;;; lang/c99/body.scm
;;;
;;; Copyright (C) 2015-2017 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/>.

;; @section The C99 Parser Body
;; This code provides the front end to the C99 parser, including the lexical
;; analyzer and optional CPP processing.  In @code{'file} mode the lex'er
;; passes CPP statements to the parser; in @code{'code} mode the lex'er
;; parses and evaluates the CPP statements.  In the case of included files
;; (e.g., via @code{#include <file.h>}) the include files are parsed if
;; not in the @code{td-dict}.  The @code{td-dict} is a dictionary that maps
;; include file names to typedefs (e.g., @code{stdio.h} to @code{FILE}).

(use-modules ((srfi srfi-9) #:select (define-record-type)))
(use-modules ((sxml xpath) #:select (sxpath)))

(define c99-std-dict
  '(("alloca.h")
    ("complex.h" "complex" "imaginary")
    ("ctype.h")
    ("fenv.h" "fenv_t" "fexcept_t")
    ("float.h" "float_t")
    ("inttypes.h"
     "int8_t" "uint8_t" "int16_t" "uint16_t" "int32_t" "uint32_t"
     "int64_t" "uint64_t" "uintptr_t" "intptr_t" "intmax_t" "uintmax_t"
     "int_least8_t" "uint_least8_t" "int_least16_t" "uint_least16_t"
     "int_least32_t" "uint_least32_t" "int_least64_t" "uint_least64_t"
     "imaxdiv_t")
    ("limits.h")
    ("math.h")
    ("regex.h" "regex_t" "regmatch_t")
    ("setjmp.h" "jmp_buf")
    ("signal.h" "sig_atomic_t")
    ("stdarg.h" "va_list")
    ("stddef.h" "ptrdiff_t" "size_t" "wchar_t")
    ("stdint.h"
     "int8_t" "uint8_t" "int16_t" "uint16_t" "int32_t" "uint32_t"
     "int64_t" "uint64_t" "uintptr_t" "intptr_t" "intmax_t" "uintmax_t"
     "int_least8_t" "uint_least8_t" "int_least16_t" "uint_least16_t"
     "int_least32_t" "uint_least32_t" "int_least64_t" "uint_least64_t")
    ("stdio.h" "FILE" "size_t")
    ("stdlib.h" "div_t" "ldiv_t" "lldiv_t" "wchar_t")
    ("string.h" "size_t")
    ("strings.h" "size_t")
    ("time.h" "time_t" "clock_t" "size_t")
    ("unistd.h" "size_t" "ssize_t" "div_t" "ldiv_t")
    ("wchar.h" "wchar_t" "wint_t" "mbstate_t" "size_t")
    ("wctype.h" "wctrans_t" "wctype_t" "wint_t")
    ))

;; @subsubsection CPP if-then-else Logic Block (ITLB) Processing
;; The parser needs to have a "CPI" (CPP processing info) stack to deal with
;; types (re)defined in multiple branches of a #if...#endif statement chain.
;; If we are in "code" mode then we may be skipping code so need to track
;; when to shift and when not to.
;; 
;; The state is contained in a stack @code{ppxs}
;; States are
;; @table code
;; @item skip-done
;; skip code
;; @item skip-look
;; skipping code, but still looking for true at this level
;; @item keep
;; keep code
;; @item skip1-pop
;; skip one token and pop skip-stack
;; @end table
;; Also, if we want to pass on all the sections of an ITLB to the parser
;; we need to remove typedef names because a typedef may appear multiple
;; times, as in
;; @example
;; #ifdef SIXTYFOURBIT
;; typedef short int32_t;
;; #else
;; typedef long int32_t;
;; #endif
;; @end example
;; @noindent
;; To achieve this we keep a stack of valid typedefs.  On @code{#if} we push,
;; on @code{#elif} we shift (i.e., pop, then push) and on @code{#endif} we pop.
;;
;; The grammar looks like
;; @example
;; (code
;;  ("if" cond code "endif")
;;  ("if" cond code "else" code "endif")
;;  ("if" cond code elif-list "endif")
;;  ("if" cond code elif-list "else" code "endif")
;;  (other))
;; (elif-list
;;  ("elif" cond code)
;;  (elif-list "elif" cond code))
;; @end example
;; @noindent

