core: generate magnet link from infohash and vice versa. resolves #8590 (#10087)

* global list of public trackers
* infohash => magnet link (only in public trackers)
* magnet link => infohash

src/Jackett.Common/Indexers/BaseIndexer.cs

@@ -296,6 +296,14 @@ namespace Jackett.Common.Indexers
                 if (r.PublishDate > DateTime.Now)
                     r.PublishDate = DateTime.Now;
 
+                // generate magnet link from info hash (not allowed for private sites)
+                if (r.MagnetUri == null && !string.IsNullOrWhiteSpace(r.InfoHash) && Type != "private")
+                    r.MagnetUri = MagnetUtil.InfoHashToPublicMagnet(r.InfoHash, r.Title);
+
+                // generate info hash from magnet link
+                if (r.MagnetUri != null && string.IsNullOrWhiteSpace(r.InfoHash))
+                    r.InfoHash = MagnetUtil.MagnetToInfoHash(r.MagnetUri);
+
                 return r;
             });
             return fixedResults;

src/Jackett.Common/Utils/MagnetUtil.cs

@@ -0,0 +1,48 @@
+using System;
+using System.Collections.Specialized;
+using System.Linq;
+using System.Text;
+using Jackett.Common.Helpers;
+
+namespace Jackett.Common.Utils
+{
+    public static class MagnetUtil
+    {
+        // Update best trackers from https://github.com/ngosang/trackerslist
+        private static readonly NameValueCollection _Trackers = new NameValueCollection
+        {
+            {"tr", "udp://tracker.opentrackr.org:1337/announce"},
+            {"tr", "udp://tracker.coppersurfer.tk:6969/announce"},
+            {"tr", "udp://9.rarbg.to:2710/announce"},
+            {"tr", "udp://tracker.internetwarriors.net:1337/announce"},
+            {"tr", "udp://tracker.cyberia.is:6969/announce"},
+            {"tr", "udp://exodus.desync.com:6969/announce"},
+            {"tr", "udp://explodie.org:6969/announce"},
+            {"tr", "http://tracker1.itzmx.com:8080/announce"},
+            {"tr", "udp://tracker.tiny-vps.com:6969/announce"},
+            {"tr", "udp://open.stealth.si:80/announce"}
+        };
+
+        private static readonly string _TrackersEncoded = _Trackers.GetQueryString();
+
+        public static Uri InfoHashToPublicMagnet(string infoHash, string title)
+        {
+            if (string.IsNullOrWhiteSpace(infoHash) || string.IsNullOrWhiteSpace(title))
+                return null;
+            return new Uri($"magnet:?xt=urn:btih:{infoHash}&dn={WebUtilityHelpers.UrlEncode(title, Encoding.UTF8)}&{_TrackersEncoded}");
+        }
+
+        public static string MagnetToInfoHash(Uri magnet)
+        {
+            try
+            {
+                var xt = ParseUtil.GetArgumentFromQueryString(magnet.ToString(), "xt");
+                return xt.Split(':').Last(); // remove prefix urn:btih:
+            }
+            catch (Exception)
+            {
+                return null;
+            }
+        }
+    }
+}

src/Jackett.Test/Common/Indexers/BaseWebIndexerTests.cs

@@ -124,7 +124,7 @@ namespace Jackett.Test.Common.Indexers
         }
 
         [Test]
-        public void TestFixResults()
+        public void TestFixResultsOriginPublishDate()
         {
             var indexer = new TestWebIndexer();
             var query = new TorznabQuery();
@@ -144,6 +144,44 @@ namespace Jackett.Test.Common.Indexers
             Assert.AreEqual(DateTime.Now.Year, fixedResults.First().PublishDate.Year);
         }
 
