"use client";

import { useEffect, useState } from "react";

/**
 * "Install the app" helpers: platform/browser detection plus the small amount
 * of persistence the bottom sheet needs.
 *
 * Everything here is browser-only and side-effect free until called. The
 * install prompt is never shown on desktop, never inside an installed app, and
 * at most once per 7 days after a dismissal.
 */

export type InstallPlatform = "ios" | "android" | "other";
export type InstallBrowser = "safari" | "chrome" | "other" | "in-app";

/** Chrome's `beforeinstallprompt` event (not in the DOM typings). */
export type BeforeInstallPromptEvent = Event & {
  prompt: () => Promise<void>;
  userChoice: Promise<{ outcome: "accepted" | "dismissed"; platform: string }>;
};

declare global {
  interface Window {
    __freezmoInstallPrompt?: BeforeInstallPromptEvent;
  }
}

const DISMISS_KEY = "freezmo.install.dismissedAt";
const INSTALLED_KEY = "freezmo.install.installed";
const THEME_KEY = "freezmo.theme";

/** How long a dismissal silences the automatic prompt. */
export const INSTALL_REMIND_MS = 7 * 24 * 60 * 60 * 1000;

/** Fired by Settings to open the sheet manually (ignores the dismissal). */
export const OPEN_INSTALL_EVENT = "freezmo:open-install";
/** Fired by the inline head script when Chrome offers an install prompt. */
export const INSTALL_PROMPT_EVENT = "freezmo:installprompt";
/** Fired by the inline head script when the app gets installed. */
export const INSTALLED_EVENT = "freezmo:installed";

/**
 * iPhone/iPad (including iPadOS 13+, which reports itself as a Mac — a Mac
 * with more than one touch point is really an iPad) or Android. Everything
 * else is desktop/unknown and never sees the prompt.
 */
export function detectPlatform(
  ua: string = typeof navigator === "undefined" ? "" : navigator.userAgent,
  maxTouchPoints: number = typeof navigator === "undefined" ? 0 : navigator.maxTouchPoints || 0,
): InstallPlatform {
  if (/iPhone|iPad|iPod/i.test(ua)) return "ios";
  if (/Macintosh/i.test(ua) && maxTouchPoints > 1) return "ios";
  if (/Android/i.test(ua)) return "android";
  return "other";
}

/** Embedded webviews (Instagram, Facebook, …) can't install anything. */
const IN_APP_PATTERN =
  /(FBAN|FBAV|FB_IAB|Instagram|Line\/|Twitter|TikTok|SnapChat|Pinterest|MicroMessenger|GSA\/|; wv\))/i;

/**
 * Which browser is this? Used to adapt step 1 of the instructions:
 * iOS outside Safari (and Android outside Chrome) has to switch browsers
 * first, and in-app browsers can't install at all.
 */
export function detectBrowser(
  platform: InstallPlatform,
  ua: string = typeof navigator === "undefined" ? "" : navigator.userAgent,
): InstallBrowser {
  if (IN_APP_PATTERN.test(ua)) return "in-app";
  if (platform === "ios") {
    const otherIos = /(CriOS|FxiOS|EdgiOS|OPiOS|DuckDuckGo)/.test(ua);
    return /Safari\//.test(ua) && !otherIos ? "safari" : "other";
  }
  if (platform === "android") {
    const otherAndroid = /(SamsungBrowser|OPR\/|Firefox|EdgA|DuckDuckGo|YaBrowser|Vivaldi)/.test(ua);
    return /Chrome\//.test(ua) && !otherAndroid ? "chrome" : "other";
  }
  return "other";
}

/** True when the app is already running from the home screen / app switcher. */
export function isStandalone(): boolean {
  if (typeof window === "undefined") return false;
  try {
    const displayMode = window.matchMedia("(display-mode: standalone)").matches;
    const iosStandalone =
      (window.navigator as Navigator & { standalone?: boolean }).standalone === true;
    return displayMode || iosStandalone;
  } catch {
    return false;
  }
}

export function markInstalled(): void {
  try {
    window.localStorage.setItem(INSTALLED_KEY, "1");
  } catch {
    /* private mode */
  }
}

export function isMarkedInstalled(): boolean {
  try {
    return window.localStorage.getItem(INSTALLED_KEY) === "1";
  } catch {
    return false;
  }
}

/** Installed now, or recorded as installed earlier in this browser. */
export function isInstalled(): boolean {
  return isStandalone() || isMarkedInstalled();
}

/** True while a previous dismissal is still within its 7-day window. */
export function isDismissed(now: number = Date.now()): boolean {
  try {
    const raw = window.localStorage.getItem(DISMISS_KEY);
    if (!raw) return false;
    const at = Number.parseInt(raw, 10);
    return Number.isFinite(at) && now - at < INSTALL_REMIND_MS;
  } catch {
    return false;
  }
}

export function dismissInstallPrompt(now: number = Date.now()): void {
  try {
    window.localStorage.setItem(DISMISS_KEY, String(now));
  } catch {
    /* private mode */
  }
}

/** Opens the sheet manually (used by the Settings row). */
export function openInstallSheet(): void {
  if (typeof window === "undefined") return;
  window.dispatchEvent(new CustomEvent(OPEN_INSTALL_EVENT));
}

/**
 * The sheet follows the app's *explicit* theme choice: dark unless the user
 * picked light in the app (a system preference alone doesn't count).
 */
export function installSheetTheme(): "dark" | "light" {
  try {
    return window.localStorage.getItem(THEME_KEY) === "light" ? "light" : "dark";
  } catch {
    return "dark";
  }
}

/**
 * Settings helper: is the "Install app" row relevant here? (Mobile platform
 * and not installed yet.) Starts false so server rendering never mismatches.
 */
export function useInstallAvailable(): boolean {
  const [available, setAvailable] = useState(false);
  useEffect(() => {
    setAvailable(detectPlatform() !== "other" && !isInstalled());
  }, []);
  return available;
}