#include <iostream>
#include <sstream>
#include <memory>
#include <vector>
#include <unordered_map>
#include <variant>
#include <stdexcept>
#include <functional>
#include <filesystem>
#include <cstring>
#include <cassert>
#include <unistd.h>
#include <X11/Xlib.h>
#include <X11/Xutil.h>
#include <X11/XKBlib.h>
#include "command.h"


std::string trim(const std::string &s) {
	size_t left = 0;
	while (left < s.size() && isspace(s[left])) left++;
	size_t right = s.size() - 1;
	while (right >= left && isspace(s[right])) right--;
	return s.substr(left, right - left + 1);
}

class X_keycode {
public:
	X_keycode() : code{0} {}
	X_keycode(unsigned int code) : code{code} {}
	explicit operator unsigned int() const { return code; }
	bool operator==(X_keycode other) const { return code == other.code; }
private: unsigned int code;
};

template <>
struct std::hash<X_keycode> {
	size_t operator()(X_keycode code) const {
		return std::hash<unsigned int>{}((unsigned int)code);
	}
};

class X_keysym {
public:
	X_keysym() : sym{0} {}
	X_keysym(unsigned int sym) : sym{sym} {}
	explicit operator unsigned int() const { return sym; }
	X_keycode toCode(Display *dpy) const { return XKeysymToKeycode(dpy, sym); }
	bool operator==(X_keysym other) const { return sym == other.sym; }
private: unsigned int sym;
};

template <>
struct std::hash<X_keysym> {
	size_t operator()(X_keysym sym) const {
		return std::hash<unsigned int>{}((unsigned int)sym);
	}
};

void bel(Display *dpy) {
	XkbBell(dpy, None, 100, None);
}

template <typename Cleanup>
class UponExit {
public:
	UponExit(Cleanup cleanup) : cleanup{cleanup} {}
	~UponExit() {
		if (cleanup) (*cleanup)();
	}
	UponExit(const UponExit&) = delete;
	UponExit(UponExit &&other) : cleanup{move(other.cleanup)} {
		other.cleanup.reset();
	}
	UponExit& operator=(const UponExit&) = delete;
	UponExit& operator=(UponExit &&other) {
		cleanup = move(other.cleanup);
		other.cleanup.reset();
	}

private:
	std::optional<Cleanup> cleanup;
};

auto XGrabKeyRAII(Display *dpy, X_keycode code, int modifier, Window win) {
	XGrabKey(dpy, (unsigned int)code, modifier, win, False, GrabModeAsync, GrabModeAsync);
	return UponExit{[dpy, code, modifier, win]() {
		XUngrabKey(dpy, (unsigned int)code, modifier, win);
		XSync(dpy, False);
	}};
}

auto XGrabKeyboardRAII(Display *dpy, Window win) {
	int ret = XGrabKeyboard(dpy, win, False, GrabModeAsync, GrabModeAsync, CurrentTime);
	if (ret == AlreadyGrabbed) {
		XUngrabKeyboard(dpy, CurrentTime);
		XSync(dpy, False);
		throw std::runtime_error("Cannot grab keyboard: already grabbed");
	}
	return UponExit{[dpy]() {
		XUngrabKeyboard(dpy, CurrentTime);
		XSync(dpy, False);
	}};
}

auto XOpenDisplayRAII(const char *name) {
	Display *dpy = XOpenDisplay(name);
	if (dpy == nullptr) {
		std::cerr << "Cannot open X display" << std::endl;
		exit(1);
	}
	return std::make_pair(dpy, UponExit{[dpy]() {
		XCloseDisplay(dpy);
	}});
}

template <typename F>  // return true to stop watch and loop
void globalKeyWatch(Display *dpy, X_keysym headerSym, F callback) {
	const Window root = DefaultRootWindow(dpy);
	const X_keycode headerCode = headerSym.toCode(dpy);

	auto guard = XGrabKeyRAII(dpy, headerCode, AnyModifier, root);

	XSelectInput(dpy, root, KeyPressMask);
	while (true) {
		XEvent ev;
		XNextEvent(dpy, &ev);
		if (ev.type == KeyPress && ev.xkey.keycode == (unsigned int)headerCode) {
			if (callback(ev.xkey)) return;
		}
	}
}

template <typename F>  // return true to lose grab and loop
void globalKeyboardGrab(Display *dpy, F callback) {
	const Window root = DefaultRootWindow(dpy);

	try {
		auto guard = XGrabKeyboardRAII(dpy, root);

		while (true) {
			XEvent ev;
			XNextEvent(dpy, &ev);
			if (ev.type == KeyPress) {
				if (callback(ev.xkey)) return;
			}
		}
	} catch (std::exception &e) {
		std::cerr << e.what() << std::endl;
	}
}

class SeqMatcher {
public:
	using Callback = std::function<void()>;

	struct SymSequence {
		std::vector<X_keysym> syms;
		Callback callback;
	};

