package aws

import (
	"fmt"
	"log"
	"regexp"
	"strconv"
	"strings"

	"github.com/aws/aws-sdk-go/aws"
	"github.com/aws/aws-sdk-go/aws/awserr"
	"github.com/aws/aws-sdk-go/service/elb"
	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/schema"
)

func resourceAwsAppCookieStickinessPolicy() *schema.Resource {
	return &schema.Resource{
		// There is no concept of "updating" an App Stickiness policy in
		// the AWS API.
		Create: resourceAwsAppCookieStickinessPolicyCreate,
		Read:   resourceAwsAppCookieStickinessPolicyRead,
		Delete: resourceAwsAppCookieStickinessPolicyDelete,
		Importer: &schema.ResourceImporter{
			State: schema.ImportStatePassthrough,
		},

		Schema: map[string]*schema.Schema{
			"name": {
				Type:     schema.TypeString,
				Required: true,
				ForceNew: true,
				ValidateFunc: func(v interface{}, k string) (ws []string, es []error) {
					value := v.(string)
					if !regexp.MustCompile(`^[0-9A-Za-z-]+$`).MatchString(value) {
						es = append(es, fmt.Errorf(
							"only alphanumeric characters and hyphens allowed in %q", k))
					}
					return
				},
			},

			"load_balancer": {
				Type:     schema.TypeString,
				Required: true,
				ForceNew: true,
			},

			"lb_port": {
				Type:     schema.TypeInt,
				Required: true,
				ForceNew: true,
			},

			"cookie_name": {
				Type:     schema.TypeString,
				Required: true,
				ForceNew: true,
			},
		},
	}
}

func resourceAwsAppCookieStickinessPolicyCreate(d *schema.ResourceData, meta interface{}) error {
	elbconn := meta.(*AWSClient).elbconn

	// Provision the AppStickinessPolicy
	acspOpts := &elb.CreateAppCookieStickinessPolicyInput{
		CookieName:       aws.String(d.Get("cookie_name").(string)),
		LoadBalancerName: aws.String(d.Get("load_balancer").(string)),
		PolicyName:       aws.String(d.Get("name").(string)),
	}

	if _, err := elbconn.CreateAppCookieStickinessPolicy(acspOpts); err != nil {
		return fmt.Errorf("Error creating AppCookieStickinessPolicy: %s", err)
	}

	setLoadBalancerOpts := &elb.SetLoadBalancerPoliciesOfListenerInput{
		LoadBalancerName: aws.String(d.Get("load_balancer").(string)),
		LoadBalancerPort: aws.Int64(int64(d.Get("lb_port").(int))),
		PolicyNames:      []*string{aws.String(d.Get("name").(string))},
	}

	if _, err := elbconn.SetLoadBalancerPoliciesOfListener(setLoadBalancerOpts); err != nil {
		return fmt.Errorf("Error setting AppCookieStickinessPolicy: %s", err)
	}

	d.SetId(fmt.Sprintf("%s:%d:%s",
		*acspOpts.LoadBalancerName,
		*setLoadBalancerOpts.LoadBalancerPort,
		*acspOpts.PolicyName))
	return nil
}

func resourceAwsAppCookieStickinessPolicyRead(d *schema.ResourceData, meta interface{}) error {
	elbconn := meta.(*AWSClient).elbconn

	lbName, lbPort, policyName := resourceAwsAppCookieStickinessPolicyParseId(d.Id())

	request := &elb.DescribeLoadBalancerPoliciesInput{
		LoadBalancerName: aws.String(lbName),
		PolicyNames:      []*string{aws.String(policyName)},
	}

	getResp, err := elbconn.DescribeLoadBalancerPolicies(request)
	if err != nil {
		if ec2err, ok := err.(awserr.Error); ok {
			if ec2err.Code() == "PolicyNotFound" || ec2err.Code() == "LoadBalancerNotFound" {
				log.Printf("[WARN] Load Balancer / Load Balancer Policy (%s) not found, removing from state", d.Id())
				d.SetId("")
			}
			return nil
		}
		return fmt.Errorf("Error retrieving policy: %s", err)
	}
	if len(getResp.PolicyDescriptions) != 1 {
		return fmt.Errorf("Unable to find policy %#v", getResp.PolicyDescriptions)
	}

