/// SPDX-License-Identifier: GPL-3.0-or-later
/// SPDX-FileCopyrightText: Copyright © 2023 Tony Garnock-Jones <tonyg@leastfixedpoint.com>

import { Turn, Facet, Dataflow, Dataspace, Ref } from "@syndicate-lang/core";
import { HtmlFragmentsTemplate, HtmlFragment, template } from "./html";
export * from "./html";

export assertion type LocationHash(hash: string);
export type LocationHash = ReturnType<typeof LocationHash>;

export function boot(ds = Dataspace.global) {
    spawnLocationHashTracker(ds);
}

type Wrapped = {
    wrapped: EventListenerOrEventListenerObject,
    options?: AddEventListenerOptions | boolean,
};

export class Widget implements EventTarget {
    facet: Facet;
    node: Dataflow.Field<ChildNode | null>;
    callbacks =
        new Map<string, Map<EventListenerOrEventListenerObject, Wrapped>>();
    _parent: Dataflow.Field<ParentNode | null>;

    constructor (private nodeGenerator: (t: HtmlFragmentsTemplate) => HtmlFragment) {
        this.facet = Turn.activeFacet;

        on stop {
            this.node.value?.remove();
        }

        field node: ChildNode | null = null;
        this.node = node;

        field parent: ParentNode | null = null;
        this._parent = parent;

        dataflow {
            const oldNode = this.node.value;

            const fragments = template`${this.nodeGenerator(template)}`;
            const newNodes = fragments.nodes();
            if (newNodes.length > 1) {
                throw new Error(`@syndicate-lang/html2: Multiple nodes returned from template: ${fragments.toString()}`);
            }
            const newNode = newNodes[0];

            if (oldNode !== newNode) {
                if (oldNode !== null) {
                    for (const [type, cbs] of this.callbacks.entries()) {
                        for (const entry of cbs.values()) {
                            oldNode.removeEventListener(type, entry.wrapped, entry.options);
                        }
                    }
                }

                if (newNode !== null) {
                    for (const [type, cbs] of this.callbacks.entries()) {
                        for (const entry of cbs.values()) {
                            newNode.addEventListener(type, entry.wrapped, entry.options);
                        }
                    }
                }

                const wasFocus = oldNode && document.activeElement === oldNode;
                oldNode?.parentNode?.replaceChild(newNode, oldNode);
                if (wasFocus) {
                    if (newNode && newNode instanceof HTMLElement) {
                        newNode.focus();
                    }
                }

                this.node.value = newNode;
            }
        }

        dataflow {
            if (this.node.value === null) return;
            const p = this._parent.value;
            if (this.node.value.parentNode !== p) {
                if (p === null) {
                    this.node.value.remove();
                } else {
                    p.appendChild(this.node.value);
                }
            }
        }
    }

    get parent(): ParentNode | null {
        return this._parent.value;
    }

    set parent(p: string | ParentNode | null) {
        this.setParent(p);
    }

    setParent(p: string | ParentNode | null, wrt: ParentNode = document): this {
        if (typeof p === 'string') {
            p = wrt.querySelector(p);
        }
        this._parent.value = p;
        return this;
    }

    on(type: string, callback: EventListenerOrEventListenerObject): this {
        this.addEventListener(type, callback);
        return this;
    }

    once(type: string, callback: EventListenerOrEventListenerObject): this {
        this.addEventListener(type, callback, { once: true });
        return this;
    }

    off(type: string, callback: EventListenerOrEventListenerObject): this {
        this.removeEventListener(type, callback);
        return this;
    }

    addEventListener(
        type: string,
        callback: EventListenerOrEventListenerObject | null,
        options?: AddEventListenerOptions | boolean,
    ): void {
        if (callback === null) return;

        let cbs = this.callbacks.get(type);
        if (cbs === void 0) {
            cbs = new Map();
            this.callbacks.set(type, cbs);
        } else {
            if (cbs.has(callback)) return;
        }

        const entry: Wrapped = {
            wrapped: (typeof callback === 'function')
                ? evt => this.facet.turn(() => callback(evt))
                : evt => this.facet.turn(() => callback.handleEvent(evt)),
            options,
        };
        cbs.set(callback, entry);

        this.node.value?.addEventListener(type, entry.wrapped, options);
    }

    dispatchEvent(event: Event): boolean {
        return !this.node.value || this.node.value.dispatchEvent(event);
    }

    removeEventListener(
        type: string,
        callback: EventListenerOrEventListenerObject | null,
        options?: boolean | EventListenerOptions | undefined,
    ): void {
        if (callback === null) return;

        const cbs = this.callbacks.get(type);
        if (cbs === void 0) return;

        const r = cbs.get(callback);
        if (r === void 0) return;

        this.node.value?.removeEventListener(type, r.wrapped, options);

        cbs.delete(callback);
        if (cbs.size === 0) this.callbacks.delete(type);
    }
}

function spawnLocationHashTracker(ds: Ref) {
    spawn named 'LocationHashTracker' {
        at ds {
            field hashValue: string = '/';
            assert LocationHash(hashValue.value);

            const loadHash = () => {
                var h = window.location.hash;
                if (h.length && h[0] === '#') {
                    h = h.slice(1);
                }
                hashValue.value = h || '/';
            };
            const facet = Turn.activeFacet;
            const handlerClosure = () => facet.turn(loadHash);

            loadHash();
            window.addEventListener('hashchange', handlerClosure);
            on stop window.removeEventListener('hashchange', handlerClosure);

            on message LocationHash($newHash: string) => {
                window.location.hash = newHash;
            }
        }
    }
}