(define-module (c preprocessor)
  :use-module (srfi srfi-1)
  :use-module (srfi srfi-9 gnu)
  :use-module (ice-9 rdelim)
  :use-module (ice-9 regex)
  :use-module (hnh util object)

  :use-module (hnh util)
  :use-module (hnh util object)
  )

(define (read-lines port)
  (let loop ((done '()))
    (let ((line (read-line port)))
      (if (eof-object? line)
          (reverse done)
          (loop (cons line done))))))

;; The source line of a give readen line
(define line-number (make-object-property))
;; The source file of a given readen line
(define line-file (make-object-property))


(define (mark-with-property! items property property-value)
  (for-each (lambda (item) (set! (property item) property-value))
            items))

(define trigraph-rx (make-regexp "??([=()/'<>!-])"))
(define (expand-trigraphs line)
  (regexp-substitute/global
   #f trigraph-rx
   line
   'pre (lambda (m) (case (string-ref (match:substring m 1) 1)
                 ((#\=) "#")
                 ((#\() "[")
                 ((#\)) "]")
                 ((#\/) "\\")
                 ((#\') "^")
                 ((#\<) "{")
                 ((#\>) "}")
                 ((#\!) "|")
                 ((#\-) "~")))
   'post))

(define (number-lines lines)
  (for-each (lambda (line number)
              (set! (line-number line) number))
            lines
            (iota (length lines) 1))
  lines)

;; Should this line be merged with the next
(define (line-continued? line)
  (case (string-length line)
    ((0) #f)
    ((1) (string=? "\\" line))
    (else
     (let ((len (string-length line)))
       ;; TODO can extra backslashes change this?
       (and (char=? #\\ (string-ref line (- len 1)))
            (not (char=? #\\ (string-ref line (- len 2)))))))))

(define (transfer-line-number to from)
  (set! (line-number to) (line-number from))
  to)

;; Merge two lines, assuming that upper ends with a backslash
(define (merge-lines upper lower)
  (let ((new-string (string-append (string-drop-right upper 1) lower)))
    (transfer-line-number new-string upper)
    new-string))

(define (fold-lines lines)
  (fold-right (lambda (line done)
                (if (line-continued? line)
                    (cons (merge-lines line (car done)) (cdr done))
                    (cons line done)))
              '()
              lines))


(define comment-rx (make-regexp "(//|/[*]|[*]/)"))

(define (strip-comments lines)
  (let loop ((in-comment #f) (lines lines) (done '()))
    (if (null? lines)
        (reverse done)
        (let ((line (car lines)))
          (cond ((regexp-exec comment-rx line)
                 => (lambda (m)
                      (format (current-output-port) "~s ~s substr = ~s~%" in-comment (line-number line) (match:substring m))
                      (cond ((and in-comment (string=? "*/" (match:substring m)))
                             (loop #f (cons (transfer-line-number (match:suffix m) line)
                                            (cdr lines))
                                   done))
                            (in-comment (loop #t (cdr lines) done))
                            ((string=? "//" (match:substring m))
                             (loop #f (cdr lines) (cons (transfer-line-number (match:prefix m) line)
                                                        done)))
                            ((string=? "/*" (match:substring m))
                             (loop #t (cons (transfer-line-number (match:suffix m) line) (cdr lines)) done))
                            (else
                             (scm-error 'cpp-error "strip-comments"
                                        "Unexpected */ in file ~a on line ~a"
                                        (list (line-file line) (line-number line))
                                        #f)))))
                (else (loop in-comment (cdr lines) (cons line done))))))))


(define-immutable-record-type <preprocessor-directive>
  (make-preprocessor-directive type body)
  proprocessor-directive?
  (type directive-type)
  (body directive-body))

(define cpp-directive-rx (make-regexp "\\s*#\\s*((\\w+)(.*))?"))
(define (preprocessor-directive? line)
  (cond ((regexp-exec cpp-directive-rx line)
         => (lambda (m)
              (if (match:substring m 2)
                  (make-preprocessor-directive
                   (string->symbol (match:substring m 2))
                   (string-trim-both (match:substring m 3) char-set:whitespace))
                  'sort-of)))
        (else #f)))

;; defined

;; TODO _Pragma


(define (expand-function-line-macro environment macro . params)
  (expand-macro environment (apply-macro macro (map (lambda (param) (expand-macro environment param)) params))))

;; (define (environment-ref ))

(define (list-of? lst predicate)
  (every predicate lst))


;; Parantheses when defining macro
(define (parse-parameter-string string)
  (map string-trim-both
       (string-split (string-trim-both string (char-set #\( #\)))
                     #\,)))


(define-type (object-macro)
  (body type: string?))

