// SPDX-License-Identifier: AGPL-3.0-only
// Provenance-includes-location: https://github.com/cortexproject/cortex/blob/master/pkg/ruler/api.go
// Provenance-includes-license: Apache-2.0
// Provenance-includes-copyright: The Cortex Authors.

package ruler

import (
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"strconv"
	"strings"
	"time"

	"github.com/go-kit/log"
	"github.com/go-kit/log/level"
	"github.com/gorilla/mux"
	"github.com/grafana/dskit/tenant"
	"github.com/pkg/errors"
	v1 "github.com/prometheus/client_golang/api/prometheus/v1"
	"github.com/prometheus/prometheus/model/labels"
	"github.com/prometheus/prometheus/model/rulefmt"
	"google.golang.org/api/googleapi"
	"gopkg.in/yaml.v3"

	"github.com/grafana/mimir/pkg/mimirpb"
	"github.com/grafana/mimir/pkg/ruler/rulespb"
	"github.com/grafana/mimir/pkg/ruler/rulestore"
	"github.com/grafana/mimir/pkg/util/spanlogger"
)

var (
	// errNoValidOrgIDFound is returned when no valid org id is found in the request context.
	errNoValidOrgIDFound = errors.New("no valid org id found")
	// errTenantRuleEvaluationDisabled is returned when all rule evaluation types are disabled for the tenant.
	errTenantRuleEvaluationDisabled = errors.New("all rule evaluation is disabled for user")
)

// In order to reimplement the prometheus rules API, a large amount of code was copied over
// This is required because the prometheus api implementation does not allow us to return errors
// on rule lookups, which might fail in Mimir's case.

type response struct {
	Status    string       `json:"status"`
	Data      interface{}  `json:"data"`
	ErrorType v1.ErrorType `json:"errorType"`
	Error     string       `json:"error"`
	Warnings  []string     `json:"warnings,omitempty"`
}

// AlertDiscovery has info for all active alerts.
type AlertDiscovery struct {
	Alerts []*Alert `json:"alerts"`
}

// Alert has info for an alert.
type Alert struct {
	Labels          labels.Labels `json:"labels"`
	Annotations     labels.Labels `json:"annotations"`
	State           string        `json:"state"`
	ActiveAt        *time.Time    `json:"activeAt,omitempty"`
	KeepFiringSince *time.Time    `json:"keepFiringSince,omitempty"`
	Value           string        `json:"value"`
}

// RuleDiscovery has info for all rules
type RuleDiscovery struct {
	RuleGroups []*RuleGroup `json:"groups"`
	NextToken  string       `json:"groupNextToken,omitempty"`
}

// RuleGroup has info for rules which are part of a group
type RuleGroup struct {
	Name string `json:"name"`
	File string `json:"file"`
	// In order to preserve rule ordering, while exposing type (alerting or recording)
	// specific properties, both alerting and recording rules are exposed in the
	// same array.
	Rules          []rule    `json:"rules"`
	Interval       float64   `json:"interval"`
	LastEvaluation time.Time `json:"lastEvaluation"`
	EvaluationTime float64   `json:"evaluationTime"`
	SourceTenants  []string  `json:"sourceTenants"`
}

type rule interface{}

type alertingRule struct {
	// State can be "unknown", "pending", "firing", "inactive".
	State          string        `json:"state"`
	Name           string        `json:"name"`
	Query          string        `json:"query"`
	Duration       float64       `json:"duration"`
	KeepFiringFor  float64       `json:"keepFiringFor"`
	Labels         labels.Labels `json:"labels"`
	Annotations    labels.Labels `json:"annotations"`
	Alerts         []*Alert      `json:"alerts"`
	Health         string        `json:"health"`
	LastError      string        `json:"lastError"`
	Type           v1.RuleType   `json:"type"`
	LastEvaluation time.Time     `json:"lastEvaluation"`
	EvaluationTime float64       `json:"evaluationTime"`
}

