// The rewrite rules that send a shared link here catch the original link on
// the way back out too, so in Safari "Open on <platform>" lands back on this
// page. Handing the address to a different browser is the way out, and the
// only way to do that from a web page is that browser's own URL scheme --
// which every one of them spells differently. Some swap the scheme, some
// prefix it, some take the whole address as a query parameter.

/** http -> googlechrome://, https -> googlechromes:// */
const chrome = (url) => url.replace(/^http(s?):/, 'googlechrome$1:');

// Edge keeps the original scheme either way, but on macOS it stays in the
// address and the scheme is prefixed, while on iOS it is folded into the
// scheme itself.
const edgeMacos = (url) => `microsoft-edge:${url}`;
const edgeIos = (url) => url.replace(/^http(s?):/, 'microsoft-edge-http$1:');

/** Firefox and Orion take the address as a parameter instead. */
const openUrl = (scheme) => (url) => `${scheme}://open-url?url=${encodeURIComponent(url)}`;

// `null` means the browser is there but ships no scheme to reach it on that
// system, so there is nothing to offer beyond the plain link.
export const BROWSERS = [
  { id: 'default', label: 'Default browser', macos: null, ios: null },
  { id: 'chrome', label: 'Chrome', macos: chrome, ios: chrome },
  { id: 'edge', label: 'Edge', macos: edgeMacos, ios: edgeIos },
  { id: 'firefox', label: 'Firefox', macos: null, ios: openUrl('firefox') },
  { id: 'orion', label: 'Orion', macos: openUrl('orion'), ios: openUrl('orion') },
];

/**
 * iPadOS calls itself MacIntel, so the platform string alone cannot tell the
 * two apart; the touch points can. Everything else gets the desktop table --
 * the only desktop this is ever opened on is a Mac.
 *
 * @param {{ platform?: string, maxTouchPoints?: number }} [nav]
 */
export function detectOs(nav = globalThis.navigator) {
  const platform = nav?.platform ?? '';
  if (/^iP(hone|ad|od)/.test(platform)) return 'ios';
  if (platform === 'MacIntel' && (nav?.maxTouchPoints ?? 0) > 1) return 'ios';
  return 'macos';
}

/** The browsers worth offering here: the default, plus the ones this system
 *  actually has a scheme for. */
export function browsersFor(os) {
  return BROWSERS.filter((browser) => browser.id === 'default' || browser[os]);
}

function browserById(id) {
  return BROWSERS.find((browser) => browser.id === id);
}

/**
 * The address to open. A browser with no scheme on this system, an unknown
 * id, or anything that is not an ordinary web link is handed back untouched:
 * a dead custom scheme opens nothing at all, which is worse than the plain
 * link opening in the wrong browser.
 */
export function openUrlFor(url, browserId, os) {
  const rewrite = browserById(browserId)?.[os];
  if (!rewrite || !/^https?:\/\//i.test(url)) return url;
  return rewrite(url);
}