/*
 *  mod_loader.cpp
 *
 */

// required to use activation context API structures
#define _WIN32_WINNT 0x0501

#include "firebird.h"
#include "../jrd/os/mod_loader.h"
#include <windows.h>

typedef Firebird::string string;
typedef Firebird::PathName PathName;

/// This is the Win32 implementation of the mod_loader abstraction.

HINSTANCE hDllInst = 0;
BOOL bEmbedded = false;

/// activation context API prototypes
typedef HANDLE (WINAPI * PFN_CAC)(PCACTCTXA pActCtx);

typedef BOOL (WINAPI * PFN_FINDAC)(DWORD dwFlags, 
								   const GUID *lpExtensionGuid, 
								   ULONG ulSectionId, 
								   LPCSTR lpStringToFind, 
								   PACTCTX_SECTION_KEYED_DATA ReturnedData);

typedef void (WINAPI * PFN_RAC)(HANDLE hActCtx);

typedef BOOL (WINAPI * PFN_AAC)(HANDLE hActCtx, ULONG_PTR *lpCookie);

typedef BOOL (WINAPI * PFN_DAC)(DWORD dwFlags, ULONG_PTR ulCookie);
/// end of activation context API prototypes


template <typename PFN>
class WinApiFunction
{
public:
	WinApiFunction(const char *dllName, const char *fnName)
	{
		m_ptr = NULL;
		const HMODULE hDll = GetModuleHandle(dllName);
		if (hDll)
			m_ptr = (PFN) GetProcAddress(hDll, fnName);
	}

	~WinApiFunction()
	{}

	PFN operator* () const
	{ return m_ptr; }

	operator bool() const
	{ return (m_ptr != NULL); }

private:
	PFN m_ptr;
};

const char* sKernel32 = "kernel32.dll";


class ContextActivator
{
public:
	ContextActivator() :
	  mFindActCtxSectionString(sKernel32, "FindActCtxSectionStringA"),
	  mCreateActCtx(sKernel32, "CreateActCtxA"),
	  mReleaseActCtx(sKernel32, "ReleaseActCtx"),
	  mActivateActCtx(sKernel32, "ActivateActCtx"),
	  mDeactivateActCtx(sKernel32, "DeactivateActCtx")
	{
		hActCtx = INVALID_HANDLE_VALUE;

// if we don't use MSVC then we don't use MS CRT ?
#ifndef _MSC_VER
		return;
#endif

		if (!bEmbedded || !mCreateActCtx)
			return;

		ACTCTX_SECTION_KEYED_DATA ackd;
		memset(&ackd, 0, sizeof(ackd));
		ackd.cbSize = sizeof(ackd);

		// if CRT already present in some activation context then nothing to do
		if ((*mFindActCtxSectionString) 
				(0, NULL, 
				ACTIVATION_CONTEXT_SECTION_DLL_REDIRECTION, 
#if _MSC_VER == 1400
				"msvcr80.dll",
#else
				#error Specify CRT DLL name here !
#endif
				&ackd))
			return;

		// create and use activation context from our own manifest
		ACTCTXA actCtx;
		memset(&actCtx, 0, sizeof(actCtx));
		actCtx.cbSize = sizeof(actCtx);
		actCtx.dwFlags = ACTCTX_FLAG_RESOURCE_NAME_VALID | ACTCTX_FLAG_HMODULE_VALID;
		actCtx.lpResourceName = ISOLATIONAWARE_MANIFEST_RESOURCE_ID;
		actCtx.hModule = hDllInst; 

		if (actCtx.hModule)
		{
			char name[1024];
			GetModuleFileName(actCtx.hModule, name, sizeof(name));
			actCtx.lpSource = name;

			hActCtx = (*mCreateActCtx) (&actCtx);
			if (hActCtx != INVALID_HANDLE_VALUE)
				(*mActivateActCtx) (hActCtx, &mCookie);
		}
	}

	~ContextActivator()
	{
		if (hActCtx != INVALID_HANDLE_VALUE)
		{
			(*mDeactivateActCtx)(0, mCookie);
			(*mReleaseActCtx)(hActCtx);
		}
	}

private:
	WinApiFunction<PFN_FINDAC> mFindActCtxSectionString;
	WinApiFunction<PFN_CAC> mCreateActCtx;
	WinApiFunction<PFN_RAC> mReleaseActCtx;
	WinApiFunction<PFN_AAC> mActivateActCtx;
	WinApiFunction<PFN_DAC> mDeactivateActCtx;
	
	HANDLE		hActCtx;
	ULONG_PTR	mCookie;
};


class Win32Module : public ModuleLoader::Module
{
public:
	Win32Module(HMODULE m) : module(m) {}
	~Win32Module();
	void *findSymbol(const string&);

private:
	HMODULE module;
};

bool ModuleLoader::isLoadableModule(const PathName& module)
{
	ContextActivator ctx;

	LPCSTR pszName = module.c_str();
	HINSTANCE hMod = LoadLibraryEx(pszName, 0,
		LOAD_WITH_ALTERED_SEARCH_PATH | LOAD_LIBRARY_AS_DATAFILE);

	if (hMod) {
		FreeLibrary((HMODULE)hMod);
	}
	return hMod != 0;
}

void ModuleLoader::doctorModuleExtention(Firebird::PathName& name)
{
	PathName::size_type pos = name.rfind(".dll");
	if (pos != PathName::npos && pos == name.length() - 4)
		return;
	name += ".dll";
}

ModuleLoader::Module *ModuleLoader::loadModule(const Firebird::PathName& modPath)
{
	ContextActivator ctx;

	HMODULE module = LoadLibraryEx(modPath.c_str(), 0, LOAD_WITH_ALTERED_SEARCH_PATH);
	if (!module)
		return 0;

	return FB_NEW(*getDefaultMemoryPool()) Win32Module(module);
}

Win32Module::~Win32Module()
{
	if (module)
		FreeLibrary(module);
}

void *Win32Module::findSymbol(const Firebird::string& symName)
{
	FARPROC result = GetProcAddress(module, symName.c_str());
	if (!result)
	{
		string newSym = '_' + symName;
		result = GetProcAddress(module, newSym.c_str());
	}
	return (void*) result;
}