<?php

//copyright Lawrence Truett and FluffyCat.com 2005, all rights reserved

  include_once('BookList.php');
  
  class Interpreter {  
  
	private $bookList;

    public function __construct($bookListIn) {
      $this->bookList = $bookListIn;
    }

    public function interpret($stringIn) {
      
      $arrayIn = explode(" ",$stringIn);
      
      $returnString = NULL;
      
      //go through the array validating 
      //  and if possible calling a book method
      //could use refactoring, some duplicate logic 
      if ('book' == $arrayIn[0]) {
        if ('author' == $arrayIn[1]) {
          if (is_numeric($arrayIn[2])) {
            $book = $this->bookList->getBook($arrayIn[2]);
            if (NULL == $book) {
              $returnString = 'Can not process, there is no book # '.
                $arrayIn[2]; 
            } else {
              $returnString = $book->getAuthor(); 
            }
          } elseif ('title' == $arrayIn[2]) {
            if (is_numeric($arrayIn[3])) {
              $book = $this->bookList->getBook($arrayIn[3]);
              if (NULL == $book) {
                $returnString = 'Can not process, there is no book # '.
                  $arrayIn[3]; 
              } else {
                $returnString = $book->getAuthorAndTitle(); 
              }
            } else {
              $returnString = 
                'Can not process, book # must be numeric.'; 
            }            
          } else {
            $returnString = 'Can not process, book # must be numeric.'; 
          }
        }
        if ('title' == $arrayIn[1]) {
          if (is_numeric($arrayIn[2])) {
            $book = $this->bookList->getBook($arrayIn[2]);
            if (NULL == $book) {
              $returnString = 'Can not process, there is no book # '.
                $arrayIn[2]; 
            } else {
              $returnString = $book->getTitle(); 
            }
          } else {
            $returnString = 'Can not process, book # must be numeric.'; 
          }
        }
      } else {
        $returnString = 'Can not process, '.
                        'can only process book author #, <b'.
                        'r> book title #, or book author title #'; 
      }
      
      return $returnString;  
    }

  }
?>