#lang scheme

(require (for-syntax syntax/parse))

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;
;;  Flat Contracts
;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

(define nat/c
  (flat-named-contract '|natural number| exact-nonnegative-integer?))

(define pos/c
  (flat-named-contract '|positive integer| exact-positive-integer?))

(define truth/c
  (flat-named-contract '|truth value| (lambda (x) #t)))

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;
;;  Function Contracts
;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

(define thunk/c (-> any/c))
(define unary/c (-> any/c any/c))
(define binary/c (-> any/c any/c any/c))
(define predicate/c (-> any/c boolean?))
(define comparison/c (-> any/c any/c boolean?))
(define predicate-like/c (-> any/c truth/c))
(define comparison-like/c (-> any/c any/c truth/c))

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;
;;  Contracted Sequences
;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

(define (sequence/c . elem/cs)
  (let* ([elem/cs (for/list ([elem/c (in-list elem/cs)])
                    (coerce-contract 'sequence/c elem/c))]
         [n-cs (length elem/cs)])
    (make-proj-contract
     (apply build-compound-type-name 'sequence/c elem/cs)
     (lambda (pos neg src name blame)
       (lambda (seq)
         (unless (sequence? seq)
           (raise-contract-error
            seq src pos name
            "expected a sequence, got: ~e"
            seq))
           (make-do-sequence
            (lambda ()
              (let*-values ([(more? next) (sequence-generate seq)])
                (values
                 (lambda (idx)
                   (call-with-values next
                     (lambda elems
                       (define n-elems (length elems))
                       (unless (= n-elems n-cs)
                         (raise-contract-error
                          seq src pos name
                          "expected a sequence of ~a values, got ~a values: ~s"
                          n-cs n-elems elems))
                       (apply
                        values
                        (for/list ([elem (in-list elems)]
                                   [elem/c (in-list elem/cs)])
                          ((((contract-projection elem/c) elem/c) pos neg src name blame) elem))))))
                 (lambda (idx) idx)
                 #f
                 (lambda (idx) (more?))
                 (lambda (elem) #t)
                 (lambda (idx elem) #t)))))))
     sequence?)))

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;
;;  Contracted Dictionaries
;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

;; A CDict is (make-contracted-dictionary (Listof (Cons Proj Proj)) Dict)
;; A Proj is (make-projection Contract Symbol Symbol Any Any)
(define-struct contracted-dictionary [projections bindings])
(define-struct projection [contract out in source name blame])

(define (dict/c key/c value/c)
  (let* ([key/c (coerce-contract 'dict/c key/c)]
         [value/c (coerce-contract 'dict/c value/c)])
    (make-proj-contract
     (build-compound-type-name 'dict/c key/c value/c)
     (lambda (pos neg src name blame)
       (lambda (dict)
         (unless (dict? dict)
           (raise-contract-error dict src pos name
                                 "expected a dictionary, got: ~e"
                                 dict))
         (wrap
          (cons (cons (make-projection key/c pos neg src name blame)
                      (make-projection value/c pos neg src name blame))
                (dict->projections dict))
          (dict->bindings dict))))
     dict?)))

(define-match-expander cdict
  (syntax-rules () [(_ p b) (struct contracted-dictionary [p b])]))

(define-match-expander proj
  (syntax-rules () [(_ c o i s n b) (struct projection [c o i s n b])]))

(define -ref
  (case-lambda
    [(dict key)
     (match dict
       [(cdict projs binds)
        (let* ([key (key-in projs key)])
          (value-out projs (dict-ref binds key)))])]
    [(dict key failure)
     (match dict
       [(cdict projs binds)
        (let* ([key (key-in projs key)])
          (let/ec return
            (define (fail)
              (return (if (procedure? failure) (failure) failure)))
            (value-out projs (dict-ref binds key fail))))])]))

(define (-set! dict key value)
  (match dict
    [(cdict projs binds)
     (dict-set! binds (key-in projs key) (value-in projs value))]))

(define (-set dict key value)
  (match dict
    [(cdict projs binds)
     (wrap projs (dict-set binds (key-in projs key) (value-in projs value)))]))

(define (-rem! dict key)
  (match dict
    [(cdict projs binds)
     (dict-remove! binds (key-in projs key))]))

(define (-rem dict key)
  (match dict
    [(cdict projs binds)
     (wrap projs (dict-remove binds (key-in projs key)))]))

