#include <windows.h>
#include <GL/gl.h>
#include <dxgi.h>

#include <cstdio>
#include <cstring>

#include "TSFuncs.hpp"

// Identifies the graphics adapter and only shrinks the shadow map when that
// adapter cannot back the size the quality setting asked for. Shader source
// is left alone: patching it in memory disabled the NVIDIA shader compile.

static char gDescription[160] = "unknown";
static const char *gVendor = "unknown";
static const char *gDescriptionPtr = gDescription;
static int gDedicatedMB = 0;
static int gShadowCap = 8192;
static bool gHaveProfile = false;
static bool gScriptsReady = false;
static bool gPublished = false;
static bool gLogged = false;
static int *gShadowSize = 0;
static int *gShadowCount = 0;
static int gUserSize = 0;
static int gUserCount = 0;
static int gAppliedSize = -1;
static int gAppliedCount = -1;
static int gLimitSize = 0;
static int gLimitCount = 0;
static int gFrameRate = 0;
static int gInRegen = 0;
static bool gSwapHooked = false;
static bool gScaleActive = false;
static bool gWasPaused = false;

static const double kFpsLow = 50.0;
static const double kFpsHigh = 70.0;
static const double kFpsUpMargin = 15.0;
static const double kLowHold = 1.0;
static const double kHighHold = 8.0;
static const double kCooldown = 2.5;
static const double kGainSettle = 2.5;
static const double kStepUpWatch = 1.0;
static const double kStepUpBan = 45.0;

// The FPS gained by lowering shadows is not spare headroom. Raising the map
// again would give that cost back and the counter would jump.
static double gClock = 0.0;
static double gFpsBeforeStep = 0.0;
static double gStepGain = 0.0;
static double gGainReadyAt = 0.0;
static double gStepUpBanUntil = 0.0;
static double gStepUpWatchAt = 0.0;
static bool gHaveGain = false;
static bool gWatchingStepUp = false;

typedef BOOL (WINAPI *SwapBuffersFn)(HDC);
static SwapBuffersFn wglSwapBuffersOriginal = 0;

static const unsigned kVendorNvidia = 0x10DE;
static const unsigned kVendorAmd = 0x1002;
static const unsigned kVendorIntel = 0x8086;

static int powerOfTwoFloor(int value)
{
	int pot = 256;
	while (pot <= 32768 / 2 && pot * 2 <= value)
		pot *= 2;
	return pot;
}

// regenerateShadowMapFBOs allocates one GL_TEXTURE_2D_ARRAY of
// GL_DEPTH_COMPONENT16: width * height * cascades * 2 bytes. 16384x4 is
// exactly 2 GiB. This 32-bit process was given that size and the driver
// returned out of memory, so the cap stays one byte under 2 GiB. 8192x4
// is 512 MB. Also stay under a quarter of dedicated memory and inside
// GL_MAX_TEXTURE_SIZE.
static int maxShadowSize(int dedicatedMB, int layers, int glMax)
{
	int glCap = powerOfTwoFloor(glMax);
	if (glCap < 1024)
		glCap = 8192;
	if (layers < 1)
		layers = 4;

	long long budget = (1ll << 31) - 1;
	if (dedicatedMB > 0) {
		const long long quarter = (long long)dedicatedMB * 1024ll * 1024ll / 4ll;
		if (quarter < budget)
			budget = quarter;
	}

	int size = 1024;
	int best = 1024;
	while (size <= glCap && size <= 32768) {
		const long long bytes = (long long)size * (long long)size * (long long)layers * 2ll;
		if (bytes > budget)
			break;
		best = size;
		if (size > 32768 / 2)
			break;
		size *= 2;
	}
	return best;
}

static bool textHas(const char *text, const char *needle)
{
	return text != 0 && needle != 0 && std::strstr(text, needle) != 0;
}

static void applyProfile(unsigned vendorId, const char *description, int dedicatedMB)
{
	const char *vendor = "unknown";
	int cap = 8192;

	if (dedicatedMB > 0)
		gDedicatedMB = dedicatedMB;
	if (description != 0 && description[0] != '\0' && std::strcmp(description, "unknown") != 0)
		std::snprintf(gDescription, sizeof gDescription, "%s", description);

