From 2a94a9f1033fc3e5fee1746c10dcaad566f268f3 Mon Sep 17 00:00:00 2001
From: ConfusedPolarBear <33811686+ConfusedPolarBear@users.noreply.github.com>
Date: Tue, 10 May 2022 02:10:39 -0500
Subject: [PATCH] Update comments and add CountBits unit test

---
 .../TestAudioFingerprinting.cs                | 12 +++++++
 .../Entrypoint.cs                             |  2 +-
 .../ScheduledTasks/FingerprinterTask.cs       | 34 +++++++++++--------
 3 files changed, 33 insertions(+), 15 deletions(-)

diff --git a/ConfusedPolarBear.Plugin.IntroSkipper.Tests/TestAudioFingerprinting.cs b/ConfusedPolarBear.Plugin.IntroSkipper.Tests/TestAudioFingerprinting.cs
index a51542a..63bca3e 100644
--- a/ConfusedPolarBear.Plugin.IntroSkipper.Tests/TestAudioFingerprinting.cs
+++ b/ConfusedPolarBear.Plugin.IntroSkipper.Tests/TestAudioFingerprinting.cs
@@ -11,6 +11,18 @@ public class TestFPCalc
         Assert.True(FPCalc.CheckFPCalcInstalled());
     }
 
+    [Theory]
+    [InlineData(0, 0)]
+    [InlineData(1, 1)]
+    [InlineData(5, 213)]
+    [InlineData(10, 56_021)]
+    [InlineData(16, 16_112_341)]
+    [InlineData(19, 2_465_585_877)]
+    public void TestBitCounting(int expectedBits, uint number)
+    {
+        Assert.Equal(expectedBits, FingerprinterTask.CountBits(number));
+    }
+
     [Fact]
     public void TestFingerprinting()
     {
diff --git a/ConfusedPolarBear.Plugin.IntroSkipper/Entrypoint.cs b/ConfusedPolarBear.Plugin.IntroSkipper/Entrypoint.cs
index 8399b58..bf8c2de 100644
--- a/ConfusedPolarBear.Plugin.IntroSkipper/Entrypoint.cs
+++ b/ConfusedPolarBear.Plugin.IntroSkipper/Entrypoint.cs
@@ -82,7 +82,7 @@ public class Entrypoint : IServerEntryPoint
 
     private void QueueLibraryContents(string rawId)
     {
-        // FIXME: do smarterer
+        // FIXME: don't do this
 
         var query = new UserViewQuery()
         {
diff --git a/ConfusedPolarBear.Plugin.IntroSkipper/ScheduledTasks/FingerprinterTask.cs b/ConfusedPolarBear.Plugin.IntroSkipper/ScheduledTasks/FingerprinterTask.cs
index 9fde572..e49d5a7 100644
--- a/ConfusedPolarBear.Plugin.IntroSkipper/ScheduledTasks/FingerprinterTask.cs
+++ b/ConfusedPolarBear.Plugin.IntroSkipper/ScheduledTasks/FingerprinterTask.cs
@@ -9,7 +9,7 @@ using Microsoft.Extensions.Logging;
 namespace ConfusedPolarBear.Plugin.IntroSkipper;
 
 /// <summary>
-/// Fingerprint all queued episodes at the set time.
+/// Fingerprint and analyze all queued episodes for common audio sequences.
 /// </summary>
 public class FingerprinterTask : IScheduledTask
 {
@@ -24,12 +24,12 @@ public class FingerprinterTask : IScheduledTask
     private const double MaximumDifferences = 3;
 
     /// <summary>
-    /// Maximum time permitted between timestamps before they are considered non-contiguous.
+    /// Maximum time (in seconds) permitted between timestamps before they are considered non-contiguous.
     /// </summary>
     private const double MaximumDistance = 3.25;
 
     /// <summary>
-    /// Seconds of audio in one number from the fingerprint. Defined by Chromaprint.
+    /// Seconds of audio in one fingerprint point. This value is defined by the Chromaprint library and should not be changed.
     /// </summary>
     private const double SamplesToSeconds = 0.128;
 
@@ -72,7 +72,7 @@ public class FingerprinterTask : IScheduledTask
     /// <summary>
     /// Analyze all episodes in the queue.
     /// </summary>
-    /// <param name="progress">Progress.</param>
+    /// <param name="progress">Task progress.</param>
     /// <param name="cancellationToken">Cancellation token.</param>
     /// <returns>Task.</returns>
     public Task ExecuteAsync(IProgress<double> progress, CancellationToken cancellationToken)
@@ -84,8 +84,11 @@ public class FingerprinterTask : IScheduledTask
         {
             var first = season.Value[0];
 
-            // Don't analyze seasons with <= 1 episode or specials
-            if (season.Value.Count <= 1 || first.SeasonNumber == 0)
+            /* Don't analyze specials or seasons with an insufficient number of episodes.
+             * A season with only 1 episode can't be analyzed as it would compare the episode to itself,
+             * which would result in the entire episode being marked as an introduction, as the audio is identical.
+             */
+            if (season.Value.Count < 2 || first.SeasonNumber == 0)
             {
                 continue;
             }
@@ -222,8 +225,6 @@ public class FingerprinterTask : IScheduledTask
 
             // TODO: if an episode fails but others in the season succeed, reanalyze it against two that succeeded.
 
-            // TODO: is this the optimal way to indicate that an intro couldn't be found?
-            // the goal here is to not waste time every task run reprocessing episodes that we know will fail.
             StoreIntro(lhsEpisode.EpisodeId, 0, 0);
             StoreIntro(rhsEpisode.EpisodeId, 0, 0);
 
@@ -353,13 +354,13 @@ public class FingerprinterTask : IScheduledTask
         // Tweak the end timestamps just a bit to ensure as little content as possible is skipped over.
         if (lContiguous.Duration >= 90)
         {
-            lContiguous.End -= 6;
-            rContiguous.End -= 6;
+            lContiguous.End -= 2 * MaximumDistance;
+            rContiguous.End -= 2 * MaximumDistance;
         }
         else if (lContiguous.Duration >= 35)
         {
-            lContiguous.End -= 3;
-            rContiguous.End -= 3;
+            lContiguous.End -= MaximumDistance;
+            rContiguous.End -= MaximumDistance;
         }
 
         return (lContiguous, rContiguous);
@@ -370,7 +371,7 @@ public class FingerprinterTask : IScheduledTask
         var intro = new Intro()
         {
             EpisodeId = episode,
-            Valid = introEnd > 0,
+            Valid = introEnd > 0,       // don't test introStart here as the intro could legitimately happen at the start.
             IntroStart = introStart,
             IntroEnd = introEnd
         };
@@ -384,7 +385,12 @@ public class FingerprinterTask : IScheduledTask
         Plugin.Instance.Intros[episode] = intro;
     }
 
-    private static int CountBits(uint number)
+    /// <summary>
+    /// Count the number of bits that are set in the provided number.
+    /// </summary>
+    /// <param name="number">Number to count bits in.</param>
+    /// <returns>Number of bits that are equal to 1.</returns>
+    public static int CountBits(uint number)
     {
         var count = 0;