	// we know the policy exists now, but we have to check if it's assigned to a listener
	assigned, err := resourceAwsELBSticknessPolicyAssigned(policyName, lbName, lbPort, elbconn)
	if err != nil {
		return err
	}
	if !assigned {
		// policy exists, but isn't assigned to a listener
		log.Printf("[DEBUG] policy '%s' exists, but isn't assigned to a listener", policyName)
		d.SetId("")
		return nil
	}

	// We can get away with this because there's only one attribute, the
	// cookie expiration, in these descriptions.
	policyDesc := getResp.PolicyDescriptions[0]
	cookieAttr := policyDesc.PolicyAttributeDescriptions[0]
	if *cookieAttr.AttributeName != "CookieName" {
		return fmt.Errorf("Unable to find cookie Name.")
	}

	d.Set("cookie_name", cookieAttr.AttributeValue)
	d.Set("name", policyName)
	d.Set("load_balancer", lbName)

	lbPortInt, _ := strconv.Atoi(lbPort)
	d.Set("lb_port", lbPortInt)

	return nil
}

// Determine if a particular policy is assigned to an ELB listener
func resourceAwsELBSticknessPolicyAssigned(policyName, lbName, lbPort string, elbconn *elb.ELB) (bool, error) {
	describeElbOpts := &elb.DescribeLoadBalancersInput{
		LoadBalancerNames: []*string{aws.String(lbName)},
	}
	describeResp, err := elbconn.DescribeLoadBalancers(describeElbOpts)
	if err != nil {
		if ec2err, ok := err.(awserr.Error); ok {
			if ec2err.Code() == "LoadBalancerNotFound" {
				return false, nil
			}
		}
		return false, fmt.Errorf("Error retrieving ELB description: %s", err)
	}

	if len(describeResp.LoadBalancerDescriptions) != 1 {
		return false, fmt.Errorf("Unable to find ELB: %#v", describeResp.LoadBalancerDescriptions)
	}

	lb := describeResp.LoadBalancerDescriptions[0]
	assigned := false
	for _, listener := range lb.ListenerDescriptions {
		if lbPort != strconv.Itoa(int(*listener.Listener.LoadBalancerPort)) {
			continue
		}

		for _, name := range listener.PolicyNames {
			if policyName == *name {
				assigned = true
				break
			}
		}
	}

	return assigned, nil
}

func resourceAwsAppCookieStickinessPolicyDelete(d *schema.ResourceData, meta interface{}) error {
	elbconn := meta.(*AWSClient).elbconn

	lbName, _, policyName := resourceAwsAppCookieStickinessPolicyParseId(d.Id())

	// Perversely, if we Set an empty list of PolicyNames, we detach the
	// policies attached to a listener, which is required to delete the
	// policy itself.
	setLoadBalancerOpts := &elb.SetLoadBalancerPoliciesOfListenerInput{
		LoadBalancerName: aws.String(d.Get("load_balancer").(string)),
		LoadBalancerPort: aws.Int64(int64(d.Get("lb_port").(int))),
		PolicyNames:      []*string{},
	}

	if _, err := elbconn.SetLoadBalancerPoliciesOfListener(setLoadBalancerOpts); err != nil {
		return fmt.Errorf("Error removing AppCookieStickinessPolicy: %s", err)
	}

	request := &elb.DeleteLoadBalancerPolicyInput{
		LoadBalancerName: aws.String(lbName),
		PolicyName:       aws.String(policyName),
	}

	if _, err := elbconn.DeleteLoadBalancerPolicy(request); err != nil {
		return fmt.Errorf("Error deleting App stickiness policy %s: %s", d.Id(), err)
	}
	return nil
}

// resourceAwsAppCookieStickinessPolicyParseId takes an ID and parses it into
// it's constituent parts. You need three axes (LB name, policy name, and LB
// port) to create or identify a stickiness policy in AWS's API.
func resourceAwsAppCookieStickinessPolicyParseId(id string) (string, string, string) {
	parts := strings.SplitN(id, ":", 3)
	return parts[0], parts[1], parts[2]
}