(define-record-type cpi
  (make-cpi-1)
  cpi?
  (debug cpi-debug set-cpi-debug!)	; debug #t #f
  (defines cpi-defs set-cpi-defs!)	; #defines
  (incdirs cpi-incs set-cpi-incs!)	; #includes
  (tn-dict cpi-tynd set-cpi-tynd!)	; typename dict (("<x>" foo_t ..
  (ptl cpi-ptl set-cpi-ptl!)		; parent typename list
  (ctl cpi-ctl set-cpi-ctl!)		; current typename list
  )

(define (make-cpi debug defines incdirs tn-dict)
  (let* ((cpi (make-cpi-1)))
    (set-cpi-debug! cpi debug)	  ; print states debug 
    (set-cpi-defs! cpi defines)	  ; list of define strings??
    (set-cpi-incs! cpi incdirs)	  ; list of include dir's
    (set-cpi-tynd! cpi tn-dict)	  ; typename dict by include-file name
    (set-cpi-ptl! cpi '())	  ; list of lists of typedef strings
    (set-cpi-ctl! cpi '())	  ; list of typedef strings
    cpi))

(define *info* (make-fluid #f))

;; given tyns
;; cadr is next level
;; caar is list of sibs
;; search (caar car tyns), then (caar cadr tyns), then ...

;; @deffn typename? name
;; Called by lexer to determine if symbol is a typename.
;; Check current sibling for each generation.
(define (typename? name)
  (let ((cpi (fluid-ref *info*)))
    (if (member name (cpi-ctl cpi)) #t
        (let iter ((ptl (cpi-ptl cpi)))
	  (if (null? ptl) #f
	      (if (member name (car ptl)) #t
		  (iter (cdr ptl))))))))

;; @deffn add-typename name
;; Helper for @code{save-typenames}.
(define (add-typename name)
  (let ((cpi (fluid-ref *info*)))
    (set-cpi-ctl! cpi (cons name (cpi-ctl cpi)))))

(define (cpi-push)	;; on #if
  (let ((cpi (fluid-ref *info*)))
    (set-cpi-ptl! cpi (cons (cpi-ctl cpi) (cpi-ptl cpi)))
    (set-cpi-ctl! cpi '())))

(define (cpi-shift)	;; on #elif #else
  (set-cpi-ctl! (fluid-ref *info*) '()))

(define (cpi-pop)	;; on #endif
  (let ((cpi (fluid-ref *info*)))
    (set-cpi-ctl! cpi (append (cpi-ctl cpi) (car (cpi-ptl cpi))))
    (set-cpi-ptl! cpi (cdr (cpi-ptl cpi)))))

;; @deffn find-new-typenames decl
;; Helper for @code{save-typenames}.
;; Given declaration return a list of new typenames (via @code{typedef}).
(define (find-new-typenames decl)

  ;; like declr->ident in util2.scm
  (define (declr->id-name declr)
    (case (car declr)
      ((ident) (sx-ref declr 1))
      ((init-declr) (declr->id-name (sx-ref declr 1)))
      ((comp-declr) (declr->id-name (sx-ref declr 1)))
      ((array-of) (declr->id-name (sx-ref declr 1)))
      ((ptr-declr) (declr->id-name (sx-ref declr 2)))
      ((ftn-declr) (declr->id-name (sx-ref declr 1)))
      ((scope) (declr->id-name (sx-ref declr 1)))
      (else (error "coding bug: " declr))))
       
  (let* ((spec (sx-ref decl 1))
	 (stor (sx-find 'stor-spec spec))
	 (id-l (sx-ref decl 2)))
    (if (and stor (eqv? 'typedef (caadr stor)))
	(let iter ((res '()) (idl (cdr id-l)))
	  (if (null? idl) res
	      (iter (cons (declr->id-name (sx-ref (car idl) 1)) res)
		    (cdr idl))))
	'())))

