package api

import (
	"context"
	"errors"
	"fmt"
	"net/http"
	"strings"
	"time"

	"github.com/grafana/grafana/pkg/services/accesscontrol"
	"github.com/grafana/grafana/pkg/services/dashboards"
	"github.com/grafana/grafana/pkg/services/ngalert/eval"
	"github.com/grafana/grafana/pkg/services/ngalert/provisioning"
	"github.com/grafana/grafana/pkg/services/ngalert/store"
	"github.com/grafana/grafana/pkg/services/quota"
	"github.com/grafana/grafana/pkg/setting"

	"github.com/prometheus/common/model"

	"github.com/grafana/grafana/pkg/api/apierrors"
	"github.com/grafana/grafana/pkg/api/response"
	"github.com/grafana/grafana/pkg/infra/log"
	"github.com/grafana/grafana/pkg/models"
	apimodels "github.com/grafana/grafana/pkg/services/ngalert/api/tooling/definitions"
	ngmodels "github.com/grafana/grafana/pkg/services/ngalert/models"
	"github.com/grafana/grafana/pkg/services/ngalert/schedule"
	"github.com/grafana/grafana/pkg/util"
)

type ConditionValidator interface {
	// Validate validates that the condition is correct. Returns nil if the condition is correct. Otherwise, error that describes the failure
	Validate(ctx eval.EvaluationContext, condition ngmodels.Condition) error
}

type RulerSrv struct {
	xactManager        provisioning.TransactionManager
	provenanceStore    provisioning.ProvisioningStore
	store              RuleStore
	QuotaService       quota.Service
	scheduleService    schedule.ScheduleService
	log                log.Logger
	cfg                *setting.UnifiedAlertingSettings
	ac                 accesscontrol.AccessControl
	conditionValidator ConditionValidator
}

var (
	errProvisionedResource = errors.New("request affects resources created via provisioning API")
)

// RouteDeleteAlertRules deletes all alert rules the user is authorized to access in the given namespace
// or, if non-empty, a specific group of rules in the namespace.
// Returns http.StatusUnauthorized if user does not have access to any of the rules that match the filter.
// Returns http.StatusBadRequest if all rules that match the filter and the user is authorized to delete are provisioned.
func (srv RulerSrv) RouteDeleteAlertRules(c *models.ReqContext, namespaceTitle string, group string) response.Response {
	namespace, err := srv.store.GetNamespaceByTitle(c.Req.Context(), namespaceTitle, c.SignedInUser.OrgID, c.SignedInUser, true)
	if err != nil {
		return toNamespaceErrorResponse(err)
	}
	var loggerCtx = []interface{}{
		"namespace",
		namespace.Title,
	}
	var ruleGroup string
	if group != "" {
		ruleGroup = group
		loggerCtx = append(loggerCtx, "group", group)
	}
	logger := srv.log.New(loggerCtx...)

	hasAccess := func(evaluator accesscontrol.Evaluator) bool {
		return accesscontrol.HasAccess(srv.ac, c)(accesscontrol.ReqOrgAdminOrEditor, evaluator)
	}

	provenances, err := srv.provenanceStore.GetProvenances(c.Req.Context(), c.SignedInUser.OrgID, (&ngmodels.AlertRule{}).ResourceType())
	if err != nil {
		return ErrResp(http.StatusInternalServerError, err, "failed to fetch provenances of alert rules")
	}

	deletedGroups := make(map[ngmodels.AlertRuleGroupKey][]ngmodels.AlertRuleKey)
	err = srv.xactManager.InTransaction(c.Req.Context(), func(ctx context.Context) error {
		unauthz, provisioned := false, false
		q := ngmodels.ListAlertRulesQuery{
			OrgID:         c.SignedInUser.OrgID,
			NamespaceUIDs: []string{namespace.Uid},
			RuleGroup:     ruleGroup,
		}
		if err = srv.store.ListAlertRules(ctx, &q); err != nil {
			return err
		}