(define (-size dict)
  (match dict
    [(cdict projs binds)
     (dict-count binds)]))

(define (-fst dict)
  (match dict
    [(cdict projs binds)
     (dict-iterate-first binds)]))

(define (-nxt dict iter)
  (match dict
    [(cdict projs binds)
     (dict-iterate-next binds iter)]))

(define (-key dict iter)
  (match dict
    [(cdict projs binds)
     (key-out projs (dict-iterate-key binds iter))]))

(define (-val dict iter)
  (match dict
    [(cdict projs binds)
     (value-out projs (dict-iterate-value binds iter))]))

(define (key-in projs key)
  (if (null? projs)
      key
      (key-in (cdr projs) (project-in (caar projs) key))))

(define (value-in projs value)
  (if (null? projs)
      value
      (value-in (cdr projs) (project-in (cdar projs) value))))

(define (key-out projs key)
  (if (null? projs)
      key
      (project-out (caar projs) (key-out (cdr projs) key))))

(define (value-out projs value)
  (if (null? projs)
      value
      (project-out (cdar projs) (value-out (cdr projs) value))))

(define (project-in p x)
  (match p
    [(proj c o i s n b)
     ((((contract-projection c) c) i o s n (not b)) x)]))

(define (project-out p x)
  (match p
    [(proj c o i s n b)
     ((((contract-projection c) c) o i s n b) x)]))

(define (dict->bindings dict)
  (match dict
    [(cdict projs binds) binds]
    [_ dict]))

(define (dict->projections dict)
  (match dict
    [(cdict projs binds) projs]
    [_ null]))

(define (wrap projs binds)
  ((dict->wrapper binds) projs binds))

(define (dict->wrapper dict)
  (if (dict-mutable? dict)
      (if (dict-can-functional-set? dict)
          (if (dict-can-remove-keys? dict) make-:!+- make-:!+_)
          (if (dict-can-remove-keys? dict) make-:!_- make-:!__))
      (if (dict-can-functional-set? dict)
          (if (dict-can-remove-keys? dict) make-:_+- make-:_+_)
          (if (dict-can-remove-keys? dict) make-:__- make-:___))))

;; The __- case (removal without functional or mutable update) is nonsensical.
(define prop:!+- (vector -ref -set! -set -rem! -rem -size -fst -nxt -key -val))
(define prop:!+_ (vector -ref -set! -set  #f    #f  -size -fst -nxt -key -val))
(define prop:!_- (vector -ref -set!  #f  -rem!  #f  -size -fst -nxt -key -val))
(define prop:!__ (vector -ref -set!  #f   #f    #f  -size -fst -nxt -key -val))
(define prop:_+- (vector -ref  #f   -set  #f   -rem -size -fst -nxt -key -val))
(define prop:_+_ (vector -ref  #f   -set  #f   -rem -size -fst -nxt -key -val))
(define prop:__- (vector -ref  #f    #f   #f    #f  -size -fst -nxt -key -val))
(define prop:___ (vector -ref  #f    #f   #f    #f  -size -fst -nxt -key -val))

;; The __- case (removal without functional or mutable update) is nonsensical.
(define-struct (:!+- contracted-dictionary) [] #:property prop:dict prop:!+-)
(define-struct (:!+_ contracted-dictionary) [] #:property prop:dict prop:!+_)
(define-struct (:!_- contracted-dictionary) [] #:property prop:dict prop:!_-)
(define-struct (:!__ contracted-dictionary) [] #:property prop:dict prop:!__)
(define-struct (:_+- contracted-dictionary) [] #:property prop:dict prop:_+-)
(define-struct (:_+_ contracted-dictionary) [] #:property prop:dict prop:_+_)
(define-struct (:__- contracted-dictionary) [] #:property prop:dict prop:__-)
(define-struct (:___ contracted-dictionary) [] #:property prop:dict prop:___)

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;
;;  Exports
;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

(provide/contract

 [nat/c flat-contract?]
 [pos/c flat-contract?]
 [truth/c flat-contract?]

 [thunk/c contract?]
 [unary/c contract?]
 [binary/c contract?]
 [predicate/c contract?]
 [comparison/c contract?]
 [predicate-like/c contract?]
 [comparison-like/c contract?]

 [sequence/c (->* [] [] #:rest (listof contract?) contract?)]
 [dict/c (-> contract? contract? contract?)]
 )