// *****************************************************************************
// Copyright (C) 2017 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 WITH Classpath-exception-2.0
// *****************************************************************************

import { injectable, inject, named } from 'inversify';
import { Disposable } from '../disposable';
import { CommandRegistry, Command } from '../command';
import { ContributionProvider } from '../contribution-provider';
import { CompositeMenuNode, CompositeMenuNodeWrapper } from './composite-menu-node';
import { CompoundMenuNode, MenuAction, MenuNode, MenuPath, MutableCompoundMenuNode, SubMenuOptions } from './menu-types';
import { ActionMenuNode } from './action-menu-node';

export const MenuContribution = Symbol('MenuContribution');

/**
 * Representation of a menu contribution.
 *
 * Note that there are also convenience classes which combine multiple contributions into one.
 * For example to register a view together with a menu and keybinding you could use
 * {@link AbstractViewContribution} instead.
 *
 * ### Example usage
 *
 * ```ts
 * import { MenuContribution, MenuModelRegistry, MAIN_MENU_BAR } from '@theia/core';
 *
 * @injectable()
 * export class NewMenuContribution implements MenuContribution {
 *    registerMenus(menus: MenuModelRegistry): void {
 *         const menuPath = [...MAIN_MENU_BAR, '99_mymenu'];
 *         menus.registerSubmenu(menuPath, 'My Menu');
 *
 *         menus.registerMenuAction(menuPath, {
 *            commandId: MyCommand.id,
 *            label: 'My Action'
 *         });
 *     }
 * }
 * ```
 */
export interface MenuContribution {
    /**
     * Registers menus.
     * @param menus the menu model registry.
     */
    registerMenus(menus: MenuModelRegistry): void;
}

/**
 * The MenuModelRegistry allows to register and unregister menus, submenus and actions
 * via strings and {@link MenuAction}s without the need to access the underlying UI
 * representation.
 */
@injectable()
export class MenuModelRegistry {
    protected readonly root = new CompositeMenuNode('');
    protected readonly independentSubmenus = new Map<string, MutableCompoundMenuNode>();

    constructor(
        @inject(ContributionProvider) @named(MenuContribution)
        protected readonly contributions: ContributionProvider<MenuContribution>,
        @inject(CommandRegistry) protected readonly commands: CommandRegistry
    ) { }

    onStart(): void {
        for (const contrib of this.contributions.getContributions()) {
            contrib.registerMenus(this);
        }
    }

    /**
     * Adds the given menu action to the menu denoted by the given path.
     *
     * @returns a disposable which, when called, will remove the menu action again.
     */
    registerMenuAction(menuPath: MenuPath, item: MenuAction): Disposable {
        const menuNode = new ActionMenuNode(item, this.commands);
        return this.registerMenuNode(menuPath, menuNode);
    }

    /**
     * Adds the given menu node to the menu denoted by the given path.
     *
     * @returns a disposable which, when called, will remove the menu node again.
     */
    registerMenuNode(menuPath: MenuPath | string, menuNode: MenuNode, group?: string): Disposable {
        const parent = this.getMenuNode(menuPath, group);
        return parent.addNode(menuNode);
    }

    getMenuNode(menuPath: MenuPath | string, group?: string): MutableCompoundMenuNode {
        if (typeof menuPath === 'string') {
            const target = this.independentSubmenus.get(menuPath);
            if (!target) { throw new Error(`Could not find submenu with id ${menuPath}`); }
            if (group) {
                return this.findSubMenu(target, group);
            }
            return target;
        } else {
            return this.findGroup(group ? menuPath.concat(group) : menuPath);
        }
    }

    /**
     * Register a new menu at the given path with the given label.
     * (If the menu already exists without a label, iconClass or order this method can be used to set them.)
     *
     * @param menuPath the path for which a new submenu shall be registered.
     * @param label the label to be used for the new submenu.
     * @param options optionally allows to set an icon class and specify the order of the new menu.
     *
     * @returns if the menu was successfully created a disposable will be returned which,
     * when called, will remove the menu again. If the menu already existed a no-op disposable
     * will be returned.
     *
     * Note that if the menu already existed and was registered with a different label an error
     * will be thrown.
     */
    registerSubmenu(menuPath: MenuPath, label: string, options?: SubMenuOptions): Disposable {
        if (menuPath.length === 0) {
            throw new Error('The sub menu path cannot be empty.');
        }
        const index = menuPath.length - 1;
        const menuId = menuPath[index];
        const groupPath = index === 0 ? [] : menuPath.slice(0, index);
        const parent = this.findGroup(groupPath, options);
        let groupNode = this.findSubMenu(parent, menuId, options);
        if (!groupNode) {
            groupNode = new CompositeMenuNode(menuId, label, options, parent);
            return parent.addNode(groupNode);
        } else {
            groupNode.updateOptions({ ...options, label });
            return Disposable.NULL;
        }
    }

