IF.Lastfm/IF.Lastfm.Core/LastFm.cs

using System.Collections.Generic;
using System.Linq;
using System.Net.Http;
using System.Text;
using IF.Lastfm.Core.Api;
using IF.Lastfm.Core.Api.Enums;
using IF.Lastfm.Core.Api.Helpers;
using Newtonsoft.Json;
using Newtonsoft.Json.Linq;

namespace IF.Lastfm.Core
{
    public class LastFm : ILastFm
    {
        #region Constants

        public const string ApiRoot = "http://ws.audioscrobbler.com/2.0/";
        private const string ApiRootFormat = "{0}://ws.audioscrobbler.com/2.0/?method={1}&api_key={2}{3}";

        private const string ResponseFormat = "json";

        public const string DefaultLanguageCode = "en";
        public const int DefaultPageLength = 20;
        
        #endregion

        #region Api objects

        public IAuth Auth { get; set; }

        #endregion

        #region Api helper methods

        public static string FormatApiUrl(string method, string apikey, Dictionary<string, string> parameters = null, bool secure = false)
        {
            if (parameters == null)
            {
                parameters = new Dictionary<string, string>();
            }

            parameters.Add("format", ResponseFormat);

            var querystring = LastFm.FormatQueryParameters(parameters.OrderBy(kv => kv.Key));

            var protocol = secure
                               ? "https"
                               : "http";

            return string.Format(ApiRootFormat, protocol, method, apikey, querystring);
        }

        public static FormUrlEncodedContent CreatePostBody(string method, string apikey, string apisig,
                                                          IEnumerable<KeyValuePair<string, string>> parameters)
        {
            var init = new Dictionary<string, string>
                           {
                               {"method", method},
                               {"api_key", apikey},
                               {"api_sig", apisig},
                               {"format", ResponseFormat}
                           };

            // TODO ordering
            var requestParameters = init.Concat(parameters);

            return new FormUrlEncodedContent(requestParameters);
        }


        public static string FormatQueryParameters(IEnumerable<KeyValuePair<string, string>> parameters)
        {
            const string parameterFormat = "&{0}={1}";

            var builder = new StringBuilder();

            foreach (var pair in parameters)
            {
                builder.Append(string.Format(parameterFormat, pair.Key, pair.Value));
            }

            return builder.ToString();
        }

        public static bool IsResponseValid(string json, out LastFmApiError error)
        {
            // hmmm
            if (!json.Contains("error"))
            {
                error = LastFmApiError.None;
                return true;
            }

            error = LastFmApiError.Unknown;
            JObject jo;
            try
            {
                jo = JsonConvert.DeserializeObject<JObject>(json);
            }
            catch (JsonException)
            {
                return false;
            }

            var code = jo.Value<int>("error");

            switch (code)
            {
                case 2:
                    error = LastFmApiError.ServiceServiceWhereArtThou;
                    break;
                case 3:
                    error = LastFmApiError.BadMethod;
                    break;
                case 4:
                    error = LastFmApiError.BadAuth;
                    break;
                case 5:
                    error = LastFmApiError.BadFormat;
                    break;
                case 6:
                    error = LastFmApiError.MissingParameters;
                    break;
                case 7:
                    error = LastFmApiError.BadResource;
                    break;
                case 8:
                    error = LastFmApiError.Failure;
                    break;
                case 9:
                    error = LastFmApiError.SessionExpired;
                    break;
                case 10:
                    error = LastFmApiError.BadApiKey;
                    break;
                case 11:
                    error = LastFmApiError.ServiceDown;
                    break;
                case 13:
                    error = LastFmApiError.BadMethodSignature;
                    break;
                case 16:
                    error = LastFmApiError.TemporaryFailure;
                    break;
                case 26:
                    error = LastFmApiError.KeySuspended;
                    break;
                case 29:
                    error = LastFmApiError.RateLimited;
                    break;
            }

            return false;
        }

        #endregion
    }
}