		if len(q.Result) == 0 {
			logger.Debug("no alert rules to delete from namespace/group")
			return nil
		}

		var deletionCandidates = make(map[ngmodels.AlertRuleGroupKey][]*ngmodels.AlertRule)
		for _, rule := range q.Result {
			key := rule.GetGroupKey()
			deletionCandidates[key] = append(deletionCandidates[key], rule)
		}
		rulesToDelete := make([]string, 0, len(q.Result))
		for groupKey, rules := range deletionCandidates {
			if !authorizeAccessToRuleGroup(rules, hasAccess) {
				unauthz = true
				continue
			}
			if containsProvisionedAlerts(provenances, rules) {
				provisioned = true
				continue
			}
			uid := make([]string, 0, len(rules))
			keys := make([]ngmodels.AlertRuleKey, 0, len(rules))
			for _, rule := range rules {
				uid = append(uid, rule.UID)
				keys = append(keys, rule.GetKey())
			}
			rulesToDelete = append(rulesToDelete, uid...)
			deletedGroups[groupKey] = keys
		}
		if len(rulesToDelete) > 0 {
			return srv.store.DeleteAlertRulesByUID(ctx, c.SignedInUser.OrgID, rulesToDelete...)
		}
		// if none rules were deleted return an error.
		// Check whether provisioned check failed first because if it is true, then all rules that the user can access (actually read via GET API) are provisioned.
		if provisioned {
			return errProvisionedResource
		}
		if unauthz {
			if group == "" {
				return fmt.Errorf("%w to delete any existing rules in the namespace", ErrAuthorization)
			}
			return fmt.Errorf("%w to delete group of the rules", ErrAuthorization)
		}
		return nil
	})

	if err != nil {
		if errors.Is(err, ErrAuthorization) {
			return ErrResp(http.StatusUnauthorized, err, "failed to delete rule group")
		}
		if errors.Is(err, errProvisionedResource) {
			return ErrResp(http.StatusBadRequest, err, "failed to delete rule group")
		}
		return ErrResp(http.StatusInternalServerError, err, "failed to delete rule group")
	}

	logger.Debug("rules have been deleted from the store. updating scheduler")
	for _, ruleKeys := range deletedGroups {
		srv.scheduleService.DeleteAlertRule(ruleKeys...)
	}

	return response.JSON(http.StatusAccepted, util.DynMap{"message": "rules deleted"})
}

// RouteGetNamespaceRulesConfig returns all rules in a specific folder that user has access to
func (srv RulerSrv) RouteGetNamespaceRulesConfig(c *models.ReqContext, namespaceTitle string) response.Response {
	namespace, err := srv.store.GetNamespaceByTitle(c.Req.Context(), namespaceTitle, c.SignedInUser.OrgID, c.SignedInUser, false)
	if err != nil {
		return toNamespaceErrorResponse(err)
	}

	q := ngmodels.ListAlertRulesQuery{
		OrgID:         c.SignedInUser.OrgID,
		NamespaceUIDs: []string{namespace.Uid},
	}
	if err := srv.store.ListAlertRules(c.Req.Context(), &q); err != nil {
		return ErrResp(http.StatusInternalServerError, err, "failed to update rule group")
	}

	result := apimodels.NamespaceConfigResponse{}

	hasAccess := func(evaluator accesscontrol.Evaluator) bool {
		return accesscontrol.HasAccess(srv.ac, c)(accesscontrol.ReqViewer, evaluator)
	}

	provenanceRecords, err := srv.provenanceStore.GetProvenances(c.Req.Context(), c.SignedInUser.OrgID, (&ngmodels.AlertRule{}).ResourceType())
	if err != nil {
		return ErrResp(http.StatusInternalServerError, err, "failed to get provenance for rule group")
	}

	ruleGroups := make(map[string]ngmodels.RulesGroup)
	for _, r := range q.Result {
		ruleGroups[r.RuleGroup] = append(ruleGroups[r.RuleGroup], r)
	}

