/*
Copyright 2016 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 model

import (
	"fmt"
	"k8s.io/kops/pkg/apis/kops"
	"k8s.io/kops/upup/pkg/fi"
	"k8s.io/kops/upup/pkg/fi/cloudup/awstasks"
)

// APILoadBalancerBuilder builds a LoadBalancer for accessing the API
type APILoadBalancerBuilder struct {
	*KopsModelContext
}

var _ fi.ModelBuilder = &APILoadBalancerBuilder{}

func (b *APILoadBalancerBuilder) Build(c *fi.ModelBuilderContext) error {
	// Configuration where an ELB fronts the master (apiservers in particular)

	if !b.UseLoadBalancerForAPI() {
		return nil
	}

	var elb *awstasks.LoadBalancer
	{
		elbID, err := b.GetELBName32("api")
		if err != nil {
			return err
		}

		var elbSubnets []*awstasks.Subnet
		for i := range b.Cluster.Spec.Subnets {
			subnet := &b.Cluster.Spec.Subnets[i]

			switch subnet.Type {
			case kops.SubnetTypePublic:
				if !b.Cluster.IsTopologyPublic() {
					continue
				}
			case kops.SubnetTypeUtility:
				if !b.Cluster.IsTopologyPrivate() {
					continue
				}

			case kops.SubnetTypePrivate:
				continue

			default:
				return fmt.Errorf("subnet %q had unknown type %q", subnet.Name, subnet.Type)
			}

			elbSubnets = append(elbSubnets, b.LinkToSubnet(subnet))
		}

		elb = &awstasks.LoadBalancer{
			Name: s("api." + b.ClusterName()),
			ID:   s(elbID),
			SecurityGroups: []*awstasks.SecurityGroup{
				b.LinkToELBSecurityGroup("api"),
			},
			Subnets: elbSubnets,
			Listeners: map[string]*awstasks.LoadBalancerListener{
				"443": {InstancePort: 443},
			},

			// Configure fast-recovery health-checks
			HealthCheck: &awstasks.LoadBalancerHealthCheck{
				Target:             s("TCP:443"),
				Timeout:            i64(5),
				Interval:           i64(10),
				HealthyThreshold:   i64(2),
				UnhealthyThreshold: i64(2),
			},
		}

		c.AddTask(elb)
	}

	// Create security group for API ELB
	{
		t := &awstasks.SecurityGroup{
			Name:             s(b.ELBSecurityGroupName("api")),
			VPC:              b.LinkToVPC(),
			Description:      s("Security group for api ELB"),
			RemoveExtraRules: []string{"port=443"},
		}
		c.AddTask(t)
	}

	// Allow traffic from ELB to egress freely
	{
		t := &awstasks.SecurityGroupRule{
			Name:          s("api-elb-egress"),
			SecurityGroup: b.LinkToELBSecurityGroup("api"),
			Egress:        fi.Bool(true),
			CIDR:          s("0.0.0.0/0"),
		}
		c.AddTask(t)
	}

	// Allow traffic into the ELB from APIAccess CIDRs
	{
		for _, cidr := range b.Cluster.Spec.APIAccess {
			t := &awstasks.SecurityGroupRule{
				Name:          s("https-api-elb-" + cidr),
				SecurityGroup: b.LinkToELBSecurityGroup("api"),
				CIDR:          s(cidr),
				FromPort:      i64(443),
				ToPort:        i64(443),
				Protocol:      s("tcp"),
			}
			c.AddTask(t)
		}
	}

	// Allow HTTPS to the master instances from the ELB
	{
		t := &awstasks.SecurityGroupRule{
			Name:          s("https-elb-to-master"),
			SecurityGroup: b.LinkToSecurityGroup(kops.InstanceGroupRoleMaster),
			SourceGroup:   b.LinkToELBSecurityGroup("api"),
			FromPort:      i64(443),
			ToPort:        i64(443),
			Protocol:      s("tcp"),
		}
		c.AddTask(t)
	}

	for _, ig := range b.MasterInstanceGroups() {
		t := &awstasks.LoadBalancerAttachment{
			Name: s("api-" + ig.ObjectMeta.Name),

			LoadBalancer:     b.LinkToELB("api"),
			AutoscalingGroup: b.LinkToAutoscalingGroup(ig),
		}

		c.AddTask(t)
	}

	return nil

}