// Copyright UShaderLab. All Rights Reserved.

#include "DirectoryWatcherModule.h"
#include "Editor.h"
#include "Engine/Engine.h"
#include "HAL/FileManager.h"
#include "IDirectoryWatcher.h"
#include "Interfaces/IPluginManager.h"
#include "MaterialEditingLibrary.h"
#include "MaterialShared.h"
#include "Materials/Material.h"
#include "Misc/Paths.h"
#include "Modules/ModuleManager.h"
#include "ShaderCore.h"
#include "Misc/FileHelper.h"
#include "ShaderLabDiscovery.h"
#include "ShaderLabGraphBuilder.h"
#include "ShaderLabImportResolver.h"
#include "ShaderLabMaterialInstanceConstant.h"
#include "ShaderLabMaterialRegistry.h"
#include "ShaderLabModel.h"
#include "ShaderLabParser.h"
#include "ShaderLabSubsystem.h"
#include "ShaderLabVSCodeButton.h"
#include "UObject/Package.h"
#include "UObject/UObjectIterator.h"

DEFINE_LOG_CATEGORY_STATIC(LogShaderLabEditor, Log, All);

namespace
{
	/** Editor-side reaction to a base material needing build: rebuild graph + trigger compile. */
	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(LogShaderLabEditor, 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(LogShaderLabEditor, 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();
			}
		}

		// Refresh any open Material Instance editors built on this base so newly added/removed parameters
		// (scalars, textures, static-bool switches) appear without reopening the editor. RegenerateArrays
		// pulls the parameter set from the freshly rebuilt parent; mirrors what the stock material editor
		// does after RecompileMaterial. Must run after PostEditChange so the parent's parameters are current.
		// Guarded on GEditor: this handler also runs during cook/headless registration, where there is no
		// interactive editor (and RebuildMaterialInstanceEditors dereferences GEditor).
		if (GEditor)
		{
			UMaterialEditingLibrary::RebuildMaterialInstanceEditors(&Material);
		}
	}
}

class FShaderLabEditorModule : 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).
		BuildHandle = FShaderLabMaterialRegistry::Get().OnBuildMaterial().AddStatic(&BuildAndCompile);

		StartWatchingSources();

		// "Open .usl in VSCode" toolbar button on the Material Instance Editor for ShaderLab MICs.
		ShaderLabVSCodeButton::Register();

		UE_LOG(LogShaderLabEditor, Log, TEXT("ShaderLabEditor module started."));
	}

	virtual void ShutdownModule() override
	{
		StopWatchingSources();
		ShaderLabVSCodeButton::Unregister();
		if (BuildHandle.IsValid())
		{
			FShaderLabMaterialRegistry::Get().OnBuildMaterial().Remove(BuildHandle);
			BuildHandle.Reset();
		}
	}

private:
	void StartWatchingSources()
	{
		FDirectoryWatcherModule& Module =
			FModuleManager::LoadModuleChecked<FDirectoryWatcherModule>(TEXT("DirectoryWatcher"));
		IDirectoryWatcher* Watcher = Module.Get();
		if (!Watcher)
		{
			return;
		}
		for (const FString& Root : FShaderLabDiscovery::GetSearchRoots())
		{
			if (!FPaths::DirectoryExists(Root))
			{
				continue;
			}
			FDelegateHandle Handle;
			Watcher->RegisterDirectoryChangedCallback_Handle(
				Root,
				IDirectoryWatcher::FDirectoryChanged::CreateStatic(&FShaderLabEditorModule::OnDirectoryChanged),
				Handle,
				IDirectoryWatcher::WatchOptions::IncludeDirectoryChanges);
			WatchedRoots.Add(Root, Handle);
		}
	}

	void StopWatchingSources()
	{
		if (FModuleManager::Get().IsModuleLoaded(TEXT("DirectoryWatcher")))
		{
			FDirectoryWatcherModule& Module =
				FModuleManager::GetModuleChecked<FDirectoryWatcherModule>(TEXT("DirectoryWatcher"));
			if (IDirectoryWatcher* Watcher = Module.Get())
			{
				for (const TPair<FString, FDelegateHandle>& Pair : WatchedRoots)
				{
					Watcher->UnregisterDirectoryChangedCallback_Handle(Pair.Key, Pair.Value);
				}
			}
		}
		WatchedRoots.Reset();
	}

