/*
Copyright 2023 The Kubernetes 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 scalewaytasks

import (
	"fmt"
	"strings"

	"github.com/scaleway/scaleway-sdk-go/api/lb/v1"
	"github.com/scaleway/scaleway-sdk-go/scw"
	"k8s.io/kops/upup/pkg/fi"
	"k8s.io/kops/upup/pkg/fi/cloudup/scaleway"
	"k8s.io/kops/upup/pkg/fi/cloudup/terraform"
	"k8s.io/kops/upup/pkg/fi/cloudup/terraformWriter"
)

// +kops:fitask
type LBBackend struct {
	Name      *string
	Lifecycle fi.Lifecycle

	ID                   *string
	Zone                 *string
	ForwardProtocol      *string
	ForwardPort          *int32
	ForwardPortAlgorithm *string
	StickySessions       *string
	ProxyProtocol        *string

	LoadBalancer *LoadBalancer
}

var _ fi.CloudupTask = &LBBackend{}
var _ fi.CompareWithID = &LBBackend{}

var _ fi.CloudupHasDependencies = &LBBackend{}

func (l *LBBackend) GetDependencies(tasks map[string]fi.CloudupTask) []fi.CloudupTask {
	var deps []fi.CloudupTask
	for _, task := range tasks {
		if _, ok := task.(*LoadBalancer); ok {
			deps = append(deps, task)
		}
		if _, ok := task.(*Instance); ok {
			deps = append(deps, task)
		}
	}
	return deps
}

func (l *LBBackend) CompareWithID() *string {
	return l.ID
}

func (l *LBBackend) Find(context *fi.CloudupContext) (*LBBackend, error) {
	cloud := context.T.Cloud.(scaleway.ScwCloud)
	lbService := cloud.LBService()

	if l.LoadBalancer.LBID == nil {
		return nil, nil
	}

	backendResponse, err := lbService.ListBackends(&lb.ZonedAPIListBackendsRequest{
		Zone: scw.Zone(cloud.Zone()),
		LBID: fi.ValueOf(l.LoadBalancer.LBID),
		Name: l.Name,
	})
	if err != nil {
		return nil, fmt.Errorf("listing back-ends for load-balancer %s: %w", fi.ValueOf(l.LoadBalancer.LBID), err)
	}
	if backendResponse.TotalCount != 1 {
		return nil, nil
	}
	backend := backendResponse.Backends[0]

	return &LBBackend{
		Name:                 fi.PtrTo(backend.Name),
		Lifecycle:            l.Lifecycle,
		ID:                   fi.PtrTo(backend.ID),
		Zone:                 fi.PtrTo(string(backend.LB.Zone)),
		ForwardProtocol:      fi.PtrTo(string(backend.ForwardProtocol)),
		ForwardPort:          fi.PtrTo(backend.ForwardPort),
		ForwardPortAlgorithm: fi.PtrTo(string(backend.ForwardPortAlgorithm)),
		StickySessions:       fi.PtrTo(string(backend.StickySessions)),
		ProxyProtocol:        fi.PtrTo(string(backend.ProxyProtocol)),
		LoadBalancer: &LoadBalancer{
			Name: fi.PtrTo(backend.LB.Name),
		},
	}, nil
}

func (l *LBBackend) Run(context *fi.CloudupContext) error {
	return fi.CloudupDefaultDeltaRunMethod(l, context)
}

func (_ *LBBackend) CheckChanges(actual, expected, changes *LBBackend) error {
	if actual != nil {
		if changes.Name != nil {
			return fi.CannotChangeField("Name")
		}
		if changes.ID != nil {
			return fi.CannotChangeField("ID")
		}
		if changes.Zone != nil {
			return fi.CannotChangeField("Zone")
		}
	} else {
		if expected.Name == nil {
			return fi.RequiredField("Name")
		}
		if expected.Zone == nil {
			return fi.RequiredField("Zone")
		}
	}
	return nil
}

func (l *LBBackend) RenderScw(t *scaleway.ScwAPITarget, actual, expected, changes *LBBackend) error {
	lbService := t.Cloud.LBService()
	zone := scw.Zone(fi.ValueOf(expected.Zone))

	controlPlanesIPs, err := getControlPlanesIPs(t.Cloud, expected.LoadBalancer, zone)
	if err != nil {
		return err
	}

	if actual != nil {

		_, err := lbService.UpdateBackend(&lb.ZonedAPIUpdateBackendRequest{
			Zone:                 zone,
			BackendID:            fi.ValueOf(actual.ID),
			Name:                 fi.ValueOf(actual.Name),
			ForwardProtocol:      lb.Protocol(fi.ValueOf(expected.ForwardProtocol)),
			ForwardPort:          fi.ValueOf(expected.ForwardPort),
			ForwardPortAlgorithm: lb.ForwardPortAlgorithm(fi.ValueOf(expected.ForwardPortAlgorithm)),
			StickySessions:       lb.StickySessionsType(fi.ValueOf(expected.StickySessions)),
			ProxyProtocol:        lb.ProxyProtocol(fi.ValueOf(expected.ProxyProtocol)),
		})
		if err != nil {
			return fmt.Errorf("updating back-end for load-balancer %s: %w", fi.ValueOf(actual.LoadBalancer.Name), err)
		}

