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Slack Slash Command with AWS Lambda + API Gateway Integration
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Amazon.Lambda.Core;
using Amazon.Lambda.Serialization;
using Newtonsoft.Json;
// Assembly attribute to enable the Lambda function's JSON input to be converted into a .NET class.
[assembly: LambdaSerializerAttribute(typeof(Amazon.Lambda.Serialization.Json.JsonSerializer))]
namespace SlackSlashCommandWebhook
{
public class Function
{
private static readonly string slackTokenEnvironmentKey = "SlackToken";
/// <summary>
/// A simple function that takes a string and does a ToUpper
/// </summary>
/// <param name="input"></param>
/// <param name="context"></param>
/// <returns></returns>
public async Task<Result> FunctionHandlerAsync(SlackSlashCommand input, ILambdaContext context)
{
// Parse to result
var split = input.Body.Split('&');
if (split.Length != 10) throw new ArgumentOutOfRangeException(nameof(split));
var result = new ParseResult(split);
// Authentication Validation
ValidateToken(result.Token);
// For Test purpose. You can check what was request strings.
//return new Result("in_channel", input.Body);
// Only you can see response when you change in_channel -> ephemeral.
return new Result("in_channel", "Hello from Lambda .NET Core.");
}
private void ValidateToken(string token)
{
// Get Valid Token from AWS Lambda Environment Variable
var validToken = Environment.GetEnvironmentVariable(slackTokenEnvironmentKey);
if (string.IsNullOrWhiteSpace(validToken)) throw new NullReferenceException(slackTokenEnvironmentKey);
// Validate
if (token == Environment.GetEnvironmentVariable("SlackToken")) return;
throw new UnauthorizedAccessException();
}
}
/// <summary>
/// Slack SlashCommand Recieve Type
/// </summary>
public class SlackSlashCommand
{
[JsonProperty("body")]
public string Body { get; set; }
}
/// <summary>
/// Slack Slash Command Response Type
/// </summary>
public class Result
{
[JsonProperty("response_type")]
public string ResponseType { get; set; }
[JsonProperty("text")]
public string Text { get; set; }
public Result(string response, string text)
{
ResponseType = response;
Text = text;
}
}
/// <summary>
/// Slack Slash Command Parse Class
/// </summary>
public class ParseResult
{
public string Token { get; set; }
public string TeamId { get; set; }
public string TeamDomain { get; set; }
public string ChannelId { get; set; }
public string ChannelName { get; set; }
public string UserId { get; set; }
public string UserName { get; set; }
public string Command { get; set; }
public string Text { get; set; }
public string ResponseUrl { get; set; }
public ParseResult(string[] splitArray)
{
Token = Parse(splitArray[0]);
TeamId = Parse(splitArray[1]);
TeamDomain = Parse(splitArray[2]);
ChannelId = Parse(splitArray[3]);
ChannelName = Parse(splitArray[4]);
UserId = Parse(splitArray[5]);
UserName = Parse(splitArray[6]);
Command = Parse(splitArray[7]);
Text = Parse(splitArray[8]);
ResponseUrl = Parse(splitArray[9]);
}
private string Parse(string txt)
{
return txt.Split('=').Last();
}
}
}
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