package algs51; // section 5.0
import stdlib.*;
public class Alphabet {
  public static final Alphabet BINARY         = new Alphabet("01");
  public static final Alphabet OCTAL          = new Alphabet("01234567");
  public static final Alphabet DECIMAL        = new Alphabet("0123456789");
  public static final Alphabet HEXADECIMAL    = new Alphabet("0123456789ABCDEF");
  public static final Alphabet DNA            = new Alphabet("ACTG");
  public static final Alphabet LOWERCASE      = new Alphabet("abcdefghijklmnopqrstuvwxyz");
  public static final Alphabet UPPERCASE      = new Alphabet("ABCDEFGHIJKLMNOPQRSTUVWXYZ");
  public static final Alphabet PROTEIN        = new Alphabet("ACDEFGHIKLMNPQRSTVWY");
  public static final Alphabet BASE64         = new Alphabet("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/");
  public static final Alphabet ASCII          = new Alphabet(128);
  public static final Alphabet EXTENDED_ASCII = new Alphabet(256);
  public static final Alphabet UNICODE16      = new Alphabet(65536);

  private final char[] alphabet;     // the characters in the alphabet
  private final int[] inverse;       // indices
  private final int R;               // the radix of the alphabet

  // Create a new Alphabet from chars in string.
  public Alphabet(String alpha) {

    // check that alphabet contains no duplicate chars
    boolean[] unicode = new boolean[Character.MAX_VALUE];
    for (int i = 0; i < alpha.length(); i++) {
      char c = alpha.charAt(i);
      if (unicode[c]) throw new IllegalArgumentException("Illegal alphabet: character = '" + c + "'");
      else unicode[c] = true;
    }


    alphabet = alpha.toCharArray();
    R = alpha.length();
    inverse = new int[Character.MAX_VALUE];
    for (int i = 0; i < inverse.length; i++)
      inverse[i] = -1;

    // can't use char since R can be as big as 65,536
    for (int c = 0; c < R; c++)
      inverse[alphabet[c]] = c;
  }

  // Create a new Alphabet of Unicode chars 0 to R-1
  private Alphabet(int R) {
    alphabet = new char[R];
    inverse = new int[R];
    this.R = R;

    // can't use char since R can be as big as 65,536
    for (int i = 0; i < R; i++)
      alphabet[i] = (char) i;
    for (int i = 0; i < R; i++)
      inverse[i] = i;
  }

  // Create a new Alphabet of Unicode chars 0 to 255 (extended ASCII)
  public Alphabet() {
    this(256);
  }

  // is character c in the alphabet?
  public boolean contains(char c) {
    return inverse[c] != -1;
  }

  // return radix R
  public int R() {
    return R;
  }

  // return number of bits to represent an index
  public int lgR() {
    int lgR = 0;
    for (int t = R-1; t >= 1; t /= 2)
      lgR++;
    return lgR;
  }

  // convert c to index between 0 and R-1.
  public int toIndex(char c) {
    if (c < 0 || c >= inverse.length || inverse[c] == -1) {
      throw new IllegalArgumentException("Character " + c + " not in alphabet");
    }
    return inverse[c];
  }

  // convert String s over this alphabet into a base-R integer
  public int[] toIndices(String s) {
    char[] source = s.toCharArray();
    int[] target  = new int[s.length()];
    for (int i = 0; i < source.length; i++)
      target[i] = toIndex(source[i]);
    return target;
  }

  // convert an index between 0 and R-1 into a char over this alphabet
  public char toChar(int index) {
    if (index < 0 || index >= R) {
      throw new IndexOutOfBoundsException("Alphabet out of bounds");
    }
    return alphabet[index];
  }

  // Convert base-R integer into a String over this alphabet
  public String toChars(int[] indices) {
    StringBuilder s = new StringBuilder(indices.length);
    for (int indice : indices)
      s.append(toChar(indice));
    return s.toString();
  }


  public static void main(String[] args) {
    int[] encoded1  = BASE64.toIndices("NowIsTheTimeForAllGoodMen");
    String decoded1 = BASE64.toChars(encoded1);
    StdOut.println(decoded1);

    int[] encoded2  = DNA.toIndices("AACGAACGGTTTACCCCG");
    String decoded2 = DNA.toChars(encoded2);
    StdOut.println(decoded2);

    int[] encoded3 = DECIMAL.toIndices("01234567890123456789");
    String decoded3 = DECIMAL.toChars(encoded3);
    StdOut.println(decoded3);
  }
}