				}
			} else if r.ruleCondition.QueryType() == v3.QueryTypeClickHouseSQL {
				for name := range r.ruleCondition.CompositeQuery.ClickHouseQueries {
					queryNames[name] = struct{}{}
				}
			}
		}

		// The following logic exists for backward compatibility
		// If there is no selected query, then
		// - check if F1 is present, if yes, return F1
		// - else return the query with max ascii value
		// this logic is not really correct. we should be considering
		// whether the query is enabled or not. but this is a temporary
		// fix to support backward compatibility
		if _, ok := queryNames["F1"]; ok {
			return "F1"
		}
		keys := make([]string, 0, len(queryNames))
		for k := range queryNames {
			keys = append(keys, k)
		}
		sort.Strings(keys)
		return keys[len(keys)-1]
	}
	// This should never happen
	return ""
}

func (r *ThresholdRule) buildAndRunQuery(ctx context.Context, ts time.Time, ch clickhouse.Conn) (Vector, error) {
	if r.ruleCondition == nil || r.ruleCondition.CompositeQuery == nil {
		r.SetHealth(HealthBad)
		r.SetLastError(fmt.Errorf("no rule condition"))
		return nil, fmt.Errorf("invalid rule condition")
	}

	params := r.prepareQueryRange(ts)
	err := r.populateTemporality(ctx, params, ch)
	if err != nil {
		r.SetHealth(HealthBad)
		zap.L().Error("failed to set temporality", zap.String("rule", r.Name()), zap.Error(err))
		return nil, fmt.Errorf("internal error while setting temporality")
	}

	if params.CompositeQuery.QueryType == v3.QueryTypeBuilder {
		// check if any enrichment is required for logs if yes then enrich them
		if logsv3.EnrichmentRequired(params) {
			// Note: Sending empty fields key because enrichment is only needed for json
			// TODO: Add support for attribute enrichment later
			logsv3.Enrich(params, map[string]v3.AttributeKey{})
		}
	}

	var results []*v3.Result
	var errQuriesByName map[string]error

	if r.version == "v4" {
		results, errQuriesByName, err = r.querierV2.QueryRange(ctx, params, map[string]v3.AttributeKey{})
	} else {
		results, errQuriesByName, err = r.querier.QueryRange(ctx, params, map[string]v3.AttributeKey{})
	}

	if err != nil {
		zap.L().Error("failed to get alert query result", zap.String("rule", r.Name()), zap.Error(err), zap.Any("queries", errQuriesByName))
		r.SetHealth(HealthBad)
		return nil, fmt.Errorf("internal error while querying")
	}

	if params.CompositeQuery.QueryType == v3.QueryTypeBuilder {
		results, err = postprocess.PostProcessResult(results, params)
		if err != nil {
			r.SetHealth(HealthBad)
			zap.L().Error("failed to post process result", zap.String("rule", r.Name()), zap.Error(err))
			return nil, fmt.Errorf("internal error while post processing")
		}
	}

	selectedQuery := r.GetSelectedQuery()

	var queryResult *v3.Result
	for _, res := range results {
		if res.QueryName == selectedQuery {
			queryResult = res
			break
		}
	}

	if queryResult != nil && len(queryResult.Series) > 0 {
		r.lastTimestampWithDatapoints = time.Now()
	}

	var resultVector Vector

	// if the data is missing for `For` duration then we should send alert
	if r.ruleCondition.AlertOnAbsent && r.lastTimestampWithDatapoints.Add(time.Duration(r.Condition().AbsentFor)*time.Minute).Before(time.Now()) {
		zap.L().Info("no data found for rule condition", zap.String("ruleid", r.ID()))
		lbls := labels.NewBuilder(labels.Labels{})
		if !r.lastTimestampWithDatapoints.IsZero() {
			lbls.Set("lastSeen", r.lastTimestampWithDatapoints.Format(constants.AlertTimeFormat))
		}
		resultVector = append(resultVector, Sample{
			Metric:    lbls.Labels(),
			IsMissing: true,
		})
		return resultVector, nil
	}

	for _, series := range queryResult.Series {
		smpl, shouldAlert := r.shouldAlert(*series)
		if shouldAlert {
			resultVector = append(resultVector, smpl)
		}
	}
	return resultVector, nil
}

func normalizeLabelName(name string) string {
	// See https://prometheus.io/docs/concepts/data_model/#metric-names-and-labels