;; @deffn save-typenames decl
;; Save the typenames for the lexical analyzer and return the decl.
(define (save-typenames decl)
  ;; This finds typenames using @code{find-new-typenames} and adds via
  ;; @code{add-typename}.  Then return the decl.
  (for-each add-typename (find-new-typenames decl))
  decl)

;; ------------------------------------------------------------------------

(define (p-err . args)
  (apply throw 'c99-error args))

;; @deffn read-cpp-line ch => #f | (cpp-xxxx)??
;; Given if ch is #\# read a cpp-statement.
;; The standard implies that comments are tossed here but we keep them
;; so that they can end up in the pretty-print output.
(define (read-cpp-line ch)
  (if (not (eq? ch #\#)) #f
      (let iter ((cl '()) (ch (read-char)))
	(cond
	 ((eq? ch #\newline) (unread-char ch) (list->string (reverse cl)))
	 ((eq? ch #\\)
	  (let ((c2 (read-char)))
	    (if (eq? c2 #\newline)
		(iter cl (read-char))
		(iter (cons* c2 ch cl) (read-char)))))
	 ((eq? ch #\/) ;; swallow comments, event w/ newlines
	  (let ((c2 (read-char)))
	    (cond
	     ((eqv? c2 #\*)
	      (let iter2 ((cl2 (cons* #\* #\/ cl)) (ch (read-char)))
		(cond
		 ((eq? ch #\*)
		  (let ((c2 (read-char)))
		    (if (eqv? c2 #\/)
			(iter (cons* #\/ #\* cl2) (read-char)) ;; keep comment
			(iter2 (cons #\* cl2) c2))))
		 (else
		  (iter2 (cons ch cl2) (read-char))))))
	     (else
	      (iter (cons #\/ cl) c2)))))
	 (else (iter (cons ch cl) (read-char)))))))

;; @deffn find-file-in-dirl file dirl => path
(define (find-file-in-dirl file dirl)
  (let iter ((dirl dirl))
    (if (null? dirl) #f
	(let ((p (string-append (car dirl) "/" file)))
	  (if (access? p R_OK) p (iter (cdr dirl)))))))

(define (def-xdef? name mode)
  (eqv? mode 'code))

;; @deffn gen-c-lexer [#:mode mode] [#:xdef? proc] => procedure
;; Generate a context-sensitive lexer for the C99 language.  The generated
;; lexical analyzer reads and passes comments and optionally CPP statements
;; to the parser.  The keyword argument @var{mode} will determine if CPP
;; statements are passed (@code{'file} mode) or parsed and executed
;; (@code{'file} mode) as described above.  Comments will be passed as
;; ``line'' comments or ``lone'' comments: lone comments appear on a line
;; without code.  The @code{xdef?} keyword argument allows user to pass
;; a predicate which determines whether CPP symbols in code are expanded.
;; The default predicate is
;; @example
;; (define (def-xdef? mode name) (eqv? mode 'code))
;; @end example
(define gen-c-lexer
  ;; This gets ugly in order to handle cpp.
  ;;.need to add support for num's w/ letters like @code{14L} and @code{1.3f}.
  ;; todo: I think there is a bug wrt the comment reader because // ... \n
  ;; will end up in same mode...  so after
  ;; int x; // comment
  ;; the lexer will think we are not at BOL.
  (let* ((match-table mtab)
	 (read-ident read-c-ident)
	 (read-comm read-c-comm)
	 ;;
	 (ident-like? (make-ident-like-p read-ident))
	 ;;
	 (strtab (filter-mt string? match-table)) ; strings in grammar
	 (kwstab (filter-mt ident-like? strtab))  ; keyword strings =>
	 (keytab (map-mt string->symbol kwstab))  ; keywords in grammar
	 (chrseq (remove-mt ident-like? strtab))  ; character sequences
	 (symtab (filter-mt symbol? match-table)) ; symbols in grammar
	 (chrtab (filter-mt char? match-table))	  ; characters in grammar
	 ;;
	 (read-chseq (make-chseq-reader chrseq))
	 (assc-$ (lambda (pair) (cons (assq-ref symtab (car pair)) (cdr pair))))
	 ;;
	 (t-ident (assq-ref symtab '$ident))
	 (t-typename (assq-ref symtab 'typename))
	 (xp1 (sxpath '(cpp-stmt define)))
	 (xp2 (sxpath '(decl))))
    ;; mode: 'code|'file
    ;; xdef?: (proc name mode) => #t|#f  : do we expand #define?
    (lambda* (#:key (mode 'code) (xdef? #f))
      (let ((bol #t)		      ; begin-of-line condition
	    (ppxs (list 'keep))	      ; CPP execution state stack
	    (info (fluid-ref *info*)) ; assume make and run in same thread
	    (x-def? (or xdef? def-xdef?)))
	;; Return the first (tval . lval) pair not excluded by the CPP.
	(lambda ()