type recordingRule struct {
	Name           string        `json:"name"`
	Query          string        `json:"query"`
	Labels         labels.Labels `json:"labels"`
	Health         string        `json:"health"`
	LastError      string        `json:"lastError"`
	Type           v1.RuleType   `json:"type"`
	LastEvaluation time.Time     `json:"lastEvaluation"`
	EvaluationTime float64       `json:"evaluationTime"`
}

func respondError(logger log.Logger, w http.ResponseWriter, status int, errorType v1.ErrorType, msg string) {
	b, err := json.Marshal(&response{
		Status:    "error",
		ErrorType: errorType,
		Error:     msg,
		Data:      nil,
	})

	if err != nil {
		level.Error(logger).Log("msg", "error marshaling json response", "err", err)
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}

	w.WriteHeader(status)
	if n, err := w.Write(b); err != nil {
		level.Error(logger).Log("msg", "error writing response", "bytesWritten", n, "err", err)
	}
}

func respondInvalidRequest(logger log.Logger, w http.ResponseWriter, msg string) {
	respondError(logger, w, http.StatusBadRequest, v1.ErrBadData, msg)
}

func respondUnprocessableRequest(logger log.Logger, w http.ResponseWriter, msg string) {
	respondError(logger, w, http.StatusUnprocessableEntity, v1.ErrExec, msg)
}

func respondServerError(logger log.Logger, w http.ResponseWriter, msg string) {
	respondError(logger, w, http.StatusInternalServerError, v1.ErrServer, msg)
}

// API is used to handle HTTP requests for the ruler service
type API struct {
	ruler *Ruler
	store rulestore.RuleStore

	logger log.Logger
}

// NewAPI returns a new API struct with the provided ruler and rule store
func NewAPI(r *Ruler, s rulestore.RuleStore, logger log.Logger) *API {
	return &API{
		ruler:  r,
		store:  s,
		logger: logger,
	}
}

func (a *API) PrometheusRules(w http.ResponseWriter, req *http.Request) {
	logger, ctx := spanlogger.New(req.Context(), a.logger, tracer, "API.PrometheusRules")
	defer logger.Finish()

	userID, err := tenant.TenantID(ctx)
	if err != nil || userID == "" {
		level.Error(logger).Log("msg", "error extracting org id from context", "err", err)
		respondInvalidRequest(logger, w, errNoValidOrgIDFound.Error())
		return
	}

	excludeAlerts, err := parseExcludeAlerts(req)
	if err != nil {
		respondInvalidRequest(logger, w, "invalid exclude_alerts parameter")
		return
	}

	var maxGroups int32
	if maxGroupsVal := req.URL.Query().Get("group_limit"); maxGroupsVal != "" {
		maxGroupsRaw, err := strconv.ParseInt(maxGroupsVal, 10, 32)
		maxGroups = int32(maxGroupsRaw)
		if err != nil || maxGroups < 0 {
			respondInvalidRequest(logger, w, "invalid group limit value")
			return
		}
	}

	rulesReq := RulesRequest{
		Filter:        AnyRule,
		RuleName:      req.URL.Query()["rule_name"],
		RuleGroup:     req.URL.Query()["rule_group"],
		File:          req.URL.Query()["file"],
		ExcludeAlerts: excludeAlerts,
		NextToken:     req.URL.Query().Get("group_next_token"),
		MaxGroups:     maxGroups,
	}

	// The file, rule_group and rule_name query parameters differ
	// from Vanilla prometheus: file[], rule_group[], rule_name[]
	// If they are provided in this format, use them instead.
	if req.URL.Query().Has("rule_name[]") {
		rulesReq.RuleName = req.URL.Query()["rule_name[]"]
	}
	if req.URL.Query().Has("rule_group[]") {
		rulesReq.RuleGroup = req.URL.Query()["rule_group[]"]
	}
	if req.URL.Query().Has("file[]") {
		rulesReq.File = req.URL.Query()["file[]"]
	}

