// bankai build — the production build. Only the CLIENT is bundled: the
// server side of a choo v8 app is plain ESM that Node runs as-authored,
// so there is no server build to rot. Outputs:
//   dist/assets/*            hashed client chunks + css
//   dist/.vite/manifest.json Vite's build manifest
//   dist/bankai.json         bankai's route/asset metadata for serving
//   dist/**/index.html       prerendered routes (--prerender)
//   dist/sw.js               service worker (if <entry dir>/sw.js exists),
//                            with the precached asset list defined in
//   *.br / *.gz              precompressed siblings for every text asset

import { readFile, writeFile, readdir, stat, access, mkdir } from 'node:fs/promises'
import { join, dirname, resolve } from 'node:path'
import { pathToFileURL } from 'node:url'
import { brotliCompress, gzip, constants } from 'node:zlib'
import { promisify } from 'node:util'

import bankaiPlugin, { findCss, CLIENT_ID } from './plugin.js'
import { resolveApp } from './app.js'
import { documentHead, documentTail } from './document.js'

const brotli = promisify(brotliCompress)
const gzipP = promisify(gzip)

export default async function buildApp ({ entry, outDir = 'dist', title = 'choo', prerender = [] }) {
  const { build } = await import('vite')
  entry = resolve(entry)
  outDir = resolve(outDir)
  const css = await findCss(entry)

  await build({
    appType: 'custom',
    plugins: [bankaiPlugin(entry, { css })],
    logLevel: 'warn',
    // real-world stylesheets (tachyons et al) carry IE-era hacks like
    // *zoom; strip them instead of refusing to build
    css: { lightningcss: { errorRecovery: true } },
    build: {
      outDir,
      emptyOutDir: true,
      manifest: true,
      rollupOptions: { input: { main: CLIENT_ID } }
    }
  })

  // derive the route-independent asset set from Vite's manifest
  const manifest = JSON.parse(await readFile(join(outDir, '.vite', 'manifest.json'), 'utf8'))
  const entryChunk = Object.values(manifest).find((m) => m.isEntry)
  const modulepreload = (entryChunk.imports || []).map((key) => '/' + manifest[key].file)
  const assets = {
    scripts: ['/' + entryChunk.file],
    modulepreload,
    css: collectCss(manifest, entryChunk)
  }

  const meta = { title, entry, assets, builtAt: new Date().toISOString() }
  await writeFile(join(outDir, 'bankai.json'), JSON.stringify(meta, null, 2))

  // static prerender: routes rendered through the same toStream path the
  // server uses, written as <route>/index.html
  const prerendered = []
  if (prerender.length) {
    const mod = await import(pathToFileURL(entry))
    for (const route of prerender) {
      const app = resolveApp(mod, entry)
      const state = {}
      let body = ''
      const decoder = new TextDecoder()
      for await (const chunk of app.toStream(route, state)) {
        body += decoder.decode(chunk, { stream: true })
      }
      const page = documentHead({ title: state.title || title, ...assets }) + body + documentTail(state)
      const rel = route === '/' ? 'index.html' : join(route.replace(/^\//, '').replace(/\/$/, ''), 'index.html')
      const target = join(outDir, rel)
      await mkdir(dirname(target), { recursive: true })
      await writeFile(target, page)
      prerendered.push(route)
    }
  }

  // service worker: <entry dir>/sw.js, built standalone with the asset
  // list injected — the choo-service-worker convention, manifest edition
  const swSource = join(dirname(entry), 'sw.js')
  if (await exists(swSource)) {
    const precache = [
      ...(prerendered.length ? prerendered : ['/']),
      ...assets.scripts, ...assets.modulepreload, ...assets.css
    ]
    await build({
      appType: 'custom',
      logLevel: 'warn',
      define: { __BANKAI_ASSETS__: JSON.stringify(precache) },
      build: {
        outDir,
        emptyOutDir: false,
        rollupOptions: {
          input: { sw: swSource },
          output: { entryFileNames: 'sw.js' }
        }
      }
    })
  }

  // precompress text assets so the server never compresses at request time
  const compressed = await precompress(outDir)

  return { outDir, meta, compressed, prerendered }
}

function collectCss (manifest, entryChunk) {
  const css = new Set(entryChunk.css || [])
  for (const key of entryChunk.imports || []) {
    for (const file of manifest[key].css || []) css.add(file)
  }
  return [...css].map((file) => '/' + file)
}

const COMPRESSIBLE = /\.(js|mjs|css|html|json|svg|txt|map)$/

async function precompress (dir) {
  let count = 0
  for (const name of await readdir(dir)) {
    const path = join(dir, name)
    const info = await stat(path)
    if (info.isDirectory()) {
      count += await precompress(path)
      continue
    }
    if (!COMPRESSIBLE.test(name) || info.size < 1024) continue
    const data = await readFile(path)
    await writeFile(path + '.br', await brotli(data, {
      params: { [constants.BROTLI_PARAM_QUALITY]: constants.BROTLI_MAX_QUALITY }
    }))
    await writeFile(path + '.gz', await gzipP(data, { level: constants.Z_BEST_COMPRESSION }))
    count++
  }
  return count
}

async function exists (path) {
  try {
    await access(path)
    return true
  } catch (e) {
    return false
  }
}