/**
 * Downloads power plant data from the EIA ArcGIS FeatureServer.
 *
 * Fetches all US power plants >= 50 MW with pagination,
 * then saves the combined result as data/power-plants.geojson.
 *
 * Usage: bun run scripts/download-power-plants.ts
 */

import { mkdirSync, writeFileSync } from 'fs';
import { resolve } from 'path';
import { z } from 'zod/v4';

const BASE_URL =
  'https://services2.arcgis.com/FiaPA4ga0iQKduv3/ArcGIS/rest/services/Power_Plants_in_the_US/FeatureServer/0/query';

const OUT_FIELDS = [
  'Plant_Name',
  'Plant_Code',
  'Utility_Na',
  'State',
  'County',
  'Latitude',
  'Longitude',
  'PrimSource',
  'Total_MW',
].join(',');

const PAGE_SIZE = 2000;

const ArcGISFeatureSchema = z.object({
  type: z.literal('Feature'),
  geometry: z.object({
    type: z.literal('Point'),
    coordinates: z.tuple([z.number(), z.number()]),
  }),
  properties: z.record(z.string(), z.unknown()),
});

const ArcGISResponseSchema = z.object({
  type: z.literal('FeatureCollection'),
  features: z.array(ArcGISFeatureSchema),
  properties: z.object({ exceededTransferLimit: z.boolean().optional() }).optional(),
});

type ArcGISFeature = z.infer<typeof ArcGISFeatureSchema>;
type ArcGISGeoJSONResponse = z.infer<typeof ArcGISResponseSchema>;

async function fetchPage(offset: number): Promise<ArcGISGeoJSONResponse> {
  const params = new URLSearchParams({
    where: 'Total_MW >= 50',
    outFields: OUT_FIELDS,
    f: 'geojson',
    resultRecordCount: String(PAGE_SIZE),
    resultOffset: String(offset),
  });

  const url = `${BASE_URL}?${params.toString()}`;
  console.log(`Fetching offset=${offset}...`);

  const res = await fetch(url);
  if (!res.ok) {
    throw new Error(`HTTP ${res.status}: ${res.statusText}`);
  }

  const json: unknown = await res.json();
  return ArcGISResponseSchema.parse(json);
}

async function main() {
  const allFeatures: ArcGISFeature[] = [];
  let offset = 0;

  while (true) {
    const page = await fetchPage(offset);
    const count = page.features.length;
    console.log(`  Got ${count} features`);
    allFeatures.push(...page.features);

    // ArcGIS signals more data via exceededTransferLimit or by returning a full page
    const hasMore = page.properties?.exceededTransferLimit === true || count >= PAGE_SIZE;
    if (!hasMore || count === 0) break;
    offset += PAGE_SIZE;
  }

  console.log(`\nTotal features: ${allFeatures.length}`);

  const collection: ArcGISGeoJSONResponse = {
    type: 'FeatureCollection',
    features: allFeatures,
  };

  const outDir = resolve(import.meta.dirname, '..', 'data');
  mkdirSync(outDir, { recursive: true });

  const outPath = resolve(outDir, 'power-plants.geojson');
  writeFileSync(outPath, JSON.stringify(collection, null, 2));
  console.log(`Saved to ${outPath}`);
}

main().catch((err: unknown) => {
  console.error('Download failed:', err);
  process.exit(1);
});