	ruleTypeFilter := strings.ToLower(req.URL.Query().Get("type"))
	if ruleTypeFilter != "" {
		switch ruleTypeFilter {
		case "alert":
			rulesReq.Filter = AlertingRule
		case "record":
			rulesReq.Filter = RecordingRule
		default:
			respondInvalidRequest(logger, w, fmt.Sprintf("not supported value %q", ruleTypeFilter))
			return
		}
	}

	w.Header().Set("Content-Type", "application/json")
	rulesResp, token, err := a.ruler.GetRules(ctx, rulesReq)
	if err != nil {
		if errors.Is(err, errTenantRuleEvaluationDisabled) {
			respondUnprocessableRequest(logger, w, fmt.Sprintf("rule evaluation is disabled for tenant %s", userID))
			return
		}
		respondServerError(logger, w, err.Error())
		return
	}

	groups := make([]*RuleGroup, 0, len(rulesResp.Groups))
	for _, g := range rulesResp.Groups {
		grp := RuleGroup{
			Name:           g.Group.Name,
			File:           g.Group.Namespace,
			Rules:          make([]rule, len(g.ActiveRules)),
			Interval:       g.Group.Interval.Seconds(),
			LastEvaluation: g.GetEvaluationTimestamp(),
			EvaluationTime: g.GetEvaluationDuration().Seconds(),
			SourceTenants:  g.Group.GetSourceTenants(),
		}

		for i, rl := range g.ActiveRules {
			if g.ActiveRules[i].Rule.Alert != "" {
				var alerts []*Alert
				if !excludeAlerts {
					alerts = make([]*Alert, 0, len(rl.Alerts))
					for _, a := range rl.Alerts {
						alerts = append(alerts, alertStateDescToPrometheusAlert(a))
					}
				}
				grp.Rules[i] = alertingRule{
					State:          rl.GetState(),
					Name:           rl.Rule.GetAlert(),
					Query:          rl.Rule.GetExpr(),
					Duration:       rl.Rule.For.Seconds(),
					KeepFiringFor:  rl.Rule.KeepFiringFor.Seconds(),
					Labels:         mimirpb.FromLabelAdaptersToLabels(rl.Rule.Labels),
					Annotations:    mimirpb.FromLabelAdaptersToLabels(rl.Rule.Annotations),
					Alerts:         alerts,
					Health:         rl.GetHealth(),
					LastError:      rl.GetLastError(),
					LastEvaluation: rl.GetEvaluationTimestamp(),
					EvaluationTime: rl.GetEvaluationDuration().Seconds(),
					Type:           v1.RuleTypeAlerting,
				}
			} else {
				grp.Rules[i] = recordingRule{
					Name:           rl.Rule.GetRecord(),
					Query:          rl.Rule.GetExpr(),
					Labels:         mimirpb.FromLabelAdaptersToLabels(rl.Rule.Labels),
					Health:         rl.GetHealth(),
					LastError:      rl.GetLastError(),
					LastEvaluation: rl.GetEvaluationTimestamp(),
					EvaluationTime: rl.GetEvaluationDuration().Seconds(),
					Type:           v1.RuleTypeRecording,
				}
			}
		}

		groups = append(groups, &grp)
	}

	resp := &response{
		Status:   "success",
		Data:     &RuleDiscovery{RuleGroups: groups, NextToken: token},
		Warnings: rulesResp.Warnings,
	}
	b, err := json.Marshal(resp)
	if err != nil {
		level.Error(logger).Log("msg", "error marshaling json response", "err", err)
		respondServerError(logger, w, "unable to marshal the requested data")
		return
	}
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(http.StatusOK)
	if n, err := w.Write(b); err != nil {
		level.Error(logger).Log("msg", "error writing response", "bytesWritten", n, "err", err)
	}
}

func parseExcludeAlerts(req *http.Request) (bool, error) {
	excludeAlerts := req.URL.Query().Get("exclude_alerts")
	if excludeAlerts == "" {
		return false, nil
	}

	value, err := strconv.ParseBool(excludeAlerts)
	if err != nil {
		return false, fmt.Errorf("unable to parse exclude_alerts value %w", err)
	}

