package tidbpodevicter

import (
	"context"
	"errors"
	"fmt"
	"os"
	"time"

	serverlessv1alpha1 "github.com/tidbcloud/aws-shared-provider/apis/serverless/v1alpha1"
	"github.com/tidbcloud/aws-shared-provider/pkg/manager"
	"github.com/tidbcloud/aws-shared-provider/pkg/tidbmanager"
	"github.com/tidbcloud/aws-shared-provider/pkg/types"
	"github.com/tidbcloud/aws-shared-provider/pkg/utils/query"
	"k8s.io/client-go/tools/record"
	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/log"
	"sigs.k8s.io/controller-runtime/pkg/predicate"
)

var (
	ErrNoMetric = errors.New("no metric")
)

type podDelta struct {
	namespace string
	name      string
	delta     float32
}

// String returns the general purpose string representation
func (pd podDelta) String() string {
	return fmt.Sprintf("%s/%s/%.3f", pd.namespace, pd.name, pd.delta)
}

type podScore struct {
	podDelta
	usage float32
	score int
}

// String returns the general purpose string representation
func (ps podScore) String() string {
	return fmt.Sprintf("%s/%.3f/%d", ps.podDelta.String(), ps.usage, ps.score)
}

// Reconciler reconciles a node-score-map NodeScore object.
type Reconciler struct {
	controller.Controller

	Client       client.Client
	Recorder     record.EventRecorder
	Namespace    string
	TidbManagers map[string]tidbmanager.TidbManager

	o11yQuerier query.PromQuerier
}

// Reconcile is part of the main kubernetes reconciliation loop which aims to
// move the current state of the cluster closer to the desired state.
func (r *Reconciler) Reconcile(ctx context.Context, req ctrl.Request) (ctrl.Result, error) {
	logger := log.FromContext(ctx).WithName("tidbpodevicter")
	ctx = log.IntoContext(ctx, logger)

	logger.V(2).Info("start reconcile")
	start := time.Now()
	defer func() {
		logger.V(2).Info("finish reconcile", "time", time.Since(start))
	}()

	nodeScoreMap := &serverlessv1alpha1.NodeScore{}
	if err := r.Client.Get(ctx, req.NamespacedName, nodeScoreMap); err != nil {
		logger.Error(err, "failed to get node score map")
		return ctrl.Result{}, err
	}

	if nodeEvictCpu := nodeScoreMap.Status.NodeNeedEvict.CPU; len(nodeEvictCpu) > 0 && nodeScoreMap.Spec.CPU != nil {
		r.evict(ctx, "cpu", nodeScoreMap.Spec.CPU.EvictThreshold, nodeEvictCpu)
	}
	if nodeEvictMem := nodeScoreMap.Status.NodeNeedEvict.MEM; len(nodeEvictMem) > 0 && nodeScoreMap.Spec.MEM != nil {
		r.evict(ctx, "mem", nodeScoreMap.Spec.MEM.EvictThreshold, nodeEvictMem)
	}

	return ctrl.Result{}, nil
}

// SetupWithManager sets up the controller with the Manager.
func (r *Reconciler) SetupWithManager(mgr manager.Manager) error {
	queryURL := os.Getenv(types.O11yGlobalReadURL)
	if queryURL == "" {
		return fmt.Errorf("env %s is empty", types.O11yGlobalReadURL)
	}
	r.o11yQuerier = query.NewPromQueryer(nil, queryURL)
	r.Recorder = mgr.GetEventRecorderFor("TidbPodEvicter")

	byFilterFuncs := predicate.NewPredicateFuncs(func(object client.Object) bool {
		nodeScore := object.(*serverlessv1alpha1.NodeScore)
		return nodeScore.Name == types.NodeScoreMap && nodeScore.Namespace == r.Namespace &&
			nodeScore.Status.NodeNeedEvict != nil
	})

	return ctrl.NewControllerManagedBy(mgr).Named("TidbPodEvicter").For(&serverlessv1alpha1.NodeScore{}).
		WithEventFilter(byFilterFuncs).
		Complete(r)
}