li/cil/oc/server/computer/LuaStateFactory.scala

package li.cil.oc.server.computer

import com.naef.jnlua.NativeSupport.Loader
import com.naef.jnlua.{JavaFunction, LuaState, NativeSupport}
import java.io.File
import java.io.FileOutputStream
import java.nio.channels.Channels
import scala.util.Random

case class ScalaFunction(f: (LuaState) => Int) extends JavaFunction {
  override def invoke(state: LuaState) = f(state)
}

/**
 * Factory singleton used to spawn new LuaState instances.
 *
 * This is realized as a singleton so that we only have to resolve shared
 * library references once during initialization and can then re-use the
 * already loaded ones.
 */
private[computer] object LuaStateFactory {
  // ----------------------------------------------------------------------- //
  // Initialization
  // ----------------------------------------------------------------------- //

  // Since we use native libraries we have to do some work. This includes
  // figuring out what we're running on, so that we can load the proper shared
  // libraries compiled for that system. It also means we have to unpack the
  // shared libraries somewhere so that we can load them, because we cannot
  // load them directly from a JAR.
  {
    val platform = System.getProperty("os.name").toLowerCase match {
      case name if name.startsWith("linux") => "linux"
      case name if name.startsWith("windows") => "windows"
      case name if name.startsWith("mac") => "mac"
    }
    val libPath = "/assets/opencomputers/lib/" + System.getProperty("os.arch") + "/"

    val libExt = platform match {
      case "linux" => ".so"
      case "windows" => ".dll"
      case "mac" => ".dylib"
      case _ => ""
    }
    val tmpPath = {
      val path = System.getProperty("java.io.tmpdir")
      if (path.endsWith("/") || path.endsWith("\\")) path
      else path + "/"
    }

    val library = "native"
    val libraryUrl = classOf[Computer].getResource(libPath + library + libExt)
    if (libraryUrl == null) {
      throw new NotImplementedError("Unsupported platform.")
    }
    // Found file with proper extension. Create a temporary file.
    val file = new File(tmpPath + library + libExt)
    // Try to delete an old instance of the library, in case we have an update
    // and deleteOnExit fails (which it regularly does on Windows it seems).
    try {
      file.delete()
    }
    catch {
      case t: Throwable => // Ignore.
    }
    // Copy the file contents to the temporary file.
    try {
      val in = Channels.newChannel(libraryUrl.openStream())
      val out = new FileOutputStream(file).getChannel
      out.transferFrom(in, 0, Long.MaxValue)
      in.close()
      out.close()
      file.deleteOnExit()
    }
    catch {
      // Java (or Windows?) locks the library file when opening it, so any
      // further tries to update it while another instance is still running
      // will fail. We still want to try each time, since the files may have
      // been updated.
      case t: Throwable => // Nothing.
    }

    // Remember the temporary file's location for the loader.
    val libraryPath = file.getAbsolutePath

    // Register a custom library loader with JNLua to actually load the ones we
    // just extracted.
    NativeSupport.getInstance().setLoader(new Loader {
      def load() {
        System.load(libraryPath)
      }
    })
  }

  // ----------------------------------------------------------------------- //
  // Factory
  // ----------------------------------------------------------------------- //

  def createState(): Option[LuaState] = {
    val state = new LuaState(Integer.MAX_VALUE)
    try {
      // Load all libraries.
      state.openLib(LuaState.Library.BASE)
      state.openLib(LuaState.Library.BIT32)
      state.openLib(LuaState.Library.COROUTINE)
      state.openLib(LuaState.Library.DEBUG)
      state.openLib(LuaState.Library.ERIS)
      state.openLib(LuaState.Library.MATH)
      state.openLib(LuaState.Library.STRING)
      state.openLib(LuaState.Library.TABLE)
      state.pop(8)

      // Prepare table for os stuff.
      state.newTable()
      state.setGlobal("os")

      // Remove some other functions we don't need and are dangerous.
      state.pushNil()
      state.setGlobal("dofile")
      state.pushNil()
      state.setGlobal("loadfile")
      state.pushNil()
      state.setGlobal("module")
      state.pushNil()
      state.setGlobal("require")

      // Push a couple of functions that override original Lua API functions or
      // that add new functionality to it.
      state.getGlobal("os")

      // Allow getting the real world time via os.realTime() for timeouts.
      state.pushJavaFunction(ScalaFunction(lua => {
        lua.pushNumber(System.currentTimeMillis() / 1000.0)
        1
      }))
      state.setField(-2, "realTime")

      // Allow the system to read how much memory it uses and has available.
      state.pushJavaFunction(ScalaFunction(lua => {
        lua.pushInteger(lua.getTotalMemory)
        1
      }))
      state.setField(-2, "totalMemory")

      state.pushJavaFunction(ScalaFunction(lua => {
        lua.pushInteger(lua.getFreeMemory)
        1
      }))
      state.setField(-2, "freeMemory")

      // Pop the os table.
      state.pop(1)

      state.getGlobal("math")

      // We give each Lua state it's own randomizer, since otherwise they'd
      // use the good old rand() from C. Which can be terrible, and isn't
      // necessarily thread-safe.
      val random = new Random
      state.pushJavaFunction(ScalaFunction(lua => {
        lua.getTop match {
          case 0 => lua.pushNumber(random.nextDouble())
          case 1 => {
            val u = lua.checkInteger(1)
            lua.checkArg(1, 1 < u, "interval is empty")
            lua.pushInteger(1 + random.nextInt(u))
          }
          case 2 => {
            val l = lua.checkInteger(1)
            val u = lua.checkInteger(2)
            lua.checkArg(1, l < u, "interval is empty")
            lua.pushInteger(l + random.nextInt(u - l))
          }
          case _ => throw new IllegalArgumentException("wrong number of arguments")
        }
        1
      }))
      state.setField(-2, "random")

      state.pushJavaFunction(ScalaFunction(lua => {
        random.setSeed(lua.checkInteger(1))
        0
      }))
      state.setField(-2, "randomseed")

      // Pop the math table.
      state.pop(1)

      Some(state)
    } catch {
      case ex: Throwable => {
        ex.printStackTrace()
        state.close()
        return None
      }
    }
  }
}