	if (vendorId == kVendorNvidia || textHas(description, "NVIDIA")) {
		vendor = "NVIDIA";
		cap = 8192;
	}
	else if (vendorId == kVendorAmd || textHas(description, "AMD") || textHas(description, "Radeon") || textHas(description, "ATI")) {
		vendor = "AMD";
		cap = 4096;
	}
	else if (vendorId == kVendorIntel || textHas(description, "Intel")) {
		vendor = "Intel";
		cap = gDedicatedMB >= 4096 ? 4096 : 1024;
		if (gDedicatedMB >= 1536 && gDedicatedMB < 4096)
			cap = 2048;
	}

	if (gDedicatedMB > 0 && gDedicatedMB < 512)
		cap = 1024;
	else if (gDedicatedMB > 0 && gDedicatedMB < 1536 && cap > 2048)
		cap = 2048;

	gVendor = vendor;
	gShadowCap = cap;
	gHaveProfile = vendorId != 0 || textHas(gDescription, "NVIDIA") || textHas(gDescription, "AMD") || textHas(gDescription, "Radeon") || textHas(gDescription, "Intel");
}

static void detectAdapter()
{
	IDXGIFactory *factory = 0;
	if (FAILED(CreateDXGIFactory(IID_IDXGIFactory, (void **)&factory)) || factory == 0)
		return;

	IDXGIAdapter *best = 0;
	DXGI_ADAPTER_DESC bestDesc;
	std::memset(&bestDesc, 0, sizeof bestDesc);
	SIZE_T bestMemory = 0;

	for (UINT index = 0; index < 8; ++index) {
		IDXGIAdapter *adapter = 0;
		if (FAILED(factory->EnumAdapters(index, &adapter)) || adapter == 0)
			break;

		DXGI_ADAPTER_DESC desc;
		std::memset(&desc, 0, sizeof desc);
		if (SUCCEEDED(adapter->GetDesc(&desc)) && desc.DedicatedVideoMemory >= bestMemory) {
			if (best != 0)
				best->Release();
			best = adapter;
			bestDesc = desc;
			bestMemory = desc.DedicatedVideoMemory;
		}
		else
			adapter->Release();
	}

	if (best != 0) {
		char name[128];
		WideCharToMultiByte(CP_UTF8, 0, bestDesc.Description, -1, name, sizeof name, 0, 0);
		int dedicatedMB = (int)(bestDesc.DedicatedVideoMemory / (1024u * 1024u));
		applyProfile(bestDesc.VendorId, name, dedicatedMB);
		best->Release();
	}

	factory->Release();
}

static void refineFromGl()
{
	if (!gHaveProfile)
		detectAdapter();
	if (wglGetCurrentContext() == 0)
		return;

	const char *vendor = (const char *)glGetString(GL_VENDOR);
	const char *renderer = (const char *)glGetString(GL_RENDERER);
	if (vendor != 0 || renderer != 0) {
		const char *who = renderer != 0 ? renderer : vendor;
		unsigned id = 0;
		if (textHas(vendor, "NVIDIA") || textHas(renderer, "NVIDIA"))
			id = kVendorNvidia;
		else if (textHas(vendor, "AMD") || textHas(vendor, "ATI") || textHas(renderer, "Radeon"))
			id = kVendorAmd;
		else if (textHas(vendor, "Intel") || textHas(renderer, "Intel"))
			id = kVendorIntel;
		if (id != 0)
			applyProfile(id, who, gDedicatedMB);
	}

	for (int i = 0; i < 8; ++i) {
		if (glGetError() == GL_NO_ERROR)
			break;
	}

	GLint maxTex = 0;
	glGetIntegerv(GL_MAX_TEXTURE_SIZE, &maxTex);

	GLint dedicatedKB = 0;
	glGetIntegerv(0x9047, &dedicatedKB);
	if (glGetError() != GL_NO_ERROR)
		dedicatedKB = 0;
	if (dedicatedKB > 0) {
		int nvMB = dedicatedKB / 1024;
		if (nvMB > gDedicatedMB)
			gDedicatedMB = nvMB;
	}

	int layers = gUserCount > 0 ? gUserCount : 4;
	int cap = maxShadowSize(gDedicatedMB, layers, (int)maxTex);
	if (cap >= 1024)
		gShadowCap = cap;
}

static void publishVars()
{
	if (gPublished || !gScriptsReady)
		return;

	tsf_AddVar("$ShaderFit::Vendor", &gVendor);
	tsf_AddVar("$ShaderFit::Renderer", &gDescriptionPtr);
	tsf_AddVar("$ShaderFit::DedicatedMB", &gDedicatedMB);
	tsf_AddVar("$ShaderFit::ShadowCap", &gShadowCap);
	tsf_AddVar("$ShaderFit::FrameRate", &gFrameRate);
	gPublished = true;
}

static bool varIsOff(const char *value)
{
	return value != 0 && (value[0] == '0' || std::strcmp(value, "false") == 0);
}

