/**
 * Every browser and platform fact this plugin reads, in one seam.
 *
 * Nothing here owns state or decides anything: the window's visibility, the
 * notification permission, the notification icon, and the one platform hint the
 * settings copy uses. Each read is contained, because a page a plugin does not
 * control may hide any of them — and because a contained read is what lets the
 * delivery path keep going when the answer is unreadable.
 *
 * @module @dsh-plugin/session-notify/client/platform
 */

/**
 * The window's Notification constructor, or undefined when this environment has
 * none (a plain Node test, or a browser without the API).
 * @returns the constructor, or undefined.
 */
export function notificationApi() {
  const Ctor = globalThis.Notification
  return typeof Ctor === 'function' ? Ctor : undefined
}

/** Permission lookup that never throws in a browser without the API. */
export function notificationPermission() {
  const Ctor = notificationApi()
  if (Ctor === undefined) return 'unsupported'
  const permission = Ctor.permission
  if (permission === 'granted' || permission === 'denied' || permission === 'default') return permission
  return 'default'
}

/**
 * Whether the Harness window is somewhere the user cannot see the app.
 *
 * Two independent browser facts are consulted, and ANY of them counts as "not
 * in the foreground": the page's visibility and the document's focus. They are
 * read at delivery time rather than remembered from an event, because a missed
 * blur in the desktop shell made this plugin believe the window was in front
 * and swallow the alert.
 * @returns whether the alert must go to the system notification channel.
 */
export function windowIsAway() {
  try {
    if (document.visibilityState === 'hidden') return true
  } catch {
    /* an unreadable visibility state leaves the focus fact */
  }
  try {
    if (typeof document.hasFocus === 'function') return !document.hasFocus()
  } catch {
    /* an unreadable focus state leaves the default below */
  }
  return false
}

/** Read the window's live focus state rather than a cached value. */
export function currentFocus() {
  return !windowIsAway()
}

/** Focus the window without letting a refusal stop the navigation. */
export function focusWindow() {
  try {
    globalThis.focus?.()
  } catch {
    /* focus is best effort on every platform */
  }
}

/**
 * The system-notification icon, built once when this bundle materializes: this
 * deployment's own static URL when the page serves this package's assets, else
 * the SVG inline. Icons are cosmetic on every platform, so each step is
 * contained — and materialization happens on first import, not when the bundle
 * script runs, so a page that never activates the plugin never gets here.
 * @type {string | undefined} an icon URL, or undefined when neither form works.
 */
export const systemIcon = (() => {
  try {
    const url = new URL('./icon.svg', document.baseURI).href
    if (url !== '') return url
  } catch {
    /* fall through to the inline form */
  }
  try {
    const svg = '<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 16 16"><path d="M8 2.35C5.7 2.35 3.83 4.22 3.83 6.52V9.02L3.06 11.1C2.99 11.29 3.13 11.48 3.33 11.48H12.67C12.87 11.48 13.01 11.29 12.94 11.1L12.17 9.02V6.52C12.17 4.22 10.3 2.35 8 2.35Z" fill="none" stroke="%23247bbf" stroke-width="1.2"/><path d="M6.3 12.75C6.52 13.66 7.2 14.28 8 14.28C8.8 14.28 9.48 13.66 9.7 12.75" fill="none" stroke="%23247bbf" stroke-width="1.2" stroke-linecap="round"/></svg>'
    return `data:image/svg+xml,${svg}`
  } catch {
    return undefined
  }
})()

/** One best-effort platform hint, used for settings help text only. */
export function platformKey() {
  try {
    const agent = navigator.userAgentData
    const platform = String((agent?.platform ?? navigator.platform) || navigator.userAgent || '')
    if (/win/i.test(platform)) return 'win'
    if (/mac|iphone|ipad/i.test(platform)) return 'mac'
    if (/linux|x11/i.test(platform)) return 'linux'
  } catch {
    /* an unreadable navigator keeps the neutral hint */
  }
  return 'plain'
}