package java.lang;

import java.io.InputStream;
import java.io.FileInputStream;
import java.io.OutputStream;
import java.io.FileOutputStream;
import java.io.FileDescriptor;

public class Runtime {
  private static final Runtime instance = new Runtime();

  private Runtime() { }

  public static Runtime getRuntime() {
    return instance;
  }

  public void load(String path) {
    if (path != null) {
      load(path, false);
    } else {
      throw new NullPointerException();
    }
  }

  public void loadLibrary(String path) {
    if (path != null) {
      load(path, true);
    } else {
      throw new NullPointerException();
    }
  }

  public Process exec(String command) {
    int[] process = new int[4];
    exec(command, process);
    return new MyProcess(process[0], process[1], process[2], process[3]);
  }

  public Process exec(String[] command) {
    int[] process = new int[4];
    exec(command, process);
    return new MyProcess(process[0], process[1], process[2], process[3]);
  }

  private static native void exec(String command, int[] process);

  private static native void exec(String[] command, int[] process);

  private static native int exitValue(int pid);

  private static native int waitFor(int pid);

  private static native void load(String name, boolean mapName);

  public native void gc();

  public native void exit(int code);

  public native long freeMemory();

  private static class MyProcess extends Process {
    private int pid;
    private final int in;
    private final int out;
    private final int err;
    private int exitCode;

    public MyProcess(int pid, int in, int out, int err) {
      this.pid = pid;
      this.in = in;
      this.out = out;
      this.err = err;
    }

    public void destroy() {
      throw new RuntimeException("not implemented");
    }

    public int exitValue() {
      if (pid != 0) {
        exitCode = Runtime.exitValue(pid);
      }
      return exitCode;
    }

    public InputStream getInputStream() {
      return new FileInputStream(new FileDescriptor(in));
    }

    public OutputStream getOutputStream() {
      return new FileOutputStream(new FileDescriptor(out));
    }

    public InputStream getErrorStream() {
      return new FileInputStream(new FileDescriptor(err));
    }

    public int waitFor() throws InterruptedException {
      if (pid != 0) {
        exitCode = Runtime.waitFor(pid);
        pid = 0;
      }
      return exitCode;
    }
  }
}