(module integer-set mzscheme
  (require (only racket/base foldr)
           racket/contract/base)
  
  #;(define-syntax test-block
    (syntax-rules ()
      ((_ defs (code right-ans) ...)
       (let* defs
         (let ((real-ans code))
           (unless (equal? real-ans right-ans)
             (printf "Test failed: ~e gave ~e.  Expected ~e\n"
                     'code real-ans 'right-ans))) ...))))

  (define-syntax test-block
    (syntax-rules ()
      ((_ x ...) (void))))
    
  ;; An integer-set is (make-integer-set (listof (cons int int)))
  ;; Each cons represents a range of integers, and the entire
  ;; set is the union of the ranges.  The ranges must be disjoint and
  ;; increasing.  Further, adjacent ranges must have at least
  ;; one number between them.
  (define-struct integer-set (contents))
  
  ;; well-formed-set? : X -> bool
  (define (well-formed-set? x)
    (let loop ((set x)
               (current-num -inf.0))
      (or
       (null? set)
       (and (pair? set)
            (pair? (car set))
            (exact-integer? (caar set))
            (exact-integer? (cdar set))
            (< (add1 current-num) (caar set))
            (<= (caar set) (cdar set))
            (loop (cdr set) (cdar set))))))
  (test-block ()
              ((well-formed-set? '((0 . 4) (7 . 9))) #t)
              ((well-formed-set? '((-1 . 4))) #t)
              ((well-formed-set? '((11 . 10))) #f)
              ((well-formed-set? '((0 . 10) (8 . 12))) #f)
              ((well-formed-set? '((10 . 20) (1 . 2))) #f)
              ((well-formed-set? '((-10 . -20))) #f)
              ((well-formed-set? '((-20 . -10))) #t)
              ((well-formed-set? '((1 . 1))) #t)
              ((well-formed-set? '((1 . 1) (2 . 3))) #f)
              ((well-formed-set? '((1 . 1) (3 . 3))) #t)
              ((well-formed-set? null) #t))
               

  
  ;; make-range : int * int -> integer-set
  ;; creates a set of integers between i and j.  i <= j
  (define make-range
    (case-lambda 
      (() (make-integer-set null))
      ((i) (make-integer-set (list (cons i i))))
      ((i j) (make-integer-set (list (cons i j))))))
  (test-block ()
              ((integer-set-contents (make-range)) '())
              ((integer-set-contents (make-range 12)) '((12 . 12)))
              ((integer-set-contents (make-range 97 110)) '((97 . 110)))
              ((integer-set-contents (make-range 111 111)) '((111 . 111))))
   
  
  ;; sub-range? : (cons int int) (cons int int) -> bool
  ;; true iff the interval [(car r1), (cdr r1)] is a subset of
  ;; [(car r2), (cdr r2)]
  (define (sub-range? r1 r2)
    (and (>= (car r1) (car r2))
         (<= (cdr r1) (cdr r2))))
    
  ;; overlap? : (cons int int) (cons int int) -> bool
  ;; true iff the intervals [(car r1), (cdr r1)] and [(car r2), (cdr r2)]
  ;; have non-empty intersections and (car r1) >= (car r2)
  (define (overlap? r1 r2)
    (and (>= (car r1) (car r2))
         (>= (cdr r1) (cdr r2))
         (<= (car r1) (cdr r2))))
    
