(import (scheme base) (scheme write) (scheme cyclone ast) (scheme cyclone util) (scheme cyclone pretty-print))

;; TODO: scan sexp, is sym only called in tail-call position?
(define (local-tail-call-only? sexp sym)
  (call/cc
    (lambda (return)
      (define (scan exp fail?)
        (cond
         ((ast:lambda? exp)
          (return #f)) ;; Could be OK if not ref'd...
         ;((quote? exp) exp)
         ;((const? exp) exp)
         ((ref? exp) 
          (if (equal? exp sym)
              (return #f))) ;; Assume not a tail call
         ((define? exp) 
          (return #f)) ;; Fail fast
         ((set!? exp)
          (return #f)) ;; Fail fast
         ((if? exp)       
          (scan (if->condition exp) #t) ;; fail if found under here
          (scan (if->then exp) fail?)
          (scan (if->else exp) fail?))
         ((app? exp)
          (cond
            ((and (equal? (car exp) sym)
                  (not fail?))
             (map (lambda (e) (scan e fail?)) (cdr exp))) ;; Sym is OK, skip
            (else
             (map (lambda (e) (scan e fail?)) exp))))
         (else exp)))
      (scan sexp #f)
      (return #t))))

(define (tail-calls->values sexp sym)
  (call/cc
    (lambda (return)
      (define (scan exp)
      (write `(DEBUG scan ,exp)) (newline)
        (cond
         ((ast:lambda? exp)
          (return #f)) ;; Could be OK if not ref'd...
         ((ref? exp) 
          (if (equal? exp sym)
              (return #f))) ;; Assume not a tail call
         ((define? exp) 
          (return #f)) ;; Fail fast
         ((set!? exp)
          (return #f)) ;; Fail fast
         ((if? exp)       
          `(if ,(if->condition exp) 
               ,(scan (if->then exp))
               ,(scan (if->else exp))))
         ((app? exp)
          (cond
            ((and (equal? (car exp) sym)
                  (= (length exp) 2)
             )
             (cadr exp))
            (else
             (return #f))))
         (else exp)))
      (return
        (scan sexp)))))

(define (find-local-vars sexp)
  (define (scan exp)
    (cond
     ((ast:lambda? exp)
      (for-each
        scan
        (ast:lambda-body exp)))
     ((quote? exp) exp)
     ((const? exp) exp)
     ((ref? exp) exp)
     ((define? exp) 
      (for-each
        scan
        (define->exp exp)))
     ((set!? exp)
      (for-each
        scan
        (set!->exp exp)))
     ((if? exp)       
      (scan (if->condition exp))
      (scan (if->then exp))
      (scan (if->else exp)))
     ((app? exp)
      (cond
        ((and
          (ast:lambda? (car exp))
          (equal? (length exp) 2)
          (ast:lambda? (cadr exp))
          (equal? 1 (length (ast:lambda-args (cadr exp))))
          (local-tail-call-only? 
            (ast:lambda-body (car exp)) 
            (car (ast:lambda-args (car exp)))))
         (write `(tail-call-only? passed for ,exp)) (newline)
         (write `(replace with ,(tail-calls->values 
                                  (car (ast:lambda-body (car exp)))
                                  (car (ast:lambda-args (car exp))))))
         (newline)
         (let ((value (tail-calls->values
                        (car (ast:lambda-body (car exp)))
                        (car (ast:lambda-args (car exp)))))
               (var (car (ast:lambda-args (cadr exp))))
               (body (ast:lambda-body (cadr exp))))
          `((let ((,var ,value))
            ,body))))
        (else
          (map scan exp))))
     (else 'todo)
  ))
  (scan sexp))

(define sexp
             '(lambda
                (k$1073 i$88$682 first$89$683 row$90$684)
                (if (Cyc-fast-eq
                      i$88$682
                      number-of-cols$68$671)
                  (k$1073
                    (Cyc-fast-eq
                      i$88$682
                      number-of-cols$68$671))
                  ((lambda
                     (k$1080)
                     (if (Cyc-fast-eq
                           (car first$89$683)
                           (car row$90$684))
                       (k$1080 if-equal$76$674)
                       (k$1080 if-different$77$675)))
                   (lambda
                     (r$1079)
                     (Cyc-seq
                       (vector-set!
                         vec$79$677
                         i$88$682
                         r$1079)
                       ((cell-get lp$80$87$681)
                        k$1073
                        (Cyc-fast-plus i$88$682 1)
                        (cdr first$89$683)
                        (cdr row$90$684))))))))

;(pretty-print
;  (ast:ast->pp-sexp
;    (ast:sexp->ast sexp)))

(pretty-print
  (find-local-vars (ast:sexp->ast sexp)))