// @ts-check
/**
 * The notebook chooser: the "Notebook" button's dialog, which shows the
 * notebooks and the pages kept in them, and loads the chosen page.
 */

import { listKeptPages, listNotebooks, readPage } from './notebook.js';

/**
 * @param {string} id
 * @returns {HTMLElement}
 */
function element(id) {
  return /** @type {HTMLElement} */ (document.getElementById(id));
}

/**
 * @param {string} pageName
 * @returns {string}  "2026_10_02_01.svg" shown as "2026-10-02 (1)".
 */
function pageTitle(pageName) {
  const match = /^(\d{4})_(\d{2})_(\d{2})_(\d+)\.svg$/.exec(pageName);
  return match ? `${match[1]}-${match[2]}-${match[3]} (${Number(match[4])})` : pageName;
}

export class NotebookChooser {
  /**
   * @param {(notebook: string, pageName: string, text: string) => void} onChosen
   *     Called with the chosen page file.
   */
  constructor(onChosen) {
    this.onChosen = onChosen;
    this.dialog = /** @type {HTMLDialogElement} */ (element('notebook_chooser'));
    this.notebook = '';
    /** Counts openings, so that pictures fetched for an earlier one are dropped. */
    this.opening = 0;
    /** @type {string[]} */
    this.pictureAddresses = [];

    element('chooser_close').addEventListener('click', () => this.dialog.close());
    this.dialog.addEventListener('close', () => this.forgetPictures());
  }

  /**
   * Show the notebooks, or the pages of the only notebook.
   * @param {string} [notebook]  Open on this notebook.
   */
  async open(notebook) {
    this.opening += 1;
    this.dialog.showModal();
    element('chooser_message').textContent = '';
    element('chooser_pages').replaceChildren();     // Nothing stale while the lists load.
    try {
      const { notebooks } = await listNotebooks();
      this.showNotebooks(notebooks);
      // The notebook being written in is chosen already, its pages shown;
      // the list is always there to see (Andy, 2026-10-06).
      const chosen = notebook && notebooks.includes(notebook) ? notebook
        : notebooks.length === 1 ? notebooks[0] : '';
      await this.showPages(chosen);
    } catch (error) {
      element('chooser_message').textContent = error instanceof Error ? error.message : String(error);
    }
  }

  /** @param {string[]} notebooks */
  showNotebooks(notebooks) {
    const list = element('chooser_notebooks');
    list.replaceChildren();
    for (const notebook of notebooks) {
      const button = document.createElement('button');
      button.type = 'button';
      button.textContent = notebook;
      button.addEventListener('click', () => { this.showPages(notebook); });
      list.append(button);
    }
  }

  /** @param {string} notebook */
  async showPages(notebook) {
    this.notebook = notebook;
    for (const button of element('chooser_notebooks').querySelectorAll('button')) {
      button.setAttribute('aria-pressed', String(button.textContent === notebook));
    }
    const grid = element('chooser_pages');
    grid.replaceChildren();
    this.forgetPictures();
    if (!notebook) {
      element('chooser_message').textContent = 'Choose a notebook.';
      return;
    }
    const opening = this.opening += 1;
    const pages = await listKeptPages(notebook);
    if (opening !== this.opening) return;
    element('chooser_message').textContent = pages.length ? '' : 'This notebook has no kept pages.';

    /** @type {Map<string, HTMLImageElement>} */
    const pictures = new Map();
    for (const pageName of pages) {
      const card = document.createElement('button');
      card.type = 'button';
      card.className = 'page_card';
      const picture = document.createElement('img');
      picture.alt = '';
      pictures.set(pageName, picture);
      const title = document.createElement('span');
      title.textContent = pageTitle(pageName);
      card.append(picture, title);
      card.addEventListener('click', async () => {
        const text = await readPage(notebook, pageName);
        if (text === null) return;
        this.dialog.close();
        this.onChosen(notebook, pageName, text);
      });
      grid.append(card);
    }

    // The pictures are the page files themselves, fetched one by one.
    for (const [pageName, picture] of pictures) {
      const text = await readPage(notebook, pageName);
      if (opening !== this.opening) return;
      if (text === null) continue;
      const address = URL.createObjectURL(new Blob([text], { type: 'image/svg+xml' }));
      this.pictureAddresses.push(address);
      picture.src = address;
    }
  }

  forgetPictures() {
    for (const address of this.pictureAddresses) URL.revokeObjectURL(address);
    this.pictureAddresses = [];
  }
}