	  (define (exec-cpp-stmts?)	; exec (vs pass to parser) CPP stmts?
	    (eqv? mode 'code))
      
	  (define (add-define tree)
	    (let* ((tail (cdr tree))
		   (name (car (assq-ref tail 'name)))
		   (args (assq-ref tail 'args))
		   (repl (car (assq-ref tail 'repl)))
		   (cell (cons name (if args (cons args repl) repl))))
	      (set-cpi-defs! info (cons cell (cpi-defs info)))))
	  
	  (define (rem-define name)
	      (set-cpi-defs! info (delete name (cpi-defs info))))
	  
	  ;; Evaluate expression text in #if of #elif statement.
	  (define (eval-cpp-cond-text text)
	    (with-throw-handler
	     'cpp-error
	     (lambda ()
	       (let* ((defs (cpi-defs info))
		      (rhs (cpp-expand-text text defs))
		      (exp (parse-cpp-expr rhs)))
		 (eval-cpp-expr exp defs)))
	     (lambda (key fmt . args)
	       (report-error fmt args)
	       (throw 'c99-error "CPP error"))))
	    
	  (define (eval-cpp-stmt stmt)
	    (case (car stmt)
	      ((include)
	       (let* ((parg (cadr stmt)) (leng (string-length parg))
		      (file (substring parg 1 (1- leng)))
		      (path (find-file-in-dirl file (cpi-incs info)))
		      (tynd (assoc-ref (cpi-tynd info) file)))
		 (cond
		  (tynd (for-each add-typename tynd)) ; in dot-h dict
		  ((not path) (p-err "not found: ~S" file))
		  ((exec-cpp-stmts?) (push-input (open-input-file path)))
		  (else		; include as tree
		   (let* ((tree (with-input-from-file path run-parse)))
		     (if (not tree) (p-err "included from ~S" path))
		     (for-each add-define (xp1 tree)) ; add def's 
		     (set! stmt (append stmt (list tree)))))))
	       (if (exec-cpp-stmts?) (set! ppxs (cons 'skip1-pop ppxs))))
	      ((define)
	       (add-define stmt)
	       (if (exec-cpp-stmts?) (set! ppxs (cons 'skip1-pop ppxs))))
	      ((undef)
	       (rem-define (cadr stmt))
	       (if (exec-cpp-stmts?) (set! ppxs (cons 'skip1-pop ppxs))))
	      ((if) ;; covers (if ifdef ifndef)
	       (cond
		((exec-cpp-stmts?)
		 (let ((val (eval-cpp-cond-text (cadr stmt))))
		   (cond
		    ((not val) (p-err "unresolved: ~S" (cadr stmt)))
		    ((zero? val) (set! ppxs (cons* 'skip1-pop 'skip-look ppxs)))
		    (else (set! ppxs (cons* 'skip1-pop (car ppxs) ppxs))))))
		(else (cpi-push))))
	      ((elif)
	       (cond
		((exec-cpp-stmts?)
		 (let ((val (eval-cpp-cond-text (cadr stmt))))
		   (cond
		    ((not val)
		     (p-err "unresolved: ~S" (cadr stmt)))
		    ((eq? 'keep (car ppxs))
		     (set! ppxs (cons* 'skip1-pop 'skip-done (cdr ppxs))))
		    ((zero? val) (set! ppxs (cons* 'skip1-pop ppxs)))
		    ((eq? 'skip-look (car ppxs))
		     (set! ppxs (cons* 'skip1-pop 'keep (cdr ppxs))))
		    (else
		     (set! ppxs (cons* 'skip1-pop 'skip-done (cdr ppxs)))))))
		(else (cpi-shift))))
	      ((else)
	       (cond
		((exec-cpp-stmts?)
		 (cond
		  ((eq? 'skip-look (car ppxs))
		   (set! ppxs (cons* 'skip1-pop 'keep (cdr ppxs))))
		  (else
		   (set! ppxs (cons* 'skip1-pop 'skip-done (cdr ppxs))))))
		(else (cpi-shift))))
	      ((endif)
	       (cond
		((exec-cpp-stmts?)
		 (set! ppxs (cons 'skip1-pop (cdr ppxs))))
		(else (cpi-pop))))
	      ((error)
	       (if (exec-cpp-stmts?)
		   (report-error "error: #error ~A" (cdr stmt))))
	      ((pragma)
	       ;; standard says implementation-defined if line is expanded
	       #t)
	      (else
	       (error "unhandled cpp stmt")))
	    (case (car stmt)
	      ((pragma) (cons 'cpp-pragma (cdr stmt)))
	      (else (cons 'cpp-stmt stmt))))
	  
