/*
    * Copyright (C) 2020-2023 Dipl.-Inform. Kai Hofmann. All rights reserved!
    */
   package de.powerstat.validation.values;
   
   
   import java.util.Locale;
   import java.util.Objects;
   import java.util.regex.Pattern;
  
  import de.powerstat.validation.interfaces.IValueObject;
  
  
  /**
   * Electronic mail.
   *
   * Probably DSGVO relevant.
   *
   * TODO Hostname exists?
   * TODO email exists check
   */
  public final class EMail implements Comparable<EMail>, IValueObject
   {
    /* *
     * Cache for singletons.
     */
    // private static final Map<String, EMail> CACHE = new WeakHashMap<>();
  
    /**
     * Local part regexp.
     */
    private static final Pattern LOCAL_REGEXP = Pattern.compile("^[A-Za-z0-9.!#$%&'*+/=?^_`{|}~-]+$"); //$NON-NLS-1$
  
    /**
     * EMail.
     */
    private final String email;
  
    /**
     * EMails domain part.
     */
    private final Hostname domainPart;
  
    /**
     * EMails local part.
     */
    private final String localPart;
  
  
    /**
     * Constructor.
     *
     * Comments, double quotes and UTF-8 characters within the emails local part are not yet supported.
     *
     * @param email EMail
     * @throws NullPointerException if email is null
     * @throws IllegalArgumentException if email is not an supported email address
     */
    private EMail(final String email)
     {
      super();
      Objects.requireNonNull(email, "email"); //$NON-NLS-1$
      if ((email.length() < 6) || (email.length() > 254))
       {
        throw new IllegalArgumentException("To short or long for an email address"); //$NON-NLS-1$
       }
      final String[] parts = email.split("@"); //$NON-NLS-1$
      if (parts.length != 2)
       {
        throw new IllegalArgumentException("Not an email address, missing or to much @"); //$NON-NLS-1$
       }
      if (parts[0].length() > 64)
       {
        throw new IllegalArgumentException("Local part greater than 64 characters"); //$NON-NLS-1$
       }
      if (parts[1].charAt(0) == '[')
       {
        parts[1] = (parts[1].toLowerCase(Locale.getDefault()).startsWith("[ipv6:")) ? parts[1].substring(6) : parts[1].substring(1); //$NON-NLS-1$
        if (!parts[1].endsWith("]")) //$NON-NLS-1$
         {
          throw new IllegalArgumentException("Missing end of IPv4/IPv6 address"); //$NON-NLS-1$
         }
        parts[1] = parts[1].substring(0, parts[1].length() - 1);
       }
      this.domainPart = Hostname.of(parts[1]); // Check hostname and store for isReachable
      if ((parts[0].charAt(0) == '(') || (parts[0].charAt(parts[0].length() - 1) == ')'))
       {
        throw new IllegalArgumentException("Comments in email addresses are not supported"); //$NON-NLS-1$
       }
      if (parts[0].indexOf('"') > -1)
       {
        throw new IllegalArgumentException("Double quotes in email addresses are not supported"); //$NON-NLS-1$
       }
      if ((parts[0].charAt(0) == '.') || (parts[0].charAt(parts[0].length() - 1) == '.'))
       {
        throw new IllegalArgumentException("A dot is not allowed at start or end of an emails local part"); //$NON-NLS-1$
       }
      if (parts[0].contains("..")) //$NON-NLS-1$
       {
       throw new IllegalArgumentException("Two or more dots behind each other are not allowed within an emails local part"); //$NON-NLS-1$
      }
     if (!EMail.LOCAL_REGEXP.matcher(parts[0]).matches())
      {
       throw new IllegalArgumentException("Illegal character found in emails local part or unsupported UTF-8 character"); //$NON-NLS-1$
      }
     this.localPart = parts[0]; // Store for check receiver
     this.email = email;
    }
 
 
   /**
    * EMail factory.
    *
    * @param email EMail
    * @return EMail object
    */
   public static EMail of(final String email)
    {
     /*
     synchronized (EMail.class)
      {
       EMail obj = EMail.CACHE.get(email);
       if (obj != null)
        {
         return obj;
        }
       obj = new EMail(email);
       EMail.CACHE.put(email, obj);
       return obj;
      }
     */
     return new EMail(email);
    }
 
 
   /**
    * Returns the value of this EMail as a string.
    *
    * @return The text value represented by this object after conversion to type string.
    */
   @Override
   public String stringValue()
    {
     return this.email;
    }
 
 
   /**
    * Get emails domain part string.
    *
    * @return Domain part string
    */
   public String getDomainPart()
    {
     return this.domainPart.stringValue();
    }
 
 
   /**
    * Get emails reverse domain part string.
    *
    * @return Reverse domain part string
    */
   public String getReverseDomainPart()
    {
     return this.domainPart.getReverseHostname();
    }
 
 
   /**
    * Get emails local part string.
    *
    * @return Local part string
    */
   public String getLocalPart()
    {
     return this.localPart;
    }
 
 
   /**
    * Calculate hash code.
    *
    * @return Hash
    * @see java.lang.Object#hashCode()
    */
   @Override
   public int hashCode()
    {
     return this.email.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 EMail))
      {
       return false;
      }
     final EMail other = (EMail)obj;
     return this.email.equals(other.email);
    }
 
 
   /**
    * Returns the string representation of this EMail.
    *
    * The exact details of this representation are unspecified and subject to change, but the following may be regarded as typical:
    *
    * "EMail[email=user@example.com]"
    *
    * @return String representation of this EMail
    * @see java.lang.Object#toString()
    */
   @Override
   public String toString()
    {
     final var builder = new StringBuilder();
     builder.append("EMail[email=").append(this.email).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 EMail obj)
    {
     Objects.requireNonNull(obj, "obj"); //$NON-NLS-1$
     return this.email.compareTo(obj.email); // TODO hostname, username
    }
 
  }