/*************************************************************
 *
 *  Copyright (c) 2019 The MathJax Consortium
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

/**
 * @fileoverview  Implements a subclass of ContextMenu specific to MathJax
 *
 * @author dpvc@mathjax.org (Davide Cervone)
 */

import {MathItem} from '../../core/MathItem.js';
import {MmlNode} from '../../core/MmlTree/MmlNode.js';
import {SelectableInfo} from './SelectableInfo.js';

/*==========================================================================*/

/**
 * The subclass of ContextMenu that handles the needs of the MathJax
 *   contextual menu (in particular, tying it to a MathItem).
 */
export class MJContextMenu extends ContextMenu.ContextMenu {

    /**
     * The MathItem that has posted the menu
     */
    public mathItem: MathItem<HTMLElement, Text, Document> = null;

    /**
     * The annotation selected in the Annotation submenu (neede for the info box to be able to show it)
     */
    public annotation: string = '';

    /**
     * The info box for showing annotations (created by the Menu object that contains this MJContextMenu)
     */
    public showAnnotation: SelectableInfo;

    /**
     * The function to copy the selected annotation (set by the containing Menu item)
     */
    public copyAnnotation: () => void;

    /**
     * The annotation types to look for in a MathItem
     */
    public annotationTypes: {[type: string]: string[]} = {};

    /*======================================================================*/

    /**
     * Before posting the menu, set the name for the ShowAs and CopyToClipboard menus,
     *   enable/disable the semantics check item, and get the annotations for the MathItem
     *
     * @override
     */
    public post(x?:any, y?: number) {
        if (this.mathItem) {
            if (y !== undefined) {
                // FIXME:  handle error output jax
                const input = this.mathItem.inputJax.name;
                const original = this.findID('Show', 'Original');
                original.content = (input === 'MathML' ? 'Original MathML' : input + ' Commands');
                const clipboard = this.findID('Copy', 'Original');
                clipboard.content = original.content;
                const semantics = this.findID('Settings', 'semantics');
                input === 'MathML' ? semantics.disable() : semantics.enable();
                this.getAnnotationMenu();
            }
            super.post(x, y);
        }
    }

    /**
     * Clear the stored MathItem when the menu is removed
     *
     * @override
     */
    public unpost() {
        super.unpost();
        this.mathItem = null;
    }

    /*======================================================================*/

    /**
     * Find an item in the menu (recursively descending into submenus, if needed)
     *
     * @param {string[]} names   The menu IDs to look for
     * @returns {string}         The menu item (or null if not found)
     */
    public findID(...names: string[]) {
        let menu = this as ContextMenu.Menu;
        let item = null as ContextMenu.Item;
        for (const name of names) {
            if (menu) {
                item = menu.find(name);
                menu = (item instanceof ContextMenu.Submenu ? item.getSubmenu() : null);
            } else {
                item = null;
            }
        }
        return item;
    }

    /*======================================================================*/

    /**
     * Look up the annotations in the MathItem and set the ShowAs and CopyToClipboard menus
     */
    protected getAnnotationMenu() {
        const annotations = this.getAnnotations(this.getSemanticNode());
        this.createAnnotationMenu('Show', annotations, () => this.showAnnotation.post());
        this.createAnnotationMenu('Copy', annotations, () => this.copyAnnotation());
    }

    /**
     * Find the top-most semantics element that encloses the contents of the expression (if any)
     *
     * @returns {MmlNode}   The semantics node that was found
     */
    protected getSemanticNode() {
        let node: MmlNode = this.mathItem.root;
        while (node && !node.isKind('semantics'))  {
            if (node.isToken || node.childNodes.length !== 1) return;
            node = node.childNodes[0] as MmlNode;
        }
        return node;
    }

    /**
     * @param {MmlNode} node           The semantics node whose annotations are to be obtained
     * @returns {[string, string][]}   Array of [type, text] where the type is the annotation type
     *                                   and text is the content of the annotation of that type
     */
    protected getAnnotations(node: MmlNode) {
        const annotations = [] as [string, string][];
        if (!node) return annotations;
        for (const child of node.childNodes as MmlNode[]) {
            if (child.isKind('annotation')) {
                const match = this.annotationMatch(child);
                if (match) {
                    const value = child.childNodes.reduce((text, chars) => text + chars.toString(), '');
                    annotations.push([match, value]);
                }
            }
        }
        return annotations;
    }

    /**
     * @param {MmlNode} child    The annotation node to check if its encoding is one of the displayable ones
     * @returns {string}         The annotation type if it does, or null if it doesn't
     */
    protected annotationMatch(child: MmlNode) {
        const encoding = child.attributes.get('encoding') as string;
        for (const type of Object.keys(this.annotationTypes)) {
            if (this.annotationTypes[type].indexOf(encoding) >= 0) {
                return type;
            }
        }
        return null;
    }

    /**
     * Create a submenu from the available annotations and attach it to the proper menu item
     *
     * @param {string} id                        The id of the menu to attach to (Show or Copy)
     * @param {[string, string][]} annotations   The annotations to use for the submenu
     * @param {() => void} action                The action to perform when the annotation is selected
     */
    protected createAnnotationMenu(id: string, annotations: [string, string][], action: () => void) {
        const menu = this.findID(id, 'Annotation') as ContextMenu.Submenu;
        menu.setSubmenu(ContextMenu.SubMenu.parse({
            items: annotations.map(([type, value]) => {
                return {
                    type: 'command',
                    id: type,
                    content: type,
                    action: () => {
                        this.annotation = value;
                        action();
                    }
                };
            }),
            id: 'annotations'
        }, menu));
        if (annotations.length) {
            menu.enable();
        } else {
            menu.disable();
        }
    }

    /*======================================================================*/

}