/*
 * This file is part of budgie-desktop
 *
 * Copyright © 2015-2021 Budgie Desktop Developers
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 */

public class KeyboardLayoutPlugin : Budgie.Plugin, Peas.ExtensionBase {
	public Budgie.Applet get_panel_widget(string uuid) {
		return new KeyboardLayoutApplet();
	}
}

public const string DEFAULT_LOCALE = "en_US";
public const string DEFAULT_LAYOUT = "us";
public const string DEFAULT_VARIANT = "";

errordomain InputMethodError {
	UNKNOWN_IME
}

/**
 * Reflects the ibus-manager in budgie-wm, with very limited functionality,
 * simply to enable us to mimick the behavior over there.
 */
class AppletIBusManager : GLib.Object {
	private HashTable<string,weak IBus.EngineDesc> engines = null;
	private List<IBus.EngineDesc>? enginelist = null;
	private bool did_ibus_init = false;
	private bool ibus_available = true;
	private IBus.Bus? bus = null;

	public AppletIBusManager() {
		Object();
		this.reset_ibus();
	}

	/**
	 * Run init separately so that the owner can connect to the ready() signal
	 */
	public void do_init() {
		this.engines = new HashTable<string,weak IBus.EngineDesc>(str_hash, str_equal);
		if (Environment.find_program_in_path("ibus-daemon") == null) {
			message("ibus-daemon unsupported on this system");
			this.ibus_available = false;
			this.ready();
			return;
		}

		/* Get the bus */
		bus = new IBus.Bus.async();

		/* Hook up basic signals */
		bus.connected.connect(this.ibus_connected);
		bus.disconnected.connect(this.ibus_disconnected);
		bus.set_watch_dbus_signal(true);

		/* Should have ibus running already */
		if (bus.is_connected()) {
			this.ibus_connected();
		}
	}

	public signal void ready();

	/**
	 * Something on ibus changed so we'll reset our state
	 */
	private void reset_ibus() {
		this.engines = new HashTable<string,weak IBus.EngineDesc>(str_hash, str_equal);
	}

	private void on_engines_get(Object? o, AsyncResult? res) {
		try {
			this.enginelist = this.bus.list_engines_async_finish(res);
			this.reset_ibus();
			/* Store reference to the engines */
			foreach (var engine in this.enginelist) {
				this.engines[engine.get_name()] = engine;
			}
		} catch (Error e) {
			message("Failed to get engines: %s", e.message);
			this.reset_ibus();
			return;
		}
		this.ready();
	}

	/**
	 * We gained connection to the ibus daemon
	 */
	private void ibus_connected() {
		/*
		 * Init ibus if necessary, to ensure we have the types available to
		 * glib. After this, try and gain all the engines
		 */
		if (!did_ibus_init) {
			IBus.init();
			did_ibus_init = true;
		}
		this.bus.list_engines_async.begin(-1, null, on_engines_get);
	}

	/**
	 * Lost connection to ibus
	 */
	private void ibus_disconnected() {
		this.reset_ibus();
	}

	/**
	 * Attempt to grab the ibus engine for the given name if it
	 * exists, or returns null
	 */
	public unowned IBus.EngineDesc? get_engine(string name) {
		if (this.engines == null) {
			return null;
		}
		return this.engines.lookup(name);
	}
}

class InputSource {
	public bool xkb = false;
	public string? layout = null;
	public string? variant = null;
	public string? description = null;
	public uint idx = 0;
	public string? ibus_engine = null;

	public InputSource(AppletIBusManager? iman, string id, uint idx, string? layout, string? variant, string? description = null, bool xkb = false) throws Error {
		this.idx = idx;
		this.layout = layout;
		this.variant = variant;
		this.xkb = xkb;

		if (description != null) {
			this.description = description;
		} else {
			this.description = this.layout;
		}

		/* Attempt to fetch engine in the ibus daemon engine list */
		if (iman == null) {
			return;
		}
		var engine = iman.get_engine(id);
		if (engine == null) {
			if (!xkb) {
				throw new InputMethodError.UNKNOWN_IME("Unknown input method: id");
			}
			return;
		}

		/* Get useful display string */
		string? language = Gnome.get_language_from_code(engine.language, null);
		if (language == null) {
			language = Gnome.get_language_from_locale(engine.language, null);
		}
		this.description = "%s (%s)".printf(language, engine.name);

		string? e_variant = engine.layout_variant;
		if (e_variant != null && e_variant.length > 0) {
			this.variant = e_variant;
		}
		this.layout = engine.language;
		this.ibus_engine = id;
	}
}


class InputSourceMenuItem : Gtk.Button {
	private Gtk.Label tick_label;
	public uint idx;

	public InputSourceMenuItem(string? description, uint idx) {
		Object(can_focus: false);

		this.idx = idx;

		set_relief(Gtk.ReliefStyle.NONE);
		set_halign(Gtk.Align.FILL);

