// Copyright UShaderLab. All Rights Reserved.

#include "Engine/Engine.h"
#include "HAL/FileManager.h"
#include "Interfaces/IPluginManager.h"
#include "MaterialShared.h"
#include "Materials/Material.h"
#include "Misc/CoreDelegates.h"
#include "Misc/EngineVersionComparison.h"
#include "Misc/Paths.h"
#include "Modules/ModuleManager.h"
#include "ShaderCore.h"
#include "ShaderLabGraphBuilder.h"
#include "ShaderLabIDEPrepare.h"
#include "ShaderLabMaterialInstanceConstant.h"
#include "ShaderLabMaterialRegistry.h"
#include "ShaderLabModel.h"
#include "UObject/UObjectIterator.h"

// FCoreDelegates::OnPostEngineInit became the accessor GetOnPostEngineInit() in UE 5.8; 5.7 exposes the
// delegate member directly. Mirror the same bridge the runtime subsystem uses so the shared plugin builds
// on both engines.
#if UE_VERSION_OLDER_THAN(5, 8, 0)
	#define SHADERLAB_ON_POST_ENGINE_INIT FCoreDelegates::OnPostEngineInit
#else
	#define SHADERLAB_ON_POST_ENGINE_INIT FCoreDelegates::GetOnPostEngineInit()
#endif

DEFINE_LOG_CATEGORY_STATIC(LogShaderLabBuilder, Log, All);

namespace
{
	/**
	 * Fill a base material shell: rebuild its expression graph from the model, then recompile it and every
	 * dependent instance. Runs whenever the registry asks (startup discovery + editor hot reload) in ANY
	 * uncooked run — the editor AND a `-game` launch on the editor binary. In `-game` the project is uncooked,
	 * so each instance must translate its own static-permutation shader map from THIS graph at load: an empty
	 * shell here is exactly why materials used to fall back to the default material in `-game`.
	 */
	void BuildAndCompile(UMaterial& Material, const FShaderLabModel& Model)
	{
		// Absolute, forward-slashed source path for the poison node's `#line` mapping (matches the graph
		// builder's own convention so compiler errors click through to the .usl).
		FString SrcPath = FPaths::ConvertRelativePathToFull(Model.SourceFilePath);
		SrcPath.ReplaceInline(TEXT("\\"), TEXT("/"));

		if (Model.LoadErrors.Num() > 0)
		{
			// Parse-stage failure: the .usl never produced a valid model. Route the diagnostics through
			// the shader compiler as a poison material so they surface in the MIC editor / cook, not just
			// the log.
			for (const FString& E : Model.LoadErrors)
			{
				UE_LOG(LogShaderLabBuilder, Error, TEXT("ShaderLab parse '%s': %s"), *Model.ShaderName, *E);
			}
			FShaderLabGraphBuilder::BuildPoisonInto(Material, Model.LoadErrors, SrcPath);
		}
		else
		{
			TArray<FString> Errors;
			if (!FShaderLabGraphBuilder::BuildInto(Material, Model, Errors))
			{
				for (const FString& E : Errors)
				{
					UE_LOG(LogShaderLabBuilder, Error, TEXT("ShaderLab build '%s': %s"), *Model.ShaderName, *E);
				}
				// BuildInto already cleared the graph before failing — don't leave the base silently empty.
				// Replace it with a poison material so the build errors compile-fail with the same
				// visibility as an HLSL error, instead of vanishing into the log.
				FShaderLabGraphBuilder::BuildPoisonInto(Material, Errors, SrcPath);
			}
		}

		// Recompile the base AND propagate to everything that depends on it. A bare PostEditChange
		// recompiles only the base shell; the instances carry their own static-permutation shader maps
		// (and the level components render those), so on a hot-reload they must be recompiled and
		// re-pushed too. FMaterialUpdateContext does exactly that on scope exit: recompile the listed
		// material, then recache every dependent instance and refresh the components/viewports using it.
		{
			FMaterialUpdateContext UpdateContext;
			UpdateContext.AddMaterial(&Material);
			Material.PreEditChange(nullptr);
			Material.PostEditChange();
		}

		// Re-derive the cook-inclusion data (CachedExpressionData copy + profile overrides) on every ROOT
		// UShaderLabMaterialInstanceConstant of this base. The FMaterialUpdateContext above recompiles the
		// dependent shader maps but does NOT refresh that derived data (it's built once at PostLoad and pinned by
		// bLoadedCachedExpressionData=true), so a hot-reload that added/removed an MPC or profile would otherwise
		// leave a resident MIC stale — and an in-editor iterative cook would serialize the stale references.
		//
		// Inheritance chain: only a ROOT (immediate parent == this base) carries the derived data; CHILD instances
		// (parent is another instance, however deep) hold none and resolve up the chain to the root at query time,
		// and their shared shader maps were just recompiled by FMaterialUpdateContext — so refreshing the roots is
		// sufficient and children need no separate pass. RefreshShaderLabDerivedData self-guards via
		// GetShaderLabRootBase(), so it is a safe no-op on anything that isn't a root of this base. Skip CDOs and
		// objects being GC'd.
		for (TObjectIterator<UShaderLabMaterialInstanceConstant> It(
				/*AdditionalExclusionFlags*/ RF_ClassDefaultObject,
				/*bIncludeDerivedClasses*/ true,
				/*InternalExclusionFlags*/ EInternalObjectFlags::Garbage); It; ++It)
		{
			if (It->Parent == &Material)
			{
				It->RefreshShaderLabDerivedData();
			}
		}

