#include <iostream>
#include <vector>
#include <string>
#include <optional>
#include <utility>
#include <cstring>
#include "xutil.h"
#include "keysym_table.h"


namespace {
	void usage(const char *argv0) {
		std::cerr
			<< "Usage:\n"
			<< "  " << argv0 << " --which\n"
			<< "  " << argv0 << " <key>\n"
			<< "  " << argv0 << " [<key> <output> | s:<keysym> <output> | c:<keycode> <output>]*\n"
			<< "\n"
			<< "Keys are specified with the X11 keysym name, its keysym ID (prefixed with 's:'),\n"
			<< "or its keycode (prefixed with 'c:'). The keycode is typically non-portable\n"
			<< "because it depends on the particular keyboard hardware.\n"
			<< "xev(1) prints the keysym name and the keysym ID (in hexadecimal).\n"
			<< "Keysym IDs and keycodes can be given in decimal and in hexadecimal (with 0x).\n"
			<< "Examples:\n"
			<< "- KP_1 and s:0xffb1 are valid key values for the '1' key on the numpad.\n"
			<< "- XF86Launch7 and s:0x1008ff47 are valid key values for F16 on an Apple keyboard.\n"
			<< "The values can also be found in /usr/include/xkbcommon/xkbcommon-keysyms.h .\n"
			<< "\n"
			<< "If a single key is given, the program grabs that key and exits when the key is\n"
			<< "pressed. If multiple keys are given, the output string corresponding to the\n"
			<< "pressed key will be printed before exiting.\n"
			<< "\n"
			<< "In --which mode, the program will grab the entire keyboard, wait until the first\n"
			<< "pressed key, and print its keycode for use with 'c:'.\n"
			;
	}

	std::vector<std::pair<x::Keycode, std::string>> parse_watchlist(Display *dpy, int argc, char **argv) {
		std::vector<std::pair<x::Keycode, std::string>> watchlist;

		if (argc <= 1) {
			usage(argv[0]);
			exit(1);
		}

		for (int i = 1; i < argc; i++) {
			if (strcmp(argv[i], "--help") == 0 || strcmp(argv[i], "-h") == 0) {
				usage(argv[0]);
				exit(0);
			}

			std::optional<x::Keycode> mcode;

			if ((argv[i][0] == 's' || argv[i][0] == 'c') && argv[i][1] == ':') {
				unsigned number;
				if (argv[i][2] == '0' && argv[i][3] == 'x') {
					char *endp;
					number = strtol(argv[i] + 2, &endp, 16);
					if (argv[i][2] == '\0' || *endp != '\0') {
						std::cerr << "Invalid hexadecimal number in '" << argv[i] << "'\n";
						exit(1);
					}
				} else {
					char *endp;
					number = strtol(argv[i] + 2, &endp, 10);
					if (argv[i][2] == '\0' || *endp != '\0') {
						std::cerr << "Invalid decimal number in '" << argv[i] << "'\n";
						exit(1);
					}
				}
				if (argv[i][0] == 's') mcode = x::Keysym{number}.toCode(dpy);
				else mcode = x::Keycode{number};
			}

			if (!mcode) {
				for (size_t j = 0; j < keysym_table.size(); j++) {
					if (strcmp(argv[i], keysym_table[j].first) == 0) {
						mcode = keysym_table[j].second.toCode(dpy);
						break;
					}
				}
			}

			if (!mcode) {
				std::cerr << "Unknown key name '" << argv[i] << "'\n";
				exit(1);
			}

			std::string output;
			if (i == 1 && argc == 2) {
				// empty output
			} else if (i >= argc - 1) {
				std::cerr << "Missing output for key '" << argv[i] << "'\n";
				exit(1);
			} else {
				output = argv[i+1];
				i++;  // skip output
			}

			watchlist.emplace_back(*mcode, std::move(output));
		}

		return watchlist;
	}
}

int main(int argc, char **argv) {
	auto dpypair = x::XOpenDisplayRAII(nullptr);
	Display *dpy = dpypair.first;

	if (argc >= 2 && strcmp(argv[1], "--which") == 0) {
		x::globalKeyboardGrab(dpy, [](const XKeyEvent &ev) -> bool {
			std::cout << "c:" << ev.keycode << std::endl;
			return true;
		});
		return 0;
	}

	std::vector<std::pair<x::Keycode, std::string>> watchlist = parse_watchlist(dpy, argc, argv);

	Window root = DefaultRootWindow(dpy);

	std::vector<x::UponExit<std::function<void()>>> cleaners;
	cleaners.reserve(watchlist.size());

	for (const auto &p : watchlist) {
		cleaners.push_back(x::XGrabKeyRAII(dpy, p.first, AnyModifier, root));
	}

	XSelectInput(dpy, root, KeyPressMask);
	while (true) {
		XEvent ev;
		XNextEvent(dpy, &ev);
		if (ev.type != KeyPress) continue;
		for (const auto &p : watchlist) {
			if (ev.xkey.keycode == (unsigned int)p.first) {
				if (p.second.size() > 0) std::cout << p.second << std::endl;
				return 0;
			}
		}
	}
}