function log(message, cls = 'cyan') {
  const el = document.createElement('pre')
  el.classList.add(cls)
  el.innerText = message
  document.body.append(el)
}

class App {
  jApiBaseUrl = 'https://data.jsdelivr.com/v1/'
  jCdnBaseUrl = 'https://cdn.jsdelivr.net/npm/'

  scripts = {
    '@rollup/browser': {
      version: '3.20.4',
      path: 'dist/rollup.browser.js',
      sha: 'sha256-GgOznxZmgghx1a7CH09B+VmDKtziPO5tAnC5gC+/5Kw=',
    },
  }

  topLevelDeps = [
    "@codemirror/autocomplete",
    "@codemirror/commands",
    "@codemirror/language",
    "@codemirror/lint",
    "@codemirror/search",
    "@codemirror/state",
    "@codemirror/view",
    "@codemirror/lang-javascript",
  ]

  constructor() {
    this.downloads = []
    this.run().catch(e => {
      log(`${e}`)
    })
  }

  checkOk(resp) {
    if (!resp.ok) {
      throw new Error(`HTTP request failed: ${resp.status}`)
    }
  }

  async loadDep(dep) {
    this.scripts[dep] = {}
    const dataResp = await fetch(
      this.jApiBaseUrl +
      `packages/npm/${dep}/resolved`,
      {
        headers: {
          'User-Agent':
            'https://codeberg.org/macchiato',
        },
      },
    )
    this.checkOk(dataResp)
    const {version} = await dataResp.json()
    this.scripts[dep].version = version
    const pkgResp = await fetch(
      this.jCdnBaseUrl +
      `${dep}@${version}/package.json`
    )
    this.checkOk(pkgResp)
    log(dep)
    const pkg = await pkgResp.json()
    this.scripts[dep].path = (
      pkg.module ?? pkg.main
    )
    this.downloads.push(this.getScript(dep))
    const deps = Object.keys(
      pkg.dependencies || {}
    ).filter(dep => !(dep in this.scripts))
    await Promise.allSettled(deps.map(dep => (
      this.loadDep(dep)
    )))
  }

  async checkIntegrity(resp, name, script) {
    const blob = await resp.blob()
    const ab = await blob.arrayBuffer()
    const hash = await crypto.subtle.digest(
      "SHA-256", ab
    )
    const checkValue = 'sha256-' + btoa(
      String.fromCharCode(
        ...new Uint8Array(hash)
      )
    )
    if (checkValue !== script.sha) {
      throw new Error(
        'failed integrity check: ' +
        `${checkValue} !== ${script.sha}`
      )
    }
    return ab
  }

  async getScript(name) {
    log('[downloading] ' + name, 'green')
    const script = this.scripts[name]
    if (script.text) {
      return script.text
    }
    const url = (
      this.jCdnBaseUrl +
      `${name}@${script.version}/${script.path}`
    )
    const resp = await fetch(url)
    this.checkOk(resp)
    if (script.sha) {
      const ab = await this.checkIntegrity(
        resp, name, script
      )
      script.text = new TextDecoder().decode(ab)
    } else {
      script.text = await resp.text
      script.sha = resp.integrity
    }
    log('[downloaded] ' + url, 'green')
    return script.text
  }

  async loadScript(name) {
    const text = await this.getScript(name)
    const s = document.createElement('script')
    s.text = text
    document.head.append(s)
  }

  async run() {
    await Promise.allSettled(
      this.topLevelDeps.map(dep => (
        this.loadDep(dep)
      ))
    )
    await Promise.allSettled(this.downloads)
    //await this.loadScript('@rollup/browser')
    //const { rollup } = window.rollup
    //output.value = `${typeof rollup}`
  }
}

new App()