Feat/chain count threshold

src/c#/GeneralUpdate.Bowl/GeneralUpdate.Bowl.csproj

@@ -14,7 +14,7 @@
         <RepositoryType>public</RepositoryType>
         <PackageTags>upgrade,update,crash,recovery,rollback,monitor,backup</PackageTags>
         <PackageReleaseNotes>10.5.0-beta.1: Refactored to instance-based async design with DI support. Removed IPC dependency and macOS platform support.</PackageReleaseNotes>
-        <Version>10.5.0-beta.6</Version>
+        <Version>10.5.0-beta.7</Version>
         <PackageIcon>bowl.jpeg</PackageIcon>
         <TargetFrameworks>netstandard2.0;</TargetFrameworks>
     </PropertyGroup>

src/c#/GeneralUpdate.Core/Configuration/ConfigurationMapper.cs

@@ -103,6 +103,7 @@ public static UpdateContext MapToUpdateContext(UpdateRequest source, UpdateConte
             target.UpgradeClientVersion = source.UpgradeClientVersion;
             target.ProductId = source.ProductId;
             target.CustomHeaders = source.CustomHeaders;
+            target.MaxChainBeforeFallback = source.MaxChainBeforeFallback;
 
             return target;
         }

src/c#/GeneralUpdate.Core/Configuration/UpdateConfiguration.cs

@@ -245,5 +245,23 @@ public abstract class UpdateConfiguration
         /// </remarks>
         /// </remarks>
         public Dictionary<string, string> CustomHeaders { get; set; }
+
+        /// <summary>
+        ///     Maximum number of chain (delta) packages allowed before falling back to a single
+        ///     full replacement package. When the number of chain packages for an AppType exceeds
+        ///     this limit, the download plan switches to the full package for that AppType —
+        ///     even if the combined chain size is smaller than the full package.
+        /// </summary>
+        /// <remarks>
+        ///     <para>
+        ///         A full package is also selected when the combined download size of all chain
+        ///         packages equals or exceeds the full package size, regardless of the count.
+        ///     </para>
+        ///     <para>
+        ///         Set to <c>0</c> or a negative value to disable the count-based fallback
+        ///         (only the size comparison applies).
+        ///     </para>
+        /// </remarks>
+        public int MaxChainBeforeFallback { get; set; } = 8;
     }
 }

src/c#/GeneralUpdate.Core/Download/DownloadPlanBuilder.cs

@@ -28,8 +28,10 @@ namespace GeneralUpdate.Core.Download;
 ///         if the current client version is below the minimum, the package is skipped.</description></item>
 /// </list>
 /// <para>
-/// All packages are treated uniformly; the builder evaluates chain vs full packages
-/// based on total download size.
+/// Chain vs full evaluation uses a count-first heuristic:
+/// a full package is selected when the number of chain packages exceeds
+/// <c>MaxChainBeforeFallback</c> (default 8), or when the combined download size
+/// of all chain packages equals or exceeds the full package size.
 /// </para>
 /// </remarks>
 public static class DownloadPlanBuilder
@@ -108,10 +110,17 @@ public static bool HasUpdate(
     /// <param name="upgradeClientVersion">
     /// The current upgrade (updater) version, or null to fall back to <paramref name="clientVersion"/>.
     /// </param>
+    /// <param name="maxChainBeforeFallback">
+    /// Maximum number of chain packages allowed before falling back to a single full package.
+    /// Default is <c>8</c>. Set to <c>0</c> to disable the count-based fallback; set to
+    /// a negative value to always prefer chain packages when their combined size is smaller
+    /// than the full package.
+    /// </param>
     public static DownloadPlan Build(
         IEnumerable<DownloadAsset> assets,
         string clientVersion,
-        string? upgradeClientVersion)
+        string? upgradeClientVersion,
+        int maxChainBeforeFallback = 8)
     {
         if (assets == null) return DownloadPlan.Empty;
         var parsedClient = ParseVersion(clientVersion);
@@ -171,7 +180,7 @@ public static DownloadPlan Build(
             .Where(a => a.PackageType == (int)Configuration.PackageType.Full)
             .ToList();
 
-        // ── Chain vs Full size-based decision ──
+        // ── Chain vs Full: count-first heuristic ──
         if (chainCandidates.Count > 0 && fullCandidates.Count > 0)
         {
             var bestFull = fullCandidates
@@ -181,19 +190,28 @@ public static DownloadPlan Build(
             long chainTotal = chainCandidates
                 .Where(a => a.AppType == bestFull.AppType)
                 .Sum(a => a.Size);
-            var threshold = (long)(bestFull.Size * 0.8);
+            int chainCount = chainCandidates.Count(a => a.AppType == bestFull.AppType);
 
