import json
import os
import time
import boto3

_ddb = None
_sqs = None


def get_ddb():
    global _ddb
    if _ddb is None:
        _ddb = boto3.resource('dynamodb')
    return _ddb


def get_sqs():
    global _sqs
    if _sqs is None:
        _sqs = boto3.client('sqs')
    return _sqs


def handler(event, context):
    table_name = os.environ['USERS_TABLE_NAME']
    queue_url = os.environ['MESSAGE_QUEUE_URL']

    # Scan for active users
    table = get_ddb().Table(table_name)
    response = table.scan(
        FilterExpression='#s = :active',
        ExpressionAttributeNames={'#s': 'status'},
        ExpressionAttributeValues={':active': 'active'},
    )
    users = response.get('Items', [])

    # 30-min bucket for deduplication
    bucket_ts = str(int(time.time()) // 1800)
    sqs = get_sqs()

    sent = 0
    for user in users:
        actor_id = user['actor_id']
        # Extract chat_id from actor_id (format: "telegram:<chat_id>")
        if not actor_id.startswith('telegram:'):
            continue
        chat_id = actor_id.split(':', 1)[1]

        msg = {
            'chat_id': chat_id,
            'channel': 'telegram',
            'messages': [{
                'text': '[HEARTBEAT]',
                'from_name': user.get('display_name', ''),
                'from_username': user.get('telegram_username', ''),
            }],
        }

        sqs.send_message(
            QueueUrl=queue_url,
            MessageBody=json.dumps(msg),
            MessageGroupId=actor_id,
            MessageDeduplicationId=f'heartbeat-{actor_id}-{bucket_ts}',
        )
        sent += 1

    print(f'[heartbeat-runner] Sent {sent} heartbeat messages')
    return {'statusCode': 200, 'sent': sent}