implemented frontend part of progressive form and trackers

2 weeks ago · 06abd9883a
parent 98fc37530d
commit 06abd9883a
9 changed files with 228 additions and 28 deletions
--- a/README.md
+++ b/README.md
@ -30,5 +30,6 @@ Source: https://www.programmfabrik.de/en/assignment-frontend-backend-developer-j
 * ~0.5 hours to set up the project;
 * ~5 hours to implement game board serialization, tic-tac-toe rules and game solver (with tests);
-* ~1 hour to set up the backend / frontend structure with JSX templating and static resources
+* ~1 hour to set up the backend / frontend structure with JSX templating and static resources;
 * ~2 hours to implement progressively enhanced form and query string value trackers (both on backend and in web components);
 * ...
--- a/src/backend/main.tsx
+++ b/src/backend/main.tsx
@ -2,8 +2,10 @@ import type { RequestHandler } from "express";
 import { safeGetQueryValue, sendHtml } from "./utils.ts";
 export const mainPageHandler: RequestHandler = (req, res) => {
-  const a = parseInt(safeGetQueryValue(req, "a") ?? "0", 10);
+  const counters = {
-  const b = parseInt(safeGetQueryValue(req, "b") ?? "0", 10);
+    a: parseInt(safeGetQueryValue(req, "a") ?? "0", 10),
    b: parseInt(safeGetQueryValue(req, "b") ?? "0", 10),
  };
  sendHtml(
    res,
    <html>
@ -13,34 +15,51 @@ export const mainPageHandler: RequestHandler = (req, res) => {
          because we're loading the compiled file on frontend, from path relative to the root page,
          and because TS won't rewrite the extension here.
        */}
        <script src="frontend/app.js" type="module"></script>
        <link rel="stylesheet" href="frontend/static/style.css" />
        <script src="frontend/app.js" type="module"></script>
        <title>Hi</title>
      </head>
      <body>
-        <p>Hello world!</p>
+        <section>
          <p>
            Just a small demo of progressive form and tracker web components.
            <br />
            It works both with JS and without JS; it does not require network connection when JS is used; and it
            supports history navigation (you can go back & forward and see how the state changes).
          </p>
          <ul>
            {(["a", "b"] as const).map((key) => (
              <li>
-            Value of "a": <span class="counter">{a}</span>
+                <form method="post" is="progressive-form">
-          </li>
+                  <button
-          <li>
+                    type="submit"
-            Value of "b": <span class="counter">{b}</span>
+                    name={key}
                    value={`${counters[key] - 1}`}
                    is="button-query-tracker"
                    track={key}
                    delta="-1"
                  >
                    -
                  </button>{" "}
                  <button
                    type="submit"
                    name={key}
                    value={`${counters[key] + 1}`}
                    is="button-query-tracker"
                    track={key}
                    delta="+1"
                  >
                    +
                  </button>
                </form>{" "}
                Value of "{key}":{" "}
                <span class="counter" is="span-query-tracker" track={key}>
                  {counters[key]}
                </span>
              </li>
            ))}
          </ul>
-        <form method="post">
+        </section>
          <p>
            <button type="submit" name={`a`} value={`${a + 1}`}>
              Increase "a"
            </button>
          </p>
        </form>
        <form method="post">
          <p>
            <button type="submit" name={`b`} value={`${b + 1}`}>
              Increase "b"
            </button>
          </p>
        </form>
      </body>
    </html>,
  );
--- a/src/frontend/app.ts
+++ b/src/frontend/app.ts
@ -1,6 +1,14 @@
 import { computeAllSolutions } from "../shared/solver.ts";
 import { rules } from "../shared/tictactoe-rules.ts";
 import { ProgressiveForm } from "./progressive-form.ts";
 import { ButtonTracker, SpanTracker } from "./query-tracker.ts";
 customElements.define("progressive-form", ProgressiveForm, { extends: "form" });
 customElements.define("span-query-tracker", SpanTracker, { extends: "span" });
 customElements.define("button-query-tracker", ButtonTracker, { extends: "button" });
 document.addEventListener("DOMContentLoaded", function () {
  const allSolutions = computeAllSolutions(3, 3, rules);
  console.log(allSolutions.size);
  console.log(allSolutions);
 });
--- a/src/frontend/navigation-utils.ts
+++ b/src/frontend/navigation-utils.ts
@ -0,0 +1,31 @@
 // Until https://developer.mozilla.org/en-US/docs/Web/API/Navigation_API support is widespread
 let lastUrl = document.location.href;
 const observers = new Set<() => void>();
 const checkChanges = () => {
  if (document.location.href !== lastUrl) {
    lastUrl = document.location.href;