// Off and Minimum both leave the shadow map at size 0. Minimum also keeps the
// shader name "minimum" while Enabled stays on.
static bool shaderModeUsesShadows()
{
	if (gScriptsReady) {
		if (varIsOff(tsf_GetVar("$Shader::Enabled")))
			return false;
		const char *name = tsf_GetVar("$Shader::ShaderName");
		if (name != 0 && std::strcmp(name, "minimum") == 0)
			return false;
	}
	if (gShadowSize == 0 || gShadowCount == 0)
		return false;
	return *gShadowSize > 0 && *gShadowCount > 0;
}

static void resetStepMemory()
{
	gFpsBeforeStep = 0.0;
	gStepGain = 0.0;
	gGainReadyAt = 0.0;
	gStepUpBanUntil = 0.0;
	gStepUpWatchAt = 0.0;
	gHaveGain = false;
	gWatchingStepUp = false;
}

static void pauseShadowScaling()
{
	gLimitSize = 0;
	gLimitCount = 0;
	gScaleActive = false;
	resetStepMemory();
	BlPrintf("%s: shadow scaling paused", PROJECT_NAME);
}

static void rememberUserChoice()
{
	if (gShadowSize == 0 || gShadowCount == 0)
		return;

	int size = *gShadowSize;
	int count = *gShadowCount;
	if (size == gAppliedSize && count == gAppliedCount)
		return;
	gUserSize = size;
	gUserCount = count;
	gLimitSize = 0;
	gLimitCount = 0;
	if (size <= 0) {
		gLimitSize = 0;
		gLimitCount = 0;
		gAppliedSize = size;
		gAppliedCount = count;
	}
}

static void applyShadowLevel()
{
	refineFromGl();
	publishVars();
	if (!gLogged) {
		BlPrintf("%s: %s, %s, %d MB, shadow cap %d",
			PROJECT_NAME, gVendor, gDescription, gDedicatedMB, gShadowCap);
		gLogged = true;
	}
	if (gShadowSize == 0 || gShadowCount == 0)
		return;

	rememberUserChoice();
	if (gUserSize <= 0)
		return;

	int wantSize = gUserSize;
	int wantCount = gUserCount > 0 ? gUserCount : *gShadowCount;
	if (gLimitSize > 0)
		wantSize = gLimitSize;
	if (gLimitCount > 0)
		wantCount = gLimitCount;
	if (wantSize > gShadowCap && wantSize > gUserSize)
		wantSize = gShadowCap;
	if (wantCount < 1)
		wantCount = 1;

	if (*gShadowSize != wantSize)
		*gShadowSize = wantSize;
	if (*gShadowCount != wantCount)
		*gShadowCount = wantCount;
	gAppliedSize = *gShadowSize;
	gAppliedCount = *gShadowCount;
}

static bool stepShadowsDown()
{
	int size = gLimitSize > 0 ? gLimitSize : gUserSize;
	int count = gLimitCount > 0 ? gLimitCount : gUserCount;
	if (size > 1024) {
		int next = size / 2;
		if (next < 1024)
			next = 1024;
		gLimitSize = next;
		gLimitCount = count;
		return true;
	}
	if (count > 1) {
		gLimitSize = size;
		gLimitCount = count - 1;
		return true;
	}
	return false;
}

static bool stepShadowsUp()
{
	int size = gLimitSize > 0 ? gLimitSize : gUserSize;
	int count = gLimitCount > 0 ? gLimitCount : gUserCount;
	if (count < gUserCount)
		count += 1;
	else if (size < gShadowCap) {
		int next = size * 2;
		if (next > gShadowCap)
			next = gShadowCap;
		if (next <= size)
			return false;
		size = next;
	}
	else
		return false;

