import App       from /**/"./App.js";
import Component from /**/"./Component.js";
import Group     from /**/"./Group.js";
import MenuBar   from /**/"./MenuBar.js";
import MenuItem  from /**/"./MenuItem.js";

// Pseudo environment context
let _package = {};

// GUI widget toolkit root
class Toolkit {

    //////////////////////////////// Constants ////////////////////////////////

    // Event keys
    static group  = Symbol(); // Events emitted by Toolkit.Group
    static target = Symbol(); // Event target as a Toolkit.Component



    ///////////////////////// Initialization Methods //////////////////////////

    Toolkit() { throw new Error("Cannot be instantiated."); }

    static {

        // Environment members
        Object.assign(_package, {
            componentKey: Symbol("Toolkit component"),
            darkQuery   : window.matchMedia("(prefers-color-scheme:dark)"),
            nextId      : 0n,
            override    : this.#override,
            underride   : this.#underride
        });

        // Register package classes with the Toolkit namespace
        _package.register = ()=>{
            this.Component = Component(this, _package);
            this.App       = App      (this, _package);
            this.Group     = Group    (this, _package);
            this.MenuBar   = MenuBar  (this, _package);
            this.MenuItem  = MenuItem (this, _package);
            Object.freeze(this);
            Object.seal  (this);
        };

    }



    ///////////////////////////// Static Methods //////////////////////////////

    // Resolve the Toolkit.Component for an HTML element
    static component(element) {
        return element[_package.componentKey] ?? null;
    }

    // Terminate an event
    static consume(event) {
        event.preventDefault();
        event.stopPropagation();
    }

    // Generate a unique element ID
    static id() {
        return "tk-" + _package.nextId++;
    }

    // Determine whether the user dark mode preference is active
    static isDark() {
        return _package.darkQuery.matches;
    }

    // Determine whether an element is fully visible
    static isVisible(element, cache = null) {
        cache ??= new Map();
        for (let e = element; e instanceof Element; e = e.parentNode) {
            let style;
            if (!cache.has(e))
                cache.set(e, style = getComputedStyle(e));
            else style = cache.get(e);
            if (style.display == "none" || style.visibility == "hidden")
                return false;
        }
        return true;
    }

    // Generate a list of focusable descendant elements
    static listFocusable(element) {
        let cache = new Map();
        return Array.from(element.querySelectorAll(
            "*:is(a[href],area,button,details,input,textarea,select," +
            "[tabindex='0']):not([disabled])"
        )).filter(e=>this.isVisible(e, cache));
    }

    static stylesheet(url) {
        let style = document.createElement("link");
        style.rel  = "stylesheet";
        style.href = url;
        return style;
    }
    


    ///////////////////////////// Package Methods /////////////////////////////

    // Process overrides for Toolkit.Component initialization
    static #override(fromCaller, fromSelf) {
        fromCaller     = Object.assign({}, fromCaller ?? {});
        fromSelf       = Object.assign({}, fromSelf   ?? {});
        fromSelf.style = Object.assign(
            fromSelf.style ?? {}, fromCaller.style ?? {});
        delete fromCaller.style;
        Object.assign(fromSelf, fromCaller);
        return fromSelf;
    }

    // Extract override properties for later processing
    static #underride(overrides, underrides) {
        let ret = {};
        for (let entry of Object.entries(underrides)) {
            ret[entry[0]] = overrides[entry[0]] ?? underrides[entry[1]];
            delete overrides[entry[0]];
        }
        return ret;
    }

}

_package.register();

export default Toolkit;