import webPush, { type PushSubscription } from "web-push";
import type { Language } from "@/lib/i18n";
import { formatProvinceName } from "@/lib/provinces";
import type { WeatherWarning } from "@/types/imgw";
import type { WarningPushSubscription } from "@/types/notifications";

const VAPID_PUBLIC_KEY = process.env.WEB_PUSH_VAPID_PUBLIC_KEY;
const VAPID_PRIVATE_KEY = process.env.WEB_PUSH_VAPID_PRIVATE_KEY;
const VAPID_SUBJECT = process.env.WEB_PUSH_VAPID_SUBJECT ?? "mailto:alerts@wtr.local";

let configured = false;

export function getVapidPublicKey() {
  return VAPID_PUBLIC_KEY ?? null;
}

export function isWebPushConfigured() {
  return Boolean(VAPID_PUBLIC_KEY && VAPID_PRIVATE_KEY);
}

function ensureWebPushConfigured() {
  if (!VAPID_PUBLIC_KEY || !VAPID_PRIVATE_KEY) throw new Error("Web Push VAPID keys are not configured.");
  if (!configured) {
    webPush.setVapidDetails(VAPID_SUBJECT, VAPID_PUBLIC_KEY, VAPID_PRIVATE_KEY);
    configured = true;
  }
}

function getWarningLevelLabel(warning: WeatherWarning, language: Language) {
  if (warning.level === null) return language === "pl" ? "stopień nieokreślony" : "level not specified";
  return language === "pl" ? `stopień ${warning.level}` : `level ${warning.level}`;
}

function formatWarningValidity(warning: WeatherWarning, language: Language) {
  if (!warning.validFrom && !warning.validTo) return null;
  const locale = language === "pl" ? "pl-PL" : "en-GB";
  const formatter = new Intl.DateTimeFormat(locale, {
    day: "2-digit",
    month: "2-digit",
    hour: "2-digit",
    minute: "2-digit",
  });
  const from = warning.validFrom ? formatter.format(new Date(warning.validFrom)) : null;
  const to = warning.validTo ? formatter.format(new Date(warning.validTo)) : null;
  if (from && to) return language === "pl" ? `od ${from} do ${to}` : `from ${from} to ${to}`;
  if (from) return language === "pl" ? `od ${from}` : `from ${from}`;
  return language === "pl" ? `do ${to}` : `until ${to}`;
}

function buildWarningPayload(preference: WarningPushSubscription, warning: WeatherWarning) {
  const province = formatProvinceName(preference.province, preference.language);
  const title = warning.title || (preference.language === "pl" ? "Ostrzeżenie meteorologiczne" : "Weather warning");
  const validity = formatWarningValidity(warning, preference.language);
  const level = getWarningLevelLabel(warning, preference.language);
  const bodyParts = preference.language === "pl"
    ? [`${province}: ${level}`, validity, warning.probability !== null ? `prawdopodobieństwo ${warning.probability}%` : null]
    : [`${province}: ${level}`, validity, warning.probability !== null ? `${warning.probability}% probability` : null];

  return {
    title: `IMGW: ${title}`,
    body: bodyParts.filter(Boolean).join(" · "),
    url: "/warnings",
    warningId: warning.id,
  };
}

export async function sendWarningNotification(preference: WarningPushSubscription, warning: WeatherWarning) {
  ensureWebPushConfigured();
  const payload = JSON.stringify(buildWarningPayload(preference, warning));
  await webPush.sendNotification(preference.subscription as PushSubscription, payload);
}

export async function sendTestNotification(preference: WarningPushSubscription) {
  ensureWebPushConfigured();
  const province = formatProvinceName(preference.province, preference.language);
  const payload = JSON.stringify({
    title: preference.language === "pl" ? "wtr.: test powiadomień IMGW" : "wtr.: IMGW notification test",
    body: preference.language === "pl"
      ? `Powiadomienia są aktywne dla województwa: ${province}.`
      : `Notifications are active for: ${province}.`,
    url: "/settings",
  });
  await webPush.sendNotification(preference.subscription as PushSubscription, payload);
}