		// The graph is now built + compiled and the derived data refreshed. Notify the editor layer so it can
		// refresh any open Material Instance editors — kept out of this UncookedOnly module because that reaction
		// needs the MaterialEditor module, which is absent in `-game`. No listeners there; a no-op broadcast.
		FShaderLabMaterialRegistry::Get().OnMaterialGraphBuilt().Broadcast(Material);
	}
}

class FShaderLabBuilderModule : public IModuleInterface
{
public:
	virtual void StartupModule() override
	{
		// Map the plugin's Shaders/ directory so generated Custom nodes can #include
		// "/Plugin/ShaderLab/Private/ShaderLabCommon.ush" at shader-compile time.
		if (const TSharedPtr<IPlugin> Plugin = IPluginManager::Get().FindPlugin(TEXT("UShaderLab")))
		{
			const FString ShaderDir = FPaths::Combine(Plugin->GetBaseDir(), TEXT("Shaders"));
			if (!AllShaderSourceDirectoryMappings().Contains(TEXT("/Plugin/ShaderLab")))
			{
				AddShaderSourceDirectoryMapping(TEXT("/Plugin/ShaderLab"), ShaderDir);
			}
		}

		// Map the project's Shaders/ directory to the virtual root "/Project" so user .ush library
		// files placed there (alongside .usl) can be #included from a shader's Includes { } block.
		{
			const FString ProjectShaderDir = FPaths::Combine(FPaths::ProjectDir(), TEXT("Shaders"));
			if (FPaths::DirectoryExists(ProjectShaderDir) && !AllShaderSourceDirectoryMappings().Contains(TEXT("/Project")))
			{
				AddShaderSourceDirectoryMapping(TEXT("/Project"), ProjectShaderDir);
			}
		}

		// Map the plugin's Intermediate/ShaderLabGen directory (a build-time artifact dir) so the graph
		// builder can #include per-shader generated local-code headers (`/UShaderLabGen/<Name>.gen.ush`).
		// AddShaderSourceDirectoryMapping requires the real dir to already exist, so create it first.
		{
			const FString GenDir = FShaderLabGraphBuilder::GetGeneratedShaderDir();
			const TCHAR* GenRoot = FShaderLabGraphBuilder::GetGeneratedVirtualRoot();
			if (!GenDir.IsEmpty())
			{
				IFileManager::Get().MakeDirectory(*GenDir, /*Tree*/ true);
				if (FPaths::DirectoryExists(GenDir) && !AllShaderSourceDirectoryMappings().Contains(GenRoot))
				{
					AddShaderSourceDirectoryMapping(GenRoot, GenDir);
				}
			}
		}

		// Fill in / recompile base materials whenever the registry asks (startup + hot reload). This is the
		// binding that was previously in the Editor module and never fired in `-game`; hosting it here (a
		// module loaded for all uncooked runs) is the fix for invisible materials under `-game`.
		BuildHandle = FShaderLabMaterialRegistry::Get().OnBuildMaterial().AddStatic(&BuildAndCompile);

		// First-launch convenience: auto-generate the .usl IDE authoring assets if the project is missing them
		// (a fresh clone lacks .vscode — it is git-ignored). Deferred to post-engine-init so shader-source
		// mappings (added above) and UMaterial reflection are ready; the callback self-gates to an interactive
		// editor session (no cook / -game / commandlet / unattended).
		PostEngineInitHandle = SHADERLAB_ON_POST_ENGINE_INIT.AddStatic(&ShaderLabIDE_EnsureGeneratedIfMissing);

		UE_LOG(LogShaderLabBuilder, Log, TEXT("ShaderLabBuilder module started."));
	}

	virtual void ShutdownModule() override
	{
		if (BuildHandle.IsValid())
		{
			FShaderLabMaterialRegistry::Get().OnBuildMaterial().Remove(BuildHandle);
			BuildHandle.Reset();
		}
		if (PostEngineInitHandle.IsValid())
		{
			SHADERLAB_ON_POST_ENGINE_INIT.Remove(PostEngineInitHandle);
			PostEngineInitHandle.Reset();
		}
	}

private:
	FDelegateHandle BuildHandle;
	FDelegateHandle PostEngineInitHandle;
};

IMPLEMENT_MODULE(FShaderLabBuilderModule, UShaderLabBuilder)