  
  ;; merge-helper : (listof (cons int int)) (listof (cons int int)) -> (listof (cons int int))
  (define (merge-helper s1 s2)
    (cond
      ((null? s2) s1)
      ((null? s1) s2)
      (else 
       (let ((r1 (car s1))
             (r2 (car s2)))
         (cond
           ((sub-range? r1 r2) (merge-helper (cdr s1) s2))
           ((sub-range? r2 r1) (merge-helper s1 (cdr s2)))
           ((or (overlap? r1 r2) (= (car r1) (add1 (cdr r2))))
            (merge-helper (cons (cons (car r2) (cdr r1)) (cdr s1)) (cdr s2)))
           ((or (overlap? r2 r1) (= (car r2) (add1 (cdr r1))))
            (merge-helper (cdr s1) (cons (cons (car r1) (cdr r2)) (cdr s2))))
           ((< (car r1) (car r2))
            (cons r1 (merge-helper (cdr s1) s2)))
           (else
            (cons r2 (merge-helper s1 (cdr s2)))))))))
  (test-block ()
              ((merge-helper null null) null)
              ((merge-helper null '((1 . 10))) '((1 . 10)))
              ((merge-helper '((1 . 10)) null) '((1 . 10)))
              ;; r1 in r2
              ((merge-helper '((5 . 10)) '((5 . 10))) '((5 . 10)))
              ((merge-helper '((6 . 9)) '((5 . 10))) '((5 . 10)))
              ((merge-helper '((7 . 7)) '((5 . 10))) '((5 . 10)))
              ;; r2 in r1
              ((merge-helper '((5 . 10)) '((5 . 10))) '((5 . 10)))
              ((merge-helper '((5 . 10)) '((6 . 9))) '((5 . 10)))
              ((merge-helper '((5 . 10)) '((7 . 7))) '((5 . 10)))
              ;; r2 and r1 are disjoint
              ((merge-helper '((5 . 10)) '((12 . 14))) '((5 . 10) (12 . 14)))
              ((merge-helper '((12 . 14)) '((5 . 10))) '((5 . 10) (12 . 14)))
              ;; r1 and r1 are adjacent
              ((merge-helper '((5 . 10)) '((11 . 13))) '((5 . 13)))
              ((merge-helper '((11 . 13)) '((5 . 10))) '((5 . 13)))
              ;; r1 and r2 overlap
              ((merge-helper '((5 . 10)) '((7 . 14))) '((5 . 14)))
              ((merge-helper '((7 . 14)) '((5 . 10))) '((5 . 14)))
              ((merge-helper '((5 . 10)) '((10 . 14))) '((5 . 14)))
              ((merge-helper '((7 . 10)) '((5 . 7))) '((5 . 10)))
              ;; with lists
              ((merge-helper '((1 . 1) (3 . 3) (5 . 10) (100 . 200))
                      '((2 . 2) (10 . 12) (300 . 300)))
               '((1 . 3) (5 . 12) (100 . 200) (300 . 300)))
              ((merge-helper '((1 . 1) (3 . 3) (5 . 5) (8 . 8) (10 . 10) (12 . 12))
                      '((2 . 2) (4 . 4) (6 . 7) (9 . 9) (11 . 11)))
               '((1 . 12)))
              ((merge-helper '((2 . 2) (4 . 4) (6 . 7) (9 . 9) (11 . 11))
                      '((1 . 1) (3 . 3) (5 . 5) (8 . 8) (10 . 10) (12 . 12)))
               '((1 . 12))))
                      
  ;; merge : integer-set integer-set -> integer-set
  ;; Union of s1 and s2
  (define (merge s1 s2)
    (make-integer-set (merge-helper (integer-set-contents s1) (integer-set-contents s2))))
  
  ;; split-sub-range : (cons int int) (cons int int) -> char-set
  ;; (subrange? r1 r2) must hold.
  ;; returns [(car r2), (cdr r2)] - ([(car r1), (cdr r1)] intersect [(car r2), (cdr r2)]).
  (define (split-sub-range r1 r2)
    (let ((r1-car (car r1))
          (r1-cdr (cdr r1))
          (r2-car (car r2))
          (r2-cdr (cdr r2)))
      (cond
        ((and (= r1-car r2-car) (= r1-cdr r2-cdr)) null)
        ((= r1-car r2-car) (list (cons (add1 r1-cdr) r2-cdr)))
        ((= r1-cdr r2-cdr) (list (cons r2-car (sub1 r1-car))))
        (else
         (list (cons r2-car (sub1 r1-car)) (cons (add1 r1-cdr) r2-cdr))))))

  (test-block ()
              ((split-sub-range '(1 . 10) '(1 . 10)) '())
              ((split-sub-range '(1 . 5) '(1 . 10)) '((6 . 10)))
              ((split-sub-range '(2 . 10) '(1 . 10)) '((1 . 1)))
              ((split-sub-range '(2 . 5) '(1 . 10)) '((1 . 1) (6 . 10))))
  
