Creating Amazon SQS queues

NuGet packages:

Programming elements:

using System;
using System.Threading.Tasks;
using System.Collections.Generic;
using Amazon.SQS;
using Amazon.SQS.Model;

namespace SQSCreateQueue
{
  // = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
  // Class to create a queue
  class Program
  {
    private const string MaxReceiveCount = "10";
    private const string ReceiveMessageWaitTime = "2";
    private const int MaxArgs = 3;

    static async Task Main(string[] args)
    {
      // Parse the command line and show help if necessary
      var parsedArgs = CommandLine.Parse(args);
      if(parsedArgs.Count > MaxArgs)
        CommandLine.ErrorExit(
          "\nToo many command-line arguments.\nRun the command with no arguments to see help.");

      // Create the Amazon SQS client
      var sqsClient = new AmazonSQSClient();

      // In the case of no command-line arguments, just show help and the existing queues
      if(parsedArgs.Count == 0)
      {
        PrintHelp();
        Console.WriteLine("\nNo arguments specified.");
        Console.Write("Do you want to see a list of the existing queues? ((y) or n): ");
        string response = Console.ReadLine();
        if((string.IsNullOrEmpty(response)) || (response.ToLower() == "y"))
          await ShowQueues(sqsClient);
        return;
      }

      // Get the application arguments from the parsed list
      string queueName =
        CommandLine.GetArgument(parsedArgs, null, "-q", "--queue-name");
      string deadLetterQueueUrl =
        CommandLine.GetArgument(parsedArgs, null, "-d", "--dead-letter-queue");
      string maxReceiveCount =
        CommandLine.GetArgument(parsedArgs, MaxReceiveCount, "-m", "--max-receive-count");
      string receiveWaitTime =
        CommandLine.GetArgument(parsedArgs, ReceiveMessageWaitTime, "-w", "--wait-time");

      if(string.IsNullOrEmpty(queueName))
        CommandLine.ErrorExit(
          "\nYou must supply a queue name.\nRun the command with no arguments to see help.");

      // If a dead-letter queue wasn't given, create one
      if(string.IsNullOrEmpty(deadLetterQueueUrl))
      {
        Console.WriteLine("\nNo dead-letter queue was specified. Creating one...");
        deadLetterQueueUrl = await CreateQueue(sqsClient, queueName + "__dlq");
        Console.WriteLine($"Your new dead-letter queue:");
        await ShowAllAttributes(sqsClient, deadLetterQueueUrl);
      }

      // Create the message queue
      string messageQueueUrl = await CreateQueue(
        sqsClient, queueName, deadLetterQueueUrl, maxReceiveCount, receiveWaitTime);
      Console.WriteLine($"Your new message queue:");
      await ShowAllAttributes(sqsClient, messageQueueUrl);
    }


    //
    // Method to show a list of the existing queues
    private static async Task ShowQueues(IAmazonSQS sqsClient)
    {
      ListQueuesResponse responseList = await sqsClient.ListQueuesAsync("");
      Console.WriteLine();
      foreach(string qUrl in responseList.QueueUrls)
      {
        // Get and show all attributes. Could also get a subset.
        await ShowAllAttributes(sqsClient, qUrl);
      }
    }


    //
    // Method to create a queue. Returns the queue URL.
    private static async Task<string> CreateQueue(
      IAmazonSQS sqsClient, string qName, string deadLetterQueueUrl=null,
      string maxReceiveCount=null, string receiveWaitTime=null)
    {
      var attrs = new Dictionary<string, string>();

      // If a dead-letter queue is given, create a message queue
      if(!string.IsNullOrEmpty(deadLetterQueueUrl))
      {
        attrs.Add(QueueAttributeName.ReceiveMessageWaitTimeSeconds, receiveWaitTime);
        attrs.Add(QueueAttributeName.RedrivePolicy,
          $"{{\"deadLetterTargetArn\":\"{await GetQueueArn(sqsClient, deadLetterQueueUrl)}\"," +
          $"\"maxReceiveCount\":\"{maxReceiveCount}\"}}");
        // Add other attributes for the message queue such as VisibilityTimeout
      }

      // If no dead-letter queue is given, create one of those instead
      //else
      //{
      //  // Add attributes for the dead-letter queue as needed
      //  attrs.Add();
      //}

