// My annotated and cut down js/ui/panel.js from gnome-shell/47.rc.
// All annotations are what I guessed, interpreted and copied while reading the
// code and comparing to other panel.js versions and might be wrong. They are
// prefixed with "Annotation:" to indicate that they're my comments, not
// comments that orginally existed.

// Taken from: https://gitlab.gnome.org/GNOME/gnome-shell/-/blob/47.rc/js/ui/panel.js
// On: 2024-09-12
// License: This code is licensed under GPLv2.

// Taken from: https://gitlab.gnome.org/GNOME/gnome-shell/-/blob/47.rc/js/ui/sessionMode.js
// On: 2023-09-12
// License: This code is licensed under GPLv2.

// I'm using the word "item" to refer to the thing, which gets added to the top
// (menu)bar / panel, where an item has a role/name and an indicator.

// Annotation: [...] Cut out bunch of stuff here, which isn't relevant for this
// Extension.

import Clutter from 'gi://Clutter';

// Annotation: [...] Cut out bunch of stuff here, which isn't relevant for this
// Extension.

import GObject from 'gi://GObject';

// Annotation: [...] Cut out bunch of stuff here, which isn't relevant for this
// Extension.

import St from 'gi://St';

// Annotation: [...] Cut out bunch of stuff here, which isn't relevant for this
// Extension.

import * as CtrlAltTab from './ctrlAltTab.js';

// Annotation: [...] Cut out bunch of stuff here, which isn't relevant for this
// Extension.

import * as PopupMenu from './popupMenu.js';
import * as PanelMenu from './panelMenu.js';

// Annotation: [...] Cut out bunch of stuff here, which isn't relevant for this
// Extension.

import * as Main from './main.js';

// Annotation: [...] Cut out bunch of stuff here, which isn't relevant for this
// Extension.

import {DateMenuButton} from './dateMenu.js';
import {ATIndicator} from './status/accessibility.js';
import {InputSourceIndicator} from './status/keyboard.js';
import {DwellClickIndicator} from './status/dwellClick.js';
import {ScreenRecordingIndicator, ScreenSharingIndicator} from './status/remoteAccess.js';

// Annotation: [...] Cut out bunch of stuff here, which isn't relevant for this
// Extension.

// Of note (for PANEL_ITEM_IMPLEMENTATIONS):
// const AppMenuButton = [...]
// const ActivitiesButton = [...]
// const QuickSettings = [...]

const PANEL_ITEM_IMPLEMENTATIONS = {
    'activities': ActivitiesButton,
    'appMenu': AppMenuButton,
    'quickSettings': QuickSettings,
    'dateMenu': DateMenuButton,
    'a11y': ATIndicator,
    'keyboard': InputSourceIndicator,
    'dwellClick': DwellClickIndicator,
    'screenRecording': ScreenRecordingIndicator,
    'screenSharing': ScreenSharingIndicator,
};

export const Panel = GObject.registerClass(
class Panel extends St.Widget {
    // Annotation: Initializes the top (menu)bar / panel.
    // Does relevant stuff like:
    // - Defining this._leftBox, this._centerBox and this._rightBox.
    // - Finally calling this._updatePanel().
    // Compared to panel_46.4_2024-09-11.js: Nothing changed.
    _init() {
        super._init({
            name: 'panel',
            reactive: true,
        });

        this.set_offscreen_redirect(Clutter.OffscreenRedirect.ALWAYS);

        this._sessionStyle = null;

        this.statusArea = {};

        this.menuManager = new PopupMenu.PopupMenuManager(this);

        this._leftBox = new St.BoxLayout({name: 'panelLeft'});
        this.add_child(this._leftBox);
        this._centerBox = new St.BoxLayout({name: 'panelCenter'});
        this.add_child(this._centerBox);
        this._rightBox = new St.BoxLayout({name: 'panelRight'});
        this.add_child(this._rightBox);

        this.connect('button-press-event', this._onButtonPress.bind(this));
        this.connect('touch-event', this._onTouchEvent.bind(this));

