#define VIRTUAL_MEMORY_BASE ((void*)0x0000010000000000ULL)

void* heap_alloc(u64);
void heap_dealloc(void*);



LRESULT CALLBACK win32_window_proc(HWND passed_window, UINT message, WPARAM wparam, LPARAM lparam) {
	
	if (window._initialized) {
		assert(passed_window == window._os_handle, "Event from another window?? wut (%d)", message);
	}
	
    switch (message) {
        case WM_CLOSE:
            DestroyWindow(window._os_handle);
            break;
        case WM_DESTROY:
            PostQuitMessage(0);
            break;
        default:
            return DefWindowProc(passed_window, message, wparam, lparam);
    }
    return 0;
}


void os_init(u64 program_memory_size) {
	
	SYSTEM_INFO si;
    GetSystemInfo(&si);
	os.granularity = cast(u64)si.dwAllocationGranularity;
	os.page_size = cast(u64)si.dwPageSize;
	
	os.static_memory_start = 0;
	os.static_memory_end = 0;
	
	MEMORY_BASIC_INFORMATION mbi;
    
    
    unsigned char* addr = 0;
    while (VirtualQuery(addr, &mbi, sizeof(mbi))) {
        if (mbi.Type == MEM_IMAGE) {
            if (os.static_memory_start == NULL) {
                os.static_memory_start = mbi.BaseAddress;
            }
            os.static_memory_end = (unsigned char*)mbi.BaseAddress + mbi.RegionSize;
        }
        addr += mbi.RegionSize;
    }


	program_memory_mutex = os_make_mutex();
	os_grow_program_memory(program_memory_size);
	
	Allocator heap_allocator;
	
	heap_allocator.proc = heap_allocator_proc;
	heap_allocator.data = 0;
	
	heap_init();
	context.allocator = heap_allocator;
	
	os.crt = os_load_dynamic_library(const_string("msvcrt.dll"));
	assert(os.crt != 0, "Could not load win32 crt library. Might be compiled with non-msvc? #Incomplete #Portability");
	os.crt_vsnprintf = (Crt_Vsnprintf_Proc)os_dynamic_library_load_symbol(os.crt, const_string("vsnprintf"));
	assert(os.crt_vsnprintf, "Missing vsnprintf in crt");
	os.crt_vprintf = (Crt_Vprintf_Proc)os_dynamic_library_load_symbol(os.crt, const_string("vprintf"));
	assert(os.crt_vprintf, "Missing vprintf in crt");
	os.crt_vsprintf = (Crt_Vsprintf_Proc)os_dynamic_library_load_symbol(os.crt, const_string("vsprintf"));
	assert(os.crt_vsprintf, "Missing vsprintf in crt");
	os.crt_memcpy = (Crt_Memcpy_Proc)os_dynamic_library_load_symbol(os.crt, const_string("memcpy"));
	assert(os.crt_memcpy, "Missing memcpy in crt");
	os.crt_memcmp = (Crt_Memcmp_Proc)os_dynamic_library_load_symbol(os.crt, const_string("memcmp"));
	assert(os.crt_memcmp, "Missing crt_memcmp in crt");
	os.crt_memset = (Crt_Memset_Proc)os_dynamic_library_load_symbol(os.crt, const_string("memset"));
	assert(os.crt_memset, "Missing memset in crt");
	
	window.title = fixed_string("Unnamed Window");
	window.width = 1280;
	window.height = 720;
	window.x = 0;
	window.y = 0;
	window.should_close = false;
	window._initialized = false;
	window.clear_color.r = 0.392f; 
	window.clear_color.g = 0.584f;
	window.clear_color.b = 0.929f;
	window.clear_color.a = 1.0f;
	
	WNDCLASSEX wc = (WNDCLASSEX){0};
    MSG msg;
    HINSTANCE instance = GetModuleHandle(NULL);
    assert(instance != INVALID_HANDLE_VALUE, "Failed getting current HINSTANCE");

    wc.cbSize = sizeof(WNDCLASSEX);
    wc.style = CS_OWNDC;
    wc.lpfnWndProc = win32_window_proc;
    wc.hInstance = instance;
    wc.hIcon = LoadIcon(NULL, IDI_APPLICATION);
    wc.hCursor = LoadCursor(NULL, IDC_ARROW);
    wc.hbrBackground = (HBRUSH)(COLOR_WINDOW + 1);
    wc.lpszClassName = "sigma balls";
    wc.hIconSm = LoadIcon(NULL, IDI_APPLICATION);

	BOOL ok = RegisterClassEx(&wc);
	assert(ok, "Failed registering window class (error code %lu)", GetLastError());
	
