// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
// SPDX-License-Identifier: Apache-2.0

package main

import (
	"fmt"
	"os"
	"path/filepath"

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

// Attempts to allocate an VPC Elastic IP Address for region. The IP
// address will be associated with the instance ID passed in.
//
// Usage:
//
//	go run ec2_allocate_address.go INSTANCE_ID
func main() {
	if len(os.Args) != 2 {
		exitErrorf("instance ID required\nUsage: %s instance_id",
			filepath.Base(os.Args[0]))
	}
	instanceID := os.Args[1]

	// Initialize a session in us-west-2 that the SDK will use to load
	// credentials from the shared credentials file ~/.aws/credentials.
	sess, err := session.NewSession(&aws.Config{
		Region: aws.String("us-west-2")},
	)

	// Create an EC2 service client.
	svc := ec2.New(sess)

	// Attempt to allocate the Elastic IP address.
	allocRes, err := svc.AllocateAddress(&ec2.AllocateAddressInput{
		Domain: aws.String("vpc"),
	})
	if err != nil {
		exitErrorf("Unable to allocate IP address, %v", err)
	}

	// Associate the new Elastic IP address with an existing EC2 instance.
	assocRes, err := svc.AssociateAddress(&ec2.AssociateAddressInput{
		AllocationId: allocRes.AllocationId,
		InstanceId:   aws.String(instanceID),
	})
	if err != nil {
		exitErrorf("Unable to associate IP address with %s, %v",
			instanceID, err)
	}

	fmt.Printf("Successfully allocated %s with instance %s.\n\tallocation id: %s, association id: %s\n",
		*allocRes.PublicIp, instanceID, *allocRes.AllocationId, *assocRes.AssociationId)
}

func exitErrorf(msg string, args ...interface{}) {
	fmt.Fprintf(os.Stderr, msg+"\n", args...)
	os.Exit(1)
}