		Gtk.Box layout = new Gtk.Box(Gtk.Orientation.HORIZONTAL, 0);
		add(layout);
		Gtk.Label desc_label = new Gtk.Label(description);
		layout.pack_start(desc_label, false, false, 0);
		desc_label.halign = Gtk.Align.START;

		show_all();
		set_no_show_all(true);

		tick_label = new Gtk.Label("  ✓");
		layout.pack_end(tick_label, false, false, 0);
		tick_label.hide();

		get_style_context().add_class("indicator-item");
		get_style_context().add_class("menuitem");

		set_can_focus(false);
	}

	public void set_ticked(bool ticked) {
		if (ticked) {
			tick_label.show();
		} else {
			tick_label.hide();
		}
	}
}

public class KeyboardLayoutApplet : Budgie.Applet {
	private Gtk.EventBox widget;
	private Gtk.EventBox img_wrap;
	private Gtk.Box layout;
	private Gtk.Image img;

	/* Tracking input-source settings */
	private Settings? settings;

	/* Keyboard tracking */
	Array<InputSource> sources;
	InputSource fallback;
	private Gnome.XkbInfo? xkb;

	/* Allow showing ie/gb/ type labels */
	private Gtk.Stack label_stack;

	/* For left click interaction... */
	private Budgie.Popover popover;
	private Gtk.ListBox listbox;
	private Budgie.PopoverManager? manager = null;

	/* ibus interfacing */
	private AppletIBusManager? ibus_manager = null;

	public KeyboardLayoutApplet() {
		/* Graphical stuff */
		widget = new Gtk.EventBox();

		/* Hook up the popover clicks */
		widget.button_press_event.connect((e) => {
			if (e.button != 1) {
				return Gdk.EVENT_PROPAGATE;
			}
			if (popover.get_visible()) {
				popover.hide();
			} else {
				this.manager.show_popover(widget);
			}
			return Gdk.EVENT_STOP;
		});

		get_style_context().add_class("keyboard-indicator");

		/* Layout */
		layout = new Gtk.Box(Gtk.Orientation.HORIZONTAL, 0);
		widget.add(layout);

		/* Image */
		img = new Gtk.Image.from_icon_name("input-keyboard-symbolic", Gtk.IconSize.MENU);
		img_wrap = new Gtk.EventBox();
		img_wrap.add(img);
		layout.pack_start(img_wrap, false, false, 0);
		add(widget);

		/* Stack o' labels */
		label_stack = new Gtk.Stack();
		label_stack.set_transition_type(Gtk.StackTransitionType.SLIDE_UP_DOWN);
		layout.pack_start(label_stack, false, false, 0);

		/* Popover menu magicks */
		popover = new Budgie.Popover(img_wrap);
		popover.get_style_context().add_class("user-menu");
		listbox = new Gtk.ListBox();
		listbox.set_can_focus(false);
		listbox.set_selection_mode(Gtk.SelectionMode.NONE);
		listbox.get_style_context().add_class("content-box");
		popover.add(listbox);
		popover.get_child().show_all();

		/* Settings/init */
		xkb = new Gnome.XkbInfo();
		settings = new Settings("org.gnome.desktop.input-sources");

		/* Hook up the ibus manager */
		this.ibus_manager = new AppletIBusManager();
		update_fallback();
		this.ibus_manager.ready.connect(this.on_ibus_ready);
		this.ibus_manager.do_init();

		/* Go show up */
		show_all();
	}

	public override void panel_position_changed(Budgie.PanelPosition position) {
		Gtk.Orientation orient = Gtk.Orientation.HORIZONTAL;
		int margin = 4;
		if (position == Budgie.PanelPosition.LEFT || position == Budgie.PanelPosition.RIGHT) {
			orient = Gtk.Orientation.VERTICAL;
			margin = 0;
		}
		img.set_margin_end(margin);
		this.layout.set_orientation(orient);
	}

	/**
	 * Only begin listing sources and such when ibus becomes available
	 * or we explicitly find it won't work
	 */
	private void on_ibus_ready() {
		settings.changed.connect(on_settings_changed);

		/* Forcibly init ourselves */
		on_settings_changed("sources");
		on_settings_changed("current");
	}

	/**
	 * Tell the WM to change the keyboard to the current selection
	 */
	private void on_row_activate(Gtk.Button item) {
		var btn = item as InputSourceMenuItem;
		uint idx = btn.idx;

		this.settings.set_uint("current", idx);
		popover.hide();
	}

	/**
	 * Reset the menu/stack
	 */
	private void reset_keyboards() {
		foreach (Gtk.Widget child in label_stack.get_children()) {
			child.destroy();
		}
		foreach (Gtk.Widget child in listbox.get_children()) {
			child.destroy();
		}

		for (int i = 0; i < sources.length; i++) {
			var kbinfo = sources.index(i);

