// In-page "Download this video ▾" panel (docs/05 §3). Lists variants the daemon
// enumerated via media.listVariants — the extension never parses the manifest itself.
// DRM-protected variants (and a wholly DRM-protected manifest) are shown greyed out
// with "Protected content" rather than attempted.

import type { MediaVariant } from '../shared/protocol/index.js';

export interface VariantsPort {
  listVariants(manifestUrl: string): Promise<{ variants: MediaVariant[]; drmProtected: boolean } | { error: string }>;
  addVariant(manifestUrl: string, variantId: string): Promise<{ taskId: string } | { error: string }>;
}

function variantLabel(v: MediaVariant): string {
  const bits = [v.resolution, v.codec, v.bitrateBps ? `${Math.round(v.bitrateBps / 1000)} kbps` : null].filter(Boolean);
  return bits.length > 0 ? bits.join(' · ') : v.variantId;
}

const PANEL_ID = 'velox-video-panel';

export class VideoPanel {
  private root: HTMLElement | null = null;

  constructor(
    private readonly port: VariantsPort,
    private readonly doc: Document = document,
  ) {}

  /** Shows (or replaces) the floating panel for one detected manifest URL. */
  show(manifestUrl: string): void {
    this.remove();

    const root = this.doc.createElement('div');
    root.id = PANEL_ID;
    Object.assign(root.style, {
      position: 'fixed',
      bottom: '16px',
      right: '16px',
      zIndex: '2147483647',
      font: '13px sans-serif',
    } satisfies Partial<CSSStyleDeclaration>);

    const button = this.doc.createElement('button');
    button.textContent = 'Download this video ▾';
    root.appendChild(button);

    const menu = this.doc.createElement('ul');
    menu.hidden = true;
    Object.assign(menu.style, { listStyle: 'none', margin: '4px 0 0', padding: '4px' } satisfies Partial<CSSStyleDeclaration>);
    root.appendChild(menu);

    button.addEventListener('click', () => {
      menu.hidden = !menu.hidden;
      if (!menu.hidden) void this.populate(menu, manifestUrl);
    });

    this.doc.body.appendChild(root);
    this.root = root;
  }

  remove(): void {
    this.root?.remove();
    this.root = null;
  }

  private async populate(menu: HTMLUListElement, manifestUrl: string): Promise<void> {
    menu.replaceChildren(this.loadingItem());
    const result = await this.port.listVariants(manifestUrl);

    if ('error' in result) {
      menu.replaceChildren(this.messageItem(`Could not read variants: ${result.error}`));
      return;
    }
    if (result.drmProtected || result.variants.length === 0) {
      menu.replaceChildren(this.messageItem(result.drmProtected ? 'Protected content' : 'No downloadable variants found'));
      return;
    }

    menu.replaceChildren(
      ...result.variants.map((v) => {
        const li = this.doc.createElement('li');
        const item = this.doc.createElement('button');
        item.textContent = v.drm ? `${variantLabel(v)} — Protected content` : variantLabel(v);
        item.disabled = v.drm;
        if (!v.drm) {
          item.addEventListener('click', () => void this.port.addVariant(manifestUrl, v.variantId));
        }
        li.appendChild(item);
        return li;
      }),
    );
  }

  private loadingItem(): HTMLLIElement {
    return this.messageItem('Loading…');
  }

  private messageItem(text: string): HTMLLIElement {
    const li = this.doc.createElement('li');
    li.textContent = text;
    return li;
  }
}