	  (define (eval-cpp-line line)
	    (with-throw-handler
	     'cpp-error
	     (lambda () (eval-cpp-stmt (read-cpp-stmt line)))
	     (lambda (key fmt . rest)
	       (display "body.399\n")
	       (report-error fmt rest)
	       (throw 'c99-error "CPP error"))))

	  ;; Composition of @code{read-cpp-line} and @code{eval-cpp-line}.
	  (define (read-cpp ch)
	    (and=> (read-cpp-line ch) eval-cpp-line))

	  (define (read-token)
	    (let iter ((ch (read-char)))
	      (cond
	       ((eof-object? ch)
		(if (pop-input) (iter (read-char)) (assc-$ '($end . ""))))
	       ((eq? ch #\newline) (set! bol #t) (iter (read-char)))
	       ((char-set-contains? c:ws ch) (iter (read-char)))
	       (bol
		(cond
		 ((read-comm ch bol) => assc-$)
		 ((read-cpp ch) =>
		  (lambda (res) ;; if '() stmt expanded so re-read
		    (if (pair? res) (assc-$ res) (iter (read-char)))))
		 (else (set! bol #f) (iter ch))))
	       ((read-ident ch) =>
		(lambda (name)
		  (let ((symb (string->symbol name)))
		    (cond
		     ((and (x-def? name mode)
			   (expand-cpp-mref name (cpi-defs info)))
		      => (lambda (st)
			   (push-input (open-input-string st))
			   (iter (read-char))))
		     ((assq-ref keytab symb)
		      => (lambda (t) (cons t name)))
		     ((typename? name)
		      (cons (assq-ref symtab 'typename) name))
		     (else
		      (cons (assq-ref symtab '$ident) name))))))
	       ((read-c-num ch) => assc-$)
	       ((read-c-string ch) => assc-$)
	       ((read-c-chlit ch) => assc-$)
	       ((read-comm ch bol) => assc-$)
	       ((read-chseq ch) => identity)
	       ((assq-ref chrtab ch) => (lambda (t) (cons t (string ch))))
	       ((eqv? ch #\\) ;; C allows \ at end of line to continue
		(let ((ch (read-char)))
		  (cond ((eqv? #\newline ch) (iter (read-char))) ;; extend line
			(else (unread-char ch) (cons #\\ "\\"))))) ;; parse err
	       (else (cons ch (string ch))))))

	  ;; Loop between reading tokens and skipping tokens via CPP logic.
	  (let iter ((pair (read-token)))
	    (case (car ppxs)
	      ((keep) pair)
	      ((skip-done skip-look)
	       (iter (read-token)))
	      ((skip1-pop)
	       (set! ppxs (cdr ppxs))
	       (iter (read-token)))))
	  )))))
  
;; --- last line ---