import * as winston from 'winston';
import { SQS, SNS } from 'aws-sdk';
import { SendMessageBatchRequestEntry } from 'aws-sdk/clients/sqs';
const sns = new SNS({ region: 'us-east-1' });

export const sqs = new SQS({ region: 'us-east-1' });

export interface EnsureQueueResult {
  queueName: string;
  queueUrl: string;
  queueArn: string;
  topicArns: string[];
  topicNames: string[];
}

/**
 * http://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/SQS.html
 * http://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/SNS.html
 * @param  {string}                     queueName [description]
 * @param  {string[]                =         []}          topicNames [description]
 * @return {Promise<EnsureQueueResult>}           [description]
 */
export async function ensureQueue(
  queueName: string,
  topicNames: string[] = []
): Promise<EnsureQueueResult> {
  // idempotent call to create the queue
  winston.info('ensure queue', queueName);
  await sqs
    .createQueue({ QueueName: queueName, Attributes: { MessageRetentionPeriod: '60' } })
    .promise();

  // retrieve the url
  let queueUrlResult = await sqs.getQueueUrl({ QueueName: queueName }).promise();
  let queueUrl = queueUrlResult.QueueUrl;
  winston.info('queueUrl', queueUrl);

  // retrive the arn for use with topics
  let queueAttributes = await sqs
    .getQueueAttributes({ QueueUrl: queueUrl, AttributeNames: ['QueueArn'] })
    .promise();
  let queueArn = queueAttributes.Attributes.QueueArn;
  winston.info('queueArn', queueArn);

  // attach to each topic
  let topicArns = [];
  for (let topicName of topicNames) {
    winston.info('subscribing to', topicName);

    // idempotent call to create the sns topic
    let topicResult = await sns.createTopic({ Name: topicName }).promise();
    let topicArn = topicResult.TopicArn;
    topicArns.push(topicArn);

    // subscribe to topic
    await sns
      .subscribe({
        TopicArn: topicArn,
        Protocol: 'sqs',
        Endpoint: queueArn,
      })
      .promise();
  }

  // attach policy to queue
  // refer to: http://docs.aws.amazon.com/sns/latest/dg/SendMessageToSQS.html
  await sqs
    .setQueueAttributes({
      QueueUrl: queueUrl,
      Attributes: {
        Policy: `{
  "Version":"2012-10-17",
  "Statement":[
    {
      "Sid":"${queueName}Policy",
      "Effect":"Allow",
      "Principal":"*",
      "Action":"sqs:SendMessage",
      "Resource":"${queueArn}",
      "Condition":{
        "ForAnyValue:ArnEquals":{
          "aws:SourceArn":["${topicArns.join('","')}"]
        }
      }
    }
  ]
}`,
      },
    })
    .promise();

  return {
    queueName,
    queueUrl,
    queueArn,
    topicArns,
    topicNames,
  };
}

/**
 * [receiveMessages description]
 * @param  {string}            queueUrl [description]
 * @param  {SQS.Message[]) =>       void}        callback [description]
 * @return {Promise<void>}              [description]
 */
export async function receiveMessages(
  queueUrl: string,
  callback: (messages: SQS.Message[]) => void
): Promise<void> {
  winston.info('receive messages', queueUrl);
  let keepRunning = true;

  while (keepRunning) {
    try {
      let results = await sqs
        .receiveMessage({ QueueUrl: queueUrl, MaxNumberOfMessages: 10 })
        .promise();
      callback(results.Messages);
    } catch (ex) {
      // this needs to be here incase we have an issue with the AWS-SDK
      // which occassionally happens. we want this loop to continue.
      winston.error(ex);
    }
  }
}

/**
 * [deleteMessage description]
 * @param  {string}        queueUrl      [description]
 * @param  {string}        receiptHandle [description]
 * @return {Promise<void>}               [description]
 */
export async function deleteMessage(queueUrl: string, receiptHandle: string): Promise<void> {
  await sqs
    .deleteMessage({
      QueueUrl: queueUrl,
      ReceiptHandle: receiptHandle,
    })
    .promise();
}

////////////////////

/**
 * Publishes a number of messages to the SQS queue
 * @param queueUrl
 * @param entries
 */
export async function sendMessageBatch(queueUrl: string, entries: SendMessageBatchRequestEntry[]) {
  entries = entries.slice();
  let chain = Promise.resolve();
  while (entries.length) {
    let id = 0;
    let chunk = entries.splice(0, 10);

    chain.then(() => {
      return sqs
        .sendMessageBatch({
          QueueUrl: queueUrl,
          Entries: chunk,
        })
        .promise();
    });
  }
  return chain;
}