#include "keyboard.h"

#include <QDebug>
#include <QGuiApplication>

// Qt is the worst.
//
// Assume your keyboard has a key labelled both . and >, as they do on US and UK keyboards. Call it the dot key.
// Perform the following:
//	1.	press dot key;
//	2.	press shift key;
//	3.	release dot key;
//	4.	release shift key.
//
// Per empirical testing, and key repeat aside, on both macOS and Ubuntu 19.04 that sequence will result in
// _three_ keypress events, but only _two_ key release events. You'll get presses for Qt::Key_Period, Qt::Key_Greater
// and Qt::Key_Shift. You'll get releases only for Qt::Key_Greater and Qt::Key_Shift.
//
// How can you detect at runtime that Key_Greater and Key_Period are the same physical key?
//
// You can't. On Ubuntu they have the same values for QKeyEvent::nativeScanCode(), which are unique to the key,
// but they have different ::nativeVirtualKey()s.
//
// On macOS they have the same ::nativeScanCode() only because on macOS [almost] all keys have the same
// ::nativeScanCode(). So that's not usable. They have the same ::nativeVirtualKey()s, but since that isn't true
// on Ubuntu, that's also not usable.
//
// So how can you track the physical keys on a keyboard via Qt?
//
// You can't. Qt is the worst. SDL doesn't have this problem, including in X11, but I'm not sure I want the extra
// dependency. I may need to reassess.

#ifdef Q_OS_LINUX
#define HAS_X11
#endif

#ifdef HAS_X11
#include <QX11Info>

#include <X11/Xutil.h>
#include <X11/keysym.h>
#endif

KeyboardMapper::KeyboardMapper() {
#ifdef HAS_X11
	struct DesiredMapping {
		KeySym source;
		Inputs::Keyboard::Key destination;
	};

	constexpr DesiredMapping mappings[] = {
	{XK_Escape, Escape},
	{XK_F1, F1},	{XK_F2, F2},	{XK_F3, F3},	{XK_F4, F4},	{XK_F5, F5},
	{XK_F6, F6},	{XK_F7, F7},	{XK_F8, F8},	{XK_F9, F9},	{XK_F10, F10},
	{XK_F11, F11},	{XK_F12, F12},
	{XK_Sys_Req, PrintScreen},
	{XK_Scroll_Lock, ScrollLock},
	{XK_Pause, Pause},

	{XK_grave, BackTick},
	{XK_1, k1},	{XK_2, k2},	{XK_3, k3},	{XK_4, k4},	{XK_5, k5},
	{XK_6, k6},	{XK_7, k7},	{XK_8, k8},	{XK_9, k9},	{XK_0, k0},
	{XK_minus, Hyphen},
	{XK_equal, Equals},
	{XK_BackSpace, Backspace},

	{XK_Tab, Tab},
	{XK_Q, Q},	{XK_W, W},	{XK_E, E},	{XK_R, R},	{XK_T, T},
	{XK_Y, Y},	{XK_U, U},	{XK_I, I},	{XK_O, O},	{XK_P, P},
	{XK_bracketleft, OpenSquareBracket},
	{XK_bracketright, CloseSquareBracket},
	{XK_backslash, Backslash},

	{XK_Caps_Lock, CapsLock},
	{XK_A, A},	{XK_S, S},	{XK_D, D},	{XK_F, F},	{XK_G, G},
	{XK_H, H},	{XK_J, J},	{XK_K, K},	{XK_L, L},
	{XK_semicolon, Semicolon},
	{XK_apostrophe, Quote},
	{XK_Return, Enter},

	{XK_Shift_L, LeftShift},
	{XK_Z, Z},	{XK_X, X},	{XK_C, C},	{XK_V, V},
	{XK_B, B},	{XK_N, N},	{XK_M, M},
	{XK_comma, Comma},
	{XK_period, FullStop},
	{XK_slash, ForwardSlash},
	{XK_Shift_R, RightShift},

	{XK_Control_L, LeftControl},
	{XK_Control_R, RightControl},
	{XK_Alt_L, LeftOption},
	{XK_Alt_R, RightOption},
	{XK_Meta_L, LeftMeta},
	{XK_Meta_R, RightMeta},
	{XK_space, Space},

