Converter.scala

/*
 * Copyright 2020 Daniel Spiewak
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package transcoder

import cats.effect.{Blocker, ExitCode, IO, IOApp}

import fs2.{io, text, Stream}, io.file

import scala.jdk.CollectionConverters._

import java.io.File
import java.nio.charset.Charset

object Converter extends IOApp {

  private val AllCharsets = Charset.availableCharsets().asScala.toList

  def run(args: List[String]): IO[ExitCode] = {
    val main = for {
      blocker <- Stream.resource(Blocker[IO])

      workers = args map { name =>
        val jfile = new File(name)
        val parent = jfile.getParent()

        val decoded = file.readAll[IO](jfile.toPath, blocker, 1024 * 1024)
          .through(text.utf8Decode)
        
        decoded.broadcastTo {
          AllCharsets map { case (name, charset) =>
            text.encode(charset)
              .andThen(file.writeAll[IO](new File(parent, jfile.getName() + s".$name").toPath, blocker))
              .andThen(_.handleErrorWith(_ => Stream.empty))
              .andThen(_.drain)
          }: _*
        }
      }

      _ <- Stream.emits(workers).parJoinUnbounded
    } yield ()

    main.compile.drain.as(ExitCode.Success)
  }
}