	if (size == gUserSize && count == gUserCount) {
		gLimitSize = 0;
		gLimitCount = 0;
	}
	else {
		gLimitSize = size;
		gLimitCount = count;
	}
	return true;
}

static void rebuildShadows();
static void regenerateFitted();

static void sampleFrameRate()
{
	static LARGE_INTEGER freq;
	static LARGE_INTEGER last;
	static bool haveLast = false;
	static double avg = 60.0;
	static double warm = 0.0;
	static double lowHold = 0.0;
	static double highHold = 0.0;
	static double cooldown = 0.0;

	if (!shaderModeUsesShadows()) {
		if (gScaleActive) {
			pauseShadowScaling();
			gWasPaused = true;
		}
		haveLast = false;
		warm = 0.0;
		lowHold = 0.0;
		highHold = 0.0;
		cooldown = 0.0;
		avg = 60.0;
		return;
	}
	if (!gScaleActive) {
		gScaleActive = true;
		haveLast = false;
		warm = 0.0;
		lowHold = 0.0;
		highHold = 0.0;
		cooldown = 0.0;
		avg = 60.0;
		if (gWasPaused) {
			gWasPaused = false;
			BlPrintf("%s: shadow scaling resumed", PROJECT_NAME);
		}
	}

	if (freq.QuadPart == 0)
		QueryPerformanceFrequency(&freq);

	LARGE_INTEGER now;
	QueryPerformanceCounter(&now);
	if (!haveLast) {
		last = now;
		haveLast = true;
		return;
	}

	double dt = (double)(now.QuadPart - last.QuadPart) / (double)freq.QuadPart;
	last = now;
	if (dt <= 0.0 || dt > 0.25)
		return;

	warm += dt;
	gClock += dt;
	if (cooldown > 0.0)
		cooldown -= dt;
	avg += ((1.0 / dt) - avg) * 0.1;
	gFrameRate = (int)(avg + 0.5);
	if (gGainReadyAt > 0.0 && gClock >= gGainReadyAt) {
		gStepGain = avg - gFpsBeforeStep;
		if (gStepGain < 0.0)
			gStepGain = 0.0;
		gHaveGain = true;
		gGainReadyAt = 0.0;
	}
	if (warm < 1.0 || cooldown > 0.0 || gUserSize <= 0 || gInRegen != 0)
		return;

	if (gWatchingStepUp && gClock >= gStepUpWatchAt) {
		if (avg < kFpsLow) {
			gWatchingStepUp = false;
			gStepUpBanUntil = gClock + kStepUpBan;
			gStepGain = gFpsBeforeStep - avg;
			if (gStepGain < kFpsUpMargin)
				gStepGain = kFpsUpMargin;
			gHaveGain = true;
			gGainReadyAt = 0.0;
			if (stepShadowsDown()) {
				BlPrintf("%s: keeping this shadow level, raising it fell to %d fps", PROJECT_NAME, gFrameRate);
				lowHold = 0.0;
				highHold = 0.0;
				cooldown = kCooldown;
				rebuildShadows();
			}
			return;
		}
		if (gClock >= gStepUpWatchAt + 3.0) {
			gWatchingStepUp = false;
			gHaveGain = true;
			gStepGain = 0.0;
		}
	}

	if (avg < kFpsLow) {
		lowHold += dt;
		highHold = 0.0;
	}
	else if (avg > kFpsHigh) {
		highHold += dt;
		lowHold = 0.0;
	}
	else {
		lowHold = 0.0;
		highHold = 0.0;
	}

	bool changed = false;
	bool steppedDown = false;
	if (lowHold >= kLowHold) {
		changed = stepShadowsDown();
		steppedDown = changed;
	}
	else if (highHold >= kHighHold && gGainReadyAt == 0.0 && gClock >= gStepUpBanUntil
		&& (!gHaveGain || (avg - gStepGain) >= (kFpsLow + kFpsUpMargin))) {
		changed = stepShadowsUp();
	}
	if (!changed)
		return;

	if (steppedDown) {
		gFpsBeforeStep = avg;
		gHaveGain = false;
		gGainReadyAt = gClock + kGainSettle;
		gWatchingStepUp = false;
	}
	else {
		gFpsBeforeStep = avg;
		gWatchingStepUp = true;
		gStepUpWatchAt = gClock + kStepUpWatch;
		gHaveGain = false;
		gGainReadyAt = 0.0;
	}

	lowHold = 0.0;
	highHold = 0.0;
	cooldown = kCooldown;
	rebuildShadows();
}

static BOOL WINAPI wglSwapBuffersHook(HDC dc)
{
	BOOL ok = wglSwapBuffersOriginal(dc);
	sampleFrameRate();
	return ok;
}

static void installSwapHook()
{
	if (gSwapHooked)
		return;