-            if (chainTotal >= threshold)
+            // Local helper: build a "switch to full" plan that replaces same-AppType
+            // chain packages with bestFull, while keeping chains for other AppTypes
+            // (and any same-AppType chains whose version exceeds the full's version).
+            DownloadPlan SwitchToFull(string reason)
             {
-                GeneralTracer.Info($"DownloadPlanBuilder: chain total {chainTotal} >= 80% of full size {bestFull.Size}, switching to full package {bestFull.Name}");
-                var bestFullSv = Lookup(bestFull);
+                GeneralTracer.Info($"DownloadPlanBuilder: {reason}, switching to full package {bestFull.Name} (chain count {chainCount}, chain total {chainTotal}, full size {bestFull.Size})");
+                var fullVersion = Lookup(bestFull);
                 var planAssets = new List<DownloadAsset> { bestFull };
                 planAssets.AddRange(chainCandidates
                     .Where(a => a.AppType != bestFull.AppType
-                                || (Lookup(a) is { } av && bestFullSv != null && av > bestFullSv))
+                                || (Lookup(a) is { } av && fullVersion != null && av > fullVersion))
                     .OrderBy(a => Lookup(a)));
                 return new DownloadPlan(planAssets, isForcibly);
             }
+
+            if (maxChainBeforeFallback > 0 && chainCount > maxChainBeforeFallback)
+                return SwitchToFull($"chain count {chainCount} exceeds MaxChainBeforeFallback {maxChainBeforeFallback}");
+
+            if (chainTotal >= bestFull.Size)
+                return SwitchToFull($"chain total {chainTotal} >= full size {bestFull.Size}");
         }
 
         // ── Chain plan with fallback fulls ──

src/c#/GeneralUpdate.Core/GeneralUpdate.Core.csproj

@@ -13,7 +13,7 @@
         <PackageReleaseNotes>10.5.0-beta.1: Zero-config SetSource() API, manifest.json auto-discovery, IUpdateHooks extension points, appsettings.json LoadFromConfiguration() support, SSL/HttpClient lifecycle fixes, and OSS update flow improvements.</PackageReleaseNotes>
         <PackageLicenseExpression>Apache-2.0</PackageLicenseExpression>
         <PackageReadmeFile>README.md</PackageReadmeFile>
-        <Version>10.5.0-beta.6</Version>
+        <Version>10.5.0-beta.7</Version>
         <TargetFrameworks>netstandard2.0;net8.0;net10.0</TargetFrameworks>
         <IsAotCompatible Condition="'$(TargetFramework)' != 'netstandard2.0'">true</IsAotCompatible>
         <EnableTrimAnalyzer Condition="'$(TargetFramework)' != 'netstandard2.0'">true</EnableTrimAnalyzer>

src/c#/GeneralUpdate.Core/Strategy/ClientStrategy.cs

@@ -475,7 +475,8 @@ private async Task ExecuteStandardWorkflowAsync()
         var downloadPlan = Download.DownloadPlanBuilder.Build(
             sourceResult.Assets,
             localClientVersion,
-            resolvedUpgradeVersion);
+            resolvedUpgradeVersion,
+            _configInfo.MaxChainBeforeFallback);
         _configInfo.LastVersion = downloadPlan.Assets.LastOrDefault()?.Version;
         GeneralTracer.Info($"ClientStrategy: Scenario={scenario}, AssetCount={downloadPlan.Assets.Count}");
 

src/c#/GeneralUpdate.Differential/GeneralUpdate.Differential.csproj

@@ -5,7 +5,7 @@
     <RepositoryUrl>https://github.com/JusterZhu/GeneralUpdate</RepositoryUrl>
     <Description>Binary diff/patch algorithms (BSDIFF, HDiffPatch) with Brotli compression for generating and applying incremental updates. Includes parallel file processing with progress reporting and cancellation support.</Description>
     <Authors>JusterZhu</Authors>
-    <Version>10.5.0-beta.6</Version>
+    <Version>10.5.0-beta.7</Version>
     <PackageProjectUrl>https://github.com/GeneralLibrary/GeneralUpdate</PackageProjectUrl>
     <Copyright>Copyright © 2020-2026 JusterZhu. All rights reserved.</Copyright>
     <LangVersion>default</LangVersion>

src/c#/GeneralUpdate.Drivelution/GeneralUpdate.Drivelution.csproj

@@ -11,7 +11,7 @@
     <EnableTrimAnalyzer>true</EnableTrimAnalyzer>
     <TrimMode>full</TrimMode>
     <!-- NuGet Package Metadata -->
-    <Version>10.5.0-beta.6</Version>
+    <Version>10.5.0-beta.7</Version>
     <Authors>JusterZhu</Authors>
     <Company>juster.zhu</Company>
     <Title>GeneralUpdate.Drivelution</Title>