  
  ;; split-acc : (listof (cons int int))^5 -> integer-set^3
  (define (split-acc s1 s2 i s1-i s2-i)
    (cond
      ((null? s1) (values (make-integer-set (reverse i))
                          (make-integer-set (reverse s1-i))
                          (make-integer-set (reverse (append (reverse s2) s2-i)))))
      ((null? s2) (values (make-integer-set (reverse i))
                          (make-integer-set (reverse (append (reverse s1) s1-i)))
                          (make-integer-set (reverse s2-i))))
      (else
       (let ((r1 (car s1))
             (r2 (car s2)))
         (cond
           ((sub-range? r1 r2)
            (split-acc (cdr s1) (append (split-sub-range r1 r2) (cdr s2))
                       (cons r1 i) s1-i s2-i))
           ((sub-range? r2 r1)
            (split-acc (append (split-sub-range r2 r1) (cdr s1)) (cdr s2)
                       (cons r2 i) s1-i s2-i))
           ((overlap? r1 r2)
            (split-acc (cons (cons (add1 (cdr r2)) (cdr r1)) (cdr s1))
                       (cdr s2)
                       (cons (cons (car r1) (cdr r2)) i)
                       s1-i 
                       (cons (cons (car r2) (sub1 (car r1))) s2-i)))
           ((overlap? r2 r1)
            (split-acc (cdr s1)
                       (cons (cons (add1 (cdr r1)) (cdr r2)) (cdr s2))
                       (cons (cons (car r2) (cdr r1)) i)
                       (cons (cons (car r1) (sub1 (car r2)))s1-i )
                       s2-i))
           ((< (car r1) (car r2))
            (split-acc (cdr s1) s2 i (cons r1 s1-i) s2-i))
           (else
            (split-acc s1 (cdr s2) i s1-i (cons r2 s2-i))))))))
  
  ;; split : integer-set integer-set -> integer-set integer-set integer-set
  ;; returns (s1 intersect s2), s1 - (s1 intersect s2) and s2 - (s1 intersect s2)
  ;; Of course, s1 - (s1 intersect s2) = s1 intersect (complement s2) = s1 - s2
  (define (split s1 s2)
    (split-acc (integer-set-contents s1) (integer-set-contents s2) null null null))
    
  ;; intersect: integer-set integer-set -> integer-set
  (define (intersect s1 s2)
    (let-values (((i s1-s2 s2-s1) (split s1 s2)))
      i))
         
  ;; difference: integer-set integer-set -> integer-set
  (define (difference s1 s2)
    (let-values (((i s1-s2 s2-s1) (split s1 s2)))
      s1-s2))
  
  ;; xor: integer-set integer-set -> integer-set
  (define (xor s1 s2)
    (let-values (((i s1-s2 s2-s1) (split s1 s2)))
      (merge s1-s2 s2-s1)))
  
  (test-block ((s (lambda (s1 s2)
                    (map integer-set-contents
                         (call-with-values (lambda () (split (make-integer-set s1)
                                                             (make-integer-set s2))) list)))))
              ((s null null) '(() () ()))
              ((s '((1 . 10)) null) '(() ((1 . 10)) ()))
              ((s null '((1 . 10))) '(() () ((1 . 10))))
              ((s '((1 . 10)) null) '(() ((1 . 10)) ()))
              ((s '((1 . 10)) '((1 . 10))) '(((1 . 10)) () ()))
              ((s '((1 . 10)) '((2 . 5))) '(((2 . 5)) ((1 . 1) (6 . 10)) ()))
              ((s '((2 . 5)) '((1 . 10))) '(((2 . 5)) () ((1 . 1) (6 . 10))))
              ((s '((2 . 5)) '((5 . 10))) '(((5 . 5)) ((2 . 4)) ((6 . 10))))
              ((s '((5 . 10)) '((2 . 5))) '(((5 . 5)) ((6 . 10)) ((2 . 4))))
              ((s '((2 . 10)) '((5 . 14))) '(((5 . 10)) ((2 . 4)) ((11 . 14))))
              ((s '((5 . 14)) '((2 . 10))) '(((5 . 10)) ((11 . 14)) ((2 . 4))))
              ((s '((10 . 20)) '((30 . 50))) '(() ((10 . 20)) ((30 . 50))))
              ((s '((100 . 200)) '((30 . 50))) '(() ((100 . 200)) ((30 . 50))))
              ((s '((1 . 5) (7 . 9) (100 . 200) (500 . 600) (600 . 700))
                  '((2 . 8) (50 . 60) (101 . 104) (105 . 220)))
               '(((2 . 5) (7 . 8) (101 . 104) (105 . 200))
                 ((1 . 1) (9 . 9) (100 . 100) (500 . 600) (600 . 700))
                 ((6 . 6) (50 . 60) (201 . 220))))
              ((s '((2 . 8) (50 . 60) (101 . 104) (105 . 220))
                  '((1 . 5) (7 . 9) (100 . 200) (500 . 600) (600 . 700)))
               '(((2 . 5) (7 . 8) (101 . 104) (105 . 200))
                 ((6 . 6) (50 . 60) (201 . 220))
                 ((1 . 1) (9 . 9) (100 . 100) (500 . 600) (600 . 700))))
              )
  