	HMODULE gl = GetModuleHandleA("opengl32.dll");
	void *target = gl == 0 ? 0 : (void *)GetProcAddress(gl, "wglSwapBuffers");
	if (target == 0)
		return;
	if (MH_CreateHook(target, (void *)wglSwapBuffersHook, (void **)&wglSwapBuffersOriginal) != MH_OK)
		return;
	if (MH_EnableHook(target) != MH_OK)
		return;
	gSwapHooked = true;
}

BlFunctionDef(void, , regenerateShadowMapFBOs);
BlFunctionHookDef(regenerateShadowMapFBOs);

static unsigned char *shaderEnabledFlag()
{
	unsigned char *base = reinterpret_cast<unsigned char *>(GetModuleHandle(NULL));
	return base + (0x7C2142 - 0x400000);
}

static void regenerateFitted()
{
	unsigned char *enabled = shaderEnabledFlag();
	unsigned char wasEnabled = *enabled;
	int tried = gShadowSize != 0 ? *gShadowSize : 0;
	regenerateShadowMapFBOsOriginal();
	if (wasEnabled != 0 && *enabled == 0 && tried > 8192 && gShadowSize != 0) {
		BlPrintf("%s: %d did not fit, keeping 8192", PROJECT_NAME, tried);
		gShadowCap = 8192;
		gLimitSize = 8192;
		*gShadowSize = 8192;
		gAppliedSize = 8192;
		*enabled = 1;
		regenerateShadowMapFBOsOriginal();
	}
}

void regenerateShadowMapFBOsHook()
{
	if (gInRegen != 0) {
		regenerateShadowMapFBOsOriginal();
		return;
	}
	gInRegen += 1;
	installSwapHook();
	applyShadowLevel();
	regenerateFitted();
	gInRegen -= 1;
}

static void rebuildShadows()
{
	if (regenerateShadowMapFBOsOriginal == 0 || gInRegen != 0)
		return;
	gInRegen += 1;
	applyShadowLevel();
	int size = gShadowSize != 0 ? *gShadowSize : 0;
	int count = gShadowCount != 0 ? *gShadowCount : 0;
	BlPrintf("%s: %d fps, shadows %dx%d", PROJECT_NAME, gFrameRate, size, count);
	regenerateFitted();
	gInRegen -= 1;
}

bool init()
{
	if (!tsh_InitInternal())
		return true;

	gScriptsReady = tsf_InitInternal();

	ADDR shadowFn = tsh_ScanFunctionHex((char *)"83 EC 08 56 8B 35 ? ? ? ? FF 15");
	if (shadowFn != 0) {
		gShadowSize = *(int **)(shadowFn + 6);
		gShadowCount = gShadowSize - 1;
		regenerateShadowMapFBOs = (tsh_regenerateShadowMapFBOsFnT)shadowFn;
		BlCreateHook(regenerateShadowMapFBOs);
		BlTestEnableHook(regenerateShadowMapFBOs);
	}

	BlPrintf("%s (v%s): loaded, waiting for the graphics device", PROJECT_NAME, PROJECT_VERSION);
	return true;
}

bool deinit()
{
	if (regenerateShadowMapFBOs != 0)
		MH_DisableHook((void *)regenerateShadowMapFBOs);
	if (gSwapHooked) {
		void *target = (void *)GetProcAddress(GetModuleHandleA("opengl32.dll"), "wglSwapBuffers");
		if (target != 0)
			MH_DisableHook(target);
	}
	return true;
}

bool __stdcall DllMain(HINSTANCE hinstance, unsigned int reason, void *reserved)
{
	(void)hinstance;
	(void)reserved;
	switch (reason) {
		case DLL_PROCESS_ATTACH:
			return init();
		case DLL_PROCESS_DETACH:
			return deinit();
		default:
			return true;
	}
}

extern "C" void __declspec(dllexport) __cdecl PROJECT_EXPORT() {}