	// Regular expression to match non-alphanumeric characters except underscores
	reg := regexp.MustCompile(`[^a-zA-Z0-9_]`)

	// Replace all non-alphanumeric characters except underscores with underscores
	normalized := reg.ReplaceAllString(name, "_")

	// If the first character is not a letter or an underscore, prepend an underscore
	if len(normalized) > 0 && !unicode.IsLetter(rune(normalized[0])) && normalized[0] != '_' {
		normalized = "_" + normalized
	}

	return normalized
}

func (r *ThresholdRule) Eval(ctx context.Context, ts time.Time, queriers *Queriers) (interface{}, error) {

	valueFormatter := formatter.FromUnit(r.Unit())
	res, err := r.buildAndRunQuery(ctx, ts, queriers.Ch)

	if err != nil {
		r.SetHealth(HealthBad)
		r.SetLastError(err)
		zap.L().Error("failure in buildAndRunQuery", zap.String("ruleid", r.ID()), zap.Error(err))
		return nil, err
	}

	r.mtx.Lock()
	defer r.mtx.Unlock()

	resultFPs := map[uint64]struct{}{}
	var alerts = make(map[uint64]*Alert, len(res))

	for _, smpl := range res {
		l := make(map[string]string, len(smpl.Metric))
		for _, lbl := range smpl.Metric {
			l[lbl.Name] = lbl.Value
		}

		value := valueFormatter.Format(smpl.V, r.Unit())
		threshold := valueFormatter.Format(r.targetVal(), r.Unit())
		zap.L().Debug("Alert template data for rule", zap.String("name", r.Name()), zap.String("formatter", valueFormatter.Name()), zap.String("value", value), zap.String("threshold", threshold))

		tmplData := AlertTemplateData(l, value, threshold)
		// Inject some convenience variables that are easier to remember for users
		// who are not used to Go's templating system.
		defs := "{{$labels := .Labels}}{{$value := .Value}}{{$threshold := .Threshold}}"

		// utility function to apply go template on labels and annotations
		expand := func(text string) string {

			tmpl := NewTemplateExpander(
				ctx,
				defs+text,
				"__alert_"+r.Name(),
				tmplData,
				times.Time(timestamp.FromTime(ts)),
				nil,
			)
			result, err := tmpl.Expand()
			if err != nil {
				result = fmt.Sprintf("<error expanding template: %s>", err)
				zap.L().Error("Expanding alert template failed", zap.Error(err), zap.Any("data", tmplData))
			}
			return result
		}

		lb := labels.NewBuilder(smpl.Metric).Del(labels.MetricNameLabel).Del(labels.TemporalityLabel)

		for _, l := range r.labels {
			lb.Set(l.Name, expand(l.Value))
		}

		lb.Set(labels.AlertNameLabel, r.Name())
		lb.Set(labels.AlertRuleIdLabel, r.ID())
		lb.Set(labels.RuleSourceLabel, r.GeneratorURL())

		annotations := make(labels.Labels, 0, len(r.annotations))
		for _, a := range r.annotations {
			if smpl.IsMissing {
				if a.Name == labels.AlertDescriptionLabel || a.Name == labels.AlertSummaryLabel {
					a.Value = labels.AlertMissingData
				}
			}
			annotations = append(annotations, labels.Label{Name: normalizeLabelName(a.Name), Value: expand(a.Value)})
		}

