;;; lang/c/cpp.scm
;;;
;;; Copyright (C) 2015 Matthew R. Wette
;;;
;;; This program is free software: you can redistribute it and/or modify
;;; it under the terms of the GNU General Public License as published by 
;;; the Free Software Foundation, either version 3 of the License, or 
;;; (at your option) any later version.
;;;
;;; This program is distributed in the hope that it will be useful,
;;; but WITHOUT ANY WARRANTY; without even the implied warranty of 
;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;;; GNU General Public License for more details.
;;;
;;; You should have received a copy of the GNU General Public License
;;; along with this program.  If not, see <http://www.gnu.org/licenses/>.

;; C preprocessor.  This is not complete.

(define-module (nyacc lang c99 cpp)
  #:export (parse-cpp-stmt
	    read-cpp-stmt
	    parse-cpp-expr
	    eval-cpp-expr
	    cpp-expand-text
	    expand-cpp-mref
	    )
  #:use-module (nyacc parse)
  #:use-module (nyacc lex)
  #:use-module (nyacc lang util)
  #:use-module (rnrs arithmetic bitwise)
  )

(cond-expand
 (guile-2)
 (guile
  (use-modules (ice-9 syncase)))
 (mes))

#|
  #define  #undef  #include  #if  #ifdef  #ifndef  #else  #endif  #elif
  #line  defined  #-operator  ##-operator  #pragma  #error

strategy:
  don't expand macro calls -- treat like function calls, but provide dict
todo:
  pragma
  #-op ##-op
  provide dict of #defines
  provide util to expand defines
|#

;;.@deffn skip-ws ch
;; Helper for 
(define (skip-ws ch)
  (if (eof-object? ch) ch
      (if (char-set-contains? c:ws ch)
	  (skip-ws (read-char))
	  ch)))

;; @deffn read-ellipsis ch
;; read ellipsis
(define (read-ellipsis ch)
  (cond
   ((eof-object? ch) #f)
   ((char=? ch #\.) (read-char) (read-char) "...")
   (else #f)))

;; @deffn cpp-define => #f|???
(define (cpp-define)
  ;; The (weak?) parse architecture is "unread la argument if no match"
  (letrec
      ((p-cppd ;; parse all
	(lambda ()
	  (let* ((iden (read-c-ident (skip-ws (read-char))))
		 ;;(args (or (p-args (skip-ws (read-char))) '()))
		 ;; "define ABC(ARG)" not the same as "define ABC (ARG)"
		 (args (or (p-args (read-char)) '()))
		 (rest (or (p-rest (skip-ws (read-char))) " ")))
	    (if (pair? args)
		`(define (name ,iden) ,(cons 'args args) (repl ,rest))
		`(define (name ,iden) (repl ,rest))))))
       (p-args ;; parse args
	(lambda (la) ;; unread la if no match :(
	  (if (eq? la #\()
	      (let iter ((args '()) (la (skip-ws (read-char))))
		(cond
		 ((eq? la #\)) (reverse args))
		 ((read-c-ident la) =>
		  (lambda (arg) (iter (cons arg args) (skip-ws (read-char)))))
		 ((read-ellipsis la) =>
		  (lambda (arg) (iter (cons arg args) (skip-ws (read-char)))))
		 ((eq? la #\,)
		  (iter args (skip-ws (read-char))))))
	      (begin (if (char? la) (unread-char la)) #f)))) ;; CLEANUP
       (p-rest ;; parse rest
	(lambda (la)
	  (cond ((char? la) (unread-char la) (drain-input (current-input-port)))
		(else #f)))))
    (p-cppd)))

;; @deffn cpp-include
;; Parse CPP include statement.
(define (cpp-include)
  (let* ((beg-ch (skip-ws (read-char)))
	 (end-ch (if (eq? beg-ch #\<) #\> #\"))
	 (path (let iter ((cl (list beg-ch)) (ch (read-char)))
		 (if (eq? ch end-ch) (list->string (reverse (cons ch cl)))
		     (iter (cons ch cl) (read-char))))))
    `(include ,path)))

;; @deffn read-cpp-stmt line defs => (stmt-type text)
;; Parse a line from a CPP statement and return a parse tree.
;; @example
;; (parse-cpp-stmt "define X 123") => (define "X" "123")
;; (parse-cpp-stmt "if defined(A) && defined(B) && defined(C)"
;; => (if "defined(A) && defined(B) && defined(C)")
;; @end example
;; To evaluate the @code{if} statements use @code{parse-cpp-expr} and
;; @code{eval-cpp-expr}.
(define (read-cpp-stmt line)
  (define (rd-ident) (read-c-ident (skip-ws (read-char))))
  (define (rd-num) (and=> (read-c-num (skip-ws (read-char))) cdr))
  (define (rd-rest) (let ((ch (skip-ws (read-char))))
		      (if (not (eof-object? ch)) (unread-char ch))
		      (drain-input (current-input-port))))
  (with-input-from-string line
    (lambda ()
      (let ((cmd (string->symbol (read-c-ident (skip-ws (read-char))))))
	 (case cmd
	   ((include) (cpp-include))
	   ((define) (cpp-define))
	   ((undef) `(undef ,(rd-ident)))
	   ((ifdef)
	    `(if ,(string-append "defined(" (rd-ident) ")" (rd-rest))))
	   ((ifndef)
	    `(if ,(string-append "!defined(" (rd-ident) ")" (rd-rest))))
	   ((if elif else endif line error pragma) (list cmd (rd-rest)))
	   (else '(unknown "")))))))
    
(include-from-path "nyacc/lang/c99/mach.d/cpptab.scm")
(include-from-path "nyacc/lang/c99/mach.d/cppact.scm")

(define raw-parser
  (make-lalr-parser
   (list (cons 'len-v len-v) (cons 'pat-v pat-v) (cons 'rto-v rto-v)
	 (cons 'mtab mtab) (cons 'act-v act-v))))

;; The included file "cppbody.scm" provides:
;; gen-cpp-lexer
;; parse-cpp-expr
;; eval-cpp-expr
(include-from-path "nyacc/lang/c99/cppbody.scm")
 
;; --- last line ---