commit b3ee2af7c595b9e0b901423893e11b055e80b0ce
Author: Daniel Ledda <ledda@cip.ifi.lmu.de>
Date:   Sun May 22 22:09:36 2022 +0200

    first commit

diff --git a/package.json b/package.json
new file mode 100644
index 0000000..61992fa
--- /dev/null
+++ b/package.json
@@ -0,0 +1,12 @@
+{
+  "name": "ladder",
+  "version": "1.0.0",
+  "description": "other libraries provide you with a whole framework - this is just a ladder",
+  "scripts": {  },
+  "repository": {
+    "type": "git",
+    "url": "https://git.djledda.de/djledda/ladder"
+  },
+  "author": "Daniel Ledda <dan.j.ledda@gmail.com>",
+  "license": "MIT"
+}
diff --git a/src/Publisher.ts b/src/Publisher.ts
new file mode 100644
index 0000000..f5412b0
--- /dev/null
+++ b/src/Publisher.ts
@@ -0,0 +1,91 @@
+import ISubscriber, {LEvent} from "./Subscriber";
+
+class PublisherSubscription<EventType extends LEvent> implements ISubscription {
+    private subscriber: ISubscriber<EventType>;
+    private readonly eventTypes: EventType[];
+    private unbindCallback?: () => void;
+
+    constructor(subscriber: ISubscriber<EventType>, eventTypes: EventType[]) {
+        this.subscriber = subscriber;
+        this.eventTypes = eventTypes;
+    }
+
+    setUnbind(unbind: () => void): void {
+        this.unbindCallback = unbind;
+    }
+
+    unbind(): void {
+        this.unbindCallback?.();
+    }
+
+    getEventTypes(): EventType[] {
+        return this.eventTypes;
+    }
+
+    getSubscriber(): ISubscriber<EventType> {
+        return this.subscriber;
+    }
+}
+
+interface EventSubscriberRecord<T extends LEvent> {
+    get<K extends T>(key: K): ISubscriber<K>[];
+    set<K extends T>(key: K, subscribers: ISubscriber<K>[]): EventSubscriberRecord<T>;
+}
+
+
+export class Publisher<EventType extends LEvent, PublisherType> implements IPublisher<EventType> {
+    private subscribers: EventSubscriberRecord<EventType>;
+    private parent: PublisherType;
+
+    constructor(parent: PublisherType) {
+        this.parent = parent;
+        this.subscribers = new Map();
+    }
+
+    addSubscriber(subscriber: ISubscriber<EventType>, subscribeTo: EventType | Readonly<EventType[]>): ISubscription {
+        let eventTypes: EventType[] = [];
+        if (typeof subscribeTo === "string") {
+            eventTypes.push(subscribeTo);
+        } else {
+            eventTypes = subscribeTo.slice();
+        }
+        for (const key of eventTypes) {
+            this.getSubscribers(key).push(subscriber);
+        }
+        const sub = new PublisherSubscription(subscriber, eventTypes);
+        sub.setUnbind(() => this.unbind(sub));
+        return sub;
+    }
+
+    private unbind(subscription: PublisherSubscription<EventType>): void {
+        for (const key of subscription.getEventTypes()) {
+            const subs = this.getSubscribers(key);
+            subs.splice(subs.indexOf(subscription.getSubscriber()), 1);
+        }
+    }
+
+    private getSubscribers<K extends EventType>(key: K): ISubscriber<K>[] {
+        const subscribersList = this.subscribers.get(key);
+        if (subscribersList === undefined) {
+            const newList: ISubscriber<K>[] = [];
+            this.subscribers.set(key, newList);
+            return newList;
+        } else {
+            return subscribersList;
+        }
+    }
+
+    notifySubs<K extends EventType>(eventType: K): void {
+        for (const sub of this.getSubscribers(eventType)) {
+            sub.notify(this.parent, eventType);
+        }
+    }
+}
+
+export interface IPublisher<T extends LEvent> {
+    addSubscriber(subscriber: ISubscriber<T>, subscribeTo: T | T[]): {unbind: () => void};
+}
+
+export interface ISubscription {
+    unbind(): void;
+}
\ No newline at end of file
diff --git a/src/Ref.ts b/src/Ref.ts
new file mode 100644
index 0000000..b1306d7
--- /dev/null
+++ b/src/Ref.ts
@@ -0,0 +1,99 @@
+import { ISubscription } from "./Publisher";
+
+export type MaybeRef<T> = T | Ref<T>;
+
+class RefSubscription implements ISubscription {
+    private unbindCallback?: () => void;
+
+    constructor(unbindCallback: () => void) {
+        this.unbindCallback = unbindCallback;
+    }
+
+    unbind(): void {
+        this.unbindCallback?.();
+    }
+}
+
+interface Stringable {
+    toString(): string;
+}
+
+type AllowedRef = { toString(): string } | string | null;
+
+export default class Ref<T extends AllowedRef = Stringable> {
+    private watchers: Array<(newVal: T) => void> | null = null;
+    private afterWatchers: Array<(newVal: T) => void> | null = null;
+    private value: T;
+    private asString?: string;
+    private isString: boolean;
+
+    private constructor(val: T) {
+        this.value = val;
+        this.isString = typeof val === "string";
+    }
+
+    static new<T extends AllowedRef>(val: MaybeRef<T>): Ref<T> {
+        if (val instanceof Ref) {
+            return val;
+        } else {
+            return new Ref<T>(val);
+        }
+    }
+
+    watch(watcher: (newVal: T) => void, after?: boolean): ISubscription {
+        if (after) {
+            if (this.afterWatchers === null) {
+                this.afterWatchers = [];
+            }
+            this.afterWatchers.push(watcher);
+        } else {
+            if (this.watchers === null) {
+                this.watchers = [];
+            }
+            this.watchers.push(watcher);
+        }
+        return new RefSubscription(() => this.unbind(watcher, !!after));
+    }
+