	return value, nil
}

func (a *API) PrometheusAlerts(w http.ResponseWriter, req *http.Request) {
	logger, ctx := spanlogger.New(req.Context(), a.logger, tracer, "API.PrometheusAlerts")
	defer logger.Finish()

	userID, err := tenant.TenantID(ctx)
	if err != nil || userID == "" {
		level.Error(logger).Log("msg", "error extracting org id from context", "err", err)
		respondInvalidRequest(logger, w, errNoValidOrgIDFound.Error())
		return
	}

	w.Header().Set("Content-Type", "application/json")
	rulesResp, _, err := a.ruler.GetRules(ctx, RulesRequest{Filter: AlertingRule})
	if err != nil {
		if errors.Is(err, errTenantRuleEvaluationDisabled) {
			respondUnprocessableRequest(logger, w, fmt.Sprintf("rule evaluation is disabled for tenant %s", userID))
			return
		}
		respondServerError(logger, w, err.Error())
		return
	}

	alerts := make([]*Alert, 0, len(rulesResp.Groups))
	for _, g := range rulesResp.Groups {
		for _, rl := range g.ActiveRules {
			if rl.Rule.Alert != "" {
				for _, a := range rl.Alerts {
					alerts = append(alerts, alertStateDescToPrometheusAlert(a))
				}
			}
		}
	}

	resp := &response{
		Status:   "success",
		Data:     &AlertDiscovery{Alerts: alerts},
		Warnings: rulesResp.Warnings,
	}
	b, err := json.Marshal(resp)
	if err != nil {
		level.Error(logger).Log("msg", "error marshaling json response", "err", err)
		respondServerError(logger, w, "unable to marshal the requested data")
		return
	}
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(http.StatusOK)
	if n, err := w.Write(b); err != nil {
		level.Error(logger).Log("msg", "error writing response", "bytesWritten", n, "err", err)
	}
}

var (
	// ErrNoNamespace signals that no namespace was specified in the request
	ErrNoNamespace = errors.New("a namespace must be provided in the request")
	// ErrNoGroupName signals a group name url parameter was not found
	ErrNoGroupName = errors.New("a matching group name must be provided in the request")
	// ErrNoRuleGroups signals the rule group requested does not exist
	ErrNoRuleGroups = errors.New("no rule groups found")
	// ErrBadRuleGroup is returned when the provided rule group can not be unmarshalled
	ErrBadRuleGroup = errors.New("unable to decode rule group")
)

func marshalAndSend(output interface{}, w http.ResponseWriter, logger log.Logger, headers ...http.Header) {
	d, err := yaml.Marshal(&output)
	if err != nil {
		level.Error(logger).Log("msg", "error marshalling yaml rule groups", "err", err)
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}

	w.Header().Set("Content-Type", "application/yaml")
	if len(headers) > 0 {
		for _, v := range headers {
			for headerKey, headerValue := range v {
				w.Header().Set(headerKey, strings.Join(headerValue, ","))
			}
		}
	}

	if _, err := w.Write(d); err != nil {
		level.Error(logger).Log("msg", "error writing yaml response", "err", err)
		return
	}
}

func respondAccepted(w http.ResponseWriter, logger log.Logger, headers ...http.Header) {
	b, err := json.Marshal(&response{
		Status: "success",
	})
	if err != nil {
		level.Error(logger).Log("msg", "error marshaling json response", "err", err)
		respondServerError(logger, w, "unable to marshal the requested data")
		return
	}
	w.Header().Set("Content-Type", "application/json")

	// Return a status accepted because the rule has been stored and queued for polling, but is not currently active
	w.WriteHeader(http.StatusAccepted)
	if len(headers) > 0 {
		for _, v := range headers {
			for headerKey, headerValue := range v {
				w.Header().Set(headerKey, strings.Join(headerValue, ","))
			}
		}
	}

	if n, err := w.Write(b); err != nil {
		level.Error(logger).Log("msg", "error writing response", "bytesWritten", n, "err", err)
	}
}

