import { defineConfig, loadEnv } from 'vite'
import react from '@vitejs/plugin-react'
import tailwindcss from '@tailwindcss/vite'
import { fileURLToPath, URL } from 'node:url'

// In dev, Vite serves the SPA with HMR and proxies /api to the Go backend. The
// backend listens on PANSY_PORT (default 8080); read it so the proxy target
// tracks an overridden port. The production build is embedded into the Go binary
// (see internal/webdist), so no proxy is involved there.
export default defineConfig(({ mode }) => {
  const env = loadEnv(mode, process.cwd(), '')
  const backendPort = env.PANSY_PORT || process.env.PANSY_PORT || '8080'
  return {
    plugins: [react(), tailwindcss()],
    resolve: {
      alias: {
        '@': fileURLToPath(new URL('./src', import.meta.url)),
      },
    },
    server: {
      port: 5173,
      proxy: {
        '/api': {
          target: `http://127.0.0.1:${backendPort}`,
          changeOrigin: true,
        },
      },
    },
    build: {
      outDir: 'dist',
      sourcemap: true,
      rollupOptions: {
        output: {
          // The app-wide core goes in ONE cached vendor chunk (rarely changes, so
          // it survives deploys while the tiny app chunk churns). react + react-dom
          // + scheduler MUST stay together — splitting react-dom into its own chunk
          // reorders module init across chunk boundaries and breaks React 19 at
          // load ("Cannot set 'Activity' of undefined"). Everything else — the
          // gesture engine, the assistant's markdown renderer + its ecosystem —
          // rides with whatever imports it, so a lazily-loaded route/feature keeps
          // it out of the eager first paint. The routes are code-split via
          // React.lazy (router.tsx), where the real first-paint win is.
          manualChunks(id) {
            if (!id.includes('node_modules')) return undefined
            if (
              /[/\\]node_modules[/\\](react|react-dom|scheduler|@tanstack|zustand|zod|clsx|tailwind-merge)[/\\]/.test(
                id,
              )
            ) {
              return 'vendor'
            }
            return undefined
          },
        },
      },
    },
  }
})