		// Links with timestamps should go in annotations since labels
		// is used alert grouping, and we want to group alerts with the same
		// label set, but different timestamps, together.
		if r.typ == "TRACES_BASED_ALERT" {
			link := r.prepareLinksToTraces(ts, smpl.MetricOrig)
			if link != "" && r.hostFromSource() != "" {
				annotations = append(annotations, labels.Label{Name: "related_traces", Value: fmt.Sprintf("%s/traces-explorer?%s", r.hostFromSource(), link)})
			}
		} else if r.typ == "LOGS_BASED_ALERT" {
			link := r.prepareLinksToLogs(ts, smpl.MetricOrig)
			if link != "" && r.hostFromSource() != "" {
				annotations = append(annotations, labels.Label{Name: "related_logs", Value: fmt.Sprintf("%s/logs/logs-explorer?%s", r.hostFromSource(), link)})
			}
		}

		lbs := lb.Labels()
		h := lbs.Hash()
		resultFPs[h] = struct{}{}

		if _, ok := alerts[h]; ok {
			zap.L().Error("the alert query returns duplicate records", zap.String("ruleid", r.ID()), zap.Any("alert", alerts[h]))
			err = fmt.Errorf("duplicate alert found, vector contains metrics with the same labelset after applying alert labels")
			// We have already acquired the lock above hence using SetHealth and
			// SetLastError will deadlock.
			r.health = HealthBad
			r.lastError = err
			return nil, err
		}

		alerts[h] = &Alert{
			Labels:       lbs,
			Annotations:  annotations,
			ActiveAt:     ts,
			State:        StatePending,
			Value:        smpl.V,
			GeneratorURL: r.GeneratorURL(),
			Receivers:    r.preferredChannels,
		}
	}

	zap.L().Info("alerts found", zap.String("name", r.Name()), zap.Int("count", len(alerts)))

	// alerts[h] is ready, add or update active list now
	for h, a := range alerts {
		// Check whether we already have alerting state for the identifying label set.
		// Update the last value and annotations if so, create a new alert entry otherwise.
		if alert, ok := r.active[h]; ok && alert.State != StateInactive {

			alert.Value = a.Value
			alert.Annotations = a.Annotations
			alert.Receivers = r.preferredChannels
			continue
		}

		r.active[h] = a

	}

	// Check if any pending alerts should be removed or fire now. Write out alert timeseries.
	for fp, a := range r.active {
		if _, ok := resultFPs[fp]; !ok {
			// If the alert was previously firing, keep it around for a given
			// retention time so it is reported as resolved to the AlertManager.
			if a.State == StatePending || (!a.ResolvedAt.IsZero() && ts.Sub(a.ResolvedAt) > resolvedRetention) {
				delete(r.active, fp)
			}
			if a.State != StateInactive {
				a.State = StateInactive
				a.ResolvedAt = ts
			}
			continue
		}

		if a.State == StatePending && ts.Sub(a.ActiveAt) >= r.holdDuration {
			a.State = StateFiring
			a.FiredAt = ts
		}

	}
	r.health = HealthGood
	r.lastError = err

	return len(r.active), nil
}

func (r *ThresholdRule) String() string {

	ar := PostableRule{
		AlertName:         r.name,
		RuleCondition:     r.ruleCondition,
		EvalWindow:        Duration(r.evalWindow),
		Labels:            r.labels.Map(),
		Annotations:       r.annotations.Map(),
		PreferredChannels: r.preferredChannels,
	}

	byt, err := yaml.Marshal(ar)
	if err != nil {
		return fmt.Sprintf("error marshaling alerting rule: %s", err.Error())
	}

	return string(byt)
}

func removeGroupinSetPoints(series v3.Series) []v3.Point {
	var result []v3.Point
	for _, s := range series.Points {
		if s.Timestamp >= 0 && !math.IsNaN(s.Value) && !math.IsInf(s.Value, 0) {
			result = append(result, s)
		}
	}
	return result
}

func (r *ThresholdRule) shouldAlert(series v3.Series) (Sample, bool) {
	var alertSmpl Sample
	var shouldAlert bool
	var lbls labels.Labels
	var lblsNormalized labels.Labels

	for name, value := range series.Labels {
		lbls = append(lbls, labels.Label{Name: name, Value: value})
		lblsNormalized = append(lblsNormalized, labels.Label{Name: normalizeLabelName(name), Value: value})
	}

	series.Points = removeGroupinSetPoints(series)