	{XK_Left, Left},	{XK_Right, Right},	{XK_Up, Up},	{XK_Down, Down},

	{XK_Insert, Insert},
	{XK_Delete, Delete},
	{XK_Home, Home},
	{XK_End, End},

	{XK_Num_Lock, NumLock},

	{XK_KP_Divide, KeypadSlash},
	{XK_KP_Multiply, KeypadAsterisk},
	{XK_KP_Delete, KeypadDelete},
	{XK_KP_7, Keypad7},	{XK_KP_8, Keypad8},	{XK_KP_9, Keypad9},	{XK_KP_Add, KeypadPlus},
	{XK_KP_4, Keypad4},	{XK_KP_5, Keypad5},	{XK_KP_6, Keypad6},	{XK_KP_Subtract, KeypadMinus},
	{XK_KP_1, Keypad1},	{XK_KP_2, Keypad2},	{XK_KP_3, Keypad3},	{XK_KP_Enter, KeypadEnter},
	{XK_KP_0, Keypad0},
	{XK_KP_Decimal, KeypadDecimalPoint},
	{XK_KP_Equal, KeypadEquals},

	{XK_Help, Help},

	{0}
	};

	const DesiredMapping *mapping = mappings;
	while(mapping->source != 0) {
		const auto sym = XKeysymToKeycode(QX11Info::display(), mapping->source);
		keyByKeySym[sym] = mapping->destination;
		++mapping;
	}
#endif
}

std::optional<Inputs::Keyboard::Key> KeyboardMapper::keyForEvent(QKeyEvent *event) {
	// Workaround for X11: assume PC-esque mapping.

#ifdef HAS_X11
	if(QGuiApplication::platformName() == QLatin1String("xcb")) {
		const auto sym = keyByKeySym.find(event->nativeScancode());
		if(sym == keyByKeySym.end()) return std::nullopt;
		return sym->destination;
	}
#endif

	// Fall back on a limited, faulty adaptation.
#define BIND2(qtKey, clkKey) case Qt::qtKey: return Inputs::Keyboard::Key::clkKey;
#define BIND(key) BIND2(Key_##key, key)

	switch(event->key()) {
		default: return {};

		BIND(Escape);
		BIND(F1);	BIND(F2);	BIND(F3);	BIND(F4);	BIND(F5);	BIND(F6);
		BIND(F7);	BIND(F8);	BIND(F9);	BIND(F10);	BIND(F11);	BIND(F12);
		BIND2(Key_Print, PrintScreen);
		BIND(ScrollLock);	BIND(Pause);

		BIND2(Key_AsciiTilde, BackTick);
		BIND2(Key_1, k1);	BIND2(Key_2, k2);	BIND2(Key_3, k3);	BIND2(Key_4, k4);	BIND2(Key_5, k5);
		BIND2(Key_6, k6);	BIND2(Key_7, k7);	BIND2(Key_8, k8);	BIND2(Key_9, k9);	BIND2(Key_0, k0);
		BIND2(Key_Minus, Hyphen);
		BIND2(Key_Plus, Equals);
		BIND(Backspace);

		BIND(Tab);	BIND(Q);	BIND(W);	BIND(E);	BIND(R);	BIND(T);	BIND(Y);
		BIND(U);	BIND(I);	BIND(O);	BIND(P);
		BIND2(Key_BraceLeft, OpenSquareBracket);
		BIND2(Key_BraceRight, CloseSquareBracket);
		BIND(Backslash);

		BIND(CapsLock);	BIND(A);	BIND(S);	BIND(D);	BIND(F);	BIND(G);
		BIND(H);		BIND(J);	BIND(K);	BIND(L);
		BIND(Semicolon);
		BIND2(Key_Apostrophe, Quote);
		BIND2(Key_QuoteDbl, Quote);
		// TODO: something to hash?
		BIND2(Key_Return, Enter);

		BIND2(Key_Shift, LeftShift);
		BIND(Z);	BIND(X);	BIND(C);	BIND(V);
		BIND(B);	BIND(N);	BIND(M);
		BIND(Comma);
		BIND2(Key_Period, FullStop);
		BIND2(Key_Slash, ForwardSlash);
		// Omitted: right shift.

		BIND2(Key_Control, LeftControl);
		BIND2(Key_Alt, LeftOption);
		BIND2(Key_Meta, LeftMeta);
		BIND(Space);
		BIND2(Key_AltGr, RightOption);

		BIND(Left);	BIND(Right);	BIND(Up);	BIND(Down);

		BIND(Insert); BIND(Home);	BIND(PageUp);	BIND(Delete);	BIND(End);	BIND(PageDown);

		BIND(NumLock);
	}

#undef BIND
#undef BIND2
}