(declare (unit sexc)
         (uses templates))

(import brev-separate
        (chicken pathname)
        (chicken pretty-print)
        (chicken process-context)
        (chicken string)
        fmt
        fmt-c
        getopt-long
        srfi-1                          ; list routines
        tree)

(define +debug+ #f)

(define (unkebabify sym)
  (case sym
    ((-) sym)
    ((--) sym)
    ((->) sym)
    ((-=) sym)
    (else
     (string->symbol
      (string-translate (symbol->string sym) #\- #\_)))))

(define (atom-to-fmt-c atom)
  (case atom
    ((fn) '%fun)
    ((prototype) '%prototype)
    ((var) '%var)
    ((begin) '%begin)
    ((pointer) '%pointer)
    ((array) '%array)
    ((@) 'vector-ref)
    ((include) '%include)
    ((cast) '%cast)
    (else
     (if (symbol? atom)
         (unkebabify atom)
         atom))))

(define (tree-finder symbol)
  (lambda (node)
    (or (and (tree? node)
             (eq? (car node) symbol))
        #f)))

(define (make-field-access form)
  (assert (= 2 (length form)) "Wrong field access format")
  (unkebabify
   (string->symbol
    (fmt #f (cadr form) (car form)))))

(define (walk-generic form acc)
  (cond
   ((null? form) (cons '() acc))
   ((not (list? form)) (cons (atom-to-fmt-c form) acc))

   ;; special case - replace unquote with its expansion
   ((eq? (car form) 'unquote)
    (fold
     cons
     acc
     (car                               ; bc walk-sex-tree always
                                        ; wraps its result
      (walk-sex-tree (eval (cadr form)) (list)))))

   ;; another special case - field access
   ((and (symbol? (car form))
         (char=? #\. (string-ref (symbol->string (car form)) 0)))
    (cons (make-field-access form) acc))
   ;; toplevel, or a start of a regular list form
   (else
    (let ((new-acc (list)))
      (cons (reverse
             (fold
              walk-generic
              new-acc
              form))
            acc)))))

(define (walk-function form static acc)
  (if static
      (append (walk-generic (list 'static form) (list)) acc)
      (append (walk-generic (cdr form) (list)) acc)))

(define (walk-struct form acc)
  (let ((name (unkebabify (cadr form))))
    (append (walk-generic form (list))
          (cons `(typedef struct ,name ,name) acc))))

(define (walk-extern form acc)
  (case (cadr form)
    ((fn)
     (append
      (walk-generic (list 'extern (cons 'prototype (cddr form))) (list))
      acc))
    ((var)
     (append
      (walk-generic (list 'extern (cdr form)) (list))
      acc))
    (else (error "Extern what?"))))

(define (walk-public form acc)
  (case (cadr form)
    ((fn)
     (walk-function form #f acc))
    ((var)
     (append (walk-generic (list 'static (cdr form)) (list)) acc))
    (else (error "Pub what?"))))

(define (walk-sex-tree form acc)
  (case (car form)
    ((fn) (walk-function form #t acc))
    ((extern) (walk-extern form acc))
    ((pub) (walk-public form acc))
    ((struct union) (walk-struct form acc))
    ((unquote) (fold (fn (walk-sex-tree x y))
                     acc
                     (eval (cadr form))))

    (else (append (walk-generic form (list)) acc))))

(define (process-form form acc)
  (case (car form)
    ((define) (eval form) acc)
    ((template) (eval form) acc)
    ((load) (eval form) acc)
    (else
     (walk-sex-tree form acc))))


(define (process-raw-forms raw-forms acc)
  (if (null? raw-forms)
      (reverse acc)
      (process-raw-forms (cdr raw-forms)
                         (process-form (car raw-forms) acc))))

(define (read-forms acc)
  (let ((r (read)))
    (if (eof-object? r) (reverse acc)
        (read-forms (cons r acc)))))

(define (emit-c forms)
  (for-each (lambda (form)
              (fmt #t (c-expr form))
              (fmt #t "\n"))
            forms))

;;; Main function facilities

(define opts-grammar
  `((output "Write output to file"
            (required #f)
            (value #t)
            (single-char #\o))
    (help "Show this help"
          (required #f)
          (value #f)
          (single-char #\h))
    (macro-expand "Emit macro-expanded Sex code instead of C"
                  (required #f)
                  (value #f)
                  (single-char #\m))))

(define (print-help)
  (fmt #t "Usage: sexc [OPTIONS] [FILE]\n")
  (fmt #t "Options: -o, --output <file>        Write output to file. If omitted, write to stdout\n")
  (fmt #t "         -h, --help                 Show this help\n")
  (fmt #t "         -m, --macro-expand         Emit macro-expanded Sex code instead of C\n"))

(define (help-arg? args)
  (assoc 'help args))

(define (get-arg args arg-name default)
  (let ((arg (assoc arg-name args)))
    (if arg (cdr arg)
        default)))

(define (get-input-file args)
  (let ((rest-args (assoc '@ args)))
    (if (= 1 (length rest-args))
        'stdin
        (cadr rest-args))))

(define (read-from-file file)
  (with-input-from-file (pathname-strip-directory file)
    (fn (read-forms (list)))))

(define (set-working-directory file)
  (change-directory
   (normalize-pathname
    (make-absolute-pathname
     (current-directory)
     (pathname-directory file)))))

(define (main)
  (let* ((raw-args (command-line-arguments))
         (current-dir (current-directory))
         (args (getopt-long raw-args
                            opts-grammar))
         (output (get-arg args 'output 'stdout))
         (help (help-arg? args))
         (input (get-input-file args)))
    (if help (print-help)
        (let* ((raw-forms
                (if (eq? input 'stdin)
                    (read-forms (list))
                    (begin
                      (set-working-directory input)
                      (read-from-file input))))
               (sex-forms (process-raw-forms raw-forms (list))))
          (change-directory current-dir)
          (if (get-arg args 'macro-expand #f)
              (map pp sex-forms)
              (if (not (eq? output 'stdout))
                  (with-output-to-file output
                    (lambda ()
                      (emit-c sex-forms)))
                  (emit-c sex-forms)))))))