import type { NextRequest } from "next/server";
import { OWM_TILE_LAYERS } from "@/lib/radar/layers";
import { forbidCrossSite } from "@/lib/weather/respond";

const CARTO_LAYERS: Record<string, string> = {
  "carto-dark-nolabels": "dark_nolabels",
  "carto-dark-labels": "dark_only_labels",
};

const CARTO_SUBDOMAINS = ["a", "b", "c", "d"] as const;
const MAX_ZOOM = 18;

/**
 * GET /api/tiles/[layer]/[z]/[x]/[y] → one map tile (PNG).
 *
 * Proxies both OpenWeather weather overlays (OPENWEATHER_API_KEY) and CARTO
 * dark basemap/label tiles (CARTO_API_KEY) server-side so keys stay in `.env`
 * or `.env.local` and cannot be hotlinked from other domains.
 */
export async function GET(
  request: NextRequest,
  context: { params: Promise<{ layer: string; z: string; x: string; y: string }> },
) {
  const blocked = forbidCrossSite(request);
  if (blocked) return blocked;

  const { layer, z, x, y } = await context.params;
  const [zi, xi, yi] = [z, x, y].map(Number);
  const maxIndex = 2 ** zi;

  if (
    ![zi, xi, yi].every((n) => Number.isInteger(n) && n >= 0) ||
    zi > MAX_ZOOM ||
    xi >= maxIndex ||
    yi >= maxIndex
  ) {
    return new Response("Bad tile coordinates", { status: 400 });
  }

  // 1. CARTO dark basemap & place-label tiles
  const cartoStyle = CARTO_LAYERS[layer];
  if (cartoStyle) {
    const key = (process.env.CARTO_API_KEY ?? process.env.NEXT_PUBLIC_CARTO_API_KEY ?? "").trim();
    const scale = request.nextUrl.searchParams.get("r") === "@2x" ? "@2x" : "";
    const sub = CARTO_SUBDOMAINS[(xi + yi) % CARTO_SUBDOMAINS.length];
    const query = key ? `?key=${encodeURIComponent(key)}` : "";
    const url = `https://${sub}.basemaps.cartocdn.com/${cartoStyle}/${z}/${x}/${y}${scale}.png${query}`;

    const headers: HeadersInit = {};
    const referer = request.headers.get("referer");
    const origin = request.headers.get("origin");
    if (referer) headers.Referer = referer;
    if (origin) headers.Origin = origin;

    const upstream = await fetch(
      url,
      key ? { headers, next: { revalidate: 86_400 } } : { headers, cache: "no-store" },
    ).catch(() => null);

    if (!upstream?.ok) return new Response("Tile unavailable", { status: 502 });

    // CARTO tags unauthenticated placeholder tiles with an `"wm-..."` ETag; never cache those.
    const isWatermarked = !key || Boolean(upstream.headers.get("etag")?.includes("wm-"));

    return new Response(upstream.body, {
      headers: {
        "Content-Type": "image/png",
        "Cache-Control": isWatermarked ? "no-store" : "public, max-age=86400",
      },
    });
  }

  // 2. OpenWeather weather-model overlay tiles
  const owmLayer = OWM_TILE_LAYERS[layer];
  const owmKey = process.env.OPENWEATHER_API_KEY?.trim();

  if (!owmLayer) return new Response("Unknown layer", { status: 404 });
  if (!owmKey) return new Response("OPENWEATHER_API_KEY is not set", { status: 503 });

  const upstream = await fetch(`https://tile.openweathermap.org/map/${owmLayer}/${z}/${x}/${y}.png?appid=${owmKey}`, {
    next: { revalidate: 600 },
  }).catch(() => null);

  if (!upstream?.ok) return new Response("Tile unavailable", { status: 502 });

  return new Response(upstream.body, {
    headers: {
      "Content-Type": "image/png",
      "Cache-Control": "public, max-age=600",
    },
  });
}