  ;; complement-helper : (listof (cons int int)) int int -> (listof (cons int int))
  ;; The current-nat accumulator keeps track of where the
  ;; next range in the complement should start.
  (define (complement-helper s min max)
    (cond
      ((null? s) (if (<= min max)
                     (list (cons min max))
                     null))
      (else
       (let ((s-car (car s)))
         (cond
           ((< min (car s-car))
            (cons (cons min (sub1 (car s-car)))
                  (complement-helper (cdr s) (add1 (cdr s-car)) max)))
           ((<= min (cdr s-car))
            (complement-helper (cdr s) (add1 (cdr s-car)) max))
           (else
            (complement-helper (cdr s) min max)))))))
  
    
  ;; complement : integer-set int int -> integer-set
  ;; A set of all the nats not in s and between min and max, inclusive.
  ;; min <= max
  (define (complement s min max)
    (make-integer-set (complement-helper (integer-set-contents s) min max)))
  (test-block ((c (lambda (a b c)
                    (integer-set-contents (complement (make-integer-set a) b c)))))
              ((c null 0 255) '((0 . 255)))
              ((c '((1 . 5) (7 . 7) (10 . 200)) 0 255)
               '((0 . 0) (6 . 6) (8 . 9) (201 . 255)))
              ((c '((0 . 254)) 0 255) '((255 . 255)))
              ((c '((1 . 255)) 0 255) '((0 . 0)))
              ((c '((0 . 255)) 0 255) null)
              ((c '((1 . 10)) 2 5) null)
              ((c '((1 . 5) (7 . 12)) 2 8) '((6 . 6)))
              ((c '((1 . 5) (7 . 12)) 6 6) '((6 . 6)))
              ((c '((1 . 5) (7 . 12)) 7 7) '()))
                                           
  
  ;; member?-helper : int (listof (cons int int)) -> bool
  (define (member?-helper i is)
    (and
      (pair? is)
      (or (<= (caar is) i (cdar is))
          (member?-helper i (cdr is)))))
  
  ;; member? : int integer-set -> bool
  (define (member? i is)
    (member?-helper i (integer-set-contents is)))
  (test-block ()
              ((member? 1 (make-integer-set null)) #f)
              ((member? 19 (make-integer-set '((1 . 18) (20 . 21)))) #f)
              ((member? 19 (make-integer-set '((1 . 2) (19 . 19) (20 . 21)))) #t))
     
  
  ;; get-integer : integer-set -> (union int #f)
  (define (get-integer is)
    (let ((l (integer-set-contents is)))
      (cond
        ((null? l) #f)
        (else (caar l)))))
  (test-block ()
              ((get-integer (make-integer-set null)) #f)
              ((get-integer (make-integer-set '((1 . 2) (5 . 6)))) 1))
    
  ;; is-foldr-helper : (int Y -> Y) Y int int (listof (cons int int)) -> Y
  (define (is-foldr-helper f base start stop is)
    (cond
      ((and (> start stop) (null? is)) base)
      ((> start stop)
       (is-foldr-helper f base (caar is) (cdar is) (cdr is)))
      (else
       (f start
          (is-foldr-helper f base (add1 start) stop is)))))
  
  ;; is-foldr : (int Y -> Y) Y integer-set -> Y
  (define (is-foldr f base is)
    (let ((l (integer-set-contents is)))
      (cond
        ((null? l) base)
        (else
         (is-foldr-helper f base (caar l) (cdar l) (cdr l))))))

  (test-block ()
              ((is-foldr cons null (make-integer-set null)) null)
              ((is-foldr cons null (make-integer-set '((1 . 2) (5 . 10))))
               '(1 2 5 6 7 8 9 10)))

  ;; partition : (listof integer-set) -> (listof integer-set)
  ;; The coarsest refinment r of sets such that the integer-sets in r
  ;; are pairwise disjoint.
  (define (partition sets)
    (map make-integer-set (foldr partition1 null sets)))
    