    for (const observer of observers) {
      observer();
    }
  }
 };
 let pollingInterval: number | null = null;
 const startPolling = () => {
  if (pollingInterval === null) {
    pollingInterval = window.setInterval(checkChanges, 20);
  }
 };
 export const onLocationChange = (observer: () => void) => {
  observers.add(observer);
  startPolling();
 };
 export const onLocationChangeUnsubscribe = (observer: () => void) => {
  observers.delete(observer);
 };
--- a/src/frontend/progressive-form.ts
+++ b/src/frontend/progressive-form.ts
@ -0,0 +1,26 @@
 const submitListener = function (this: HTMLFormElement, e: SubmitEvent) {
  const targetUrl = new URL(this.action);
  const formData = new FormData(this, e.submitter);
  for (const [key, value] of formData.entries()) {
    if (typeof value !== "string") {
      throw new Error("File fields are not supported; falling back to regular form submission");
    }
    targetUrl.searchParams.set(key, value);
  }
  window.history.pushState({}, "", targetUrl.toString());
  e.preventDefault();
 };
 export class ProgressiveForm extends HTMLFormElement {
  connectedCallback() {
    if (this.method.toUpperCase() !== "POST") {
      throw new Error(
        "Only supported when method=POST and progressive form router is used on backend; falling back to regular forms",
      );
    }
    this.addEventListener("submit", submitListener);
  }
 }
--- a/src/frontend/query-tracker.ts
+++ b/src/frontend/query-tracker.ts
@ -0,0 +1,99 @@
 import { onLocationChange, onLocationChangeUnsubscribe } from "./navigation-utils.ts";
 const createQueryStringTracker = (key: string, onChange: (newValue: string | null) => void) => {
  let currentValue = new URLSearchParams(window.location.search).get(key);
  const observer = () => {
    const newValue = new URLSearchParams(window.location.search).get(key);
    if (newValue !== currentValue) {
      currentValue = newValue;
      onChange(newValue);
    }
  };
  onLocationChange(observer);
  return () => {
    onLocationChangeUnsubscribe(observer);
  };
 };
 class TrackingTools<
  TElement extends HTMLElement & { handleTrackedValueUpdate(this: TElement, newValue: string | null): void },
 > {
  private currentTrackKey: string | null = null;
  private clearTracker: (() => void) | null = null;
  constructor(private readonly element: TElement) {}
  private setTrackerIfNeeded() {
    const trackKey = this.element.getAttribute("track");
    if (trackKey != this.currentTrackKey) {
      if (this.clearTracker) {
        this.clearTracker();
      }
      if (trackKey) {
        this.clearTracker = createQueryStringTracker(
          trackKey,
          this.element.handleTrackedValueUpdate.bind(this.element),
        );
      }
      this.currentTrackKey = trackKey;
    }
  }
  connectedCallback() {
    this.setTrackerIfNeeded();
  }
  attributeChangedCallback() {
    this.setTrackerIfNeeded();
  }
  disconnectedCallback() {
    if (this.clearTracker) {
      this.clearTracker();
    }
  }
 }
 export class SpanTracker extends HTMLSpanElement {
  private readonly trackingTools = new TrackingTools(this);
  handleTrackedValueUpdate(newValue: string | null) {
    this.innerText = newValue ?? "[null]";
  }
  connectedCallback() {
    this.trackingTools.connectedCallback();
  }
  attributeChangedCallback() {
    this.trackingTools.attributeChangedCallback();
  }
  disconnectedCallback() {
    this.trackingTools.disconnectedCallback();
  }
 }
 export class ButtonTracker extends HTMLButtonElement {
  private readonly trackingTools = new TrackingTools(this);
  handleTrackedValueUpdate(newValue: string | null) {
    const delta = parseInt(this.getAttribute("delta") ?? "0", 10);
    this.value = (parseInt(newValue ?? "0", 10) + delta).toString();
  }
  connectedCallback() {
    this.trackingTools.connectedCallback();
  }
  attributeChangedCallback() {
    this.trackingTools.attributeChangedCallback();
  }
  disconnectedCallback() {
    this.trackingTools.disconnectedCallback();
  }
 }
--- a/src/frontend/static/style.css
+++ b/src/frontend/static/style.css
@ -2,3 +2,7 @@
  font-weight: bold;
  color: red;
 }
 li form {
    display: inline;
 }
--- a/src/jsx-augmentations.ts
+++ b/src/jsx-augmentations.ts
@ -0,0 +1,11 @@
 declare module "preact/jsx-runtime" {
  // eslint-disable-next-line @typescript-eslint/no-namespace -- preact uses namespaces, so we have too
  namespace JSX {
    // eslint-disable-next-line @typescript-eslint/consistent-type-definitions -- this is how declaration merging is done
    interface HTMLAttributes {
      // custom attribute used by query-tracker web components
      delta?: string;
      track?: string;
    }
  }
 }
--- a/tsconfig.build.json
+++ b/tsconfig.build.json
@ -3,6 +3,7 @@
  "exclude": ["src/**/*.spec.*"],
  "compilerOptions": {
    "module": "Preserve",
    "noCheck": true,
    "noEmit": false,
    "outDir": "dist",
    "rewriteRelativeImportExtensions": true