/* An instance of this class represents a (key,value)-pair in which
** both key and value components are of type String.
** Such pairs exist to correlate codes, abbreviations, etc., with
** their corresponding full elaborations.
**
** As an example, consider that each of the states in the U.S. has a 
** two-character postal key abbreviation.  Thus, in the familiar pair
** ("PA","Pennsylvania"), the first component is the key and the second is
** the corresponding value. Similarly for ("NY", "New York"), etc. 
**
** Author: P.M.J., R.W.M. 
** last modified: 12/06/2025
*/
public class KeyValPair {

   // instance variables (fields/attributes)
   // --------------------------------------

   protected String key = "";            // 
   protected String value = "";          // 
   
   protected static final String DELIMITER = ":";
   
   // constructors
   // ------------

   /* Initilizes this KeyValPair object to have the empty string
   ** as both its key and its value/elaboration.
   */
   public KeyValPair() {}

   /* Initializes this KeyValPair object to have the given
   ** strings as its two components (key and value).
   */
   public KeyValPair(String key, String value) { setTo(key,value); }

   /* Initializes this KeyValPair object to be that described by
   ** the given string, which is expected to be in the form 
   **
   **      key : value
   **
   ** consistent with the form produced by the toString() method.
   ** If the given string is not consistent with that format, both
   ** components of this KeyValPair object will be the empty string.
   */
   public KeyValPair(String fromString) {
      setTo("","");  //Set default values
      //Separate the string into its two required parts
      int posOfDelimiter = fromString.indexOf(DELIMITER);
      if (posOfDelimiter != -1) {
         // What precedes the occurrence of the delimiter is the key,
         // and what follows it is the associated value/elaboration.
         this.key = fromString.substring(0, posOfDelimiter).trim();
         this.value = fromString.substring(posOfDelimiter + DELIMITER.length()).trim();
      }
   }

   
   // observers
   // ---------
   
   /* Returns the key component of this KeyValPair object.
   */
   public String getKey() { return this.key; }

   /* Returns the value component of this KeyValPair object.
   */
   public String getValue() { return this.value; }

   /* Returns true if and only if the given string matches 
   ** the key component of this KeyValPair object.
   */
   public boolean equalsKey(String key) { 
      return key.equals(this.getKey());
   }

   /* Returns true if and only if the given string matches
   ** the value component of this KeyValPair object.
   */
   public boolean equalsValue(String value) { 
      return value.equals(this.getValue());
   }
  
   /* Returns a string of the following form that represents 
   ** the current state and value of this KeyValPair object.
   **   
   **   key : value       
   */
   @Override
   public String toString() { return key + DELIMITER + value; }


   // private mutator
   // ---------------

   /* Makes this KeyValPair object have as its two components
   ** the specified pair of strings.
   */
   protected void setTo(String key, String value) {
      this.key = key;
      this.value = value;
   }

}