// parseNamespace parses the namespace from the provided set of params, in this
// api these params are derived from the url path
func parseNamespace(params map[string]string) (string, error) {
	namespace, exists := params["namespace"]
	if !exists {
		return "", ErrNoNamespace
	}

	namespace, err := url.PathUnescape(namespace)
	if err != nil {
		return "", err
	}

	return namespace, nil
}

// parseGroupName parses the group name from the provided set of params, in this
// api these params are derived from the url path
func parseGroupName(params map[string]string) (string, error) {
	groupName, exists := params["groupName"]
	if !exists {
		return "", ErrNoGroupName
	}

	groupName, err := url.PathUnescape(groupName)
	if err != nil {
		return "", err
	}

	return groupName, nil
}

// parseRequest parses the incoming request to parse out the userID, rules namespace, and rule group name
// and returns them in that order. It also allows users to require a namespace or group name and return
// an error if it they can not be parsed.
func (a *API) parseRequest(req *http.Request, requireNamespace, requireGroup bool) (string, string, string, error) {
	userID, err := tenant.TenantID(req.Context())
	if err != nil || userID == "" {
		level.Error(a.logger).Log("msg", "error extracting org id from context", "err", err)
		return "", "", "", errNoValidOrgIDFound
	}

	vars := mux.Vars(req)

	namespace, err := parseNamespace(vars)
	if err != nil {
		if !errors.Is(err, ErrNoNamespace) || requireNamespace {
			return "", "", "", err
		}
	}

	group, err := parseGroupName(vars)
	if err != nil {
		if !errors.Is(err, ErrNoGroupName) || requireGroup {
			return "", "", "", err
		}
	}

	return userID, namespace, group, nil
}

func (a *API) ListRules(w http.ResponseWriter, req *http.Request) {
	logger, ctx := spanlogger.New(req.Context(), a.logger, tracer, "API.ListRules")
	defer logger.Finish()

	userID, namespace, _, err := a.parseRequest(req, false, false)
	if err != nil {
		if errors.Is(err, errNoValidOrgIDFound) {
			respondInvalidRequest(logger, w, err.Error())
			return
		}
		respondServerError(logger, w, err.Error())
		return
	}

	level.Debug(logger).Log("msg", "retrieving rule groups with namespace", "userID", userID, "namespace", namespace)
	// Disable any caching when getting list of all rule groups since listing results
	// are cached and not invalidated and this API is expected to be strongly consistent.
	rgs, err := a.store.ListRuleGroupsForUserAndNamespace(ctx, userID, namespace, rulestore.WithCacheDisabled())
	if err != nil {
		http.Error(w, err.Error(), http.StatusBadRequest)
		return
	}

	if len(rgs) == 0 {
		level.Info(logger).Log("msg", "no rule groups found", "userID", userID)
		// No rule groups, short-circuit and just return an empty map with HTTP 200
		marshalAndSend(map[string]interface{}{}, w, logger)
		return
	}

	level.Debug(logger).Log("msg", "retrieved rule groups from rule store", "userID", userID, "num_groups", len(rgs))
	missing, err := a.store.LoadRuleGroups(ctx, map[string]rulespb.RuleGroupList{userID: rgs})
	if err != nil {
		http.Error(w, err.Error(), http.StatusBadRequest)
		return
	}
	if len(missing) > 0 {
		// This API is expected to be strongly consistent, but we expect the object storage to be strongly
		// consistent too. This means that if a rule group existed when we listed the storage but doesn't exist
		// (it's missing) when we load it, then it could have been deleted in the meanwhile.
		//
		// We don't want to consider this condition a failure, so we don't return an error in this case, but we
		// just log a warning because it could be of interest for an operator to further investigate it.
		level.Warn(logger).Log(
			"msg", "list rules API skipped some rule groups, because missing when loading them after listing the storage (this could be due to rule groups deleted between listing the storage and getting rule groups content)",
			"user", userID,
			"listed_rule_groups", len(rgs),
			"missing_rule_groups", len(missing),
			// Logging all rule groups may excessive, but logging at least 1 may give some hints.
			"first_missing_rule_group_namespace", missing[0].Namespace,
			"first_missing_rule_group_name", missing[0].Name)