	for groupName, rules := range ruleGroups {
		if !authorizeAccessToRuleGroup(rules, hasAccess) {
			continue
		}
		result[namespaceTitle] = append(result[namespaceTitle], toGettableRuleGroupConfig(groupName, rules, namespace.Id, provenanceRecords))
	}

	return response.JSON(http.StatusAccepted, result)
}

// RouteGetRulesGroupConfig returns rules that belong to a specific group in a specific namespace (folder).
// If user does not have access to at least one of the rule in the group, returns status 401 Unauthorized
func (srv RulerSrv) RouteGetRulesGroupConfig(c *models.ReqContext, namespaceTitle string, ruleGroup string) response.Response {
	namespace, err := srv.store.GetNamespaceByTitle(c.Req.Context(), namespaceTitle, c.SignedInUser.OrgID, c.SignedInUser, false)
	if err != nil {
		return toNamespaceErrorResponse(err)
	}

	q := ngmodels.ListAlertRulesQuery{
		OrgID:         c.SignedInUser.OrgID,
		NamespaceUIDs: []string{namespace.Uid},
		RuleGroup:     ruleGroup,
	}
	if err := srv.store.ListAlertRules(c.Req.Context(), &q); err != nil {
		return ErrResp(http.StatusInternalServerError, err, "failed to get group alert rules")
	}

	hasAccess := func(evaluator accesscontrol.Evaluator) bool {
		return accesscontrol.HasAccess(srv.ac, c)(accesscontrol.ReqViewer, evaluator)
	}

	provenanceRecords, err := srv.provenanceStore.GetProvenances(c.Req.Context(), c.SignedInUser.OrgID, (&ngmodels.AlertRule{}).ResourceType())
	if err != nil {
		return ErrResp(http.StatusInternalServerError, err, "failed to get group alert rules")
	}

	if !authorizeAccessToRuleGroup(q.Result, hasAccess) {
		return ErrResp(http.StatusUnauthorized, fmt.Errorf("%w to access the group because it does not have access to one or many data sources one or many rules in the group use", ErrAuthorization), "")
	}

	result := apimodels.RuleGroupConfigResponse{
		GettableRuleGroupConfig: toGettableRuleGroupConfig(ruleGroup, q.Result, namespace.Id, provenanceRecords),
	}
	return response.JSON(http.StatusAccepted, result)
}

// RouteGetRulesConfig returns all alert rules that are available to the current user
func (srv RulerSrv) RouteGetRulesConfig(c *models.ReqContext) response.Response {
	namespaceMap, err := srv.store.GetUserVisibleNamespaces(c.Req.Context(), c.OrgID, c.SignedInUser)
	if err != nil {
		return ErrResp(http.StatusInternalServerError, err, "failed to get namespaces visible to the user")
	}
	result := apimodels.NamespaceConfigResponse{}

	if len(namespaceMap) == 0 {
		srv.log.Debug("user has no access to any namespaces")
		return response.JSON(http.StatusOK, result)
	}

	namespaceUIDs := make([]string, len(namespaceMap))
	for k := range namespaceMap {
		namespaceUIDs = append(namespaceUIDs, k)
	}

	dashboardUID := c.Query("dashboard_uid")
	panelID, err := getPanelIDFromRequest(c.Req)
	if err != nil {
		return ErrResp(http.StatusBadRequest, err, "invalid panel_id")
	}
	if dashboardUID == "" && panelID != 0 {
		return ErrResp(http.StatusBadRequest, errors.New("panel_id must be set with dashboard_uid"), "")
	}

	q := ngmodels.ListAlertRulesQuery{
		OrgID:         c.SignedInUser.OrgID,
		NamespaceUIDs: namespaceUIDs,
		DashboardUID:  dashboardUID,
		PanelID:       panelID,
	}

