package com.nighthacking;

import java.util.List;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.usb.UsbConfiguration;
import javax.usb.UsbDevice;
import javax.usb.UsbDeviceDescriptor;
import javax.usb.UsbEndpoint;
import javax.usb.UsbException;
import javax.usb.UsbHostManager;
import javax.usb.UsbHub;
import javax.usb.UsbInterface;
import javax.usb.UsbPipe;
import javax.usb.UsbServices;
import javax.usb.event.UsbPipeDataEvent;
import javax.usb.event.UsbPipeErrorEvent;
import javax.usb.event.UsbPipeListener;

/**
 * Self-contained implementation that connects to a USB scale and outputs the
 * data returned to the command line.
 *
 * @author Stephen Chin <steveonjava@gmail.com>
 */
public class UsbScaleTest implements UsbPipeListener {

  private final UsbDevice device;
  private UsbInterface iface;
  private UsbPipe pipe;
  private byte[] data = new byte[6];

  private UsbScaleTest(UsbDevice device) {
    this.device = device;
  }

  public static void main(String[] args) throws UsbException {
    UsbScaleTest scale = UsbScaleTest.findScale();
    scale.open();
    try {
      for (int i = 0; i < 60; i++) {
        scale.syncSubmit();
      }
    } finally {
      scale.close();
    }
  }

  public static UsbScaleTest findScale() throws UsbException {
    UsbServices services = UsbHostManager.getUsbServices();
    UsbHub rootHub = services.getRootUsbHub();
    // Dymo M10 Scale:
    UsbDevice device = findDevice(rootHub, (short) 0x0922, (short) 0x8003);
    // Dymo M25 Scale:
    if (device == null) {
      device = findDevice(rootHub, (short) 0x0922, (short) 0x8004);
    }
    if (device == null) {
      return null;
    }
    return new UsbScaleTest(device);
  }

  private static UsbDevice findDevice(UsbHub hub, short vendorId, short productId) {
    for (UsbDevice device : (List<UsbDevice>) hub.getAttachedUsbDevices()) {
      UsbDeviceDescriptor desc = device.getUsbDeviceDescriptor();
      if (desc.idVendor() == vendorId && desc.idProduct() == productId) {
        return device;
      }
      if (device.isUsbHub()) {
        device = findDevice((UsbHub) device, vendorId, productId);
        if (device != null) {
          return device;
        }
      }
    }
    return null;
  }

  private void open() throws UsbException {
    UsbConfiguration configuration = device.getActiveUsbConfiguration();
    iface = configuration.getUsbInterface((byte) 0);
    // this allows us to steal the lock from the kernel
    iface.claim(usbInterface -> true);
    final List<UsbEndpoint> endpoints = iface.getUsbEndpoints();
    pipe = endpoints.get(0).getUsbPipe(); // there is only 1 endpoint
    pipe.addUsbPipeListener(this);
    pipe.open();
  }

  private void syncSubmit() throws UsbException {
    pipe.syncSubmit(data);
  }

  public void close() throws UsbException {
    pipe.close();
    iface.release();
  }

  @Override
  public void dataEventOccurred(UsbPipeDataEvent upde) {
    boolean empty = data[1] == 2;
    boolean overweight = data[1] == 6;
    boolean negative = data[1] == 5;
    boolean grams = data[2] == 2;
    int scalingFactor = data[3];
    int weight = (data[4] & 0xFF) + (data[5] << 8);
    if (empty) {
      System.out.println("EMPTY");
    } else if (overweight) {
      System.out.println("OVERWEIGHT");
    } else if (negative) {
      System.out.println("NEGATIVE");
    } else { // Use String.format since printf causes problems on remote exec
      System.out.println(String.format("Weight = %,.1f%s",
          scaleWeight(weight, scalingFactor),
          grams ? "g" : "oz"));
    }
  }

  private double scaleWeight(int weight, int scalingFactor) {
    return weight * Math.pow(10, scalingFactor);
  }

  @Override
  public void errorEventOccurred(UsbPipeErrorEvent upee) {
    Logger.getLogger(UsbScaleTest.class.getName()).log(Level.SEVERE, "Scale Error", upee);
  }
}