      // Create the queue
      CreateQueueResponse responseCreate = await sqsClient.CreateQueueAsync(
          new CreateQueueRequest{QueueName = qName, Attributes = attrs});
      return responseCreate.QueueUrl;
    }


    //
    // Method to get the ARN of a queue
    private static async Task<string> GetQueueArn(IAmazonSQS sqsClient, string qUrl)
    {
      GetQueueAttributesResponse responseGetAtt = await sqsClient.GetQueueAttributesAsync(
        qUrl, new List<string>{QueueAttributeName.QueueArn});
      return responseGetAtt.QueueARN;
    }


    //
    // Method to show all attributes of a queue
    private static async Task ShowAllAttributes(IAmazonSQS sqsClient, string qUrl)
    {
      var attributes = new List<string>{ QueueAttributeName.All };
      GetQueueAttributesResponse responseGetAtt =
        await sqsClient.GetQueueAttributesAsync(qUrl, attributes);
      Console.WriteLine($"Queue: {qUrl}");
      foreach(var att in responseGetAtt.Attributes)
        Console.WriteLine($"\t{att.Key}: {att.Value}");
    }


    //
    // Command-line help
    private static void PrintHelp()
    {
      Console.WriteLine(
      "\nUsage: SQSCreateQueue -q <queue-name> [-d <dead-letter-queue>]" +
        " [-m <max-receive-count>] [-w <wait-time>]" +
      "\n  -q, --queue-name: The name of the queue you want to create." +
      "\n  -d, --dead-letter-queue: The URL of an existing queue to be used as the dead-letter queue."+
      "\n      If this argument isn't supplied, a new dead-letter queue will be created." +
      "\n  -m, --max-receive-count: The value for maxReceiveCount in the RedrivePolicy of the queue." +
      $"\n      Default is {MaxReceiveCount}." +
      "\n  -w, --wait-time: The value for ReceiveMessageWaitTimeSeconds of the queue for long polling." +
      $"\n      Default is {ReceiveMessageWaitTime}.");
    }
  }


  // = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
  // Class that represents a command line on the console or terminal.
  // (This is the same for all examples. When you have seen it once, you can ignore it.)
  static class CommandLine
  {
    //
    // Method to parse a command line of the form: "--key value" or "-k value".
    //
    // Parameters:
    // - args: The command-line arguments passed into the application by the system.
    //
    // Returns:
    // A Dictionary with string Keys and Values.
    //
    // If a key is found without a matching value, Dictionary.Value is set to the key
    //  (including the dashes).
    // If a value is found without a matching key, Dictionary.Key is set to "--NoKeyN",
    //  where "N" represents sequential numbers.
    public static Dictionary<string,string> Parse(string[] args)
    {
      var parsedArgs = new Dictionary<string,string>();
      int i = 0, n = 0;
      while(i < args.Length)
      {
        // If the first argument in this iteration starts with a dash it's an option.
        if(args[i].StartsWith("-"))
        {
          var key = args[i++];
          var value = key;

          // Check to see if there's a value that goes with this option?
          if((i < args.Length) && (!args[i].StartsWith("-"))) value = args[i++];
          parsedArgs.Add(key, value);
        }

        // If the first argument in this iteration doesn't start with a dash, it's a value
        else
        {
          parsedArgs.Add("--NoKey" + n.ToString(), args[i++]);
          n++;
        }
      }

      return parsedArgs;
    }

    //
    // Method to get an argument from the parsed command-line arguments
    //
    // Parameters:
    // - parsedArgs: The Dictionary object returned from the Parse() method (shown above).
    // - defaultValue: The default string to return if the specified key isn't in parsedArgs.
    // - keys: An array of keys to look for in parsedArgs.
    public static string GetArgument(
      Dictionary<string,string> parsedArgs, string defaultReturn, params string[] keys)
    {
      string retval = null;
      foreach(var key in keys)
        if(parsedArgs.TryGetValue(key, out retval)) break;
      return retval ?? defaultReturn;
    }

    //
    // Method to exit the application with an error.
    public static void ErrorExit(string msg, int code=1)
    {
      Console.WriteLine("\nError");
      Console.WriteLine(msg);
      Environment.Exit(code);
    }
  }

}