		_, err = lbService.SetBackendServers(&lb.ZonedAPISetBackendServersRequest{
			Zone:      zone,
			BackendID: fi.ValueOf(actual.ID),
			ServerIP:  controlPlanesIPs,
		})
		if err != nil {
			return fmt.Errorf("updating back-end server IPs for load-balancer %s: %w", fi.ValueOf(actual.LoadBalancer.Name), err)
		}

	} else {

		backendCreated, err := lbService.CreateBackend(&lb.ZonedAPICreateBackendRequest{
			Zone:                 zone,
			LBID:                 fi.ValueOf(expected.LoadBalancer.LBID),
			Name:                 fi.ValueOf(expected.Name),
			ForwardProtocol:      lb.Protocol(fi.ValueOf(expected.ForwardProtocol)),
			ForwardPort:          fi.ValueOf(expected.ForwardPort),
			ForwardPortAlgorithm: lb.ForwardPortAlgorithm(fi.ValueOf(expected.ForwardPortAlgorithm)),
			StickySessions:       lb.StickySessionsType(fi.ValueOf(expected.StickySessions)),
			HealthCheck: &lb.HealthCheck{
				CheckMaxRetries: 5,
				TCPConfig:       &lb.HealthCheckTCPConfig{},
				Port:            fi.ValueOf(expected.ForwardPort),
				CheckTimeout:    scw.TimeDurationPtr(3000),
				CheckDelay:      scw.TimeDurationPtr(1001),
			},
			ServerIP:      controlPlanesIPs,
			ProxyProtocol: lb.ProxyProtocol(fi.ValueOf(expected.ProxyProtocol)),
		})
		if err != nil {
			return fmt.Errorf("creating back-end for load-balancer %s: %w", fi.ValueOf(expected.LoadBalancer.Name), err)
		}

		expected.ID = &backendCreated.ID

	}

	_, err = lbService.WaitForLb(&lb.ZonedAPIWaitForLBRequest{
		LBID: fi.ValueOf(expected.LoadBalancer.LBID),
		Zone: zone,
	})
	if err != nil {
		return fmt.Errorf("waiting for load-balancer %s: %w", fi.ValueOf(expected.LoadBalancer.Name), err)
	}

	return nil
}

type terraformLBBackend struct {
	LBID            *terraformWriter.Literal   `cty:"lb_id"`
	Name            *string                    `cty:"name"`
	ForwardProtocol *string                    `cty:"forward_protocol"`
	ForwardPort     *int32                     `cty:"forward_port"`
	ProxyProtocol   *string                    `cty:"proxy_protocol"`
	ServerIPs       []*terraformWriter.Literal `cty:"server_ips"`
}

func (l *LBBackend) RenderTerraform(t *terraform.TerraformTarget, actual, expected, changes *LBBackend) error {
	var serverIPs []*terraformWriter.Literal
	resources, err := t.GetResourcesByType()
	if err != nil {
		return err
	}
	servers := resources["scaleway_instance_server"]
	for _, server := range servers {
		tfInstance := server.(terraformInstance)
		if role := scaleway.InstanceRoleFromTags(tfInstance.Tags); role == scaleway.TagRoleControlPlane {
			serverIPs = append(serverIPs, terraformWriter.LiteralProperty("scaleway_instance_server", fi.ValueOf(tfInstance.Name), "private_ip"))
		}
	}

	tf := terraformLBBackend{
		LBID:            expected.LoadBalancer.TerraformLink(),
		Name:            expected.Name,
		ForwardProtocol: expected.ForwardProtocol,
		ForwardPort:     expected.ForwardPort,
		ProxyProtocol:   fi.PtrTo(strings.TrimPrefix(*expected.ProxyProtocol, "proxy_protocol_")),
		ServerIPs:       serverIPs,
	}
	return t.RenderResource("scaleway_lb_backend", fi.ValueOf(expected.Name), tf)
}

func (l *LBBackend) TerraformLink() *terraformWriter.Literal {
	return terraformWriter.LiteralProperty("scaleway_lb_backend", fi.ValueOf(l.Name), "id")
}

func getControlPlanesIPs(scwCloud scaleway.ScwCloud, lb *LoadBalancer, zone scw.Zone) ([]string, error) {
	var controlPlanePrivateIPs []string

	servers, err := scwCloud.GetClusterServers(scwCloud.ClusterName(lb.Tags), nil)
	if err != nil {
		return nil, fmt.Errorf("getting cluster servers for load-balancer's back-end: %w", err)
	}

	for _, server := range servers {
		if role := scaleway.InstanceRoleFromTags(server.Tags); role == scaleway.TagRoleWorker {
			continue
		}
		ip, err := scwCloud.GetServerIP(server.ID, server.Zone)
		if err != nil {
			return nil, fmt.Errorf("getting IP of server %s for load-balancer's back-end: %w", server.Name, err)
		}
		controlPlanePrivateIPs = append(controlPlanePrivateIPs, ip)
	}

	return controlPlanePrivateIPs, nil
}