			/* Firstly we create our display label.. */
			Gtk.EventBox wrap = new Gtk.EventBox();
			Gtk.Label displ_label = new Gtk.Label(kbinfo.layout.up());
			wrap.add(displ_label);
			displ_label.set_halign(Gtk.Align.FILL);
			wrap.get_style_context().add_class("keyboard-label");

			/* Pack the display label */
			label_stack.add_named(wrap, kbinfo.idx.to_string());
			wrap.show_all();

			/* Add a menu item in the popover.. */
			InputSourceMenuItem menu_label = new InputSourceMenuItem(kbinfo.description, kbinfo.idx);
			menu_label.clicked.connect(on_row_activate);
			menu_label.show_all();

			listbox.add(menu_label);
		}
	}

	private void on_settings_changed(string key) {
		if (key == "sources") {
			update_sources();
		} else if (key == "current") {
			update_current();
		}
	}

	/*
	 * Reset InputSource list and produce something consumable by xkb
	 *
	 * TODO: Share code between WM and plugin in private Budgie library in
	 * the C rewrite, this is a joke now.
	 */
	void update_sources() {
		sources = null;
		sources = new Array<InputSource>();

		var val = settings.get_value("sources");
		for (size_t i = 0; i < val.n_children(); i++) {
			InputSource? source = null;
			string? id = null;
			string? type = null;

			val.get_child(i, "(ss)", out id, out type);

			try {
				if (id == "xkb") {
					string[] spl = type.split("+");
					string? variant = "";
					if (spl.length > 1) {
						variant = spl[1];
					}
					string desc = this.get_xkb_description(type);
					source = new InputSource(this.ibus_manager, type, (uint)i, spl[0], variant, desc, true);
					sources.append_val(source);
				} else {
					source = new InputSource(this.ibus_manager, type, (uint)i, null, null, null, false);
					sources.append_val(source);
				}
			} catch (Error e) {
				message("Error adding source %s|%s: %s", id, type, e.message);
			}
		}

		if (sources.length == 0) {
			/* Always add fallback last, at the very worst it's the only available
			 * source and we use the locale guessed source */
			fallback.idx = sources.length;
			sources.append_val(fallback);
		}

		this.reset_keyboards();
	}

	private string get_xkb_description(string id) {
		string display_name, short_name, xkb_layout, xkb_variant = null;
		if (xkb.get_layout_info(id, out display_name, out short_name, out xkb_layout, out xkb_variant)) {
			return display_name;
		}
		return id;
	}

	void update_fallback() {
		string? type = null;
		string? id = null;
		string? locale = Intl.get_language_names()[0];
		string? display_name = null;
		string? short_name = null;
		string? xkb_layout = null;
		string? xkb_variant = null;

		if (!locale.contains("_")) {
			locale = DEFAULT_LOCALE;
		}

		if (!Gnome.get_input_source_from_locale(locale, out type, out id)) {
			Gnome.get_input_source_from_locale(DEFAULT_LOCALE, out type, out id);
		}

		try {
			if (xkb.get_layout_info(id, out display_name, out short_name, out xkb_layout, out xkb_variant)) {
				fallback = new InputSource(this.ibus_manager, id, 0, xkb_layout, xkb_variant, display_name, true);
			} else {
				fallback = new InputSource(this.ibus_manager, id, 0, DEFAULT_LAYOUT, DEFAULT_VARIANT, null, true);
			}
		} catch (Error e) {
			message("Error updating fallback source %s: %s", id, e.message);
		}
	}

	/**
	 * Update our knowledge of the currently selected keyboard layout
	 */
	private void update_current() {
		uint id = settings.get_uint("current");
		/* Safety: Check we have this guy :] */
		Gtk.Widget? child = label_stack.get_child_by_name(id.to_string());
		if (child == null) {
			message("WARNING: Missing child in layout!!");
			return;
		}

		/* Use fake menu item selection effect */
		foreach (Gtk.Widget? row in listbox.get_children()) {
			InputSourceMenuItem item = ((Gtk.Bin)row).get_child() as InputSourceMenuItem;
			if (item.idx == id) {
				item.set_ticked(true);
			} else {
				item.set_ticked(false);
			}
		}
		/* Update to the new kid */
		label_stack.set_visible_child(child);
	}

	public override void update_popovers(Budgie.PopoverManager? manager) {
		this.manager = manager;
		manager.register_popover(widget, popover);
	}
}

[ModuleInit]
public void peas_register_types(TypeModule module) {
	// boilerplate - all modules need this
	var objmodule = module as Peas.ObjectModule;
	objmodule.register_extension_type(typeof(Budgie.Plugin), typeof(KeyboardLayoutPlugin));
}