	RECT rect = {0, 0, window.width, window.height};
	DWORD style = WS_OVERLAPPEDWINDOW;
	DWORD ex_style = WS_EX_CLIENTEDGE;
	ok = AdjustWindowRectEx(&rect, style, FALSE, ex_style);
	assert(ok != 0, "AdjustWindowRectEx failed with error code %lu", GetLastError());
	
	u32 actual_window_width = rect.right - rect.left;
	u32 actual_window_height = rect.bottom - rect.top;
    // Create the window
    window._os_handle = CreateWindowEx(
        ex_style,
        "sigma balls",
        temp_convert_to_null_terminated_string(window.title),
        style,
        CW_USEDEFAULT, CW_USEDEFAULT, actual_window_width, actual_window_height,
        NULL, NULL, instance, NULL);
    assert(window._os_handle != NULL, "Window creation failed, error: %lu", GetLastError());
	window._initialized = true;
    ShowWindow(window._os_handle, SW_SHOWDEFAULT);
    UpdateWindow(window._os_handle);
    
    
    
    
    
}

bool os_grow_program_memory(u64 new_size) {
	os_lock_mutex(program_memory_mutex); // #Sync
	if (program_memory_size >= new_size) {
		os_unlock_mutex(program_memory_mutex); // #Sync
		return true;
	}

	
	
	bool is_first_time = program_memory == 0;
	
	if (is_first_time) {
		u64 aligned_size = (new_size+os.granularity) & ~(os.granularity);
		void* aligned_base = (void*)(((u64)VIRTUAL_MEMORY_BASE+os.granularity) & ~(os.granularity-1));

		u64 m = aligned_size & os.granularity;
		assert(m == 0);
		
		program_memory = VirtualAlloc(aligned_base, aligned_size, MEM_RESERVE | MEM_COMMIT, PAGE_READWRITE);
		if (program_memory == 0) { 
			os_unlock_mutex(program_memory_mutex); // #Sync
			return false;
		}
		program_memory_size = aligned_size;
	} else {
		void* tail = (u8*)program_memory + program_memory_size;
		u64 m = ((u64)program_memory_size % os.granularity);
		assert(m == 0, "program_memory_size is not aligned to granularity!");
		m = ((u64)tail % os.granularity);
		assert(m == 0, "Tail is not aligned to granularity!");
		u64 amount_to_allocate = new_size-program_memory_size;
		amount_to_allocate = ((amount_to_allocate+os.granularity)&~(os.granularity-1));
		m = ((u64)amount_to_allocate % os.granularity);
		assert(m == 0, "amount_to_allocate is not aligned to granularity!");
		// Just keep allocating at the tail of the current chunk
		void* result = VirtualAlloc(tail, amount_to_allocate, MEM_RESERVE | MEM_COMMIT, PAGE_READWRITE);
		if (result == 0) { 
			os_unlock_mutex(program_memory_mutex); // #Sync
			return false;
		}
		assert(tail == result, "It seems tail is not aligned properly. o nein");
		
		program_memory_size += amount_to_allocate;

		m = ((u64)program_memory_size % os.granularity);
		assert(m == 0, "program_memory_size is not aligned to granularity!");
	}

	
	
	os_unlock_mutex(program_memory_mutex); // #Sync
	return true;
}

Mutex_Handle os_make_mutex() {
	return CreateMutex(0, FALSE, 0);
}
void os_destroy_mutex(Mutex_Handle m) {
	CloseHandle(m);
}
void os_lock_mutex(Mutex_Handle m) {
	DWORD wait_result = WaitForSingleObject(m, INFINITE);
	
	switch (wait_result) {
        case WAIT_OBJECT_0:
            break;

        case WAIT_ABANDONED:
            break;

        default:
        	assert(false, "Unexpected mutex lock result");
            break;
    }
}
void os_unlock_mutex(Mutex_Handle m) {
	BOOL result = ReleaseMutex(m);
	assert(result, "Unlock mutex failed");
}

DWORD WINAPI win32_thread_invoker(LPVOID param) {
	Thread *t = (Thread*)param;
	temporary_storage_init();
	context = t->initial_context;
	t->proc(t);
	return 0;
}

Thread* os_make_thread(Thread_Proc proc) {
	Thread *t = (Thread*)alloc(sizeof(Thread));
	t->id = 0; // This is set when we start it
	t->proc = proc;
	t->initial_context = context;
	
	return t;
}
void os_start_thread(Thread *t) {
	t->os_handle = CreateThread(
        0,
        0,
        win32_thread_invoker,
        t,
        0,
        (DWORD*)&t->id
    );
    
    assert(t->os_handle, "Failed creating thread");
}
void os_join_thread(Thread *t) {
	WaitForSingleObject(t->os_handle, INFINITE);
	CloseHandle(t->os_handle);
}

void os_sleep(u32 ms) {
    Sleep(ms);
}

void os_yield_thread() {
    SwitchToThread();
}

#include <intrin.h>
u64 os_get_current_cycle_count() {
	return __rdtsc();
}

float64 os_get_current_time_in_seconds() {
    LARGE_INTEGER frequency, counter;
    if (!QueryPerformanceFrequency(&frequency) || !QueryPerformanceCounter(&counter)) {
        return -1.0;
    }
    return (double)counter.QuadPart / (double)frequency.QuadPart;
}