+        [Test]
+        public void TestFixResultsMagnet()
+        {
+            var indexer = new TestWebIndexer();
+            var query = new TorznabQuery();
+
+            // get info_hash from magnet
+            var results = new List<ReleaseInfo>
+            {
+                new ReleaseInfo
+                {
+                    MagnetUri = new Uri("magnet:?xt=urn:btih:3333333333333333333333333333333333333333&dn=Title&tr=udp%3A%2F%2Ftracker.com%3A6969")
+                }
+            };
+            Assert.AreEqual(null, results.First().InfoHash);
+            var fixedResults = indexer._FixResults(query, results).ToList();
+            Assert.AreEqual("3333333333333333333333333333333333333333", fixedResults.First().InfoHash);
+
+            // build magnet from info_hash (private site), not allowed
+            results = new List<ReleaseInfo>
+            {
+                new ReleaseInfo
+                {
+                    Title = "Tracker Title",
+                    InfoHash = "3333333333333333333333333333333333333333"
+                }
+            };
+            Assert.AreEqual(null, results.First().MagnetUri);
+            fixedResults = indexer._FixResults(query, results).ToList();
+            Assert.AreEqual(null, fixedResults.First().MagnetUri);
+
+            // build magnet from info_hash (public, semi-private sites)
+            indexer.SetType("public");
+            Assert.AreEqual(null, results.First().MagnetUri);
+            fixedResults = indexer._FixResults(query, results).ToList();
+            Assert.True(fixedResults.First().MagnetUri.ToString().Contains("3333333333333333333333333333333333333333"));
+        }
+
         [Test]
         public void TestAddCategoryMapping()
         {

src/Jackett.Test/Common/Utils/MagnetUtilTests.cs

@@ -0,0 +1,45 @@
+using System;
+using Jackett.Common.Utils;
+using NUnit.Framework;
+using Assert = NUnit.Framework.Assert;
+
+namespace Jackett.Test.Common.Utils
+{
+    [TestFixture]
+    public class MagnetUtilTests
+    {
+        [Test]
+        public void TestInfoHashToPublicMagnet()
+        {
+            const string infoHash = "3333333333333333333333333333333333333333";
+            const string title = "Torrent Title 😀"; // with unicode characters
+
+            // TODO: I'm not sure if unicode characters must be encoded
+            // good magnet
+            var magnet = MagnetUtil.InfoHashToPublicMagnet(infoHash, title);
+            Assert.True(magnet.ToString().StartsWith("magnet:?xt=urn:btih:3333333333333333333333333333333333333333&dn=Torrent+Title+😀&tr="));
+
+            // bad magnet (no info hash)
+            magnet = MagnetUtil.InfoHashToPublicMagnet("", title);
+            Assert.AreEqual(null, magnet);
+
+            // bad magnet (no title)
+            magnet = MagnetUtil.InfoHashToPublicMagnet(infoHash, "");
+            Assert.AreEqual(null, magnet);
+        }
+
+        [Test]
+        public void TestMagnetToInfoHash()
+        {
+            // good magnet
+            var magnet = new Uri("magnet:?xt=urn:btih:3333333333333333333333333333333333333333&dn=Torrent+Title+😀&tr=udp%3A%2F%2Ftracker.com%3A6969%2Fannounce");
+            var infoHash = MagnetUtil.MagnetToInfoHash(magnet);
+            Assert.AreEqual("3333333333333333333333333333333333333333", infoHash);
+
+            // bad magnet
+            magnet = new Uri("magnet:?tr=udp%3A%2F%2Ftracker.com%3A6969%2Fannounce");
+            infoHash = MagnetUtil.MagnetToInfoHash(magnet);
+            Assert.AreEqual(null, infoHash);
+        }
+    }
+}

src/Jackett.Test/TestHelpers/TestWebIndexer.cs

@@ -44,6 +44,7 @@ namespace Jackett.Test.TestHelpers
 
         ////////////////////////////////////////////////////////////////////////////////////////////////////////////////
         // public methods to test private methods
+        public void SetType(string type) => Type = type;
 
         public IEnumerable<ReleaseInfo> _FilterResults(TorznabQuery query, IEnumerable<ReleaseInfo> results) =>
             FilterResults(query, results);