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/**
 * 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 com.bitalino.util;

import java.math.BigDecimal;
import java.math.RoundingMode;

/**
 * This class holds methods for converting/scaling raw data from BITalino
 * included sensors to human-readable data.
 */
public class SensorDataConverter {

  private static final double VCC = 3.3; // volts
  private static final int ACC_MIN = 185;
  private static final int ACC_MAX = 275;

  /**
   * ElectroMyoGraphy conversion.
   * 
   * @param port
   *          the port where the raw value was read from.
   * @param raw
   *          the value read.
   * @return a value ranging between -1.65 and 1.65mV
   */
  public static double scaleEMG(final int port, final int raw) {
    final double result = (raw * VCC / getResolution(port) - VCC / 2);
    return new BigDecimal(result).setScale(2, RoundingMode.HALF_UP)
        .doubleValue();
  }

  /**
   * ElectroCardioGraphy conversion.
   * 
   * @param port
   *          the port where the raw value was read from.
   * @param raw
   *          the value read.
   * @return a value ranging between -0 and 3mV
   */
  public static double scaleECG(final int port, final int raw) {
    final double result = ((raw * VCC / getResolution(port)) / 1100) * 1000;
    return new BigDecimal(result).setScale(2, RoundingMode.HALF_UP)
        .doubleValue();
  }

  /**
   * Accelerometer conversion based on reference calibration values. If you want
   * to acquire more precise values, use
   * {@link #scaleAccelerometerWithPrecision(int, int, int, int)
   * scaleAccelerometerWithPrecision} method.
   * 
   * @param port
   *          the port where the raw value was read from.
   * @param raw
   *          the value read.
   * @return a value ranging between -5 and 4.5Gs
   */
  public static double scaleAccelerometer(final int port, final int raw) {
    final double result = scaleAccelerometerWithPrecision(port, raw, ACC_MIN,
        ACC_MAX);
    return new BigDecimal(result).setScale(2, RoundingMode.HALF_UP)
        .doubleValue();
  }

  /**
   * Accelerometer conversion based on parameterized calibration values.
   * 
   * @param port
   *          the port where the raw value was read from.
   * @param raw
   *          the value read.
   * @param min
   *          the calibration minimum value
   * @param max
   *          the calibration maximum value
   * @return a value ranging between -3 and 3Gs
   */
  public static double scaleAccelerometerWithPrecision(final int port,
      final int raw, final int min, final int max) {
    return 2 * ((raw - min) / (max - min)) - 1;
  }

  /**
   * Electrodermal Activity conversion.
   * 
   * @param port
   *          the port where the raw value was read from.
   * @param raw
   *          the value read.
   * @return a value ranging from 0 and 1uS (micro Siemens)
   */
  public static double scaleEDA(final int port, final int raw) {
    // need to round maximum value that otherwise is 1.05496875
    final double result = raw * 1031.25 / 1000000;
    return new BigDecimal(result).setScale(4, RoundingMode.HALF_UP)
        .doubleValue();
  }

  /**
   * Luminosity conversion.
   * 
   * @param port
   *          the port where the raw value was read from.
   * @param raw
   *          the value read.
   * @return a value ranging from 0 and 100%.
   */
  public static double scaleLuminosity(final int port, final int raw) {
    return 100 * (raw / getResolution(port));
  }

  /**
   * Returns the resolution (maximum value) for a certain port.
   * 
   * From port 0 to 3, the resolution is 10-bit, thus 2^10 - 1 = 1023. 

   * From port 4 to 5, the resolution is 6-bit, thus 2^6 - 1 = 63.
   * 
   * @param port
   * @return the resolution (maximum value) for a certain port.
   */
  private static final int getResolution(final int port) {
    return port < 4 ? 1023 : 63;
  }

}