/**
 * scripts/extract-admin0-pop.mjs — one-time extraction of the population
 * SOURCE for the region-geo manifest: `public/ne-admin0-pop.json`.
 *
 * Output = `{ "<ADM0_A3>": <POP_EST>, ... }` — the estimated population
 * (POP_EST) of every Natural Earth 1:10m **admin-0 country** code, keeping
 * the **maximum** POP_EST seen for each code (Natural Earth ships a few
 * duplicated / broken-out features per code, e.g. the `TLC` stubs, whose
 * POP_EST is 0; the real country always wins by having the larger value).
 * Only codes with a finite, positive POP_EST are recorded (a 0/null POP_EST
 * has nothing to distribute). Keys are sorted; the file is written with
 * 2-space indent + trailing newline (deterministic, committed).
 *
 * Why a separate committed file: `public/region-geo.json` (built by
 * `build-region-geo.mjs`) needs a per-country population, but the raw
 * Natural Earth GeoJSON (13 MB) is a *source* file we deliberately do NOT
 * commit (see the AGENTS.md data-pipeline note). This script distils it
 * into a tiny (a few KB) derived table that IS committed, so the region-geo
 * builder stays fully reproducible in CI without the source present.
 * Re-run only when the underlying Natural Earth data changes.
 *
 * The 1:10m admin-1 file (the one the region generator uses) carries NO
 * population; the 1:10m admin-0 file does (uppercase `POP_EST` / `ADM0_A3`).
 *
 * Usage:
 *   NE_ADMIN0=/path/to/ne_10m_admin_0_countries.geojson node scripts/extract-admin0-pop.mjs
 * (default source: /tmp/ne10m_admin0.geojson)
 */
import { readFileSync, writeFileSync } from 'node:fs';
import path from 'node:path';
import { fileURLToPath } from 'node:url';

const here = path.dirname(fileURLToPath(import.meta.url));
const root = path.resolve(here, '..');

const src = process.env.NE_ADMIN0 || '/tmp/ne10m_admin0.geojson';
let raw;
try {
  raw = readFileSync(src, 'utf8');
} catch (err) {
  console.error(
    `[extract-admin0-pop] could not read the Natural Earth admin-0 source at ${src}. ` +
      `Download it (ne_10m_admin_0_countries.geojson) and re-run with NE_ADMIN0 pointing at it.`,
  );
  throw err;
}

const geo = JSON.parse(raw);

/** ADM0_A3 -> max finite, positive POP_EST. */
const byCode = new Map();
for (const f of geo.features ?? []) {
  const p = f.properties ?? {};
  const code = typeof p.ADM0_A3 === 'string' ? p.ADM0_A3 : '';
  const pop = typeof p.POP_EST === 'number' ? p.POP_EST : NaN;
  if (!code || !Number.isFinite(pop) || pop <= 0) continue;
  const prev = byCode.get(code);
  if (prev === undefined || pop > prev) byCode.set(code, Math.round(pop));
}

if (byCode.size === 0) {
  throw new Error('[extract-admin0-pop] no finite positive POP_EST found in the source — wrong file?');
}

// Deterministic: sorted keys, 2-space indent, trailing newline.
const keys = [...byCode.keys()].sort();
const manifest = {};
for (const k of keys) manifest[k] = byCode.get(k);

const out = path.join(root, 'public', 'ne-admin0-pop.json');
writeFileSync(out, JSON.stringify(manifest, null, 2) + '\n');

let sum = 0;
for (const v of byCode.values()) sum += v;
console.log(
  `[extract-admin0-pop] wrote public/ne-admin0-pop.json — ${byCode.size} country codes, ` +
    `total population ${sum.toLocaleString('en-US')} (Natural Earth 1:10m admin-0, max POP_EST per code)`,
);