#!/usr/bin/env python3

import os
import sys
import boto3
import requests

# AWS internal REST URL to get instance-id
instance_id_url = 'http://169.254.169.254/latest/meta-data/instance-id'

ec2 = boto3.client('ec2', region_name='us-east-1')
route53 = boto3.client('route53', region_name='us-east-1')

def get_my_hostname(instance_id, tag, region='us-east-1'):
    filters = [{'Name':'resource-id','Values':[instance_id]}]
    response = ec2.describe_tags(Filters=filters)
    try:
        filtered_tags = next(item['Value'] for item in response['Tags'] if item["Key"] == tag)
    except Exception as e:
        filtered_tags = ""
    return (filtered_tags)


def get_ec2_record(ec2_name):
    response = ec2.describe_instances(
        Filters=[
                {
                    'Name': 'tag:Name',
                    'Values': [ec2_name]
            }
        ]
    )
    return response


def update_dns_record_sets(Name, value, action, type, ttl, zoneid):
    print(Name, value, action, type, ttl, zoneid)
    try:
        response = route53.change_resource_record_sets(
        HostedZoneId=zoneid,
        ChangeBatch= {
                        'Comment': 'update %s -> %s' % (Name, value),
                        'Changes': [
                            {
                             'Action': action,
                             'ResourceRecordSet': {
                                 'Name': Name,
                                 'Type': type,
                                 'TTL': ttl,
                                 'ResourceRecords': [{'Value': value}]
                            }
                        }]
        })
    except Exception as e:
        print(e)


def get_dns_record(zoneid, tagged_hostname, public_ip_name):

    old_ip_address = None
    response = route53.list_resource_record_sets(
            HostedZoneId=zoneid,
            StartRecordName=tagged_hostname,
            StartRecordType='A',
            MaxItems='1'
    )

    if response['ResourceRecordSets'][0]['Type'] == 'A' and response['ResourceRecordSets'][0]['Name'] == tagged_hostname:
        old_ip_address = response['ResourceRecordSets'][0]['ResourceRecords'][0]['Value']

    return old_ip_address, response if response['ResourceRecordSets'][0]['Name'] == tagged_hostname \
                        and response['ResourceRecordSets'][0]['ResourceRecords'][0]['Value'] != public_ip_name \
                        or response['ResourceRecordSets'][0]['Name'] != tagged_hostname else ""


# Get my own hostname based on IP
instance_id = requests.get(instance_id_url, timeout=5).text

tagged_hostname = get_my_hostname(instance_id, 'Name')
current_hostname = os.uname().nodename
if tagged_hostname and current_hostname != tagged_hostname:
    set_hostname_results = os.system(f"hostnamectl set-hostname {tagged_hostname}")
    print(f"Setting new hostname as {tagged_hostname}, with exit code {set_hostname_results}")

# Update DNS with hostname's public ip
ec2_record = get_ec2_record(tagged_hostname)

if tagged_hostname:
    try:
        public_ip = 'ec2-' + ec2_record['Reservations'][0]['Instances'][0]['PublicIpAddress'].replace('.', '-') + '.compute-1.amazonaws.com'
        zone_name = "devtech101.com" if get_my_hostname(instance_id, 'Env').startswith("prod") else "devtech101-dev.com"
        zoneid = "Z0123456789ABCD1EF1" if zone_name == 'devtech101-dev.com' else "Z0123456789ABCD1EF2" if zone_name == 'devtech101.com' else "Z0123456789ABCD1EF1"        
        os.system(f'netplan_update.sh {zone_name}')

        # Updating new dns record
        (old_public_ip, response) = get_dns_record(zoneid, tagged_hostname + '.' + zone_name + '.', public_ip)
        if response:
            print(f"Updating host: {tagged_hostname}.{zone_name} with ip address: {public_ip}")
            if old_public_ip:
                update_dns_record_sets(tagged_hostname + '.' + zone_name, old_public_ip, 'DELETE', 'A', 60, zoneid)
            update_dns_record_sets(tagged_hostname + '.' + zone_name, public_ip, 'UPSERT', 'CNAME', 60, zoneid)
        else:
            print(f"No updated necessary for host: {tagged_hostname}.{zone_name} with ip address: {public_ip}")
    except Exception as e:
        print(e)
        print("EC2 instance name not found!")