/*
    * Copyright (C) 2020-2023 Dipl.-Inform. Kai Hofmann. All rights reserved!
    */
   package de.powerstat.validation.values;
   
   
   import java.util.Objects;
   import java.util.regex.Pattern;
   
  import de.powerstat.validation.generated.GeneratedTlds;
  import de.powerstat.validation.interfaces.IValueObject;
  
  
  /**
   * Top level domain.
   *
   * Not DSGVO relevant.
   */
  public final class TopLevelDomain implements Comparable<TopLevelDomain>, IValueObject
   {
    /* *
     * Cache for singletons.
     */
    // private static final Map<String, TopLevelDomain> CACHE = new WeakHashMap<>();
  
    /**
     * Top level domain regexp.
     */
    private static final Pattern TOPLEVELDOMAIN_REGEXP = Pattern.compile("^[0-9a-zA-Z-]+$"); //$NON-NLS-1$
  
    /**
     * Top level domain.
     */
    private final String topLevelDomain;
  
  
    /**
     * Constructor.
     *
     * @param topLevelDomain Top level domain name (without dot)
     * @throws NullPointerException if top level domain is null
     * @throws IllegalArgumentException if top level domain is not a known top level domain
     */
    private TopLevelDomain(final String topLevelDomain)
     {
      super();
      Objects.requireNonNull(topLevelDomain, "topLevelDomain"); //$NON-NLS-1$
      if ((topLevelDomain.length() < 2) || (topLevelDomain.length() > 63)) // actual (2020) longest in use is 24
       {
        throw new IllegalArgumentException("To short or long for a top level domain"); //$NON-NLS-1$
       }
      if ((topLevelDomain.charAt(0) == '-') || (topLevelDomain.charAt(topLevelDomain.length() - 1) == '-'))
       {
        throw new IllegalArgumentException("Illegal character '-' at name start or end"); //$NON-NLS-1$
       }
      if (!TopLevelDomain.TOPLEVELDOMAIN_REGEXP.matcher(topLevelDomain).matches())
       {
        throw new IllegalArgumentException("Top level domain contains illegal character"); //$NON-NLS-1$
       }
      if (!GeneratedTlds.contains(topLevelDomain))
       {
        throw new IllegalArgumentException("Unknown top level domain"); //$NON-NLS-1$
       }
      this.topLevelDomain = topLevelDomain;
     }
  
  
    /**
     * TopLevelDomain factory.
     *
     * @param topLevelDomain TopLevelDomain
     * @return TopLevelDomain object
     */
    public static TopLevelDomain of(final String topLevelDomain)
     {
      /*
      synchronized (TopLevelDomain.class)
       {
        TopLevelDomain obj = TopLevelDomain.CACHE.get(topLevelDomain);
        if (obj != null)
         {
          return obj;
         }
        obj = new TopLevelDomain(topLevelDomain);
        TopLevelDomain.CACHE.put(topLevelDomain, obj);
        return obj;
       }
      */
      return new TopLevelDomain(topLevelDomain);
     }
  
  
    /**
     * Returns the value of this TopLevelDomain as a string.
     *
     * @return The text value represented by this object after conversion to type string.
     */
    @Override
    public String stringValue()
    {
     return this.topLevelDomain;
    }
 
 
   /**
    * Calculate hash code.
    *
    * @return Hash
    * @see java.lang.Object#hashCode()
    */
   @Override
   public int hashCode()
    {
     return this.topLevelDomain.hashCode();
    }
 
 
   /**
    * Is equal with another object.
    *
    * @param obj Object
    * @return true when equal, false otherwise
    * @see java.lang.Object#equals(java.lang.Object)
    */
   @Override
   public boolean equals(final Object obj)
    {
     if (this == obj)
      {
       return true;
      }
     if (!(obj instanceof TopLevelDomain))
      {
       return false;
      }
     final TopLevelDomain other = (TopLevelDomain)obj;
     return this.topLevelDomain.equals(other.topLevelDomain);
    }
 
 
   /**
    * Returns the string representation of this TopLevelDomain.
    *
    * The exact details of this representation are unspecified and subject to change, but the following may be regarded as typical:
    *
    * "TopLevelDomain[topLevelDomain=de]"
    *
    * @return String representation of this TopLevelDomain
    * @see java.lang.Object#toString()
    */
   @Override
   public String toString()
    {
     final var builder = new StringBuilder(31);
     builder.append("TopLevelDomain[topLevelDomain=").append(this.topLevelDomain).append(']'); //$NON-NLS-1$
     return builder.toString();
    }
 
 
   /**
    * Compare with another object.
    *
    * @param obj Object to compare with
    * @return 0: equal; 1: greater; -1: smaller
    * @see java.lang.Comparable#compareTo(java.lang.Object)
    */
   @Override
   public int compareTo(final TopLevelDomain obj)
    {
     Objects.requireNonNull(obj, "obj"); //$NON-NLS-1$
     return this.topLevelDomain.compareTo(obj.topLevelDomain);
    }
 
  }