// *****************************************************************************
// Copyright (C) 2018 TypeFox and others.
//
// This program and the accompanying materials are made available under the
// terms of the Eclipse Public License v. 2.0 which is available at
// http://www.eclipse.org/legal/epl-2.0.
//
// This Source Code may also be made available under the following Secondary
// Licenses when the conditions for such availability set forth in the Eclipse
// Public License v. 2.0 are satisfied: GNU General Public License, version 2
// with the GNU Classpath Exception which is available at
// https://www.gnu.org/software/classpath/license.html.
//
// SPDX-License-Identifier: EPL-2.0 OR GPL-2.0-only WITH Classpath-exception-2.0
// *****************************************************************************

import { find, toArray } from '@lumino/algorithm';
import { TabBar, Widget, DockPanel, Title } from '@lumino/widgets';
import { Signal } from '@lumino/signaling';
import { Disposable, DisposableCollection } from '../../common/disposable';
import { CorePreferences } from '../../common/core-preferences';
import { Emitter, Event, environment } from '../../common';
import { ToolbarAwareTabBar } from './tab-bars';

export const ACTIVE_TABBAR_CLASS = 'theia-tabBar-active';

export const MAIN_AREA_ID = 'theia-main-content-panel';
export const BOTTOM_AREA_ID = 'theia-bottom-content-panel';

/**
 * This specialization of DockPanel adds various events that are used for implementing the
 * side panels of the application shell.
 */
export class TheiaDockPanel extends DockPanel {

    /**
     * Emitted when a widget is added to the panel.
     */
    readonly widgetAdded = new Signal<this, Widget>(this);
    /**
     * Emitted when a widget is activated by calling `activateWidget`.
     */
    readonly widgetActivated = new Signal<this, Widget>(this);
    /**
     * Emitted when a widget is removed from the panel.
     */
    readonly widgetRemoved = new Signal<this, Widget>(this);

    protected readonly onDidChangeCurrentEmitter = new Emitter<Title<Widget> | undefined>();
    protected disableDND: boolean | undefined = false;
    protected tabWithDNDDisabledStyling?: HTMLElement = undefined;

    get onDidChangeCurrent(): Event<Title<Widget> | undefined> {
        return this.onDidChangeCurrentEmitter.event;
    }

    constructor(options?: DockPanel.IOptions,
        protected readonly preferences?: CorePreferences,
        protected readonly maximizeCallback?: (area: TheiaDockPanel) => void
    ) {
        super(options);
        this.disableDND = TheiaDockPanel.isTheiaDockPanelIOptions(options) && options.disableDragAndDrop;
        this['_onCurrentChanged'] = (sender: TabBar<Widget>, args: TabBar.ICurrentChangedArgs<Widget>) => {
            this.markAsCurrent(args.currentTitle || undefined);
            super['_onCurrentChanged'](sender, args);
        };

        this['_createTabBar'] = () => {
            // necessary for https://github.com/eclipse-theia/theia/issues/15273
            const tabBar = super['_createTabBar']();
            if (tabBar instanceof ToolbarAwareTabBar) {
                tabBar.setDockPanel(this);
            }
            if (this.disableDND) {
                tabBar['tabDetachRequested'].disconnect(this['_onTabDetachRequested'], this);
                tabBar['tabDetachRequested'].connect(this.onTabDetachRequestedWithDisabledDND, this);

                // eslint-disable-next-line @typescript-eslint/no-explicit-any, no-null/no-null
                let dragDataValue: any = null;
                Object.defineProperty(tabBar, '_dragData', {
                    get: () => dragDataValue,
                    // eslint-disable-next-line @typescript-eslint/no-explicit-any
                    set: (value: any) => {
                        dragDataValue = value;
                        // eslint-disable-next-line no-null/no-null
                        if (value === null) {
                            this.onNullTabDragDataWithDisabledDND();
                        }
                    },
                    configurable: true
                });
            }
            return tabBar;
        };
        this['_onTabActivateRequested'] = (sender: TabBar<Widget>, args: TabBar.ITabActivateRequestedArgs<Widget>) => {
            this.markAsCurrent(args.title);
            super['_onTabActivateRequested'](sender, args);
        };
        this['_onTabCloseRequested'] = (sender: TabBar<Widget>, args: TabBar.ITabCloseRequestedArgs<Widget>) => {
            if (TheiaDockPanel.isTheiaDockPanelIOptions(options) && options.closeHandler !== undefined) {
                if (options.closeHandler(sender, args)) {
                    return;
                }
            }
            super['_onTabCloseRequested'](sender, args);
        };
    }

    protected onTabDetachRequestedWithDisabledDND(sender: TabBar<Widget>, args: TabBar.ITabDetachRequestedArgs<Widget>): void {
        // don't process the detach request at all. We still want to support other drag starts, e.g. tab reorder
        // provide visual feedback that DnD is disabled by adding not-allowed class
        const tab = sender.contentNode.children[args.index] as HTMLElement;
        if (tab) {
            tab.classList.add('theia-drag-not-allowed');
            this.tabWithDNDDisabledStyling = tab;
        }
    }

    protected onNullTabDragDataWithDisabledDND(): void {
        if (this.tabWithDNDDisabledStyling) {
            this.tabWithDNDDisabledStyling.classList.remove('theia-drag-not-allowed');
            this.tabWithDNDDisabledStyling = undefined;
        }
    }