		// Filter out missing rule groups, so they're not returned by the API (they haven't been loaded,
		// so their content is empty).
		numRuleGroupsBeforeFiltering := len(rgs)
		tenantRuleGroups := map[string]rulespb.RuleGroupList{userID: rgs}
		tenantRuleGroups = FilterRuleGroupsByNotMissing(tenantRuleGroups, missing, a.logger)

		var tenantFound bool
		rgs, tenantFound = tenantRuleGroups[userID]

		if !tenantFound && len(missing) < len(rgs) {
			// This should never happen, unless a bug.
			level.Error(logger).Log(
				"msg", "list rules API has filtered out more rule groups than expected when removing missing rule groups from the response",
				"user", userID,
				"rule_groups_before_filtering", numRuleGroupsBeforeFiltering,
				"rule_groups_to_filter", len(missing))

			http.Error(w, "an error occurred when filtering missing rule groups", http.StatusInternalServerError)
			return
		}
	}

	numRules := 0
	protectedNamespaces := map[string]struct{}{}
	for _, rg := range rgs {
		numRules += len(rg.Rules)

		if a.ruler.IsNamespaceProtected(userID, rg.Namespace) {
			protectedNamespaces[rg.Namespace] = struct{}{}
		}
	}

	level.Debug(logger).Log("msg", "retrieved rules for rule groups from rule store", "userID", userID, "num_groups", len(rgs), "num_rules", numRules)

	formatted := rgs.Formatted()
	marshalAndSend(formatted, w, logger, ProtectedNamespacesHeaderFromSet(protectedNamespaces))
}

func (a *API) GetRuleGroup(w http.ResponseWriter, req *http.Request) {
	logger, ctx := spanlogger.New(req.Context(), a.logger, tracer, "API.GetRuleGroup")
	defer logger.Finish()

	userID, namespace, groupName, err := a.parseRequest(req, true, true)
	if err != nil {
		if errors.Is(err, errNoValidOrgIDFound) {
			respondInvalidRequest(logger, w, err.Error())
			return
		}
		respondServerError(logger, w, err.Error())
		return
	}

	rg, err := a.store.GetRuleGroup(ctx, userID, namespace, groupName)
	if err != nil {
		if errors.Is(err, rulestore.ErrGroupNotFound) {
			http.Error(w, err.Error(), http.StatusNotFound)
			return
		}
		http.Error(w, err.Error(), http.StatusBadRequest)
		return
	}

	var header http.Header
	if a.ruler.IsNamespaceProtected(userID, namespace) {
		header = ProtectedNamespacesHeaderFromString(namespace)
	}

	formatted := rulespb.FromProto(rg)
	marshalAndSend(formatted, w, logger, header)
}

func (a *API) CreateRuleGroup(w http.ResponseWriter, req *http.Request) {
	logger, ctx := spanlogger.New(req.Context(), a.logger, tracer, "API.CreateRuleGroup")
	defer logger.Finish()

	userID, namespace, _, err := a.parseRequest(req, true, false)
	if err != nil {
		if errors.Is(err, errNoValidOrgIDFound) {
			respondInvalidRequest(logger, w, err.Error())
			return
		}
		respondServerError(logger, w, err.Error())
		return
	}

	if a.ruler.IsNamespaceProtected(userID, namespace) {
		if err = AllowProtectionOverride(req.Header, namespace); err != nil {
			level.Warn(logger).Log("msg", "not allowed to create rule group under namespace", "err", err.Error())
			http.Error(w, "namespace is protected, no modification allowed", http.StatusForbidden)
			return
		}
	}

	payload, err := io.ReadAll(req.Body)
	if err != nil {
		level.Error(logger).Log("msg", "unable to read rule group payload", "err", err.Error())
		http.Error(w, err.Error(), http.StatusBadRequest)
		return
	}

	level.Debug(logger).Log("msg", "attempting to unmarshal rulegroup", "userID", userID, "group", string(payload))

	rg := rulefmt.RuleGroup{}
	if err = yaml.Unmarshal(payload, &rg); err != nil {
		level.Error(logger).Log("msg", "unable to unmarshal rule group payload", "err", err.Error())
		http.Error(w, ErrBadRuleGroup.Error(), http.StatusBadRequest)
		return
	}

