Mill Tailwind self-managed integration

build.mill

trait TailwindModule extends ScalaJSModule {
  def tailwindVersion: Target[String] = Task("v3.4.14")

  /** Tailwindcss download url. By default autodetected from props os.name and os.arch
    */
  def tailwindBinUrl = Task {
    def nameMatch(prefix: String) =
      sys.props("os.name").toLowerCase.startsWith(prefix.toLowerCase)

    val platform =
      if (nameMatch("mac os x")) "macos"
      else if (nameMatch("linux")) "linux"
      else if (nameMatch("windows")) "windows"

    val arch = sys.props("os.arch") match {
      case "aarch64"       => "arm64"
      case "amd64" | "x64" => "x64"
      case "arm"           => "armv7"
    }

    val version = tailwindVersion()

    s"https://github.com/tailwindlabs/tailwindcss/releases/download/$version/tailwindcss-$platform-$arch"
  }

  def tailwindBin: Target[Path] = Task {
    val binPath = T.dest / "tailwindcss"

    os.write(
      target = binPath,
      data = requests.get.stream(tailwindBinUrl()),
      perms = os.PermSet(Integer.parseInt("755", 8))
    )

    binPath
  }

  def webSrcDir: Target[Path] = Task.workspace / "web-src"

  def devDistDir: Target[Path] = Task.workspace / "dev-dist"

  def tailwindInputCss: Target[PathRef] = Task.Source {
    webSrcDir() / "tailwind.css"
  }

  def tailwindOutputName: Target[String] = "styles.css"

  def indexHtmlPath: Target[PathRef] = Task.Source {
    webSrcDir() / "index.html"
  }

  def tailwindOutput: Target[Path] = Task {
    val jsFilePath = os.list(fastLinkJS().dest.path).find(_.ext == "js").get
    val outPath = T.dest / "compiled.css"

    // format: off
    os.proc(
      tailwindBin(),
      "--input", tailwindInputCss(),
      "--output", outPath,
      "--content", s"$jsFilePath,${indexHtmlPath().path}",
    ).call(cwd = Task.workspace)
    // format: on
    outPath
  }

  def devBuild(): Command[PathRef] = Task.Command {
    val targetDir = devDistDir()
    os.copy.over(webSrcDir() / "img", targetDir / "img")
    os.copy.into(indexHtmlPath().path, targetDir, replaceExisting = true)
    os.copy.over(tailwindOutput(), targetDir / tailwindOutputName())
    os.list(fastLinkJS().dest.path).foreach(path => os.copy.into(path, targetDir, replaceExisting = true))
    PathRef(T.dest)
  }
}

// usage: mill frontend.devBuild
object frontend extends TailwindModule {
  // change "plugin" settings as desired here
}