import java.io.*;

// I den här klassen antar vi att varje sample är på 16 bitar och sparas alltså i två bytes ej big endian.
public class DSP {
  public static byte[] distort(byte[] b1, String distortion) {
    if(distortion.equals("backward")) {
      byte[] b2 = new byte[b1.length];

      for(int i = 0; i < b1.length; i = i + 2) {
        b2[i] = b1[b1.length - i - 2];
        b2[i + 1] = b1[b1.length - i - 1];
      }

      return b2;
    }

    if(distortion.equals("slow")) {
      byte[] b2 = new byte[b1.length * 2];

      for(int i = 0; i < b1.length; i = i + 2) {
        b2[2 * i] = b1[i];
        b2[2 * i + 1] = b1[i + 1];

        b2[2 * i + 2] = b1[i];
        b2[2 * i + 3] = b1[i + 1];
      }

      return b2;
    }

    if(distortion.equals("fast1")) {
      byte[] b2 = new byte[b1.length / 2];

      for(int i = 0; i < b1.length / 2; i = i + 2) {
        b2[i] = b1[2 * i];
        b2[i + 1] = b1[2 * i + 1];
      }

      return b2;
    }

    // Visar hur man kan göra det lättare med short-array
    if(distortion.equals("fast2")) {
      short[] s = byte2short(b1);
      short[] sNew = new short[s.length / 2];

      for(int i = 0; i < sNew.length; i++) {
        sNew[i] = s[2 * i];
      }

      byte[] b2 = short2byte(sNew);
      return b2;
    }

    if(distortion.equals("echo")) {
      int echos = 4;
      int delay = 10000;
      double decrease = 0.85;

      short[] s = byte2short(b1);
      short[] sNew = new short[s.length];

      for(int i = 0; i < sNew.length; i++) {
        for(int ii = 0; ii < echos; ii++) {
          if(i > (ii * delay)) {
            sNew[i] = (short)(s[i] + Math.pow(decrease, ii) * s[i - (ii * delay)]);
          }
        }

      }

      byte[] b2 = short2byte(sNew);
      return b2;
    }

    return b1;
  }

  private static byte[] short2byte(short[] sa) {
    if(sa == null) return null;
    byte[] ba = new byte[sa.length * 2];
    for(int i = 0; i < sa.length; i++) {
      short anChar = sa[i];
      ba[i * 2] = (byte)(anChar & 0xFF); 
      ba[i * 2 + 1] = (byte)((anChar >>> 8) & 0xFF); 
    }
    return ba;
  }

  private static short[] byte2short(byte[] ba) {
    if(ba == null) return null;
    short[] sa = new short[ba.length / 2];
    for(int i = 0; i < ba.length; i = i + 2) {
      sa[i / 2] = (short)((ba[i] & 0xFF) + ((((short)ba[i + 1]) << 8) & 0xFF00));
    }
    return sa;
  }
}