        Main.overview.connectObject('showing',
            () => this.add_style_pseudo_class('overview'),
            this);
        Main.overview.connectObject('hiding',
            () => this.remove_style_pseudo_class('overview'),
            this);

        Main.layoutManager.panelBox.add_child(this);
        Main.ctrlAltTabManager.addGroup(this,
            _('Top Bar'), 'shell-focus-top-bar-symbolic',
            {sortGroup: CtrlAltTab.SortGroup.TOP});

        Main.sessionMode.connect('updated', this._updatePanel.bind(this));

        global.display.connect('workareas-changed', () => this.queue_relayout());
        this._updatePanel();
    }

    // Annotation: [...] Cut out bunch of stuff here, which isn't relevant for
    // this Extension.

    // Annotation: Gets called by this._init() to populate the top (menu)bar /
    // panel initially.
    //
    // It does the following relevant stuff:
    // - Calls this._hideIndicators()
    // - Calls this._updateBox() for this._leftBox, this._centerBox and
    //   this._rightBox with panel.left, panel.center and panel.right to
    //   populate the boxes with items defined in panel.left, panel.center and
    //   panel.right.
    //
    //   panel.left, panel.center and panel.right get set via the line let panel
    //   = Main.sessionMode.panel, which uses the panel of Mains (js/ui/main.js)
    //   instance of SessionMode (js/ui/sessionMode.js).
    //
    //   And in js/ui/sessionMode.js (47.rc, 2024-09-12) you have different modes
    //   with different panel configuration. For example the "user" mode with:
    //   panel: {
    //       left: ['activities'],
    //       center: ['dateMenu'],
    //       right: ['screenRecording', 'screenSharing', 'dwellClick', 'a11y', 'keyboard', 'quickSettings'],
    //   }
    //
    //   This way this function populates the top (menu)bar / panel with the
    //   default stuff you see on a fresh Gnome.
    //
    // Compared to panel_46.4_2024-09-11.js: Nothing changed.
    _updatePanel() {
        let panel = Main.sessionMode.panel;
        this._hideIndicators();
        this._updateBox(panel.left, this._leftBox);
        this._updateBox(panel.center, this._centerBox);
        this._updateBox(panel.right, this._rightBox);

        if (panel.left.includes('dateMenu'))
            Main.messageTray.bannerAlignment = Clutter.ActorAlign.START;
        else if (panel.right.includes('dateMenu'))
            Main.messageTray.bannerAlignment = Clutter.ActorAlign.END;
        // Default to center if there is no dateMenu
        else
            Main.messageTray.bannerAlignment = Clutter.ActorAlign.CENTER;

        if (this._sessionStyle)
            this.remove_style_class_name(this._sessionStyle);

        this._sessionStyle = Main.sessionMode.panelStyle;
        if (this._sessionStyle)
            this.add_style_class_name(this._sessionStyle);
    }

    // Annotation: This function hides all items, which are in the top (menu)bar
    // panel and in PANEL_ITEM_IMPLEMENTATIONS.
    //
    // Compared to panel_46.4_2024-09-11.js: Nothing changed.
    _hideIndicators() {
        for (let role in PANEL_ITEM_IMPLEMENTATIONS) {
            let indicator = this.statusArea[role];
            if (!indicator)
                continue;
            indicator.container.hide();
        }
    }

    // Annotation: This function takes a role (of an item) and returns a
    // corresponding indicator, if either of two things are true:
    // - The indicator is already in this.statusArea.
    //   Then it just returns the indicator by using this.statusArea.
    // - The role is in PANEL_ITEM_IMPLEMENTATIONS.
    //   Then it creates a new indicator, adds it to this.statusArea and returns
    //   it.
    //
    // Compared to panel_46.4_2024-09-11.js: Nothing changed.
    _ensureIndicator(role) {
        let indicator = this.statusArea[role];
        if (!indicator) {
            let constructor = PANEL_ITEM_IMPLEMENTATIONS[role];
            if (!constructor) {
                // This icon is not implemented (this is a bug)
                return null;
            }
            indicator = new constructor(this);
            this.statusArea[role] = indicator;
        }
        return indicator;
    }

