import { createHash } from 'node:crypto'
import { readFile } from 'node:fs/promises'
import { basename, join } from 'node:path'

// Earth remains a standalone public page with its pinned import map. Bundle
// only project modules, retaining the /earth/js/ base for assets and workers.
export function earthRuntimePlugin(root) {
  const earth = join(root, 'public/earth')
  let compilation = null
  async function compile() {
    if (compilation) return compilation
    compilation = (async () => {
      const result = await Bun.build({
        entrypoints: [join(earth, 'js/main.js'), join(earth, 'js/earth-preload.js')],
        target: 'browser', format: 'esm', splitting: true, packages: 'external', minify: true,
        naming: { entry: 'runtime-[name]-[hash].js', chunk: 'runtime-[hash].js' },
      })
      if (!result.success) throw new AggregateError(result.logs, 'Earth runtime build failed')
      const assets = new Map(await Promise.all(result.outputs.map(async output => {
        const source = await output.text()
        return [basename(output.path), { source,
          etag: `"${createHash('sha256').update(source).digest('hex')}"` }]
      })))
      let html = await readFile(join(earth, 'index.html'), 'utf8')
      for (const entry of ['main', 'earth-preload']) {
        const filename = [...assets.keys()].find(name => name.startsWith(`runtime-${entry}-`))
        html = html.replace(new RegExp(`src="(?:\\./)?js/${entry}\\.js"`), `src="./js/${filename}"`)
      }
      return { assets, html }
    })().catch(error => { compilation = null; throw error })
    return compilation
  }
  return {
    name: 'earth-runtime',
    configureServer(server) {
      server.watcher.on('change', file => {
        if (file.startsWith(earth) && (file.endsWith('.js') || file === join(earth, 'index.html'))) {
          compilation = null
        }
      })
      server.middlewares.use(async (req, res, next) => {
        const url = (req.url || '').split('?')[0]
        const isPage = url === '/earth/index.html' || url === '/earth/'
        const isRuntime = /^\/earth\/js\/runtime-[\w-]+\.js$/.test(url)
        if (!isPage && !isRuntime) return next()
        try {
          const { assets, html } = await compile()
          const asset = assets.get(basename(url))
          if (!isPage && !asset) return next()
          res.setHeader('Cache-Control', 'no-cache')
          if (asset) {
            res.setHeader('ETag', asset.etag)
            if (req.headers['if-none-match'] === asset.etag) {
              res.statusCode = 304; res.end(); return
            }
          }
          res.setHeader('Content-Type', isPage ? 'text/html; charset=utf-8' : 'text/javascript; charset=utf-8')
          res.end(isPage ? html : asset.source)
        } catch (error) { next(error) }
      })
    },
    async generateBundle() {
      const { assets, html } = await compile()
      for (const [name, asset] of assets) {
        this.emitFile({ type: 'asset', fileName: `earth/js/${name}`, source: asset.source })
      }
      this.emitFile({ type: 'asset', fileName: 'earth/index.html', source: html })
    },
  }
}