	SeqMatcher(Display *dpy) : dpy{dpy} {}

	SeqMatcher(Display *dpy, std::vector<SymSequence> seqs)
			: dpy{dpy} {
		for (const auto &seq : seqs) addSequence(seq.syms, seq.callback);
	}

	void addSequence(const std::vector<X_keysym> &syms, Callback callback) {
		if (syms.empty()) {
			throw std::logic_error("Cannot register empty key sequence");
		}

		Node *current = &rootNode;
		for (X_keysym sym : syms) {
			if (std::holds_alternative<Callback>(current->v)) {
				throw std::logic_error("Overlapping key sequences (second is longer)");
			} else {
				if (!std::holds_alternative<NodeMap>(current->v)) {
					current->v.emplace<NodeMap>();
				}
				NodeMap &map = std::get<NodeMap>(current->v);
				X_keycode code = sym.toCode(dpy);
				auto it = map.find(code);
				if (it != map.end()) {
					current = it->second.get();
				} else {
					current = map.emplace(sym.toCode(dpy), std::make_unique<Node>()).first->second.get();
				}
			}
		}

		if (auto *map = std::get_if<NodeMap>(&current->v)) {
			if (!map->empty()) {
				throw std::logic_error("Overlapping key sequences (second is shorter)");
			}
		}
		if (std::holds_alternative<Callback>(current->v)) {
			throw std::logic_error("Overlapping key sequences (equally long)");
		}
		current->v.emplace<Callback>(callback);
	}

	// Returns bel()-running callback if unrecognised sequence is given
	std::optional<Callback> observe(const XKeyEvent &ev) {
		auto *map = std::get_if<NodeMap>(&curNode->v);
		assert(map);

		auto it = map->find(X_keycode{ev.keycode});
		if (it == map->end()) {
			// Sequence not found
			reset();
			return [dpy = dpy]() { bel(dpy); };
		}

		curNode = it->second.get();

		if (auto *cb = std::get_if<Callback>(&curNode->v)) {
			// Sequence completed
			reset();
			return *cb;
		}

		// Need more keys
		return std::nullopt;
	}

	void reset() {
		curNode = &rootNode;
	}

private:
	struct Node;
	using NodeMap = std::unordered_map<X_keycode, std::unique_ptr<Node>>;
	struct Node {
		std::variant<NodeMap, Callback> v;
	};

	Display *const dpy;
	Node rootNode;
	Node *curNode = &rootNode;
};

namespace sqlite {
	std::vector<std::vector<std::string>> parseCSV(std::string output) {
		std::istringstream ss{output};
		std::vector<std::vector<std::string>> table;

		std::string line;
		while (std::getline(ss, line)) {
			while (!line.empty() && strchr("\r\n", line.back()) != nullptr)
				line.pop_back();

			table.emplace_back();

			if (line.empty()) continue;

			std::vector<std::string> &row = table.back();
			row.emplace_back();
			bool inString = false;
			for (size_t i = 0; i < line.size(); i++) {
				switch (line[i]) {
					case '"':
						if (inString) {
							if (i + 1 < line.size() && line[i+1] == '"') {
								row.back().push_back('"');
								i++;
							} else {
								inString = false;
							}
						} else {
							inString = true;
						}
						break;

					case ',':
						if (inString) {
							row.back().push_back(',');
						} else {
							row.emplace_back();
						}
						break;

					default:
						row.back().push_back(line[i]);
						break;
				}
			}
		}

		return table;
	}
}

namespace got {
	std::string getDBpath() {
		return std::string{getenv("HOME")} + "/.timetrap.db";
	}

	// Returns {sheet, note}
	std::optional<std::pair<std::string, std::string>> getRunning() {
		std::string output = runCommand({"sqlite3", getDBpath(), ".mode csv", "select sheet, note from entries where end is null"});
		auto table = sqlite::parseCSV(move(output));
		if (table.empty()) return std::nullopt;
		else return std::make_pair(table[0][0], table[0][1]);
	}

	std::vector<std::string> getSheets() {
		std::string output = runCommand({"sqlite3", getDBpath(), "select distinct sheet from entries"});
		std::istringstream ss{output};
		std::vector<std::string> lines;
		std::string line;
		while (std::getline(ss, line)) {
			if (line.size() > 0) lines.push_back(move(line));
		}
		std::sort(lines.begin(), lines.end());
		return lines;
	}