+    private unbind(watcher: (newVal: T) => void, after: boolean): void {
+        if (after) {
+            if (!this.afterWatchers) {
+                return;
+            }
+            const index = this.afterWatchers.indexOf(watcher);
+            if (index !== -1) {
+                this.afterWatchers.splice(index, 1);
+            }
+        } else {
+            if (!this.watchers) {
+                return;
+            }
+            const index = this.watchers.indexOf(watcher);
+            if (index !== -1) {
+                this.watchers.splice(index, 1);
+            }
+        }
+    }
+
+    get val(): T {
+        return this.value;
+    }
+
+    set val(val: T) {
+        this.watchers?.forEach(watcher => watcher(val));
+        this.value = val;
+        this.afterWatchers?.forEach(watcher => watcher(val));
+    }
+
+    toString(): string {
+        if (!this.asString) {
+            if (this.isString) {
+                return this.val as unknown as string;
+            } else {
+                this.asString = this.val?.toString() ?? "null";
+            }
+        }
+        return this.asString;
+    }
+}
+
diff --git a/src/Rung.ts b/src/Rung.ts
new file mode 100644
index 0000000..17514e4
--- /dev/null
+++ b/src/Rung.ts
@@ -0,0 +1,119 @@
+import Ref from "./Ref";
+import { ISubscription } from "./Publisher";
+
+export type RungOptions = {};
+
+type IRenderAttributes<T extends keyof HTMLElementTagNameMap> = Partial<{
+    [K in keyof HTMLElementTagNameMap[T]]: HTMLElementTagNameMap[T][K] | Ref<HTMLElementTagNameMap[T][K]>
+}> & {
+    classes?: string[],
+    saveTo?: Ref<HTMLElementTagNameMap[T] | null>,
+};
+
+export default abstract class Rung {
+    protected el: HTMLElement | null = null;
+
+    constructor(options: RungOptions) {}
+
+    render(): HTMLElement {
+        if (!this.el) {
+            this.el = this.build();
+        }
+        return this.el;
+    }
+
+    protected getEl(): HTMLElement {
+        if (!this.el) {
+            return this.render();
+        } else {
+            return this.el;
+        }
+    }
+
+    redraw(): void {
+        const oldNode = this.el;
+        if (!oldNode || !this.el) {
+            return;
+        }
+        const parent = this.el.parentElement;
+        if (parent) {
+            this.el = this.build();
+            parent.replaceChild(this.el, oldNode);
+        } else {
+            this.render();
+        }
+    }
+
+    protected abstract build(): HTMLElement;
+}
+
+export function frag(subs?: Rung[]): DocumentFragment {
+    const frag = document.createDocumentFragment();
+    if (subs) {
+        attachSubs(frag, subs);
+    }
+    return frag;
+}
+
+export function q(text: string): Text {
+    return document.createTextNode(text);
+}
+
+export function h<T extends keyof HTMLElementTagNameMap>(type: T, attributes?: IRenderAttributes<T>, subNodes?: (Rung | Node | Ref)[]): HTMLElementTagNameMap[T] {
+    const element = document.createElement(type);
+    if (attributes) {
+        if (attributes.classes) {
+            element.classList.add(...attributes.classes);
+        }
+        if (attributes.saveTo) {
+            attributes.saveTo.val = element;
+        }
+        applyAttributes(element, attributes);
+    }
+    if (subNodes) {
+        attachSubs(element, subNodes);
+    }
+    return element;
+}
+
+function nodeRefWatcher<T>(newVal: T extends Ref<infer U> ? U : never, textNode: Text, sub: ISubscription): void {
+    if (!textNode.parentNode) {
+        sub.unbind();
+        textNode.remove();
+    } else {
+        textNode.replaceWith(newVal?.toString() ?? "<dead ref>");
+    }
+}
+
+function attachSubs(node: Element | DocumentFragment, subNodes: (Rung | Node | Ref)[]): void {
+    for (let i = 0; i < subNodes.length; i++) {
+        const subNode = subNodes[i];
+        if (subNode instanceof Rung) {
+            node.append(subNode.render());
+        } else if (subNode instanceof Ref) {
+            const textNode = q(subNode.val.toString());
+            const sub = subNode.watch((newVal) => nodeRefWatcher<Ref>(newVal, textNode, sub));
+            node.append(textNode);
+        } else {
+            node.append(subNode);
+        }
+    }
+}
+
+function applyAttributes<T extends keyof HTMLElementTagNameMap>(element: HTMLElement, attributes: IRenderAttributes<T>): void {
+    for (const key in attributes) {
+        if (Object.prototype.hasOwnProperty.call(attributes, key)) {
+            const attribute = (attributes as Record<string, unknown>)[key];
+            if (attribute) {
+                if (attribute instanceof Ref) {
+                    const attributeAsRef = attribute as Ref;
+                    const elementWithAttributeKey = element as unknown as Record<string, typeof attributeAsRef.val>;
+                    elementWithAttributeKey[key] = attributeAsRef.val;
+                    attribute.watch((newVal) => elementWithAttributeKey[key] = newVal);
+                } else {
+                    (element as unknown as ({ [key: string]: typeof attribute }))[key] = attribute;
+                }
+            }
+        }
+    }
+}
diff --git a/src/Subscriber.ts b/src/Subscriber.ts
new file mode 100644
index 0000000..35afd2b
--- /dev/null
+++ b/src/Subscriber.ts
@@ -0,0 +1,4 @@
+export type LEvent = string;
+export default interface ISubscriber<T extends LEvent> {
+    notify(publisher: unknown, event: T): void;
+}
\ No newline at end of file