	if err := srv.store.ListAlertRules(c.Req.Context(), &q); err != nil {
		return ErrResp(http.StatusInternalServerError, err, "failed to get alert rules")
	}

	hasAccess := func(evaluator accesscontrol.Evaluator) bool {
		return accesscontrol.HasAccess(srv.ac, c)(accesscontrol.ReqViewer, evaluator)
	}

	provenanceRecords, err := srv.provenanceStore.GetProvenances(c.Req.Context(), c.SignedInUser.OrgID, (&ngmodels.AlertRule{}).ResourceType())
	if err != nil {
		return ErrResp(http.StatusInternalServerError, err, "failed to get alert rules")
	}

	configs := make(map[ngmodels.AlertRuleGroupKey]ngmodels.RulesGroup)
	for _, r := range q.Result {
		groupKey := r.GetGroupKey()
		group := configs[groupKey]
		group = append(group, r)
		configs[groupKey] = group
	}

	for groupKey, rules := range configs {
		folder, ok := namespaceMap[groupKey.NamespaceUID]
		if !ok {
			srv.log.Error("namespace not visible to the user", "user", c.SignedInUser.UserID, "namespace", groupKey.NamespaceUID)
			continue
		}
		if !authorizeAccessToRuleGroup(rules, hasAccess) {
			continue
		}
		namespace := folder.Title
		result[namespace] = append(result[namespace], toGettableRuleGroupConfig(groupKey.RuleGroup, rules, folder.Id, provenanceRecords))
	}
	return response.JSON(http.StatusOK, result)
}

func (srv RulerSrv) RoutePostNameRulesConfig(c *models.ReqContext, ruleGroupConfig apimodels.PostableRuleGroupConfig, namespaceTitle string) response.Response {
	namespace, err := srv.store.GetNamespaceByTitle(c.Req.Context(), namespaceTitle, c.SignedInUser.OrgID, c.SignedInUser, true)
	if err != nil {
		return toNamespaceErrorResponse(err)
	}

	rules, err := validateRuleGroup(&ruleGroupConfig, c.SignedInUser.OrgID, namespace, func(condition ngmodels.Condition) error {
		return srv.conditionValidator.Validate(eval.Context(c.Req.Context(), c.SignedInUser), condition)
	}, srv.cfg)
	if err != nil {
		return ErrResp(http.StatusBadRequest, err, "")
	}

	groupKey := ngmodels.AlertRuleGroupKey{
		OrgID:        c.SignedInUser.OrgID,
		NamespaceUID: namespace.Uid,
		RuleGroup:    ruleGroupConfig.Name,
	}

	return srv.updateAlertRulesInGroup(c, groupKey, rules)
}

// updateAlertRulesInGroup calculates changes (rules to add,update,delete), verifies that the user is authorized to do the calculated changes and updates database.
// All operations are performed in a single transaction
func (srv RulerSrv) updateAlertRulesInGroup(c *models.ReqContext, groupKey ngmodels.AlertRuleGroupKey, rules []*ngmodels.AlertRule) response.Response {
	var finalChanges *store.GroupDelta
	hasAccess := accesscontrol.HasAccess(srv.ac, c)
	err := srv.xactManager.InTransaction(c.Req.Context(), func(tranCtx context.Context) error {
		logger := srv.log.New("namespace_uid", groupKey.NamespaceUID, "group", groupKey.RuleGroup, "org_id", groupKey.OrgID, "user_id", c.UserID)
		groupChanges, err := store.CalculateChanges(tranCtx, srv.store, groupKey, rules)
		if err != nil {
			return err
		}

		if groupChanges.IsEmpty() {
			finalChanges = groupChanges
			logger.Info("no changes detected in the request. Do nothing")
			return nil
		}