Dynamic_Library_Handle os_load_dynamic_library(string path) {
	return LoadLibraryA(temp_convert_to_null_terminated_string(path));
}
void *os_dynamic_library_load_symbol(Dynamic_Library_Handle l, string identifier) {
	return GetProcAddress(l, temp_convert_to_null_terminated_string(identifier));
}
void os_unload_dynamic_library(Dynamic_Library_Handle l) {
	FreeLibrary(l);
}


void os_write_string_to_stdout(string s) {
	HANDLE win32_stdout = GetStdHandle(STD_OUTPUT_HANDLE);
	if (win32_stdout == INVALID_HANDLE_VALUE) return;
	
	WriteFile(win32_stdout, s.data, s.count, 0, NULL);
}

void* os_get_stack_base() {
	NT_TIB* tib = (NT_TIB*)NtCurrentTeb();
    return tib->StackBase;
}
void* os_get_stack_limit() {
	NT_TIB* tib = (NT_TIB*)NtCurrentTeb();
    return tib->StackLimit;
}



Spinlock *os_make_spinlock() {
	Spinlock *l = cast(Spinlock*)alloc(sizeof(Spinlock));
	l->locked = false;
	return l;
}
void os_spinlock_lock(Spinlock *l) {
    while (true) {
        bool expected = false;
        if (os_compare_and_swap_bool(&l->locked, true, expected)) {
            return;
        }
        while (l->locked) {
            // spinny boi
        }
    }
}

void os_spinlock_unlock(Spinlock *l) {
    bool expected = true;
    bool success = os_compare_and_swap_bool(&l->locked, false, expected);
    assert(success, "This thread should have acquired the spinlock but compare_and_swap failed");
}

bool os_compare_and_swap_8(u8 *a, u8 b, u8 old) {
	// #Portability not sure how portable this is.
    return _InterlockedCompareExchange8((volatile CHAR*)a, (CHAR)b, (CHAR)old) == (CHAR)old;
}

bool os_compare_and_swap_16(u16 *a, u16 b, u16 old) {
    return InterlockedCompareExchange16((volatile SHORT*)a, (SHORT)b, (SHORT)old) == (SHORT)old;
}

bool os_compare_and_swap_32(u32 *a, u32 b, u32 old) {
    return InterlockedCompareExchange((volatile LONG*)a, (LONG)b, (LONG)old) == (LONG)old;
}

bool os_compare_and_swap_64(u64 *a, u64 b, u64 old) {
    return InterlockedCompareExchange64((volatile LONG64*)a, (LONG64)b, (LONG64)old) == (LONG64)old;
}

bool os_compare_and_swap_bool(bool *a, bool b, bool old) {
	return os_compare_and_swap_8(cast(u8*)a, cast(u8)b, cast(u8)old);
}


void os_update() {

	static Os_Window last_window;

	if (!strings_match(last_window.title, window.title)) {
		SetWindowText(window._os_handle, temp_convert_to_null_terminated_string(window.title));
	}
	
	BOOL ok;
	int screen_height = GetSystemMetrics(SM_CYSCREEN);
	DWORD style = (DWORD)GetWindowLong(window._os_handle, GWL_STYLE);
	DWORD ex_style = (DWORD)GetWindowLong(window._os_handle, GWL_EXSTYLE);
	if (last_window.x != window.x || last_window.y != window.y || last_window.width != window.width || last_window.y != window.y) {
		RECT update_rect;
		update_rect.left = window.x;
		update_rect.right = window.x + window.width;
		update_rect.bottom = screen_height-(window.y);
		update_rect.top = screen_height-(window.y+window.height);
		ok = AdjustWindowRectEx(&update_rect, style, FALSE, ex_style);
		assert(ok != 0, "AdjustWindowRectEx failed with error code %lu", GetLastError());
		
		u32 actual_x = update_rect.left;
		u32 actual_y = update_rect.top;
		u32 actual_width  = update_rect.right-update_rect.left;
		u32 actual_height = update_rect.bottom-update_rect.top;
		
		SetWindowPos(window._os_handle, 0, actual_x, actual_y, actual_width, actual_height, 0);
	}
	
	RECT client_rect;
	ok = GetClientRect(window._os_handle, &client_rect);
	assert(ok, "GetClientRect failed with error code %lu", GetLastError());
	
	// Convert the client area rectangle top-left corner to screen coordinates
	POINT top_left;
	top_left.x = client_rect.left;
	top_left.y = client_rect.top;
	ok = ClientToScreen(window._os_handle, &top_left);
	assert(ok, "ClientToScreen failed with error code %lu", GetLastError());
	
	// Convert the client area rectangle bottom-right corner to screen coordinates
	POINT bottom_right;
	bottom_right.x = client_rect.right;
	bottom_right.y = client_rect.bottom;
	ok = ClientToScreen(window._os_handle, &bottom_right);
	assert(ok, "ClientToScreen failed with error code %lu", GetLastError());

	
	window.x = (u32)top_left.x;
	window.y = (u32)(screen_height-bottom_right.y);
	window.width  = (u32)(client_rect.right - client_rect.left);
	window.height = (u32)(client_rect.bottom - client_rect.top);
	
	last_window = window;
	
	

	MSG msg;
	while (PeekMessage(&msg, NULL, 0, 0, PM_REMOVE)) {
        if (msg.message == WM_QUIT) {
            window.should_close = true;
            break;
        }
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }
}