const fs = require("fs");
const path = require("path");

const argv = process.argv.slice(2);
const dir = argv[0];

if (!dir) {
  console.log("Usage: node get-first-features.js [dir]");
  process.exit(-1);
}

const fileNames = fs.readdirSync(dir).filter(fileName => {
  const { ext } = path.parse(fileName);
  return ext === ".geojson";
});

const features = fileNames.forEach(fileName => {
  const { name } = path.parse(fileName);

  const originalFileName = path.join(dir, fileName);
  const newFileName = path.format({ dir, base: `${name}_1.json` });

  const featureCollection = JSON.parse(fs.readFileSync(originalFileName));
  console.log(fileName, featureCollection.features.length);

  const feature = featureCollection.features[0];
  fs.writeFileSync(newFileName, JSON.stringify(feature, null, 2));
});