;; Predicates

(define title
  (lambda (recipe)
    (car (recipe))))

(define ingredients
  (lambda (recipe)
    (car (cdr recipe))))

(define steps
  (lambda (recipe)
    (car (cdr (cdr recipe)))))

(define ingredient-name
  (lambda (ingredient)
    (if (= (length ingredient) 2)
        (car (cdr ingredient))
        (car (cddr ingredient)))))

(define ingredient-amount
  (lambda (ingredient)
    (car ingredient)))


;;

(define ingredient-ref
  (lambda (ingredients n)
    (if (= n 0)
        (car ingredients)
        (ingredient-ref (cdr ingredients) (- n 1)))))

(define ingredient-by-name
  (lambda (ingredients search-name)
    (let ((ingredient (car ingredients)))
      (cond [(equal? (ingredient-name ingredient)
                     search-name)
             ingredient]
            [(null? (cdr ingredients)) #f]
            [else (ingredient-by-name (cdr ingredients)
                                      search-name)]))))

(define contains-ingredient?
  (lambda (recipe search-ingredient)
    (let ((ingredients (ingredients recipe)))
      (ingredient-by-name ingredients search-ingredient))))

(define contains-ingredients?
  (lambda (recipe search-ingredients)
    (let ((ingredients (ingredients recipe)))
      (cond [(null? search-ingredients) #t]
            [(ingredient-by-name ingredients
                                 (car search-ingredients))
             (contains-ingredients? recipe
                                    (cdr search-ingredients))]
            [else #f])
      )))

(define recipes-by-ingredients
  (lambda (recipes search-ingredients list)
    (if (null? recipes)
        list
        (let* ((recipe (car recipes))
               (ingredients (ingredients recipe))
               (contains? (contains-ingredients? recipe
                                                 search-ingredients)))
          (if contains?
              (recipes-by-ingredients (cdr recipes)
                                      search-ingredients
                                      (cons recipe list))
              (recipes-by-ingredients (cdr recipes)
                                      search-ingredients
                                      list))))))