src/c#/GeneralUpdate.Extension/GeneralUpdate.Extension.csproj

@@ -5,7 +5,7 @@
     <Nullable>enable</Nullable>
     <LangVersion>latest</LangVersion>
     <!-- NuGet Package Metadata -->
-    <Version>10.5.0-beta.6</Version>
+    <Version>10.5.0-beta.7</Version>
     <Authors>JusterZhu</Authors>
     <Company>juster.zhu</Company>
     <Title>GeneralUpdate.Extension</Title>

tests/CoreTest/Download/DownloadPlanBuilderTests.cs

@@ -81,23 +81,148 @@ public void Build_NoAssetIsForcibly_IsForciblyFalse()
     }
 
     [Fact]
-    public void Build_FullPackageSelected_WhenChainExceedsThreshold()
+    public void Build_FullPackageSelected_WhenChainTotalExceedsFullSize()
     {
-        // Small chain + small full → chain_total >= 80% full → Full selected
+        // 2 chain packages (total 200), full=100 → 200 >= 100 → full selected
         var assets = new[]
         {
             Asset("chain1", "1.1.0", size: 100),
             Asset("chain2", "2.0.0", size: 100),
             Asset("full", "2.0.0", packageType: (int)PackageType.Full),
         };
-        // chain_total=200, 80% of full(100) = 80 → 200 >= 80 → full selected
         var result = DownloadPlanBuilder.Build(assets, "1.0.0");
         Assert.True(result.HasAssets);
         Assert.Single(result.Assets);
         Assert.Equal((int)PackageType.Full, result.Assets[0].PackageType);
         Assert.Equal("2.0.0", result.Assets[0].Version);
     }
 