    registerIndependentSubmenu(id: string, label: string, options?: SubMenuOptions): Disposable {
        if (this.independentSubmenus.has(id)) {
            console.debug(`Independent submenu with path ${id} registered, but given ID already exists.`);
        }
        this.independentSubmenus.set(id, new CompositeMenuNode(id, label, options));
        return { dispose: () => this.independentSubmenus.delete(id) };
    }

    linkSubmenu(parentPath: MenuPath | string, childId: string | MenuPath, options?: SubMenuOptions, group?: string): Disposable {
        const child = this.getMenuNode(childId);
        const parent = this.getMenuNode(parentPath, group);
        const wrapper = new CompositeMenuNodeWrapper(child, parent, options);
        return parent.addNode(wrapper);
    }

    /**
     * Unregister all menu nodes with the same id as the given menu action.
     *
     * @param item the item whose id will be used.
     * @param menuPath if specified only nodes within the path will be unregistered.
     */
    unregisterMenuAction(item: MenuAction, menuPath?: MenuPath): void;
    /**
     * Unregister all menu nodes with the same id as the given command.
     *
     * @param command the command whose id will be used.
     * @param menuPath if specified only nodes within the path will be unregistered.
     */
    unregisterMenuAction(command: Command, menuPath?: MenuPath): void;
    /**
     * Unregister all menu nodes with the given id.
     *
     * @param id the id which shall be removed.
     * @param menuPath if specified only nodes within the path will be unregistered.
     */
    unregisterMenuAction(id: string, menuPath?: MenuPath): void;
    unregisterMenuAction(itemOrCommandOrId: MenuAction | Command | string, menuPath?: MenuPath): void {
        const id = MenuAction.is(itemOrCommandOrId) ? itemOrCommandOrId.commandId
            : Command.is(itemOrCommandOrId) ? itemOrCommandOrId.id
                : itemOrCommandOrId;

        if (menuPath) {
            const parent = this.findGroup(menuPath);
            parent.removeNode(id);
            return;
        }

        this.unregisterMenuNode(id);
    }

    /**
     * Recurse all menus, removing any menus matching the `id`.
     *
     * @param id technical identifier of the `MenuNode`.
     */
    unregisterMenuNode(id: string): void {
        const recurse = (root: MutableCompoundMenuNode) => {
            root.children.forEach(node => {
                if (CompoundMenuNode.isMutable(node)) {
                    node.removeNode(id);
                    recurse(node);
                }
            });
        };
        recurse(this.root);
    }

    /**
     * Finds a submenu as a descendant of the `root` node.
     * See {@link MenuModelRegistry.findSubMenu findSubMenu}.
     */
    protected findGroup(menuPath: MenuPath, options?: SubMenuOptions): MutableCompoundMenuNode {
        let currentMenu: MutableCompoundMenuNode = this.root;
        for (const segment of menuPath) {
            currentMenu = this.findSubMenu(currentMenu, segment, options);
        }
        return currentMenu;
    }

    /**
     * Finds or creates a submenu as an immediate child of `current`.
     * @throws if a node with the given `menuId` exists but is not a {@link MutableCompoundMenuNode}.
     */
    protected findSubMenu(current: MutableCompoundMenuNode, menuId: string, options?: SubMenuOptions): MutableCompoundMenuNode {
        const sub = current.children.find(e => e.id === menuId);
        if (CompoundMenuNode.isMutable(sub)) {
            return sub;
        }
        if (sub) {
            throw new Error(`'${menuId}' is not a menu group.`);
        }
        const newSub = new CompositeMenuNode(menuId, undefined, options, current);
        current.addNode(newSub);
        return newSub;
    }

    /**
     * Returns the menu at the given path.
     *
     * @param menuPath the path specifying the menu to return. If not given the empty path will be used.
     *
     * @returns the root menu when `menuPath` is empty. If `menuPath` is not empty the specified menu is
     * returned if it exists, otherwise an error is thrown.
     */
    getMenu(menuPath: MenuPath = []): MutableCompoundMenuNode {
        return this.findGroup(menuPath);
    }

    /**
     * Returns the {@link MenuPath path} at which a given menu node can be accessed from this registry, if it can be determined.
     * Returns `undefined` if the `parent` of any node in the chain is unknown.
     */
    getPath(node: MenuNode): MenuPath | undefined {
        const identifiers = [];
        const visited: MenuNode[] = [];
        let next: MenuNode | undefined = node;

        while (next && !visited.includes(next)) {
            if (next === this.root) {
                return identifiers.reverse();
            }
            visited.push(next);
            identifiers.push(next.id);
            next = next.parent;
        }
        return undefined;
    }
}