;; BAGGER
;; Derived from the example on pages 132ff of the textbook.

;; Assertions in this Bagger system are of one of the following
;; disjoint formats:
;; (STEP IS <name-of-step>)
;;    Holds the name of the current step, one of
;;      check-order, bag-large-items, bag-medium-items, bag-small-items, done
;; (<bag#> IS <available-or-current-bag>)
;;    Status of each bag,
;;      available-bag, current-bag, or none (filled)
;; (<item#> <kind> <container> <size> <frozen?>) 
;;    Items to be bagged, as in table on pg 132 of textbook.
;; (<bag#> CONTAINS <item#> <size>)
;;    Contents of each bag, one assertion for each item.
;; (<item#> IN FREEZER-BAG)
;;    Item needs special packing in freezer bag.

;;;; BAGGER TEST DATA
ASSERTIONS

;; initial step
(step is check-order)

(bag1 is current-bag)
(bag2 is available-bag)
(bag3 is available-bag)
(bag4 is available-bag)

;; Similar to table on page 132 of text:
;;ITEM# KIND         CONTAINER-TYPE   SIZE   FROZEN?

(item1 Bread        Plastic-bag      Medium No)
(item2 Glop         Jar              Small  No)
(item3 Granola      Cardboard-box    Large  No)
(item4 Ice-cream    Cardboard-carton Medium Yes)
(item5 Potato-chips Plastic-bag      Medium No)
(item6 Crackers     Cardboard-box    Large  No)
(item7 Juice        Bottle           Large  No)
(item8 Peaches      Can              Large  No))

;;;; BAGGER RULES
RULES

;; How about a Pepsi with those potato chips?
(B1 IF
    (step is check-order)
    (?_ potato-chips ?_ ?_ ?_)
    AND-IF
    (= 0 (count-assertions '(?_ pepsi ?_ ?_ ?_)))
    ADD (item0 Pepsi Bottle Large No)
    SAYING "Add a bottle of Pepsi to the order.")

;; Start bagging large items.
(B2 IF
    (step is check-order)
    (?bag is current-bag)
    DELETE (step is check-order) 
    ADD (step is bag-large-items)
    SAYING "Bagging large items.")

;; Bag a large bottle if there are fewer than 3 large items in bag.
(B3 IF
    (step is bag-large-items)
    (?bag is current-bag)
    (?item ?class bottle large ?f)
    AND-IF
    (< (count-assertions '(?bag contains ?_ large)) 3)
    DELETE (?item ?class bottle large ?f) 
    ADD (?bag contains ?item large)
    SAYING "Put " ?item "," ?class "," " in " ?bag ".")

;; Bag a large item if there are fewer than 4 large items in bag.
(B4 IF
    (step is bag-large-items)
    (?bag is current-bag)
    (?item ?class ?c large ?f)
    AND-IF
    (< (count-assertions '(?bag contains ?_ large)) 4)
    DELETE (?item ?class ?c large ?f) 
    ADD (?bag contains ?item large)
    SAYING "Put " ?item "," ?class "," " in " ?bag ".")

;; Start a new bag, if large items are left unbagged.
(B5 IF
    (step is bag-large-items)
    (?bag is current-bag)
    (?item ?_ ?_ large ?_)
    (?new-bag is available-bag)
    DELETE
    (?bag is current-bag)
    (?new-bag is available-bag)
    ADD (?new-bag is current-bag)
    SAYING "Start a fresh bag.")

;; Switch to bagging medium items.
(B6 IF
    (step is bag-large-items)
    (?bag is current-bag)
    DELETE (step is bag-large-items) 
    ADD (step is bag-medium-items)
    SAYING "Bagging medium items.")

;; Place ice-cream in a freezer bag.
(B7 IF
    (step is bag-medium-items)
    (?bag is current-bag)
    (?item ice-cream ?_ ?_ yes)
    ADD (?item in freezer-bag)
    SAYING "Put " ?item ", ice-cream," " in freezer bag.")

;; Bag medium item if no large items and fewer than 6 medium items
;; in current bag.
(B8 IF
    (step is bag-medium-items)
    (?bag is current-bag)
    (?item ?class ?c medium ?f)
    AND-IF
    (= (count-assertions '(?bag contains ?_ large)) 0)
    (< (count-assertions '(?bag contains ?_ medium)) 6)
    DELETE (?item ?class ?c medium ?f) 
    ADD (?bag contains ?item medium)
    SAYING "Put " ?item "," ?class "," " in " ?bag ".")

;; Start a new bag, if medium items are left unbagged.
(B9 IF
    (step is bag-medium-items)
    (?bag is current-bag)
    (?item ?_ ?_ medium ?_)
    (?new-bag is available-bag)
    DELETE
    (?bag is current-bag)
    (?new-bag is available-bag)
    ADD (?new-bag is current-bag)
    SAYING "Start a fresh bag.")

;; Switch to bagging small items.
(B10 IF
     (step is bag-medium-items)
     (?bag is current-bag)
     DELETE (step is bag-medium-items) 
     ADD (step is bag-small-items)
     SAYING "Bagging small items.")

;; Bag small item if no large items and fewer than 10 small items
;; in current bag.
(B11 IF
     (step is bag-small-items)
     (?bag is current-bag)
     (?item ?class ?c small ?f)
     AND-IF
     (= (count-assertions '(?bag contains ?_ large)) 0)
     (< (count-assertions '(?bag contains ?_ small)) 10)
     DELETE (?item ?class ?c small ?f) 
     ADD (?bag contains ?item small)
     SAYING "Put " ?item "," ?class "," " in " ?bag ".")

;; Start a new bag, if small items are left unbagged.
(B12 IF
     (step is bag-small-items)
     (?bag is current-bag)
     (?item ?_ ?_ small ?_)
     (?new-bag is available-bag)
     DELETE
     (?bag is current-bag)
     (?new-bag is available-bag)
     ADD (?new-bag is current-bag)
     SAYING "Start a fresh bag.")

;; We're done.
(B13 IF
     (step is bag-small-items)
     (?bag is current-bag)
     DELETE
     (?bag is current-bag)
     (step is bag-small-items)
     ADD (step is done)
     SAYING "Bagging done.")