/*
Copyright 2019 The KubeSphere Authors.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
    http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package alerting

import (
	"context"
	"fmt"

	"github.com/go-logr/logr"
	promresourcesv1 "github.com/prometheus-operator/prometheus-operator/pkg/apis/monitoring/v1"
	promlabels "github.com/prometheus/prometheus/pkg/labels"
	corev1 "k8s.io/api/core/v1"
	apierrors "k8s.io/apimachinery/pkg/api/errors"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/labels"
	"k8s.io/apimachinery/pkg/types"
	"k8s.io/apimachinery/pkg/util/uuid"
	ctrl "sigs.k8s.io/controller-runtime"
	"sigs.k8s.io/controller-runtime/pkg/client"
	"sigs.k8s.io/controller-runtime/pkg/controller"
	"sigs.k8s.io/controller-runtime/pkg/handler"
	"sigs.k8s.io/controller-runtime/pkg/reconcile"
	"sigs.k8s.io/controller-runtime/pkg/source"

	alertingv2beta1 "kubesphere.io/api/alerting/v2beta1"
)

type RuleGroupReconciler struct {
	client.Client

	Log logr.Logger
}

func (r *RuleGroupReconciler) Reconcile(ctx context.Context, req reconcile.Request) (reconcile.Result, error) {

	var (
		log = r.Log.WithValues("namespace", req.Namespace)

		ruleLevel = RuleLevelNamesapce

		rulegroupNamespace = req.Namespace
		rulegroupList      = alertingv2beta1.RuleGroupList{}

		promruleNamespace = PrometheusRuleNamespace
	)

	// get all enabled rulegroups
	err := r.Client.List(ctx, &rulegroupList, &client.ListOptions{
		Namespace: rulegroupNamespace,
		LabelSelector: labels.SelectorFromSet(labels.Set{
			SourceGroupResourceLabelKeyEnable: SourceGroupResourceLabelValueEnableTrue,
		}),
	})
	if err != nil {
		return reconcile.Result{}, err
	}

	// add rule_id label that may have been missed
	var updated bool
	for i := range rulegroupList.Items {
		g := rulegroupList.Items[i]
		for j := range g.Spec.Rules {
			if g.Spec.Rules[j].Labels == nil {
				g.Spec.Rules[j].Labels = make(map[string]string)
			}
			if _, ok := g.Spec.Rules[j].Labels[alertingv2beta1.RuleLabelKeyRuleId]; !ok {
				g.Spec.Rules[j].Labels[alertingv2beta1.RuleLabelKeyRuleId] = string(uuid.NewUUID())
				err = r.Client.Update(ctx, &g)
				if err != nil {
					return reconcile.Result{}, err
				}
				updated = true
			}
		}
	}
	if updated {
		return reconcile.Result{}, nil
	}

	// labels added to rule.labels
	enforceRuleLabels := map[string]string{
		RuleLabelKeyRuleLevel: string(ruleLevel),
		RuleLabelKeyNamespace: rulegroupNamespace,
	}
	// matchers enforced to rule.expr
	enforceRuleMatchers := []*promlabels.Matcher{{
		Type:  promlabels.MatchEqual,
		Name:  RuleLabelKeyNamespace,
		Value: rulegroupNamespace,
	}}
	// labels added to PrometheusRule.metadata.labels
	promruleLabelSet := labels.Set{
		PrometheusRuleResourceLabelKeyRuleLevel:      string(ruleLevel),
		PrometheusRuleResourceLabelKeyOwnerNamespace: rulegroupNamespace,
	}

	enforceFuncs := createEnforceRuleFuncs(enforceRuleMatchers, enforceRuleLabels)

	// make PrometheusRule Groups
	rulegroups, err := makePrometheusRuleGroups(log, &rulegroupList, enforceFuncs...)
	if err != nil {
		return reconcile.Result{}, err
	}
	if len(rulegroups) == 0 {
		err = r.Client.DeleteAllOf(ctx, &promresourcesv1.PrometheusRule{}, &client.DeleteAllOfOptions{
			ListOptions: client.ListOptions{
				Namespace:     promruleNamespace,
				LabelSelector: labels.SelectorFromSet(promruleLabelSet),
			},
		})
		return reconcile.Result{}, err
	}

	var ns corev1.Namespace
	err = r.Client.Get(ctx, types.NamespacedName{Name: rulegroupNamespace}, &ns)
	if err != nil {
		return reconcile.Result{}, client.IgnoreNotFound(err)
	}
	if !ns.DeletionTimestamp.IsZero() {
		// if the namespace is being deleted, ignoring it because
		// the PrometheusRules with the namespace owner will be garbage collected by k8s.
		return reconcile.Result{}, nil
	}
	ownerReferences := []metav1.OwnerReference{{
		APIVersion: ns.APIVersion,
		Kind:       ns.Kind,
		Name:       ns.Name,
		UID:        ns.UID,
	}}

	// make desired PrometheuRule resources
	namePrefix := fmt.Sprintf("%s%s-", PrometheusRulePrefixNamespaceLevel, rulegroupNamespace)
	desired, err := makePrometheusRuleResources(rulegroups, promruleNamespace, namePrefix, promruleLabelSet, ownerReferences)
	if err != nil {
		return reconcile.Result{}, err
	}

	// get current PrometheusRules
	var current promresourcesv1.PrometheusRuleList
	err = r.Client.List(ctx, &current, &client.ListOptions{
		Namespace:     promruleNamespace,
		LabelSelector: labels.SelectorFromSet(promruleLabelSet),
	})
	if err != nil {
		return reconcile.Result{}, err
	}

	// update relevant prometheusrule resources
	err = bulkUpdatePrometheusRuleResources(r.Client, ctx, current.Items, desired)
	if err != nil && (apierrors.IsConflict(err) || apierrors.IsAlreadyExists(err)) {
		return reconcile.Result{Requeue: true}, nil
	}
	return reconcile.Result{}, err
}

func (r *RuleGroupReconciler) SetupWithManager(mgr ctrl.Manager) error {
	if r.Log.GetSink() == nil {
		r.Log = mgr.GetLogger()
	}
	if r.Client == nil {
		r.Client = mgr.GetClient()
	}

	ctr, err := controller.New("rulegroup", mgr,
		controller.Options{
			Reconciler: r,
		})

	if err != nil {
		return err
	}

	err = ctr.Watch(
		&source.Kind{Type: &alertingv2beta1.RuleGroup{}},
		handler.EnqueueRequestsFromMapFunc(func(o client.Object) []reconcile.Request {
			return []reconcile.Request{{
				NamespacedName: types.NamespacedName{
					Namespace: o.GetNamespace(),
				},
			}}
		}))
	return err
}