cinny/src/app/features/desktop/TitleBar.tsx

import React, { MouseEvent, ReactNode } from 'react';
import { useAtomValue } from 'jotai';
import { Text } from 'folds';
import { customWindowChromeAtom } from '../../state/customWindowChrome';
import { invokeTauri, isTauri } from '../../hooks/useTauri';
import * as css from './TitleBar.css';

/**
 * Detect macOS from the web side (no `tauri-plugin-os` dependency). We only need
 * a coarse "is this a Mac" signal to decide which side the window controls sit
 * on, so the UA/platform sniff is sufficient and stays cross-platform.
 */
const isMacOS = (): boolean => {
  const platform =
    (
      navigator as unknown as {
        userAgentData?: { platform?: string };
      }
    ).userAgentData?.platform ??
    navigator.platform ??
    navigator.userAgent;
  return /mac/i.test(platform);
};

const MIN_GLYPH = (
  <svg width="10" height="10" viewBox="0 0 10 10" aria-hidden>
    <rect x="1" y="4.5" width="8" height="1" fill="currentColor" />
  </svg>
);

const MAX_GLYPH = (
  <svg width="10" height="10" viewBox="0 0 10 10" aria-hidden>
    <rect x="1" y="1" width="8" height="8" fill="none" stroke="currentColor" strokeWidth="1" />
  </svg>
);

const CLOSE_GLYPH = (
  <svg width="10" height="10" viewBox="0 0 10 10" aria-hidden>
    <path d="M1 1 L9 9 M9 1 L1 9" stroke="currentColor" strokeWidth="1" fill="none" />
  </svg>
);

type ControlButtonProps = {
  label: string;
  glyph: ReactNode;
  onClick: () => void;
  close?: boolean;
};

function ControlButton({ label, glyph, onClick, close }: ControlButtonProps) {
  return (
    <button
      type="button"
      aria-label={label}
      title={label}
      onClick={onClick}
      className={`${css.ControlButton}${close ? ` ${css.ControlButtonClose}` : ''}`}
    >
      {glyph}
    </button>
  );
}

/**
 * P5-47 — TDS Custom Window Chrome titlebar.
 *
 * Renders `null` unless we're inside Tauri **and** the user opted into custom
 * window chrome. Otherwise it draws a thin (~32px) folds/TDS-styled titlebar: a
 * draggable region (explicit `window_start_drag` on mousedown, double-press to
 * maximize) with the app brand, plus minimize / maximize / close controls that
 * call the native window commands.
 *
 * OS-aware: Windows/Linux put the controls on the right; macOS mirrors them to
 * the left (the native traffic-light position) since decorations — and thus the
 * real traffic lights — are stripped while custom chrome is on.
 */
export function TitleBar() {
  const enabled = useAtomValue(customWindowChromeAtom);

  if (!isTauri() || !enabled) return null;

  const mac = isMacOS();

  // Official Tauri custom-titlebar recipe: primary-button mousedown starts an
  // OS window drag; a double press (detail === 2) toggles maximize instead. An
  // explicit `window_start_drag` invoke is used rather than
  // `data-tauri-drag-region` because the attribute only fires when the exact
  // element is the event target (children like the brand text wouldn't drag).
  const handleDragMouseDown = (evt: MouseEvent<HTMLDivElement>): void => {
    if (evt.button !== 0) return;
    if (evt.detail === 2) {
      invokeTauri('window_toggle_maximize');
    } else {
      invokeTauri('window_start_drag');
    }
  };

  const controls = (
    <div className={css.Controls}>
      <ControlButton
        label="Minimize"
        glyph={MIN_GLYPH}
        onClick={() => invokeTauri('window_minimize')}
      />
      <ControlButton
        label="Maximize"
        glyph={MAX_GLYPH}
        onClick={() => invokeTauri('window_toggle_maximize')}
      />
      <ControlButton
        label="Close"
        glyph={CLOSE_GLYPH}
        onClick={() => invokeTauri('window_close')}
        close
      />
    </div>
  );

  const dragRegion = (
    <div className={css.DragRegion} onMouseDown={handleDragMouseDown}>
      <span className={css.Brand}>
        <Text as="span" size="T200" truncate>
          Lotus Chat
        </Text>
      </span>
    </div>
  );

  return (
    <header className={css.TitleBar}>
      {mac ? (
        <>
          {controls}
          {dragRegion}
        </>
      ) : (
        <>
          {dragRegion}
          {controls}
        </>
      )}
    </header>
  );
}