	// Why do we unmarshal the rule group twice like this?
	// Prometheus' validation methods require access to the original YAML nodes to produce errors with
	// position (line and column) information, but we want to work with the non-YAML rulefmt.RuleGroup type.
	// See https://github.com/prometheus/prometheus/pull/16252 for more discussion of this.
	node := rulefmt.RuleGroupNode{}
	if err = yaml.Unmarshal(payload, &node); err != nil {
		level.Error(logger).Log("msg", "unable to unmarshal rule group payload", "err", err.Error())
		http.Error(w, ErrBadRuleGroup.Error(), http.StatusBadRequest)
		return
	}

	errs := a.ruler.manager.ValidateRuleGroup(userID, rg, node)
	if len(errs) > 0 {
		e := []string{}
		for _, err := range errs {
			level.Error(logger).Log("msg", "unable to validate rule group payload", "err", err.Error())
			e = append(e, err.Error())
		}

		http.Error(w, strings.Join(e, ", "), http.StatusBadRequest)
		return
	}

	if err := a.ruler.AssertMaxRulesPerRuleGroup(userID, namespace, len(rg.Rules)); err != nil {
		level.Warn(logger).Log("msg", "limit validation failure", "err", err.Error(), "user", userID)
		http.Error(w, err.Error(), http.StatusBadRequest)
		return
	}

	if err := a.ruler.AssertMinRuleEvaluationInterval(userID, time.Duration(rg.Interval)); err != nil {
		level.Warn(logger).Log("msg", "limit validation failure", "err", err.Error(), "user", userID)
		http.Error(w, err.Error(), http.StatusBadRequest)
		return
	}

	// Only list rule groups when enforcing a max number of groups for this tenant and namespace.
	if a.ruler.IsMaxRuleGroupsLimited(userID, namespace) {
		// Disable any caching when getting list of all rule groups since listing results
		// are cached and not invalidated and we need the most up-to-date number.
		rgs, err := a.store.ListRuleGroupsForUserAndNamespace(ctx, userID, "", rulestore.WithCacheDisabled())
		if err != nil {
			level.Error(logger).Log("msg", "unable to fetch current rule groups for validation", "err", err.Error(), "user", userID)
			http.Error(w, err.Error(), http.StatusInternalServerError)
			return
		}

		if err := a.ruler.AssertMaxRuleGroups(userID, namespace, len(rgs)+1); err != nil {
			level.Warn(logger).Log("msg", "limit validation failure", "err", err.Error(), "user", userID)
			http.Error(w, err.Error(), http.StatusBadRequest)
			return
		}
	}

	rgProto := rulespb.ToProto(userID, namespace, rg)

	level.Debug(logger).Log("msg", "attempting to store rulegroup", "userID", userID, "group", rgProto.String())
	err = a.store.SetRuleGroup(ctx, userID, namespace, rgProto)
	if err != nil {
		level.Error(logger).Log("msg", "unable to store rule group", "err", err.Error())

		// If the error is an object mutation rate limit error from GCS, a 429 is returned instead of a 500. This is a
		// user issue rather than a server error, as it indicates the user is trying to update that specific rule group
		// too fast (the rate limit is per-object).
		// This is a simple way of returning the correct response code for a problem we've seen in practice, a more
		// advanced solution would be to actually implement rate limiting for the ruler API.
		// We don't return 429s for all object storage rate limit errors, since we can't guarantee all of them are user
		// issues.
		if isGCSObjectMutationRateLimitError(err) {
			respondError(logger, w, http.StatusTooManyRequests, v1.ErrServer, "per-rule group rate limit exceeded")
			return
		}

