#lang racket/base
(require racket/pretty
         unstable/class-iop
         syntax/stx
         unstable/struct
         "interfaces.rkt")
(provide (all-defined-out))

;; Problem: If stx1 and stx2 are two distinguishable syntax objects, it
;; still may be the case that (syntax-e stx1) and (syntax-e stx2) are 
;; indistinguishable.

;; Solution: Rather than map stx to (syntax-e stx), in the cases where
;; (syntax-e stx) is confusable, map it to a different, unique, value.
;; Use syntax-dummy, and extend pretty-print-remap-stylable to look inside.

;; Old solution: same, except map identifiers to uninterned symbols instead

;; NOTE: Nulls are only wrapped when *not* list-terminators.  
;; If they were always wrapped, the pretty-printer would screw up
;; list printing (I think).

(define (pretty-print/defaults datum [port (current-output-port)])
  (parameterize
    (;; Printing parameters (defaults from MzScheme and DrScheme 4.2.2.2)
     [print-unreadable #t]
     [print-graph #f]
     [print-struct #t]
     [print-box #t]
     [print-vector-length #f]
     [print-hash-table #t]
     [print-honu #f])
    (pretty-write datum port)))

(define-struct syntax-dummy (val))
(define-struct (id-syntax-dummy syntax-dummy) (remap))

;; A SuffixOption is one of
;; - 'never             -- never
;; - 'always            -- suffix > 0
;; - 'over-limit        -- suffix > limit
;; - 'all-if-over-limit -- suffix > 0 if any over limit

;; syntax->datum/tables : stx partition% num SuffixOption
;;                        -> (values s-expr hashtable hashtable)
;; When partition is not false, tracks the partititions that subterms belong to
;; When limit is a number, restarts processing with numbering? set to true
;; 
;; Returns three values:
;;   - an S-expression
;;   - a hashtable mapping S-expressions to syntax objects
;;   - a hashtable mapping syntax objects to S-expressions
;; Syntax objects which are eq? will map to same flat values
(define (syntax->datum/tables stx partition limit suffixopt)
  (table stx partition limit suffixopt))

;; table : syntax maybe-partition% maybe-num SuffixOption -> (values s-expr hashtable hashtable)
(define (table stx partition limit suffixopt)
  (define (make-identifier-proxy id)
    (define sym (syntax-e id))
    (case suffixopt
      ((never)
       (make-id-syntax-dummy sym sym))
      ((always)
       (let ([n (send/i partition partition<%> get-partition id)])
         (if (zero? n)
             (make-id-syntax-dummy sym sym)
             (make-id-syntax-dummy (suffix sym n) sym))))
      ((over-limit)
       (let ([n (send/i partition partition<%> get-partition id)])
         (if (<= n limit)
             (make-id-syntax-dummy sym sym)
             (make-id-syntax-dummy (suffix sym n) sym))))))

  (let/ec escape
    (let ([flat=>stx (make-hasheq)]
          [stx=>flat (make-hasheq)])
      (define (loop obj)
        (cond [(hash-ref stx=>flat obj (lambda _ #f))
               => (lambda (datum) datum)]
              [(and partition (identifier? obj))
               (when (and (eq? suffixopt 'all-if-over-limit)
                          (> (send/i partition partition<%> count) limit))
                 (call-with-values (lambda () (table stx partition #f 'always))
                                   escape))
               (let ([lp-datum (make-identifier-proxy obj)])
                 (hash-set! flat=>stx lp-datum obj)
                 (hash-set! stx=>flat obj lp-datum)
                 lp-datum)]
              [(and (syntax? obj) (check+convert-special-expression obj))
               => (lambda (newobj)
                    (when partition (send/i partition partition<%> get-partition obj))
                    (let* ([inner (cadr newobj)]
                           [lp-inner-datum (loop inner)]
                           [lp-datum (list (car newobj) lp-inner-datum)])
                      (hash-set! flat=>stx lp-inner-datum inner)
                      (hash-set! stx=>flat inner lp-inner-datum)
                      (hash-set! flat=>stx lp-datum obj)
                      (hash-set! stx=>flat obj lp-datum)
                      lp-datum))]
              [(syntax? obj)
               (when partition (send/i partition partition<%> get-partition obj))
               (let ([lp-datum (loop (syntax-e obj))])
                 (hash-set! flat=>stx lp-datum obj)
                 (hash-set! stx=>flat obj lp-datum)
                 lp-datum)]
              [(pair? obj)
               (pairloop obj)]
              [(struct? obj)
               ;; Only traverse prefab structs
               (let ([pkey (prefab-struct-key obj)])
                 (if pkey
                     (let-values ([(refold fields) (unfold-pstruct obj)])
                       (refold (map loop fields)))
                     obj))]
              [(symbol? obj)
               (make-id-syntax-dummy obj obj)]
              [(null? obj)
               (make-syntax-dummy obj)]
              [(boolean? obj)
               (make-syntax-dummy obj)]
              [(number? obj)
               (make-syntax-dummy obj)]
              [(keyword? obj)
               (make-syntax-dummy obj)]
              [(vector? obj) 
               (list->vector (map loop (vector->list obj)))]
              [(box? obj)
               (box (loop (unbox obj)))]
              [else obj]))
      (define (pairloop obj)
        (cond [(pair? obj)
               (cons (loop (car obj))
                     (pairloop (cdr obj)))]
              [(null? obj)
               null]
              [(and (syntax? obj) (null? (syntax-e obj)))
               null]
              [else (loop obj)]))
      (values (loop stx)
              flat=>stx
              stx=>flat))))

;; unfold-pstruct : prefab-struct -> (values (list -> prefab-struct) list)
(define (unfold-pstruct obj)
  (define key (prefab-struct-key obj))
  (define fields (struct->list obj))
  (values (lambda (new-fields)
            (apply make-prefab-struct key new-fields))
          fields))

;; check+convert-special-expression : syntax -> #f/syntaxish
(define (check+convert-special-expression stx)
  (define stx-list (stx->list stx))
  (and stx-list (= 2 (length stx-list))
       (let ([kw (car stx-list)]
             [expr (cadr stx-list)])
         (and (identifier? kw)
              (memq (syntax-e kw) special-expression-keywords)
              (bound-identifier=? kw (datum->syntax stx (syntax-e kw)))
              (andmap (lambda (f) (equal? (f stx) (f kw)))
                      (list syntax-source
                            syntax-line
                            syntax-column
                            syntax-position
                            syntax-original?
                            syntax-source-module))
              (cons (syntax-e kw)
                    (list expr))))))

(define special-expression-keywords
  '(quote quasiquote unquote unquote-splicing syntax
    quasisyntax unsyntax unsyntax-splicing))

(define (suffix sym n)
  (string->symbol (format "~a:~a" sym n)))