	// nothing to evaluate
	if len(series.Points) == 0 {
		return alertSmpl, false
	}

	switch r.matchType() {
	case AtleastOnce:
		// If any sample matches the condition, the rule is firing.
		if r.compareOp() == ValueIsAbove {
			for _, smpl := range series.Points {
				if smpl.Value > r.targetVal() {
					alertSmpl = Sample{Point: Point{V: smpl.Value}, Metric: lblsNormalized, MetricOrig: lbls}
					shouldAlert = true
					break
				}
			}
		} else if r.compareOp() == ValueIsBelow {
			for _, smpl := range series.Points {
				if smpl.Value < r.targetVal() {
					alertSmpl = Sample{Point: Point{V: smpl.Value}, Metric: lblsNormalized, MetricOrig: lbls}
					shouldAlert = true
					break
				}
			}
		} else if r.compareOp() == ValueIsEq {
			for _, smpl := range series.Points {
				if smpl.Value == r.targetVal() {
					alertSmpl = Sample{Point: Point{V: smpl.Value}, Metric: lblsNormalized, MetricOrig: lbls}
					shouldAlert = true
					break
				}
			}
		} else if r.compareOp() == ValueIsNotEq {
			for _, smpl := range series.Points {
				if smpl.Value != r.targetVal() {
					alertSmpl = Sample{Point: Point{V: smpl.Value}, Metric: lblsNormalized, MetricOrig: lbls}
					shouldAlert = true
					break
				}
			}
		}
	case AllTheTimes:
		// If all samples match the condition, the rule is firing.
		shouldAlert = true
		alertSmpl = Sample{Point: Point{V: r.targetVal()}, Metric: lblsNormalized, MetricOrig: lbls}
		if r.compareOp() == ValueIsAbove {
			for _, smpl := range series.Points {
				if smpl.Value <= r.targetVal() {
					shouldAlert = false
					break
				}
			}
		} else if r.compareOp() == ValueIsBelow {
			for _, smpl := range series.Points {
				if smpl.Value >= r.targetVal() {
					shouldAlert = false
					break
				}
			}
		} else if r.compareOp() == ValueIsEq {
			for _, smpl := range series.Points {
				if smpl.Value != r.targetVal() {
					shouldAlert = false
					break
				}
			}
		} else if r.compareOp() == ValueIsNotEq {
			for _, smpl := range series.Points {
				if smpl.Value == r.targetVal() {
					shouldAlert = false
					break
				}
			}
		}
	case OnAverage:
		// If the average of all samples matches the condition, the rule is firing.
		var sum, count float64
		for _, smpl := range series.Points {
			if math.IsNaN(smpl.Value) || math.IsInf(smpl.Value, 0) {
				continue
			}
			sum += smpl.Value
			count++
		}
		avg := sum / count
		alertSmpl = Sample{Point: Point{V: avg}, Metric: lblsNormalized, MetricOrig: lbls}
		if r.compareOp() == ValueIsAbove {
			if avg > r.targetVal() {
				shouldAlert = true
			}
		} else if r.compareOp() == ValueIsBelow {
			if avg < r.targetVal() {
				shouldAlert = true
			}
		} else if r.compareOp() == ValueIsEq {
			if avg == r.targetVal() {
				shouldAlert = true
			}
		} else if r.compareOp() == ValueIsNotEq {
			if avg != r.targetVal() {
				shouldAlert = true
			}
		}
	case InTotal:
		// If the sum of all samples matches the condition, the rule is firing.
		var sum float64

		for _, smpl := range series.Points {
			if math.IsNaN(smpl.Value) || math.IsInf(smpl.Value, 0) {
				continue
			}
			sum += smpl.Value
		}
		alertSmpl = Sample{Point: Point{V: sum}, Metric: lblsNormalized, MetricOrig: lbls}
		if r.compareOp() == ValueIsAbove {
			if sum > r.targetVal() {
				shouldAlert = true
			}
		} else if r.compareOp() == ValueIsBelow {
			if sum < r.targetVal() {
				shouldAlert = true
			}
		} else if r.compareOp() == ValueIsEq {
			if sum == r.targetVal() {
				shouldAlert = true
			}
		} else if r.compareOp() == ValueIsNotEq {
			if sum != r.targetVal() {
				shouldAlert = true
			}
		}
	}
	return alertSmpl, shouldAlert
}