// `record` requires java14: 
//     compile:  `javac --enable-preview --source 14 Book2.java`
//     run:      `java --enable-preview Book`
//     or:       `jshell --enable-preview`      then   `/open Book2.java`
//
record Book(String title, String author, int numPages, boolean isCopyrighted) {
    
 
    /* ( Template for book-handling functions: )
      
       ... funcForBook( /* Book this * / ) {
          ... this.title
          ... this.author
          ... this.numPages
          ... this.isCopyrighted
          }
    */
    
  
    /** @return The amount of time it takes the average reader to read a book (in minutes) */
    double readingTime( /* Book this */ ) {
        return 2 * this.numPages;
        }
    
    @Override
    public String toString( /* Book this */ ) {
        return this.title
             + ", by "
             + this.author
             + " (" + this.numPages + "pp)"
             + (this.isCopyrighted  ?  " ©"  :  "" );
        }

    /** @return a book just like `a-book`, but with bigger text (hence, more pages). */
    Book enbiggen( /* Book this */ ) {
        return new Book( this.title,
                         this.author,
                         2*this.numPages,
                         this.isCopyrighted );
        }

    /** @return a brand new book, based on an original.
     *  The result's authoor will be the original author & the `newAuthor`,
     *  and the result has `numNewPages` pages added to the original.
     */
    Book deriveFrom( /* Book this, */ String newAuthor, int numNewPages  ) {
        return new Book( "Son of " + this.title,
                         this.author + " & " + newAuthor,
                         this.numPages + numNewPages,
                         false );
        }

    
    
    /* All code has to be inside a method in Java, so we'll stick our unit-tests in here. */ 
    static void testAll() {
        Book b0, b1;
        b1 = new Book( "The Cat in the Hat", "Seuss", 37, true );
        b0 = new Book( "The Soul of Wit", "Barland", 0, false );
        
        
        assert (new Book( "The Cat in the Hat", "Seuss", 37, true )).readingTime() == 74.0;
        assert b0.readingTime() == 0;
        
        
        assert b1.enbiggen().equals(new Book( "The Cat in the Hat", "Seuss", 74, true ));
        assert (new Book( "The Bat in the Mat", "Streuss", 1, true )).enbiggen()
               .equals(new Book( "The Bat in the Mat", "Streuss", 2, true ));
        assert b0.enbiggen().equals(b0);
        
        assert b1.deriveFrom("Barland", 10)
                 .equals( new Book( "Son of The Cat in the Hat"
                                  , "Seuss & Barland"
                                  , 47
                                  , false ) );
        
        assert b0.deriveFrom("Banksie", 99)
                 .equals( new Book( "Son of The Soul of Wit"
                                  , "Barland & Banksie"
                                  , 99
                                  , false ) );
        
        assert b0.equals(b0);
        assert !b0.equals(b1);
        assert b1.equals( new Book( "The Cat in the Hat", "Seuss", 37, true ) );
        assert b0.hashCode() == b0.hashCode();
        assert b1.hashCode() == new Book( "The Cat in the Hat", "Seuss", 37, true ).hashCode();
        assert b1.toStringDebug().equals( "new Book( \"The Cat in the Hat\", \"Seuss\", 37, true )" );
        }

    /** Just run our unit tests. Be sure to run `java` with `--assertionsEnabled` (or, `-ea`). */
    public static void main( String... __ ) {
        testAll();
        // Alternately, we could just stick the tests directly into `main` here, that's fine too.
        }
    
    }