		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}

	a.ruler.NotifySyncRulesAsync(userID)

	respondAccepted(w, logger)
}

func (a *API) DeleteNamespace(w http.ResponseWriter, req *http.Request) {
	logger, ctx := spanlogger.New(req.Context(), a.logger, tracer, "API.DeleteNamespace")
	defer logger.Finish()

	userID, namespace, _, err := a.parseRequest(req, true, false)
	if err != nil {
		if errors.Is(err, errNoValidOrgIDFound) {
			respondInvalidRequest(logger, w, err.Error())
			return
		}
		respondServerError(logger, w, err.Error())
		return
	}

	if a.ruler.IsNamespaceProtected(userID, namespace) {
		if err = AllowProtectionOverride(req.Header, namespace); err != nil {
			level.Warn(logger).Log("msg", "not allowed to delete namespace", "err", err.Error())
			http.Error(w, "namespace is protected, no modification allowed", http.StatusForbidden)
			return
		}
	}

	err = a.store.DeleteNamespace(ctx, userID, namespace)
	if err != nil {
		if errors.Is(err, rulestore.ErrGroupNamespaceNotFound) {
			http.Error(w, err.Error(), http.StatusNotFound)
			return
		}
		respondServerError(logger, w, err.Error())
		return
	}

	a.ruler.NotifySyncRulesAsync(userID)

	respondAccepted(w, logger)
}

func (a *API) DeleteRuleGroup(w http.ResponseWriter, req *http.Request) {
	logger, ctx := spanlogger.New(req.Context(), a.logger, tracer, "API.DeleteRuleGroup")
	defer logger.Finish()

	userID, namespace, groupName, err := a.parseRequest(req, true, true)
	if err != nil {
		if errors.Is(err, errNoValidOrgIDFound) {
			respondInvalidRequest(logger, w, err.Error())
			return
		}
		respondServerError(logger, w, err.Error())
		return
	}

	if a.ruler.IsNamespaceProtected(userID, namespace) {
		if err = AllowProtectionOverride(req.Header, namespace); err != nil {
			level.Warn(logger).Log("msg", "not allowed to delete rule group under namespace", "err", err.Error())
			http.Error(w, "namespace is protected, no modification allowed", http.StatusForbidden)
			return
		}
	}

	err = a.store.DeleteRuleGroup(ctx, userID, namespace, groupName)
	if err != nil {
		if errors.Is(err, rulestore.ErrGroupNotFound) {
			http.Error(w, err.Error(), http.StatusNotFound)
			return
		}
		respondServerError(logger, w, err.Error())
		return
	}

	a.ruler.NotifySyncRulesAsync(userID)

	respondAccepted(w, logger)
}

// alertStateDescToPrometheusAlert converts AlertStateDesc to Alert. The returned data structure is suitable
// to be exported by the user-facing API.
func alertStateDescToPrometheusAlert(d *AlertStateDesc) *Alert {
	a := &Alert{
		Labels:      mimirpb.FromLabelAdaptersToLabels(d.Labels),
		Annotations: mimirpb.FromLabelAdaptersToLabels(d.Annotations),
		State:       d.GetState(),
		ActiveAt:    &d.ActiveAt,
		Value:       strconv.FormatFloat(d.Value, 'e', -1, 64),
	}

	if !d.KeepFiringSince.IsZero() {
		a.KeepFiringSince = &d.KeepFiringSince
	}

	return a
}

// isGCSObjectMutationRateLimitError checks whether the error message is from GCS and is an object mutation rate limit.
// This is a per-object limit and is limited to 1 mutation per second (https://cloud.google.com/storage/quotas).
func isGCSObjectMutationRateLimitError(err error) bool {
	var gErr *googleapi.Error
	if errors.As(err, &gErr) {
		return gErr.Code == 429 &&
			strings.Contains(gErr.Message, "exceeded the rate limit for object mutation operations")
	}
	return false
}
