export const mac = /Mac|iPhone|iPad/.test(navigator.platform);

/** How the platform's command key reads next to a letter: ⌘K or Ctrl K. */
export function shortcut(key: string): string {
  return mac ? `⌘${key}` : `Ctrl ${key}`;
}

/** The command key by itself, as a chip in a hint: ⌘ or Ctrl. */
export const command = mac ? '⌘' : 'Ctrl';

/** How the platform's option key reads, alone or beside a key: ⌥G or Alt G. */
export function option(key = ''): string {
  return mac ? `⌥${key}` : `Alt${key && ` ${key}`}`;
}

/** The palette opened for commands only, as VS Code's. */
export const commandsKey = mac ? '⇧⌘P' : 'Ctrl Shift P';

/** Redo, the other half of `shortcut('Z')`. */
export const redo = mac ? '⇧⌘Z' : 'Ctrl Y';

/**
 * The canvas's gestures and keys, for the keys pane and the canvas's view
 * bar (which shows only what nothing on screen does): `where` limits one to
 * the bar or to the pane.
 */
export const canvasKeys: { keys: string[]; does: string; where?: 'bar' | 'pane' }[] = [
  { keys: ['spc', 'grab'], does: 'pan' },
  { keys: [option(), 'move'], does: 'move window' },
  { keys: [command, 'scroll'], does: 'zoom' },
  { keys: [option(), 'scroll'], does: 'window zoom' },
  { keys: ['+', '−'], does: 'zoom in, out', where: 'pane' },
  { keys: ['⇧1'], does: 'fit all' },
  { keys: ['⇧0'], does: 'zoom to 100%', where: 'pane' },
  { keys: ['M'], does: 'overview map', where: 'pane' },
  { keys: [option('←→↑↓')], does: 'windows', where: 'bar' },
  { keys: ['S'], does: 'new session', where: 'bar' },
  { keys: ['T'], does: 'terminal', where: 'bar' },
  { keys: ['spc', 'click', 'click'], does: 'zoom at' },
  { keys: ['click', 'click'], does: 'note' },
];

/** Whether a key press belongs to a text field rather than to the app. */
export function typing(event: KeyboardEvent): boolean {
  const target = event.target as HTMLElement | null;
  return !!target && (target.isContentEditable || /^(INPUT|TEXTAREA|SELECT)$/.test(target.tagName));
}