fix(core): deduplicate switch-to-full logic, add missing mapper, mixed-AppType tests

Code review fixes:
- Extract duplicated 'switch to full' code block into local function SwitchToFull
- Add missing MaxChainBeforeFallback mapping in ConfigurationMapper
- Add 3 mixed-AppType test cases (Client+Upgrade split scenarios)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: JusterZhu

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/Download/DownloadPlanBuilder.cs

@@ -192,29 +192,26 @@ public static DownloadPlan Build(
                 .Sum(a => a.Size);
             int chainCount = chainCandidates.Count(a => a.AppType == bestFull.AppType);
 
-            if (maxChainBeforeFallback > 0 && chainCount > maxChainBeforeFallback)
+            // 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($"DownloadPlanBuilder: chain count {chainCount} exceeds MaxChainBeforeFallback {maxChainBeforeFallback}, switching to full package {bestFull.Name} (chain total {chainTotal}, full size {bestFull.Size})");
-                var bestFullSv = Lookup(bestFull);
+                GeneralTracer.Info($"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($"chain count {chainCount} exceeds MaxChainBeforeFallback {maxChainBeforeFallback}");
+
             if (chainTotal >= bestFull.Size)
-            {
-                GeneralTracer.Info($"DownloadPlanBuilder: chain total {chainTotal} >= full size {bestFull.Size}, switching to full package {bestFull.Name}");
-                var bestFullSv = 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))
-                    .OrderBy(a => Lookup(a)));
-                return new DownloadPlan(planAssets, isForcibly);
-            }
+                return SwitchToFull($"chain total {chainTotal} >= full size {bestFull.Size}");
         }
 
         // ── Chain plan with fallback fulls ──

tests/CoreTest/Download/DownloadPlanBuilderTests.cs

@@ -163,6 +163,66 @@ public void Build_ChainSelected_WhenMaxChainBeforeFallbackIsZero()
         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()
     {