import { NextRequest, NextResponse } from "next/server";
import { BACKEND_ENTITLEMENT_HEADER } from "@/lib/backend-auth";
import { createSupabaseRouteClient, hasSupabaseServerEnv } from "@/lib/supabase/server";
import { getConfiguredSiteUrl } from "@/lib/site-url";

const API_BASE = process.env.POLYWEATHER_API_BASE_URL;

function normalizeNextPath(input: string | null) {
  const fallback = "/";
  const raw = String(input || "").trim();
  if (!raw) return fallback;
  if (!raw.startsWith("/")) return fallback;
  if (raw.startsWith("//")) return fallback;
  return raw;
}

async function warmSignupTrial(accessToken: string) {
  const token = String(accessToken || "").trim();
  if (!API_BASE || !token) return;

  const headers = new Headers({
    Accept: "application/json",
    Authorization: `Bearer ${token}`,
  });
  const backendToken = process.env.POLYWEATHER_BACKEND_ENTITLEMENT_TOKEN?.trim();
  if (backendToken) {
    headers.set(BACKEND_ENTITLEMENT_HEADER, backendToken);
  }

  const controller = new AbortController();
  const timeoutId = setTimeout(() => controller.abort(), 2500);
  try {
    await fetch(`${API_BASE}/api/auth/me`, {
      cache: "no-store",
      headers,
      signal: controller.signal,
    });
  } catch {
    // The account/terminal bootstrap will retry. Callback must not strand login.
  } finally {
    clearTimeout(timeoutId);
  }
}

export async function GET(request: NextRequest) {
  const siteUrl = getConfiguredSiteUrl();
  if (siteUrl) {
    const expectedHost = new URL(siteUrl).host;
    const requestHost =
      request.headers.get("x-forwarded-host") ||
      request.headers.get("host") ||
      "";
    if (requestHost !== expectedHost) {
      const canonicalCallbackUrl = new URL(request.nextUrl.pathname, siteUrl);
      canonicalCallbackUrl.search = request.nextUrl.search;
      return NextResponse.redirect(canonicalCallbackUrl);
    }
  }

  const nextPath = normalizeNextPath(request.nextUrl.searchParams.get("next"));
  const baseUrl = siteUrl || request.nextUrl.origin;
  const redirectUrl = new URL(nextPath, baseUrl);

  if (!hasSupabaseServerEnv()) {
    return NextResponse.redirect(redirectUrl);
  }

  const response = NextResponse.redirect(redirectUrl);
  const supabase = createSupabaseRouteClient(request, response);
  const code = request.nextUrl.searchParams.get("code");
  if (code) {
    const {
      data: { session },
    } = await supabase.auth.exchangeCodeForSession(code);
    await warmSignupTrial(session?.access_token || "");
  }

  return response;
}