	void editRunning(const std::string &descr) {
		runCommand({"got", "edit", descr});
	}

	void checkOut() {
		runCommand({"got", "out"});
	}

	void checkIn(const std::string &sheet) {
		runCommand({"got", "sheet", sheet});
		runCommand({"got", "in"});
	}
}

namespace gui {
	void showNotification(const std::string &message) {
		runCommand({"zenity", "--notification", "--text", message});
	}

	std::optional<std::string> promptText(const std::string &message) {
		auto result = readCommand({"zenity", "--entry", "--text", message});
		if (result.first == 0) return result.second;
		else return std::nullopt;
	}

	std::optional<std::string> chooseList(const std::string &message, const std::string &header, const std::vector<std::string> &options) {
		std::vector<std::string> args{
			"zenity", "--list", "--text", message, "--column", header
		};
		args.insert(args.end(), options.begin(), options.end());
		auto result = readCommand(args);
		if (result.first == 0) return trim(result.second);
		else return std::nullopt;
	}
}

int main(int argc, char **argv) {
	if (argc >= 2 && (strcmp(argv[1], "-h") == 0 || strcmp(argv[1], "--help") == 0)) {
		std::cout <<
			"GUI for GOT (https://github.com/lieuwex/got), which is a rewrite of Timetrap.\n"
			"This thing runs as a daemon; it gets activated with the Pause/Break key on\n"
			"your keyboard. The following sequences trigger actions:\n"
			"  <break> E        -- Edit the note for the currently running activity\n"
			"  <break> I        -- Check into a sheet\n"
			"  <break> O        -- Check out of the current activity\n"
			"  <break> <space>  -- Switch and check into the 'misc' sheet\n"
			"  <break> Q        -- Quit this program (killing it also works of course)\n"
			<< std::flush;
		return 0;
	}

	if (!std::filesystem::exists(got::getDBpath())) {
		std::cerr << "The GOT database (" << got::getDBpath() << ") doesn't exist!" << std::endl;
		std::cerr << "Please run 'got' at least once before using this tool." << std::endl;
		return 1;
	}

	auto dpy_pair = XOpenDisplayRAII(nullptr);
	Display *dpy = dpy_pair.first;

	bool quitRequested = false;

	SeqMatcher matcher{dpy};

	matcher.addSequence({XK_E}, []() {
		if (got::getRunning()) {
			if (auto descr = gui::promptText("Edit currently running entry's text:")) {
				got::editRunning(*descr);
			}
		} else {
			gui::showNotification("Cannot edit if not checked in");
		}
	});

	matcher.addSequence({XK_I}, []() {
		std::vector<std::string> sheets = got::getSheets();
		auto choice = gui::chooseList("Check in", "Sheet", sheets);
		if (choice) {
			auto current = got::getRunning();
			if (current) {
				got::checkOut();
				gui::showNotification("Checked out of sheet '" + current->first + "'");
			}
			got::checkIn(*choice);
			gui::showNotification("Checked in to sheet '" + *choice + "'");
		}
	});

	matcher.addSequence({XK_O}, []() {
		auto current = got::getRunning();
		if (current) {
			got::checkOut();
			gui::showNotification("Checked out of sheet '" + current->first + "'");
		} else {
			gui::showNotification("Cannot check out if not checked in");
		}
	});

	matcher.addSequence({XK_space}, []() {
		if (got::getRunning()) got::checkOut();
		got::checkIn("misc");
		gui::showNotification("Switched to 'misc'");
	});

	matcher.addSequence({XK_Break}, []() {
		auto current = got::getRunning();
		if (!current) {
			gui::showNotification("Currently checked out");
		} else {
			gui::showNotification(
				"Checked into '" + current->first + "'" +
				(current->second.empty() ? current->second : " (" + current->second + ")")
			);
		}
	});

	matcher.addSequence({XK_Q}, [&quitRequested]() {
		gui::showNotification("GOT GUI is quitting");
		quitRequested = true;
	});

	globalKeyWatch(
		dpy, XK_Break,
		[dpy, &matcher, &quitRequested](const XKeyEvent&) -> bool {
			matcher.reset();

			SeqMatcher::Callback cb;

			globalKeyboardGrab(dpy, [&matcher, &cb](const XKeyEvent &ev) -> bool {
				auto opt_cb = matcher.observe(ev);
				if (opt_cb) {
					cb = *opt_cb;
					return true;
				} else {
					return false;
				}
			});

			if (cb) cb();

			return quitRequested;
		}
	);
}