/*
Copyright 2021.

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 controllers

import (
	"context"
	"errors"
	"fmt"
	"strings"
	"time"

	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/runtime"
	ctrl "sigs.k8s.io/controller-runtime"
	"sigs.k8s.io/controller-runtime/pkg/client"
	"sigs.k8s.io/controller-runtime/pkg/event"
	"sigs.k8s.io/controller-runtime/pkg/log"
	"sigs.k8s.io/controller-runtime/pkg/predicate"

	"github.com/aws/aws-sdk-go/aws"
	"github.com/aws/aws-sdk-go/aws/awserr"
	"github.com/aws/aws-sdk-go/aws/ec2metadata"
	"github.com/aws/aws-sdk-go/aws/request"
	"github.com/aws/aws-sdk-go/aws/session"
	"github.com/aws/aws-sdk-go/service/ec2"
)

const (
	instanceSyncInterval = 60 * time.Second
)

// NodeReconciler reconciles a Node object
type NodeReconciler struct {
	client.Client
	Scheme    *runtime.Scheme
	DryRun    bool
	Instances map[string]InstanceCache
	Provider  *ec2.EC2
}

// stores instances data from cloud provider
type InstanceCache struct {
	lastCheck time.Time
}

//+kubebuilder:rbac:groups=core,resources=nodes,verbs=get;list;watch;create;update;patch;delete
//+kubebuilder:rbac:groups=core,resources=nodes/status,verbs=get;update;patch
//+kubebuilder:rbac:groups=core,resources=nodes/finalizers,verbs=update

// IsNodeReady returns true if node.Status.Conditions{KubeletReady: True}
func isNodeReady(conditions []corev1.NodeCondition) bool {
	for _, condition := range conditions {
		if condition.Type == corev1.NodeReady {
			return condition.Status == corev1.ConditionTrue
		}
	}
	return false
}

// parse node.ProviderID, return provider, id
// eg. AWS: 'aws://<availability-zone>/<instance-id>'
func parseProviderID(providerID string) (string, string, error) {
	instanceID := ""
	provider := ""

	parsedProvider := strings.Split(providerID, "://")
	if len(parsedProvider) == 2 {
		provider = parsedProvider[0]
		if provider == "aws" {
			parsedID := strings.Split(strings.Trim(parsedProvider[1], "/"), "/")
			if len(parsedID) == 2 {
				instanceID = parsedID[1]
			}
		} else {
			return "", "", errors.New("Unknown provider")
		}
	} else {
		return "", "", errors.New("Cannot parse providerID")
	}

	return provider, instanceID, nil
}

func NewProviderEC2() *ec2.EC2 {
	logger := ctrl.Log.WithName("aws")

	sess := session.Must(session.NewSession())
	sess.Handlers.Build.PushFrontNamed(request.NamedHandler{
		Name: "authenticatorUserAgent",
		Fn: request.MakeAddToUserAgentHandler(
			"kubezero-forseti", "0.0.1"),
	})
	if aws.StringValue(sess.Config.Region) == "" {
		ec2metadata := ec2metadata.New(sess)
		regionFound, err := ec2metadata.Region()
		if err != nil {
			logger.Error(err, "Region not found in shared credentials, environment variable, or instance metadata.")
			return nil
		}
		sess.Config.Region = aws.String(regionFound)
	}
	creds, err := sess.Config.Credentials.Get()
	if err != nil {
		logger.Error(err, "Unable to get AWS credentials")
	}
	logger.Info(fmt.Sprintf("AWS Credentials retrieved from provider: %s", creds.ProviderName))

	return ec2.New(sess)
}

func getNode(provider *ec2.EC2, instanceID string) (bool, error) {
	logger := ctrl.Log.WithName("aws")

	result, err := provider.DescribeInstances(&ec2.DescribeInstancesInput{
		InstanceIds: []*string{
			aws.String(instanceID),
		},
	})
	if err != nil {
		if aerr, ok := err.(awserr.Error); ok && aerr.Code() == "InvalidInstanceID.NotFound" {
			logger.V(2).Info("Instance not found")
			return false, nil
		}
		return true, err
	}
	if len(result.Reservations) == 0 || len(result.Reservations[0].Instances) == 0 {
		logger.V(2).Info("Instance not found")
		return false, nil
	}

	logger.V(2).Info(fmt.Sprintf("Instance %s found", instanceID))
	return true, nil
}

// - https://pkg.go.dev/sigs.k8s.io/controller-runtime@v0.10.0/pkg/reconcile
func (r *NodeReconciler) Reconcile(ctx context.Context, req ctrl.Request) (ctrl.Result, error) {
	logger := log.FromContext(ctx)

	var node corev1.Node
	if err := r.Get(ctx, req.NamespacedName, &node); err != nil {
		if apierrors.IsNotFound(err) {
			logger.Info("Node already deleted.")
			return ctrl.Result{}, nil
		}
		logger.Error(err, "unable to fetch Node")
		return ctrl.Result{}, err
	}

	if isNodeReady(node.Status.Conditions) {
		logger.V(2).Info("Node ready")
		return ctrl.Result{}, nil

	}

	logger.V(2).Info("Node not ready")
	instance := r.Instances[node.Name]
	retryTime := instance.lastCheck.Add(instanceSyncInterval)

	if time.Now().After(retryTime) {
		provider, instanceID, err := parseProviderID(node.Spec.ProviderID)
		if err != nil {
			logger.Error(err, "Error parsing ProviderID from node")
			return ctrl.Result{}, err
		}
		logger.V(2).Info("parsed node.Spec.ProviderID", "provider", provider, "id", instanceID)

		//TODO. convert provider aws into interface to call getNode
		exists, err := getNode(r.Provider, instanceID)

		if err != nil {
			logger.Error(err, "Error calling cloud provider")
			return ctrl.Result{}, err
		}
		instance.lastCheck = time.Now()
		r.Instances[node.Name] = instance

		// Delete node
		if exists == false {
			logger.Info(fmt.Sprintf("Instance %s for node %s does not exist", instanceID, node.Name))

			deleteOptions := []client.DeleteOption{client.PropagationPolicy(metav1.DeletePropagationBackground)}
			if r.DryRun {
				deleteOptions = append(deleteOptions, client.DryRunAll)
			}
			if err := r.Delete(ctx, &node, deleteOptions...); client.IgnoreNotFound(err) != nil {
				logger.Error(err, "unable to delete node")
				return ctrl.Result{}, err
			}

			// Also remove node from cache
			delete(r.Instances, node.Name)
			logger.Info("node deleted")
		}

		return ctrl.Result{}, nil
	}

	// Requeue at retryTime
	requeueDelay := retryTime.Sub(time.Now())
	logger.V(2).Info(fmt.Sprintf("Requeue event after %s", requeueDelay))
	return ctrl.Result{RequeueAfter: requeueDelay}, nil
}

// SetupWithManager sets up the controller with the Manager.
// skip delete events, keep create to get all events at startup
func (r *NodeReconciler) SetupWithManager(mgr ctrl.Manager) error {
	return ctrl.NewControllerManagedBy(mgr).
		For(&corev1.Node{}).
		WithEventFilter(predicate.Funcs{
			//	CreateFunc: func(e event.CreateEvent) bool {
			//		return false
			//	},
			DeleteFunc: func(e event.DeleteEvent) bool {
				return false
			},
		}).
		Complete(r)
}