    override handleEvent(event: globalThis.Event): void {
        if (this.disableDND) {
            switch (event.type) {
                case 'lm-dragenter':
                case 'lm-dragleave':
                case 'lm-dragover':
                case 'lm-drop':
                    /* no-op */
                    break;
                default:
                    super.handleEvent(event);
            }
        }
        super.handleEvent(event);
    }

    toggleMaximized(): void {
        if (this.maximizeCallback) {
            this.maximizeCallback(this);
        }
    }

    isElectron(): boolean {
        return environment.electron.is();
    }

    protected _currentTitle: Title<Widget> | undefined;
    get currentTitle(): Title<Widget> | undefined {
        return this._currentTitle;
    }

    get currentTabBar(): TabBar<Widget> | undefined {
        return this._currentTitle && this.findTabBar(this._currentTitle);
    }

    findTabBar(title: Title<Widget>): TabBar<Widget> | undefined {
        return find(this.tabBars(), bar => bar.titles.includes(title));
    }

    protected readonly toDisposeOnMarkAsCurrent = new DisposableCollection();
    markAsCurrent(title: Title<Widget> | undefined): void {
        this.toDisposeOnMarkAsCurrent.dispose();
        this._currentTitle = title;
        this.markActiveTabBar(title);
        if (title) {
            const resetCurrent = () => this.markAsCurrent(undefined);
            title.owner.disposed.connect(resetCurrent);
            this.toDisposeOnMarkAsCurrent.push(Disposable.create(() =>
                title.owner.disposed.disconnect(resetCurrent)
            ));
        }
        this.onDidChangeCurrentEmitter.fire(title);
    }

    markActiveTabBar(title?: Title<Widget>): void {
        const tabBars = toArray(this.tabBars());
        tabBars.forEach(tabBar => tabBar.removeClass(ACTIVE_TABBAR_CLASS));
        const activeTabBar = title && this.findTabBar(title);
        if (activeTabBar) {
            activeTabBar.addClass(ACTIVE_TABBAR_CLASS);
        } else if (tabBars.length > 0) {
            // At least one tabbar needs to be active
            tabBars[0].addClass(ACTIVE_TABBAR_CLASS);
        }
    }

    override addWidget(widget: Widget, options?: TheiaDockPanel.AddOptions): void {
        if (this.mode === 'single-document' && widget.parent === this) {
            return;
        }
        super.addWidget(widget, options);
        if (options?.closeRef) {
            options.ref?.close();
        }
        this.widgetAdded.emit(widget);
        this.markActiveTabBar(widget.title);
    }

    override activateWidget(widget: Widget): void {
        super.activateWidget(widget);
        this.widgetActivated.emit(widget);
        this.markActiveTabBar(widget.title);
    }

    protected override onChildRemoved(msg: Widget.ChildMessage): void {
        super.onChildRemoved(msg);
        this.widgetRemoved.emit(msg.child);
    }

    nextTabBarWidget(widget: Widget): Widget | undefined {
        const current = this.findTabBar(widget.title);
        const next = current && this.nextTabBarInPanel(current);
        return next && next.currentTitle && next.currentTitle.owner || undefined;
    }

    nextTabBarInPanel(tabBar: TabBar<Widget>): TabBar<Widget> | undefined {
        const tabBars = toArray(this.tabBars());
        const index = tabBars.indexOf(tabBar);
        if (index !== -1) {
            return tabBars[index + 1];
        }
        return undefined;
    }

    previousTabBarWidget(widget: Widget): Widget | undefined {
        const current = this.findTabBar(widget.title);
        const previous = current && this.previousTabBarInPanel(current);
        return previous && previous.currentTitle && previous.currentTitle.owner || undefined;
    }

    previousTabBarInPanel(tabBar: TabBar<Widget>): TabBar<Widget> | undefined {
        const tabBars = toArray(this.tabBars());
        const index = tabBars.indexOf(tabBar);
        if (index !== -1) {
            return tabBars[index - 1];
        }
        return undefined;
    }

    override dispose(): void {
        super.dispose();
        this.onDidChangeCurrentEmitter.dispose();
        this._currentTitle = undefined;
        this.toDisposeOnMarkAsCurrent.dispose();
    }
}
export namespace TheiaDockPanel {
    export const Factory = Symbol('TheiaDockPanel#Factory');
    export interface Factory {
        (options?: DockPanel.IOptions | TheiaDockPanel.IOptions, maximizeCallback?: (area: TheiaDockPanel) => void): TheiaDockPanel;
    }

    export interface IOptions extends DockPanel.IOptions {
        /** whether drag and drop for tabs should be disabled */
        disableDragAndDrop?: boolean;

        /**
         * @param sender the tab bar
         * @param args the widget (title)
         * @returns true if the request was handled by this handler, false if the tabbar should handle the request
         */
        closeHandler?: (sender: TabBar<Widget>, args: TabBar.ITabCloseRequestedArgs<Widget>) => boolean;
    }

    export function isTheiaDockPanelIOptions(options: DockPanel.IOptions | undefined): options is IOptions {
        if (options === undefined) {
            return false;
        }
        if ('disableDragAndDrop' in options) {
            if (options.disableDragAndDrop !== undefined && typeof options.disableDragAndDrop !== 'boolean') {
                return false;
            }
        }
        if ('closeHandler' in options) {
            if (options.closeHandler !== undefined && typeof options.closeHandler !== 'function') {
                return false;
            }
        }
        return true;
    }

    export interface AddOptions extends DockPanel.IAddOptions {
        /**
         * Whether to also close the widget referenced by `ref`.
         */
        closeRef?: boolean
    }
}