vite.config.js

import { defineConfig } from 'vite';
import { resolve, join, extname } from 'node:path';
import { existsSync, statSync, createReadStream, cpSync } from 'node:fs';

const repoRoot = resolve(import.meta.dirname ?? new URL('.', import.meta.url).pathname);

const MIME = {
  '.json': 'application/json',
  '.csv': 'text/csv',
  '.txt': 'text/plain',
};

function serveDataDirPlugin() {
  return {
    name: 'serve-data-dir',
    configureServer(server) {
      server.middlewares.use((req, res, next) => {
        if (!req.url) return next();
        const url = req.url.split('?')[0];
        if (!url.startsWith('/data/')) return next();
        // Module imports (e.g. `import FIGURES from '.../figures.json'`) must fall
        // through to Vite's JSON→ESM transform; serving them raw as
        // application/json makes the browser reject them as module scripts and
        // the app fails to boot in dev. Runtime data fetches (d3 json/csv) have
        // sec-fetch-dest "empty", not "script", so they still get served here.
        if (req.headers['sec-fetch-dest'] === 'script') return next();
        const filePath = join(repoRoot, url);
        if (!existsSync(filePath) || !statSync(filePath).isFile()) return next();
        const ext = extname(filePath);
        res.setHeader('Content-Type', MIME[ext] ?? 'application/octet-stream');
        createReadStream(filePath).pipe(res);
      });
    },
    closeBundle() {
      const src = join(repoRoot, 'data', 'processed');
      const dst = join(repoRoot, 'dist', 'data', 'processed');
      if (existsSync(src)) {
        cpSync(src, dst, { recursive: true });
        console.log('[serve-data-dir] copied data/processed → dist/data/processed');
      }
    },
  };
}

export default defineConfig({
  root: repoRoot,
  base: './',
  publicDir: 'public',
  plugins: [serveDataDirPlugin()],
  build: {
    outDir: 'dist',
    emptyOutDir: true,
    target: 'es2020',
    rollupOptions: {
      input: resolve(repoRoot, 'index.html'),
    },
  },
  server: {
    port: 5173,
    open: false,
  },
});