    // Annotation: This function takes a list of items (or rather their roles)
    // and adds the indicators of those items to a box (like this._leftBox)
    // using this._ensureIndicator() to get the indicator corresponding to the
    // given role.
    // So only items with roles this._ensureIndicator() knows, get added.
    //
    // Compared to panel_46.4_2024-09-11.js: Nothing changed.
    _updateBox(elements, box) {
        let nChildren = box.get_n_children();

        for (let i = 0; i < elements.length; i++) {
            let role = elements[i];
            let indicator = this._ensureIndicator(role);
            if (indicator == null)
                continue;

            this._addToPanelBox(role, indicator, i + nChildren, box);
        }
    }

    // Annotation: This function adds the given item to the specified top
    // (menu)bar / panel box and connects to "destroy" and "menu-set" events.
    //
    // It takes the following arguments:
    // - role: The name of the item to add.
    // - indicator: The indicator of the item to add.
    // - position: Where in the box to add the item.
    // - box: The box to add the item to.
    //   Can be one of the following:
    //   -  this._leftBox
    //   -  this._centerBox
    //   -  this._rightBox
    //
    // Compared to panel_46.4_2024-09-11.js: Nothing changed.
    _addToPanelBox(role, indicator, position, box) {
        let container = indicator.container;
        container.show();

        let parent = container.get_parent();
        if (parent)
            parent.remove_child(container);


        box.insert_child_at_index(container, position);
        this.statusArea[role] = indicator;
        let destroyId = indicator.connect('destroy', emitter => {
            delete this.statusArea[role];
            emitter.disconnect(destroyId);
        });
        indicator.connect('menu-set', this._onMenuSet.bind(this));
        this._onMenuSet(indicator);
    }

    // Annotation: This function allows you to add an item to the top (menu)bar
    // / panel.
    // While per default it adds the item to the status area (the right box of
    // the top bar), you can specify the box and add the item to any of the
    // three boxes of the top bar.
    // To add an item to the top bar, you need to give its role and indicator.
    //
    // This function takes the following arguments:
    // - role: A name for the item to add.
    // - indicator: The indicator for the item to add (must be an instance of
    //   PanelMenu.Button).
    // - position: Where in the box to add the item.
    // - box: The box to add the item to.
    //   Can be one of the following:
    //   - "left": referring to this._leftBox
    //   - "center": referring to this._centerBox
    //   - "right": referring to this._rightBox
    //   These boxes are what you see in the top bar as the left, right and
    //   center sections.
    //
    // Finally this function just calls this._addToPanelBox() for the actual
    // work, so it basically just makes sure the input to this._addToPanelBox()
    // is correct.
    //
    // Compared to panel_46.4_2024-09-11.js: Nothing changed.
    addToStatusArea(role, indicator, position, box) {
        if (this.statusArea[role])
            throw new Error(`Extension point conflict: there is already a status indicator for role ${role}`);

        if (!(indicator instanceof PanelMenu.Button))
            throw new TypeError('Status indicator must be an instance of PanelMenu.Button');

        position ??= 0;
        let boxes = {
            left: this._leftBox,
            center: this._centerBox,
            right: this._rightBox,
        };
        let boxContainer = boxes[box] || this._rightBox;
        this.statusArea[role] = indicator;
        this._addToPanelBox(role, indicator, position, boxContainer);
        return indicator;
    }

    // Of note:
    // _onMenuSet(indicator) { [...] } 

    // Annotation: [...] Cut out bunch of stuff here, which isn't relevant for
    // this Extension.
});