package org.springframework.security.oauth.provider.verifier;
   
   import org.springframework.beans.factory.InitializingBean;
   
   import java.security.SecureRandom;
   import java.util.Random;
   
   /**
    * Basic implementation of the verifier services that creates a random-value verifier and stores it in an in-memory map.
   *
   * @author Ryan Heaton
   */
  public class RandomValueVerifierServices implements OAuthVerifierServices, InitializingBean {
  
    private static final char[] DEFAULT_CODEC = "1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz".toCharArray();
  
    private Random random;
    private int verifierLengthBytes = 6;
  
    public void afterPropertiesSet() throws Exception {
      if (getRandom() == null) {
        setRandom(new SecureRandom());
      }
    }
  
    public String createVerifier() {
      byte[] verifierBytes = new byte[getVerifierLengthBytes()];
      getRandom().nextBytes(verifierBytes);
      return getVerifierString(verifierBytes);
    }
  
    /**
     * Convert these random bytes to a verifier string. The length of the byte array can be {@link #setVerifierLengthBytes(int) configured}. Default implementation
     * mods the bytes to fit into the ASCII letters 1-9, A-Z, a-z .
     * 
     * @param verifierBytes The bytes.
     * @return The string.
     */
    protected String getVerifierString(byte[] verifierBytes) {
      char[] chars = new char[verifierBytes.length];
      for (int i = 0; i < verifierBytes.length; i++) {
        chars[i] = DEFAULT_CODEC[((verifierBytes[i] & 0xFF) % DEFAULT_CODEC.length)];
      }
      return new String(chars);
    }
  
    /**
     * The random value generator used to create token secrets.
     *
     * @return The random value generator used to create token secrets.
     */
    public Random getRandom() {
      return random;
    }
  
    /**
     * The random value generator used to create token secrets.
     *
     * @param random The random value generator used to create token secrets.
     */
    public void setRandom(Random random) {
      this.random = random;
    }
  
    /**
     * The verifier length in bytes, before being encoded to a string.
     *
     * @return The verifier length in bytes, before being encoded to a string.
     */
    public int getVerifierLengthBytes() {
      return verifierLengthBytes;
    }
  
    /**
     * The verifier length in bytes, before being encoded to a string.
     *
     * @param verifierLengthBytes The verifier length in bytes, before being encoded to a string.
     */
    public void setVerifierLengthBytes(int verifierLengthBytes) {
      this.verifierLengthBytes = verifierLengthBytes;
    }
  }