// Vite plugin: a virtual client entry that mounts the user's app. The
// user writes one isomorphic module; bankai generates the two lines of
// browser glue instead of asking for a second file.

export const CLIENT_ID = 'bankai:client'
const RESOLVED_CLIENT_ID = '\0' + CLIENT_ID

// the URL a browser uses to import the virtual module through Vite's dev
// middleware ('\0' encodes as '__x00__')
export const CLIENT_URL = '/@id/__x00__' + CLIENT_ID

export default function bankaiPlugin (entry, { css } = {}) {
  return {
    name: 'bankai',
    resolveId (id) {
      if (id === CLIENT_ID) return RESOLVED_CLIENT_ID
    },
    load (id) {
      if (id === RESOLVED_CLIENT_ID) {
        return [
          // the style.css convention: CSS is a client concern, so the
          // client glue imports it and server code never sees it — the
          // v8 answer to what sheetify transforms did in v9
          ...(css ? [`import ${JSON.stringify(css)}`] : []),
          `import create from ${JSON.stringify(entry)}`,
          'const app = typeof create === "function" && !create.mount ? create() : create',
          'app.mount(app.selector || "body")'
        ].join('\n')
      }
    }
  }
}

// <entry dir>/style.css, when it exists
export async function findCss (entry) {
  const { access } = await import('node:fs/promises')
  const { join, dirname } = await import('node:path')
  const candidate = join(dirname(entry), 'style.css')
  try {
    await access(candidate)
    return candidate
  } catch (e) {
    return null
  }
}