+    [Fact]
+    public void Build_FullPackageSelected_WhenChainCountExceedsMaxChainBeforeFallback()
+    {
+        // 12 small chain packages (total 120), full=500, maxChainBeforeFallback=10
+        // → chain count 12 > 10 → full selected despite chain being much smaller
+        var assets = new List<DownloadAsset>();
+        for (int i = 1; i <= 12; i++)
+            assets.Add(Asset($"chain{i}", $"1.{i}.0", size: 10));
+        assets.Add(Asset("full", "2.0.0", size: 500, packageType: (int)PackageType.Full));
+
+        var result = DownloadPlanBuilder.Build(assets, "1.0.0", null, maxChainBeforeFallback: 10);
+        Assert.True(result.HasAssets);
+        Assert.Single(result.Assets);
+        Assert.Equal((int)PackageType.Full, result.Assets[0].PackageType);
+    }
+
+    [Fact]
+    public void Build_ChainSelected_WhenCountBelowThresholdAndTotalBelowFullSize()
+    {
+        // 3 chain packages (total 150), full=500, maxChainBeforeFallback=default(8)
+        // → chain count 3 <= 8 AND 150 < 500 → chain selected
+        var assets = new[]
+        {
+            Asset("chain1", "1.1.0", size: 50),
+            Asset("chain2", "1.2.0", size: 50),
+            Asset("chain3", "2.0.0", size: 50),
+            Asset("full", "2.0.0", size: 500, packageType: (int)PackageType.Full),
+        };
+        var result = DownloadPlanBuilder.Build(assets, "1.0.0");
+        Assert.True(result.HasAssets);
+        Assert.Equal(3, result.Assets.Count);
+        Assert.All(result.Assets, a => Assert.Equal((int)PackageType.Chain, a.PackageType));
+    }
+
+    [Fact]
+    public void Build_FullPackageSelected_WhenChainTotalEqualsFullSize()
+    {
+        // chain total == full size → full selected (boundary: >= not >)
+        var assets = new[]
+        {
+            Asset("chain1", "1.1.0", size: 200),
+            Asset("chain2", "2.0.0", size: 300),
+            Asset("full", "2.0.0", size: 500, packageType: (int)PackageType.Full),
+        };
+        var result = DownloadPlanBuilder.Build(assets, "1.0.0", null, maxChainBeforeFallback: 10);
+        Assert.True(result.HasAssets);
+        Assert.Single(result.Assets);
+        Assert.Equal((int)PackageType.Full, result.Assets[0].PackageType);
+    }
+
+    [Fact]
+    public void Build_ChainSelected_WhenMaxChainBeforeFallbackIsZero()
+    {
+        // maxChainBeforeFallback=0 disables count-based fallback
+        // 25 chain packages (total 400), full=500 → 400 < 500 → chain selected
+        var assets = new List<DownloadAsset>();
+        for (int i = 1; i <= 25; i++)
+            assets.Add(Asset($"chain{i}", $"1.{i}.0", size: 16));
+        assets.Add(Asset("full", "2.0.0", size: 500, packageType: (int)PackageType.Full));
+
+        var result = DownloadPlanBuilder.Build(assets, "1.0.0", null, maxChainBeforeFallback: 0);
+        Assert.True(result.HasAssets);
+        Assert.Equal(25, result.Assets.Count);
+        Assert.All(result.Assets, a => Assert.Equal((int)PackageType.Chain, a.PackageType));
+    }
+
+    [Fact]
+    public void Build_MixedAppType_FullSwitchKeepsOtherAppTypeChains()
+    {
+        // Client full v2.0 + 12 Client chains (trigger count) + 3 Upgrade chains.
+        // → Client chains replaced by Client full, Upgrade chains kept.
+        var assets = new List<DownloadAsset>();
+        for (int i = 1; i <= 12; i++)
+            assets.Add(AssetWithType($"client-chain{i}", $"1.{i}.0", size: 10, appType: (int)AppType.Client));
+        for (int i = 1; i <= 3; i++)
+            assets.Add(AssetWithType($"upgrade-chain{i}", $"1.{i}.0", size: 10, appType: (int)AppType.Upgrade));
+        assets.Add(AssetWithType("client-full", "2.0.0", size: 500, packageType: (int)PackageType.Full, appType: (int)AppType.Client));
+
+        var result = DownloadPlanBuilder.Build(assets, "1.0.0", "1.0.0", maxChainBeforeFallback: 8);
+        Assert.True(result.HasAssets);
+        // 1 Client full + 3 Upgrade chains = 4 assets
+        Assert.Equal(4, result.Assets.Count);
+        Assert.Contains(result.Assets, a => a.PackageType == (int)PackageType.Full && a.AppType == (int)AppType.Client);
+        Assert.Equal(3, result.Assets.Count(a => a.AppType == (int)AppType.Upgrade));
+    }
+
+    [Fact]
+    public void Build_MixedAppType_OnlyFullForUpgrade_DoesNotAffectClientChains()
+    {
+        // Upgrade full v2.0 + 3 Upgrade chains (below threshold) + 5 Client chains.
+        // No Client full → count/size check scoped to Upgrade chains only.
+        // 3 Upgrade chains ≤ 8, total 30 < 500 → chain plan with Upgrade fallback.
+        var assets = new List<DownloadAsset>();
+        for (int i = 1; i <= 5; i++)
+            assets.Add(AssetWithType($"client-chain{i}", $"1.{i}.0", size: 20, appType: (int)AppType.Client));
+        for (int i = 1; i <= 3; i++)
+            assets.Add(AssetWithType($"upgrade-chain{i}", $"1.{i}.0", size: 10, appType: (int)AppType.Upgrade));
+        assets.Add(AssetWithType("upgrade-full", "2.0.0", size: 500, packageType: (int)PackageType.Full, appType: (int)AppType.Upgrade));
+
+        var result = DownloadPlanBuilder.Build(assets, "1.0.0", "1.0.0", maxChainBeforeFallback: 8);
+        Assert.True(result.HasAssets);
+        // All 8 chain packages selected, none replaced
+        Assert.Equal(8, result.Assets.Count);
+        Assert.All(result.Assets, a => Assert.Equal((int)PackageType.Chain, a.PackageType));
+    }
+
+    [Fact]
+    public void Build_MixedAppType_CountTriggersForClient_UpgradeChainsUnaffected()
+    {
+        // Client full + 12 Client chains (triggers count) + 12 Upgrade chains (no Upgrade full).
+        // → Client chains replaced by Client full, all 12 Upgrade chains kept.
+        var assets = new List<DownloadAsset>();
+        for (int i = 1; i <= 12; i++)
+            assets.Add(AssetWithType($"client-chain{i}", $"1.{i}.0", size: 5, appType: (int)AppType.Client));
+        for (int i = 1; i <= 12; i++)
+            assets.Add(AssetWithType($"upgrade-chain{i}", $"1.{i}.0", size: 5, appType: (int)AppType.Upgrade));
+        assets.Add(AssetWithType("client-full", "2.0.0", size: 500, packageType: (int)PackageType.Full, appType: (int)AppType.Client));
+
+        var result = DownloadPlanBuilder.Build(assets, "1.0.0", "1.0.0", maxChainBeforeFallback: 8);
+        Assert.True(result.HasAssets);
+        // 1 Client full + 12 Upgrade chains (no Upgrade full → kept as-is)
+        Assert.Equal(13, result.Assets.Count);
+        Assert.Equal(12, result.Assets.Count(a => a.AppType == (int)AppType.Upgrade));
+        Assert.Single(result.Assets, a => a.PackageType == (int)PackageType.Full);
+    }
+
     [Fact]
     public void Build_MinClientVersionTooHigh_FilteredOut()
     {