import "./style.css";
import { lessons } from "./lessons";

function getRequiredElement<T extends Element>(selector: string, parent: ParentNode = document): T {
  const element = parent.querySelector<T>(selector);

  if (!element) {
    throw new Error(`Required element was not found: ${selector}`);
  }

  return element;
}

const app = getRequiredElement<HTMLDivElement>("#app");

app.innerHTML = `
  <div class="shell">
    <aside class="sidebar">
      <div class="brand">
        <p class="eyebrow">Vite + TypeScript</p>
        <h1>TypeScript Learning Lab</h1>
        <p class="intro">
          保留原来的 8 个练习目录，同时给这一章补上一个可直接运行的学习面板。
        </p>
      </div>
      <nav class="lesson-nav" aria-label="TypeScript lessons"></nav>
    </aside>
    <main class="content">
      <section class="hero card">
        <p class="badge">06-typescript</p>
        <h2 id="lesson-title"></h2>
        <p id="lesson-focus" class="focus"></p>
        <p id="lesson-summary" class="summary"></p>
      </section>
      <section >
        <article class="card">
          <div class="card-head">
            <h3>知识点</h3>
          </div>
          <ul id="lesson-points" class="point-list"></ul>
        </article>
      </section>
      <section >
        <article class="card code-card">
          <div class="card-head">
            <h3>Starter</h3>
          </div>
          <pre><code id="starter-code"></code></pre>
        </article>
      </section>
    </main>
  </div>
`;

const nav = getRequiredElement<HTMLElement>(".lesson-nav");
const title = getRequiredElement<HTMLElement>("#lesson-title");
const focus = getRequiredElement<HTMLElement>("#lesson-focus");
const summary = getRequiredElement<HTMLElement>("#lesson-summary");
const pointList = getRequiredElement<HTMLElement>("#lesson-points");
const starterCode = getRequiredElement<HTMLElement>("#starter-code");

let activeLessonId = lessons[0]?.id ?? "";

function renderLessonList(): void {
  nav.innerHTML = lessons
    .map((lesson) => {
      const isActive = lesson.id === activeLessonId;
      return `
        <button
          class="lesson-link ${isActive ? "is-active" : ""}"
          type="button"
          data-id="${lesson.id}"
        >
          <span class="lesson-index">${lesson.id}</span>
          <span class="lesson-meta">
            <strong>${lesson.title}</strong>
            <small>${lesson.focus}</small>
          </span>
        </button>
      `;
    })
    .join("");
}

function renderActiveLesson(): void {
  const lesson = lessons.find((item) => item.id === activeLessonId);

  if (!lesson) {
    return;
  }

  title.textContent = `${lesson.id}. ${lesson.title}`;
  focus.textContent = lesson.focus;
  summary.textContent = lesson.summary;
  pointList.innerHTML = lesson.keyPoints.map((item) => `<li>${item}</li>`).join("");
  starterCode.textContent = lesson.starterCode;
  renderLessonList();
}

nav.addEventListener("click", (event) => {
  const target = event.target as HTMLElement;
  const button = target.closest<HTMLButtonElement>("[data-id]");

  if (!button) {
    return;
  }

  activeLessonId = button.dataset.id ?? activeLessonId;
  renderActiveLesson();
});

renderActiveLesson();