  ;; partition1 : integer-set (listof (listof (cons int int))) -> (listof (listof (cons int int)))
  ;; All the integer-sets in sets must be pairwise disjoint.  Splits set
  ;; against each element in sets.
  (define (partition1 set sets)
    (let ((set (integer-set-contents set)))
      (cond
        ((null? set) sets)
        ((null? sets) (list set))
        (else
         (let ((set2 (car sets)))
           (let-values (((i s1 s2) (split-acc set set2 null null null)))
             (let ((rest (partition1 s1 (cdr sets)))
                   (i (integer-set-contents i))
                   (s2 (integer-set-contents s2)))
               (cond
                 ((null? i)
                  (cons s2 rest))
                 ((null? s2)
                  (cons i rest))
                 (else
                  (cons i (cons s2 rest)))))))))))
  (test-block ((->is (lambda (str)
                     (foldr (lambda (c cs)
                              (merge (make-range (char->integer c))
                                     cs))
                            (make-range)
                            (string->list str))))
               (->is2 (lambda (str)
                      (integer-set-contents (->is str)))))
              ((partition null) null)
              ((map integer-set-contents (partition (list (->is "1234")))) (list (->is2 "1234")))
              ((map integer-set-contents (partition (list (->is "1234") (->is "0235"))))
               (list (->is2 "23") (->is2 "05") (->is2 "14")))
              ((map integer-set-contents (partition (list (->is "12349") (->is "02359") (->is "67") (->is "29"))))
               (list (->is2 "29") (->is2 "67") (->is2 "3") (->is2 "05") (->is2 "14")))
              ((partition1 (->is "bcdjw") null) (list (->is2 "bcdjw")))
              ((partition1 (->is "") null) null)
              ((partition1 (->is "") (list (->is2 "a") (->is2 "b") (->is2 "1")))
               (list (->is2 "a") (->is2 "b") (->is2 "1")))
              ((partition1 (->is "bcdjw")
                           (list (->is2 "z")
                                 (->is2 "ab")
                                 (->is2 "dj")))
               (list (->is2 "z") (->is2 "b") (->is2 "a") (->is2 "dj") (->is2 "cw"))))

  
  ;; card : integer-set -> nat
  (define (card s)
    (foldr (lambda (range sum) (+ 1 sum (- (cdr range) (car range))))
           0
           (integer-set-contents s)))
  (test-block ()
              ((card (make-integer-set null)) 0)
              ((card (make-integer-set '((1 . 1)))) 1)
              ((card (make-integer-set '((-1 . 10)))) 12)
              ((card (make-integer-set '((-10 . -5) (-1 . 10) (12 . 12)))) 19))
             
    
  ;; subset?-helper : (listof (cons int int)) (listof (cons int int)) -> bool
  (define (subset?-helper l1 l2)
    (cond
      ((null? l1) #t)
      ((null? l2) #f)
      (else
       (let ((r1 (car l1))
             (r2 (car l2)))
         (cond
           ((sub-range? r1 r2) (subset?-helper (cdr l1) l2))
           ((<= (car r1) (cdr r2)) #f)
           (else (subset?-helper l1 (cdr l2))))))))
  (test-block ()
              ((subset?-helper null null) #t)
              ((subset?-helper null '((1 . 1))) #t)
              ((subset?-helper '((1 . 1)) null) #f)
              ((subset?-helper '((1 . 1)) '((0 . 10))) #t)
              ((subset?-helper '((1 . 1)) '((2 . 10))) #f)
              ((subset?-helper '((-4 . -4) (2 . 10)) '((-20 . -17) (-15 . -10) (-5 . -4) (-2 . 0) (1 . 12))) #t)
              ((subset?-helper '((-4 . -3) (2 . 10)) '((-20 . -17) (-15 . -10) (-5 . -4) (-2 . 0) (1 . 12))) #f)
              ((subset?-helper '((-4 . -4) (2 . 10)) '((-20 . -17) (-15 . -10) (-5 . -4) (-2 . 0) (3 . 12))) #f))
              
  
         
  ;; subset? : integer-set integer-set -> bool
  (define (subset? s1 s2)
    (subset?-helper (integer-set-contents s1) (integer-set-contents s2)))
    
  (provide well-formed-set?)

  (provide/contract (struct integer-set ((contents well-formed-set?)))
                    (make-range 
                     (->i () ((i exact-integer?) (j (i) (and/c exact-integer? (>=/c i)))) [res integer-set?]))
                    (rename merge union (integer-set? integer-set? . -> . integer-set?))
                    (split (integer-set? integer-set? . -> . (values integer-set? integer-set? integer-set?)))
                    (intersect (integer-set? integer-set? . -> . integer-set?))
                    (difference (integer-set? integer-set? . -> . integer-set?))
                    (xor (integer-set? integer-set? . -> . integer-set?))
                    (complement (->i ((s integer-set?) (min exact-integer?) (max (min) (and/c exact-integer? (>=/c min))))
                                     [res integer-set?]))
                    (member? (exact-integer? integer-set? . -> . any))
                    (get-integer (integer-set? . -> . (or/c #f exact-integer?)))
                    (rename is-foldr foldr (any/c any/c integer-set? . -> . any))
                    (partition ((listof integer-set?) . -> . (listof integer-set?)))
                    (card (integer-set? . -> . natural-number/c))
                    (subset? (integer-set? integer-set? . -> . any)))

  ) 
