make fraction of popular maps configurable in dynamic configs

ZkData/Ef/DynamicConfig.cs

@@ -1,3 +1,4 @@
+using System.ComponentModel;
 using System.ComponentModel.DataAnnotations;
 using System.ComponentModel.DataAnnotations.Schema;
 using System.Data.Entity;
@@ -35,6 +36,10 @@ public class DynamicConfig
 
         public int MaximumStatLimitedBattlePlayers { get; set; } // if a battle has more than this number of players, maxelo/minelo, maxrank/minrank and maxleve/minlevel are disabled
 
+        [Description("Map vote always tries to include some of the most popular maps (precentile <0.2), this value controls how big fraction of offers is most popular maps.")]
+        public double MapVoteFractionOfPopularMaps { get; set; } = 0.5;
+
+
         public static DynamicConfig Instance;
 
         static DynamicConfig()

ZkData/Migrations/202404060935038_AddPopularMapsFraction.cs

@@ -0,0 +1,18 @@
+namespace ZkData.Migrations
+{
+    using System;
+    using System.Data.Entity.Migrations;
+
+    public partial class AddPopularMapsFraction : DbMigration
+    {
+        public override void Up()
+        {
+            AddColumn("dbo.DynamicConfigs", "MapVoteFractionOfPopularMaps", c => c.Double(nullable: false, defaultValue: 0.5));
+        }
+
+        public override void Down()
+        {
+            DropColumn("dbo.DynamicConfigs", "MapVoteFractionOfPopularMaps");
+        }
+    }
+}

ZkData/ZkData.csproj

@@ -491,6 +491,10 @@
     <Compile Include="Migrations\202303191424586_RemoveGlacierId.Designer.cs">
       <DependentUpon>202303191424586_RemoveGlacierId.cs</DependentUpon>
     </Compile>
+    <Compile Include="Migrations\202404060935038_AddPopularMapsFraction.cs" />
+    <Compile Include="Migrations\202404060935038_AddPopularMapsFraction.Designer.cs">
+      <DependentUpon>202404060935038_AddPopularMapsFraction.cs</DependentUpon>
+    </Compile>
     <Compile Include="SpringFilesUnitsyncAttempt.cs" />
     <Compile Include="SteamWebApi.cs" />
     <Compile Include="UserLanguageNoteAttribute.cs" />
@@ -939,6 +943,9 @@
     <EmbeddedResource Include="Migrations\202303191424586_RemoveGlacierId.resx">
       <DependentUpon>202303191424586_RemoveGlacierId.cs</DependentUpon>
     </EmbeddedResource>
+    <EmbeddedResource Include="Migrations\202404060935038_AddPopularMapsFraction.resx">
+      <DependentUpon>202404060935038_AddPopularMapsFraction.cs</DependentUpon>
+    </EmbeddedResource>
     <EmbeddedResource Include="ZkDataResources.resx">
       <Generator>ResXFileCodeGenerator</Generator>
       <LastGenOutput>ZkDataResources.Designer.cs</LastGenOutput>

ZkLobbyServer/ServerBattle.cs

@@ -1077,9 +1077,19 @@ private async Task<bool> CreateMultiMapPoll()
             pickedMaps.Add(HostedMap?.ResourceID ?? 0);
             using (var db = new ZkDataContext())
             {
+                var popularMapCount = Math.Round(NumberOfMapChoices * DynamicConfig.Instance.MapVoteFractionOfPopularMaps).Clamp(0, NumberOfMapChoices - 1);
+
                 for (int i = 0; i < NumberOfMapChoices; i++)
                 {
-                    Resource map = MapPicker.GetRecommendedMap(GetContext(), (MinimalMapSupportLevel < MapSupportLevel.Featured) ? MapSupportLevel.Featured : MinimalMapSupportLevel, db.Resources.Where(x => !pickedMaps.Contains(x.ResourceID)));
+                    Resource map = null;
+                    if (i < popularMapCount)
+                    {
+                        map = MapPicker.GetRecommendedMap(GetContext(), (MinimalMapSupportLevel < MapSupportLevel.Supported) ? MapSupportLevel.Supported : MinimalMapSupportLevel, MapRatings.GetMapRanking(Mode).TakeWhile(x => x.Percentile < 0.2).Select(x => x.Map).Where(x => !pickedMaps.Contains(x.ResourceID)).AsQueryable()); //choose the popular maps
+                    }
+                    if (map == null)
+                    {
+                        map = MapPicker.GetRecommendedMap(GetContext(), (MinimalMapSupportLevel < MapSupportLevel.Featured) ? MapSupportLevel.Supported : MinimalMapSupportLevel, db.Resources.Where(x => !pickedMaps.Contains(x.ResourceID)));
+                    }
                     pickedMaps.Add(map.ResourceID);
                     options.Add(new PollOption()
                     {