		// if RBAC is disabled the permission are limited to folder access that is done upstream
		if !srv.ac.IsDisabled() {
			err = authorizeRuleChanges(groupChanges, func(evaluator accesscontrol.Evaluator) bool {
				return hasAccess(accesscontrol.ReqOrgAdminOrEditor, evaluator)
			})
			if err != nil {
				return err
			}
		}

		if err := verifyProvisionedRulesNotAffected(c.Req.Context(), srv.provenanceStore, c.OrgID, groupChanges); err != nil {
			return err
		}

		finalChanges = store.UpdateCalculatedRuleFields(groupChanges)
		logger.Debug("updating database with the authorized changes", "add", len(finalChanges.New), "update", len(finalChanges.New), "delete", len(finalChanges.Delete))

		if len(finalChanges.Update) > 0 || len(finalChanges.New) > 0 {
			updates := make([]ngmodels.UpdateRule, 0, len(finalChanges.Update))
			inserts := make([]ngmodels.AlertRule, 0, len(finalChanges.New))
			for _, update := range finalChanges.Update {
				logger.Debug("updating rule", "rule_uid", update.New.UID, "diff", update.Diff.String())
				updates = append(updates, ngmodels.UpdateRule{
					Existing: update.Existing,
					New:      *update.New,
				})
			}
			for _, rule := range finalChanges.New {
				inserts = append(inserts, *rule)
			}
			_, err = srv.store.InsertAlertRules(tranCtx, inserts)
			if err != nil {
				return fmt.Errorf("failed to add rules: %w", err)
			}
			err = srv.store.UpdateAlertRules(tranCtx, updates)
			if err != nil {
				return fmt.Errorf("failed to update rules: %w", err)
			}
		}

		if len(finalChanges.Delete) > 0 {
			UIDs := make([]string, 0, len(finalChanges.Delete))
			for _, rule := range finalChanges.Delete {
				UIDs = append(UIDs, rule.UID)
			}

			if err = srv.store.DeleteAlertRulesByUID(tranCtx, c.SignedInUser.OrgID, UIDs...); err != nil {
				return fmt.Errorf("failed to delete rules: %w", err)
			}
		}

		if len(finalChanges.New) > 0 {
			limitReached, err := srv.QuotaService.CheckQuotaReached(tranCtx, "alert_rule", &quota.ScopeParameters{
				OrgID:  c.OrgID,
				UserID: c.UserID,
			}) // alert rule is table name
			if err != nil {
				return fmt.Errorf("failed to get alert rules quota: %w", err)
			}
			if limitReached {
				return ngmodels.ErrQuotaReached
			}
		}
		return nil
	})

	if err != nil {
		if errors.Is(err, ngmodels.ErrAlertRuleNotFound) {
			return ErrResp(http.StatusNotFound, err, "failed to update rule group")
		} else if errors.Is(err, ngmodels.ErrAlertRuleFailedValidation) || errors.Is(err, errProvisionedResource) {
			return ErrResp(http.StatusBadRequest, err, "failed to update rule group")
		} else if errors.Is(err, ngmodels.ErrQuotaReached) {
			return ErrResp(http.StatusForbidden, err, "")
		} else if errors.Is(err, ErrAuthorization) {
			return ErrResp(http.StatusUnauthorized, err, "")
		} else if errors.Is(err, store.ErrOptimisticLock) {
			return ErrResp(http.StatusConflict, err, "")
		}
		return ErrResp(http.StatusInternalServerError, err, "failed to update rule group")
	}

	for _, rule := range finalChanges.Update {
		srv.scheduleService.UpdateAlertRule(ngmodels.AlertRuleKey{
			OrgID: c.SignedInUser.OrgID,
			UID:   rule.Existing.UID,
		}, rule.Existing.Version+1)
	}

	if len(finalChanges.Delete) > 0 {
		keys := make([]ngmodels.AlertRuleKey, 0, len(finalChanges.Delete))
		for _, rule := range finalChanges.Delete {
			keys = append(keys, rule.GetKey())
		}
		srv.scheduleService.DeleteAlertRule(keys...)
	}