	/** Resolve a virtual shader path to disk via the registered shader-source directory mappings. */
	static bool ResolveVirtualToDisk(const FString& VirtualPath, FString& OutDiskPath)
	{
		FString Best, BestDir;
		for (const TPair<FString, FString>& Pair : AllShaderSourceDirectoryMappings())
		{
			if ((VirtualPath.StartsWith(Pair.Key + TEXT("/")) || VirtualPath == Pair.Key) && Pair.Key.Len() > Best.Len())
			{
				Best = Pair.Key;
				BestDir = Pair.Value;
			}
		}
		if (Best.IsEmpty()) { return false; }
		FString Rest = VirtualPath.Mid(Best.Len());
		Rest.RemoveFromStart(TEXT("/"));
		OutDiskPath = FPaths::Combine(BestDir, Rest);
		return true;
	}

	static FString NormalizePath(const FString& Path)
	{
		FString N = FPaths::ConvertRelativePathToFull(Path);
		N.ReplaceInline(TEXT("\\"), TEXT("/"));
		return N;
	}

	/**
	 * Every discovered `.usl` shader whose transitive `.uslfunc` import closure contains ChangedDiskPath —
	 * i.e. the shaders that must be rebuilt when that library changes. Resolves each shader's imports so
	 * both direct and nested (library-imports-library) dependencies are caught.
	 */
	static TArray<FString> FindShadersImporting(const FString& ChangedDiskPathNormalized)
	{
		TArray<FString> Result;
		for (const FString& Usl : FShaderLabDiscovery::FindShaderLabFiles())
		{
			FString Source;
			if (!FFileHelper::LoadFileToString(Source, *Usl))
			{
				continue;
			}
			FShaderLabModel Model;
			TArray<FShaderLabParseError> ParseErrors;
			if (!FShaderLabParser::Parse(Source, Usl, Model, ParseErrors) || Model.Imports.Num() == 0)
			{
				continue;
			}
			FShaderLabImportResolver::FSourceLoader Loader =
				[](const FString& VPath, FString& OutSrc, FString& OutDisk, FString& OutErr) -> bool
			{
				if (!ResolveVirtualToDisk(VPath, OutDisk)) { OutErr = TEXT("unmapped"); return false; }
				if (!FFileHelper::LoadFileToString(OutSrc, *OutDisk)) { OutErr = TEXT("read failed"); return false; }
				return true;
			};
			FShaderLabResolvedProgram Program;
			TArray<FString> ResolveErrors;
			if (!FShaderLabImportResolver::Resolve(Model, Loader, Program, ResolveErrors))
			{
				continue;
			}
			for (const FShaderLabResolvedLibrary& Lib : Program.Libraries)
			{
				if (NormalizePath(Lib.Model.SourceFilePath) == ChangedDiskPathNormalized)
				{
					Result.Add(Usl);
					break;
				}
			}
		}
		return Result;
	}

	static void OnDirectoryChanged(const TArray<FFileChangeData>& Changes)
	{
		UShaderLabSubsystem* Subsystem = GEngine ? GEngine->GetEngineSubsystem<UShaderLabSubsystem>() : nullptr;
		if (!Subsystem)
		{
			return;
		}
		TSet<FString> Rebuilt;
		auto RebuildOnce = [&](const FString& Normalized)
		{
			if (Rebuilt.Contains(Normalized)) { return; }
			Rebuilt.Add(Normalized);
			Subsystem->RebuildFromFile(Normalized);
			UE_LOG(LogShaderLabEditor, Log, TEXT("ShaderLab hot-reloaded '%s'"), *Normalized);
		};

		for (const FFileChangeData& Change : Changes)
		{
			if (Change.Action == FFileChangeData::FCA_Removed)
			{
				continue; // Leave the existing in-memory material in place on delete.
			}
			const FString Ext = FPaths::GetExtension(Change.Filename);
			const FString Normalized = NormalizePath(Change.Filename);
			if (Ext.Equals(TEXT("usl"), ESearchCase::IgnoreCase))
			{
				RebuildOnce(Normalized);
			}
			else if (Ext.Equals(TEXT("uslfunc"), ESearchCase::IgnoreCase))
			{
				// A library changed: rebuild every shader that (transitively) imports it, so their promoted
				// parameters and emitted function HLSL refresh — the dependency-aware hot reload.
				for (const FString& Dependent : FindShadersImporting(Normalized))
				{
					RebuildOnce(NormalizePath(Dependent));
				}
			}
		}
	}

	FDelegateHandle BuildHandle;
	TMap<FString, FDelegateHandle> WatchedRoots;
};

IMPLEMENT_MODULE(FShaderLabEditorModule, UShaderLabEditor)