import { NextResponse, type NextRequest } from "next/server";
import { fetchJson } from "@/lib/weather/http";
import { errorResponse, forbidCrossSite } from "@/lib/weather/respond";
import type { RadarFrame } from "@/lib/weather/types";

/**
 * GET /api/radar → RainViewer frames, oldest first, ready for Leaflet.
 *
 * RainViewer publishes an index of frames. Each frame's `path` is a hash, not a
 * timestamp, so tile URLs must always be built from this index — never guessed.
 * Docs: https://www.rainviewer.com/api/weather-maps-api.html
 */

interface RainViewerIndex {
  host: string;
  radar: { past: { time: number; path: string }[] };
}

// Last 7 frames ≈ one hour. Keeps tile requests well under RainViewer's
// limit of 100 requests per minute per IP.
const FRAME_COUNT = 7;
const COLOR_SCHEME = 2; // "Universal Blue", the only scheme still offered
const OPTIONS = "1_1"; // smoothed, snow shown in its own colors

export async function GET(request: NextRequest) {
  const blocked = forbidCrossSite(request);
  if (blocked) return blocked;

  try {
    const index = await fetchJson<RainViewerIndex>("https://api.rainviewer.com/public/weather-maps.json", "RainViewer", {
      cacheSeconds: 300, // new frames arrive every 10 minutes
    });

    const frames: RadarFrame[] = index.radar.past.slice(-FRAME_COUNT).map((frame) => ({
      time: new Date(frame.time * 1000).toISOString(),
      url: `${index.host}${frame.path}/256/{z}/{x}/{y}/${COLOR_SCHEME}/${OPTIONS}.png`,
    }));

    return NextResponse.json(frames);
  } catch (error) {
    return errorResponse(error);
  }
}