WIP: Add configuration weights for tracks

Range is [0..100] but it's relative to total/sum. The algorithm guards
against "all set to zero" scenario.

MuzikaGromche/Plugin.cs

@@ -4,6 +4,7 @@ using System.Collections.Generic;
 using System.Linq;
 using System.Security.Cryptography;
 using BepInEx;
+using BepInEx.Configuration;
 using HarmonyLib;
 using UnityEngine;
 using UnityEngine.Networking;
@@ -60,23 +61,15 @@ namespace MuzikaGromche
         public static Track ChooseTrack()
         {
             var seed = RoundManager.Instance.dungeonGenerator.Generator.ChosenSeed;
-            var sha = SHA256.Create();
+            int[] weights = [.. Tracks.Select(track => track.Weight.Value)];
-            var hash = sha.ComputeHash(BitConverter.GetBytes(seed));
+            var rwi = new RandomWeightedIndex(weights);
-            var trackId = 0;
+            var trackId = rwi.GetRandomWeightedIndex(seed);
-            foreach (var t in hash)
-            {
-                // modulus division on byte array
-                trackId *= 256 % Tracks.Length;
-                trackId %= Tracks.Length;
-                trackId += t % Tracks.Length;
-                trackId %= Tracks.Length;
-            }
 #if DEBUG
             // Override for testing
             trackId = IndexOfTrack("DeployDestroy");
 #endif
             var track = Tracks[trackId];
-            Debug.Log($"Seed is {seed}, chosen track is \"{track.Name}\", {trackId} out of {Tracks.Length} tracks");
+            Debug.Log($"Seed is {seed}, chosen track is \"{track.Name}\", #{trackId} of {rwi}");
             return Tracks[trackId];
         }
 
@@ -158,6 +151,13 @@ namespace MuzikaGromche
                     track.LoadedStart = DownloadHandlerAudioClip.GetContent(requests[i * 2]);
                     track.LoadedLoop = DownloadHandlerAudioClip.GetContent(requests[i * 2 + 1]);
                 }
+                // Initialize config
+                var chanceRange = new AcceptableValueRange<int>(0, 100);
+                foreach (var track in Tracks)
+                {
+                    string description = $"Random (relative) chance of selecting track {track.Name}. Set to zero to effectively disable the track.";
+                    track.Weight = Config.Bind("Tracks", track.Name, 50, new ConfigDescription(description, chanceRange));
+                }
                 new Harmony(PluginInfo.PLUGIN_NAME).PatchAll(typeof(JesterPatch));
             }
             else
@@ -186,6 +186,9 @@ namespace MuzikaGromche
         public AudioClip LoadedStart;
         public AudioClip LoadedLoop;
 
+        // How often this track should be chosen, relative to the sum of weights of all tracks.
+        public ConfigEntry<int> Weight;
+
         public string FileNameStart => $"{Name}Start.{Ext}";
         public string FileNameLoop => $"{Name}Loop.{Ext}";
         private string Ext => AudioType switch
@@ -197,6 +200,93 @@ namespace MuzikaGromche
         };
     }
 
+    public readonly struct RandomWeightedIndex
+    {
+        public RandomWeightedIndex(int[] weights)
+        {
+            Weights = weights;
+            TotalWeights = Weights.Sum();
+            if (TotalWeights == 0)
+            {
+                // If everything is set to zero, everything is equally possible
+                Weights = [.. Weights.Select(_ => 1)];
+                TotalWeights = Weights.Length;
+            }
+        }
+
+        private byte[] GetHash(int seed)
+        {
+            var buffer = new byte[4 * (1 + Weights.Length)];
+            var offset = 0;
+            System.Buffer.BlockCopy(BitConverter.GetBytes(seed), 0, buffer, offset, sizeof(int));
+            // Make sure that tweaking weights even a little drastically changes the outcome
+            foreach (var weight in Weights)
+            {
+                offset += 4;
+                System.Buffer.BlockCopy(BitConverter.GetBytes(weight), 0, buffer, offset, sizeof(int));
+            }
+            var sha = SHA256.Create();
+            var hash = sha.ComputeHash(buffer);
+            return hash;
+        }
+
+        private int GetRawIndex(byte[] hash)
+        {
+            if (TotalWeights == 0)
+            {
+                // Should not happen, but what if Weights array is empty?
+                return -1;
+            }
+
+            var index = 0;
+            foreach (var t in hash)
+            {
+                // modulus division on byte array
+                index *= 256 % TotalWeights;
+                index %= TotalWeights;
+                index += t % TotalWeights;
+                index %= TotalWeights;
+            }
+            return index;
+        }
+
+        private int GetRawIndex(int rawIndex)
+        {
+            if (rawIndex < 0 || rawIndex >= TotalWeights)
+            {
+                return -1;
+            }
+
+            int sum = 0;
+            foreach (var (weight, index) in Weights.Select((x, i) => (x, i)))
+            {
+                sum += weight;
+                if (rawIndex < sum)
+                {
+                    // Found
+                    return index;
+                }
+            }
+
+            return -1;
+        }
+
+        public int GetRandomWeightedIndex(int seed)
+        {
+            var hash = GetHash(seed);
+            var index = GetRawIndex(hash);
+            return GetRawIndex(index);
+        }
+
+        public override string ToString()
+        {
+            return $"Weighted(Total={TotalWeights}, Weights=[{string.Join(',', Weights)}])";
+        }
+
+        readonly private int[] Weights;
+        readonly public int TotalWeights { get; }
+    }
+
     [HarmonyPatch(typeof(JesterAI))]
     internal class JesterPatch
     {