import { NextResponse } from "next/server";
import { fetchServerForecast } from "@/lib/server-forecast";
import { fetchMeteoWarnings } from "@/lib/server-warnings";
import { getPushSubscriptions, hasSentTomorrowBrief, markTomorrowBriefSent, removePushSubscription } from "@/lib/push-store";
import { isWebPushConfigured, sendTomorrowBriefNotification } from "@/lib/push-service";
import { buildTomorrowWeatherBrief } from "@/lib/weather-brief";
import { DEFAULT_WIND_SPEED_UNIT } from "@/lib/weather-utils";

export const runtime = "nodejs";

function isCronAuthorized(request: Request) {
  const secret = process.env.NOTIFICATIONS_CRON_SECRET;
  if (!secret) return process.env.NODE_ENV !== "production";
  const authHeader = request.headers.get("authorization");
  const secretHeader = request.headers.get("x-cron-secret");
  return authHeader === `Bearer ${secret}` || secretHeader === secret;
}

function getWarsawDateKey(date = new Date(), dayOffset = 0) {
  const parts = new Intl.DateTimeFormat("en-CA", {
    timeZone: "Europe/Warsaw",
    year: "numeric",
    month: "2-digit",
    day: "2-digit",
  }).formatToParts(date);
  const part = (type: Intl.DateTimeFormatPartTypes) => parts.find((entry) => entry.type === type)?.value ?? "";
  if (dayOffset === 0) return `${part("year")}-${part("month")}-${part("day")}`;

  const shiftedDate = new Date(Date.UTC(Number(part("year")), Number(part("month")) - 1, Number(part("day")) + dayOffset, 12));
  const shiftedParts = new Intl.DateTimeFormat("en-CA", {
    timeZone: "Europe/Warsaw",
    year: "numeric",
    month: "2-digit",
    day: "2-digit",
  }).formatToParts(shiftedDate);
  const shiftedPart = (type: Intl.DateTimeFormatPartTypes) => shiftedParts.find((entry) => entry.type === type)?.value ?? "";
  return `${shiftedPart("year")}-${shiftedPart("month")}-${shiftedPart("day")}`;
}

export async function GET(request: Request) {
  if (!isCronAuthorized(request)) {
    return NextResponse.json({ error: "Unauthorized." }, { status: 401 });
  }
  if (!isWebPushConfigured()) {
    return NextResponse.json({ error: "Web Push is not configured." }, { status: 503 });
  }

  const now = new Date();
  const targetDateKey = getWarsawDateKey(now, 1);
  const subscriptions = getPushSubscriptions().filter((subscription) => (
    subscription.enabled
    && subscription.tomorrowBriefEnabled
    && Number.isFinite(subscription.latitude)
    && Number.isFinite(subscription.longitude)
  ));
  let warningsUnavailable = false;
  const warnings = await fetchMeteoWarnings(AbortSignal.timeout(12_000)).catch(() => {
    warningsUnavailable = true;
    return [];
  });
  let sent = 0;
  let skipped = 0;
  let failed = 0;

  for (const subscription of subscriptions) {
    if (hasSentTomorrowBrief(subscription.endpoint, targetDateKey)) {
      skipped += 1;
      continue;
    }

    try {
      const forecast = await fetchServerForecast(subscription.latitude as number, subscription.longitude as number);
      const brief = buildTomorrowWeatherBrief({
        forecast,
        warnings,
        province: subscription.province,
        countyTeryt: subscription.countyTeryt,
        locationName: subscription.locationName ?? "wtr.",
        language: subscription.language,
        windSpeedUnit: subscription.windSpeedUnit ?? DEFAULT_WIND_SPEED_UNIT,
        now,
      });
      if (!brief) {
        skipped += 1;
        continue;
      }
      await sendTomorrowBriefNotification(subscription, brief);
      markTomorrowBriefSent(subscription.endpoint, targetDateKey);
      sent += 1;
    } catch (error) {
      failed += 1;
      const statusCode = typeof error === "object" && error !== null && "statusCode" in error ? Number(error.statusCode) : null;
      if (statusCode === 404 || statusCode === 410) removePushSubscription(subscription.endpoint);
    }
  }

  return NextResponse.json({
    ok: true,
    date: targetDateKey,
    subscriptions: subscriptions.length,
    warningsUnavailable,
    sent,
    skipped,
    failed,
  });
}