TinyTwitter.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net;
using System.Security.Cryptography;
using System.Text;
using System.Text.RegularExpressions;

namespace TinyTwitter
{
    public class OAuthInfo
    {
        public string ConsumerKey { get; set; }
        public string ConsumerSecret { get; set; }
        public string AccessToken { get; set; }
        public string AccessSecret { get; set; }
    }

    public class TinyTwitter
    {
        private readonly OAuthInfo oauth;

        public TinyTwitter(OAuthInfo oauth)
        {
            this.oauth = oauth;
        }

        public void UpdateStatus(string message)
        {
            new RequestBuilder(oauth, "POST", "https://api.twitter.com/1.1/statuses/update.json")
                .AddParameter("status", message)
                .Execute();
        }

        #region RequestBuilder

        private class RequestBuilder
        {
            private const string VERSION = "1.0";
            private const string SIGNATURE_METHOD = "HMAC-SHA1";

            private readonly OAuthInfo oauth;
            private readonly string method;
            private readonly IDictionary<string, string> customParameters;
            private readonly string url;

            public RequestBuilder(OAuthInfo oauth, string method, string url)
            {
                this.oauth = oauth;
                this.method = method;
                this.url = url;
                customParameters = new Dictionary<string, string>();
            }

            public RequestBuilder AddParameter(string name, string value)
            {
                customParameters.Add(name, value.EncodeRFC3986());
                return this;
            }

            public string Execute()
            {
                var timespan = GetTimestamp();
                var nonce = CreateNonce();

                var parameters = new Dictionary<string, string>(customParameters);
                AddOAuthParameters(parameters, timespan, nonce);

                var signature = GenerateSignature(parameters);
                var headerValue = GenerateAuthorizationHeaderValue(parameters, signature);

                var request = (HttpWebRequest)WebRequest.Create(GetRequestUrl());
                request.Method = method;
                request.ContentType = "application/x-www-form-urlencoded";

                request.Headers.Add("Authorization", headerValue);

                WriteRequestBody(request);

                // It looks like a bug in HttpWebRequest. It throws random TimeoutExceptions
                // after some requests. Abort the request seems to work. More info: 
                // http://stackoverflow.com/questions/2252762/getrequeststream-throws-timeout-exception-randomly

                var response = request.GetResponse();

                string content;

                using (var stream = response.GetResponseStream())
                {
                    using var reader = new StreamReader(stream);
                    content = reader.ReadToEnd();
                }

                request.Abort();

                return content;
            }

            private void WriteRequestBody(HttpWebRequest request)
            {
                if (method == "GET")
                    return;

                var requestBody = Encoding.ASCII.GetBytes(GetCustomParametersString());
                using var stream = request.GetRequestStream();
                stream.Write(requestBody, 0, requestBody.Length);
            }

            private string GetRequestUrl()
            {
                if (method != "GET" || customParameters.Count == 0)
                    return url;

                return string.Format("{0}?{1}", url, GetCustomParametersString());
            }

            private string GetCustomParametersString()
            {
                return customParameters.Select(x => string.Format("{0}={1}", x.Key, x.Value)).Join("&");
            }

            private static string GenerateAuthorizationHeaderValue(IEnumerable<KeyValuePair<string, string>> parameters, string signature)
            {
                return new StringBuilder("OAuth ")
                    .Append(parameters.Concat(new KeyValuePair<string, string>("oauth_signature", signature))
                                .Where(x => x.Key.StartsWith("oauth_"))
                                .Select(x => string.Format("{0}=\"{1}\"", x.Key, x.Value.EncodeRFC3986()))
                                .Join(","))
                    .ToString();
            }

            private string GenerateSignature(IEnumerable<KeyValuePair<string, string>> parameters)
            {
                var dataToSign = new StringBuilder()
                    .Append(method).Append("&")
                    .Append(url.EncodeRFC3986()).Append("&")
                    .Append(parameters
                                .OrderBy(x => x.Key)
                                .Select(x => string.Format("{0}={1}", x.Key, x.Value))
                                .Join("&")
                                .EncodeRFC3986());

                var signatureKey = string.Format("{0}&{1}", oauth.ConsumerSecret.EncodeRFC3986(), oauth.AccessSecret.EncodeRFC3986());
                var sha1 = new HMACSHA1(Encoding.ASCII.GetBytes(signatureKey));

                var signatureBytes = sha1.ComputeHash(Encoding.ASCII.GetBytes(dataToSign.ToString()));
                return Convert.ToBase64String(signatureBytes);
            }

            private void AddOAuthParameters(IDictionary<string, string> parameters, string timestamp, string nonce)
            {
                parameters.Add("oauth_version", VERSION);
                parameters.Add("oauth_consumer_key", oauth.ConsumerKey);
                parameters.Add("oauth_nonce", nonce);
                parameters.Add("oauth_signature_method", SIGNATURE_METHOD);
                parameters.Add("oauth_timestamp", timestamp);
                parameters.Add("oauth_token", oauth.AccessToken);
            }

            private static string GetTimestamp()
            {
                return ((int)(DateTime.UtcNow - new DateTime(1970, 1, 1)).TotalSeconds).ToString();
            }

            private static string CreateNonce()
            {
                return new Random().Next(0x0000000, 0x7fffffff).ToString("X8");
            }
        }

        #endregion
    }

    public static class TinyTwitterHelperExtensions
    {
        public static string Join<T>(this IEnumerable<T> items, string separator)
        {
            return string.Join(separator, items.ToArray());
        }

        public static IEnumerable<T> Concat<T>(this IEnumerable<T> items, T value)
        {
            return items.Concat(new[] { value });
        }

        public static string EncodeRFC3986(this string value)
        {
            // From Twitterizer http://www.twitterizer.net/

            if (string.IsNullOrEmpty(value))
                return string.Empty;

            var encoded = Uri.EscapeDataString(value);

            return Regex
                .Replace(encoded, "(%[0-9a-f][0-9a-f])", c => c.Value.ToUpper())
                .Replace("(", "%28")
                .Replace(")", "%29")
                .Replace("$", "%24")
                .Replace("!", "%21")
                .Replace("*", "%2A")
                .Replace("'", "%27")
                .Replace("%7E", "~");
        }
    }
}