HttpTransformer.cs

using System;
using System.Collections.Generic;
using CKAN.NetKAN.Model;
using log4net;

namespace CKAN.NetKAN.Transformers
{
    /// <summary>
    /// An <see cref="ITransformer"/> that looks up data from an arbitrary HTTP endpoint.
    /// </summary>
    internal sealed class HttpTransformer : ITransformer
    {
        private static readonly ILog Log = LogManager.GetLogger(typeof(HttpTransformer));

        public string Name { get { return "http"; } }

        public IEnumerable<Metadata> Transform(Metadata metadata, TransformOptions opts)
        {
            if (metadata.Kref != null && metadata.Kref.Source == "http")
            {
                var json = metadata.Json();

                Log.InfoFormat("Executing HTTP transformation with {0}", metadata.Kref);
                Log.DebugFormat("Input metadata:{0}{1}", Environment.NewLine, json);

                if (Uri.IsWellFormedUriString(metadata.Kref.Id, UriKind.Absolute))
                {
                    var resolvedUri = Net.ResolveRedirect(new Uri(metadata.Kref.Id));

                    Log.InfoFormat("URL {0} resolved to {1}", metadata.Kref.Id, resolvedUri);

                    if (resolvedUri != null)
                    {
                        json["download"] = resolvedUri;

                        Log.DebugFormat("Transformed metadata:{0}{1}", Environment.NewLine, json);

                        yield return new Metadata(json);
                    }
                    else
                    {
                        throw new Kraken("Could not resolve HTTP $kref URL, exceeded number of redirects.");
                    }
                }
                else
                {
                    throw new Kraken("Invalid URL in HTTP $kref: " + metadata.Kref.Id);
                }
            }
            else
            {
                yield return metadata;
            }
        }
    }
}