	if finalChanges.IsEmpty() {
		return response.JSON(http.StatusAccepted, util.DynMap{"message": "no changes detected in the rule group"})
	}

	return response.JSON(http.StatusAccepted, util.DynMap{"message": "rule group updated successfully"})
}

func toGettableRuleGroupConfig(groupName string, rules ngmodels.RulesGroup, namespaceID int64, provenanceRecords map[string]ngmodels.Provenance) apimodels.GettableRuleGroupConfig {
	rules.SortByGroupIndex()
	ruleNodes := make([]apimodels.GettableExtendedRuleNode, 0, len(rules))
	var interval time.Duration
	if len(rules) > 0 {
		interval = time.Duration(rules[0].IntervalSeconds) * time.Second
	}
	for _, r := range rules {
		ruleNodes = append(ruleNodes, toGettableExtendedRuleNode(*r, namespaceID, provenanceRecords))
	}
	return apimodels.GettableRuleGroupConfig{
		Name:     groupName,
		Interval: model.Duration(interval),
		Rules:    ruleNodes,
	}
}

func toGettableExtendedRuleNode(r ngmodels.AlertRule, namespaceID int64, provenanceRecords map[string]ngmodels.Provenance) apimodels.GettableExtendedRuleNode {
	provenance := ngmodels.ProvenanceNone
	if prov, exists := provenanceRecords[r.ResourceID()]; exists {
		provenance = prov
	}
	gettableExtendedRuleNode := apimodels.GettableExtendedRuleNode{
		GrafanaManagedAlert: &apimodels.GettableGrafanaRule{
			ID:              r.ID,
			OrgID:           r.OrgID,
			Title:           r.Title,
			Condition:       r.Condition,
			Data:            r.Data,
			Updated:         r.Updated,
			IntervalSeconds: r.IntervalSeconds,
			Version:         r.Version,
			UID:             r.UID,
			NamespaceUID:    r.NamespaceUID,
			NamespaceID:     namespaceID,
			RuleGroup:       r.RuleGroup,
			NoDataState:     apimodels.NoDataState(r.NoDataState),
			ExecErrState:    apimodels.ExecutionErrorState(r.ExecErrState),
			Provenance:      provenance,
		},
	}
	forDuration := model.Duration(r.For)
	gettableExtendedRuleNode.ApiRuleNode = &apimodels.ApiRuleNode{
		For:         &forDuration,
		Annotations: r.Annotations,
		Labels:      r.Labels,
	}
	return gettableExtendedRuleNode
}

func toNamespaceErrorResponse(err error) response.Response {
	if errors.Is(err, ngmodels.ErrCannotEditNamespace) {
		return ErrResp(http.StatusForbidden, err, err.Error())
	}
	if errors.Is(err, dashboards.ErrDashboardIdentifierNotSet) {
		return ErrResp(http.StatusBadRequest, err, err.Error())
	}
	return apierrors.ToFolderErrorResponse(err)
}

// verifyProvisionedRulesNotAffected check that neither of provisioned alerts are affected by changes.
// Returns errProvisionedResource if there is at least one rule in groups affected by changes that was provisioned.
func verifyProvisionedRulesNotAffected(ctx context.Context, provenanceStore provisioning.ProvisioningStore, orgID int64, ch *store.GroupDelta) error {
	provenances, err := provenanceStore.GetProvenances(ctx, orgID, (&ngmodels.AlertRule{}).ResourceType())
	if err != nil {
		return err
	}
	errorMsg := strings.Builder{}
	for group, alertRules := range ch.AffectedGroups {
		if !containsProvisionedAlerts(provenances, alertRules) {
			continue
		}
		if errorMsg.Len() > 0 {
			errorMsg.WriteRune(',')
		}
		errorMsg.WriteString(group.String())
	}
	if errorMsg.Len() == 0 {
		return nil
	}
	return fmt.Errorf("%w: alert rule group [%s]", errProvisionedResource, errorMsg.String())
}