li/cil/oc/server/fs/Capacity.scala

package li.cil.oc.server.fs

import java.io
import li.cil.oc.Config
import li.cil.oc.api.fs.Mode

trait Capacity extends OutputStreamFileSystem {
  private var used = computeSize("/")

  def capacity: Int

  override protected def delete(path: String) = {
    val freed = Config.fileCost + size(path)
    if (super.delete(path)) {
      used -= freed
      true
    }
    else false
  }

  override protected abstract def openOutputStream(path: String, mode: Mode.Value): Option[io.OutputStream] = {
    val delta =
      if (exists(path))
        if (mode == Mode.Write)
          -size(path) // Overwrite, file gets cleared.
        else
          0 // Append, no immediate changes.
      else
        Config.fileCost // File creation.
    super.openOutputStream(path, mode) match {
      case None => None
      case Some(stream) =>
        used += delta
        Some(new CountingOutputStream(this, stream))
    }
  }

  private def computeSize(path: String): Long =
    Config.fileCost +
      size(path) +
      (if (isDirectory(path))
        list(path).get.foldLeft(0L)((acc, child) => acc + computeSize(path + child))
      else 0)

  private class CountingOutputStream(val owner: Capacity, val inner: io.OutputStream) extends io.OutputStream {
    override def write(b: Int) = {
      if (owner.capacity - owner.used < 1)
        throw new io.IOException("not enough space")
      inner.write(b)
      owner.used = owner.used + 1
    }

    override def write(b: Array[Byte], off: Int, len: Int) = {
      if (owner.capacity - owner.used < len)
        throw new io.IOException("not enough space")
      inner.write(b, off, len)
      owner.used = owner.used + len
    }

    override def flush() = inner.flush()

    override def close() = inner.close()
  }

}