(define-type (function-macro)
  (formals type: (list-of? string?))
  (body type: string?))


;; The interesting part
;; environment, (list string) -> (values (list string) (list strings))
;; multiple lines since since a function-like macro can extend over multiple lines
;; (define (expand-macros environment strings)
;;   )


(define (crash-if-not-if body guilty)
  (scm-error 'cpp-error guilty
             "else, elif, and endif invalid outside if scope: ~s~%file: ~s line: ~s"
             (list body (line-file body) (line-number body))))

;; (environment, lines) -> environment x lines
(define (parse-directives environment lines)
  (let loop ((environment environment) (lines lines) (done '()))
    (let* ((line (car line))
           (directive? (preprocessor-directive? line)))
      (case directive?
        ((#f)                ; regular line
         (loop environment (cdr lines)
               ;; TODO this doesn't work, since parse-macros works on multiple lines
               (cons (parse-macros environment (car lines)) done)))
        ((sort-of)           ; a no-op directive
         (loop environment (cdr lines) done))
        (else                ; an actual directive
         (case (car (cpp-if-status environment))
           ((outside)
            (case (directive-type m)
              ((ifndef endif else)
               (scm-error 'cpp-error "parse-directives"
                          "Unexpected directive: ~s"
                          (list line) #f))
              (else          ; inside if, ifelse or else
               ;; outside active-if inactive-if
               (case (directive-type m)
                 ;; stack ending directives
                 ((endif)
                  (case (car (cpp-if-status environment))
                    ((outside) (crash-if-not-if (directive-body m) "endif"))
                    (else (loop (modify environment cpp-if-status cdr)
                                (cdr lines)
                                done))))

                 ;; stack nudging directives
                 ((else)
                  (case (car (cpp-if-status environment))
                    ((outside) (crash-if-not-if (directive-body m) "else"))
                    (else (loop (modify environment (lens-compose cpp-if-status car*)
                                        (lambda (old)
                                          (case old
                                            ((active-if)   'inactive-if)
                                            ((inactive-if) 'active-if))))
                                (cdr lines)
                                done))))
                 ((elif)
                  (case (car (cpp-if-status environment))
                    ((outside) (crash-if-not-if (directive-body m) "elif"))
                    (else 'TODO ;; TODO
                     )
                    ))

                 ;; stack creating directives
                 ;; on inactive-if each creates a new frame, which also is inactive
                 ((ifndef)
                  (case (car (cpp-if-status environment))
                    ((inactive-if) (loop (modify environment cpp-if-status
                                                 xcons 'inactive-if)
                                         (cdr lines)
                                         done))
                    (else (loop (modify environment cpp-if-status
                                        xcons (if (in-environment? environment (directive-body directive?))
                                                  'inactive-if 'active-if))
                                (cdr lines)
                                done))))

                 ((ifdef)
                  (case (car (cpp-if-status environment))
                    ((inactive-if) (loop (modify environment cpp-if-status
                                                 xcons 'inactive-if)
                                         (cdr lines)
                                         done))
                    (else
                     (loop (modify environment cpp-if-status
                                   xcons (if (in-environment? environment (directive-body directive?))
                                             'active-if 'inactive-if))
                           (cdr lines)
                           done))))

                 ((if)
                  (case (car (cpp-if-status environment))
                    ((inactive-if) (loop (modify environment cpp-if-status
                                                 xcons 'inactive-if)
                                         (cdr lines)
                                         done))
                    (else 'TODO ;; TODO
                     )))


                 ;; other directives
                 ((include) (cond ((string-match "[<\"](.*)"
                                                 => (lambda (m)
                                                      (let ((fileneme (string-drop-right (directive-body m) 1)))
                                                        (case (string-ref (match:substring m 1) 0)
                                                          ;; TODO include-path
                                                          ((#\<) (handle-file environment filename))
                                                          ((#\") (handle-file environment filename))))))
                                   (else (scm-error 'cpp-error "parse-directives"
                                                    "Invalid include"
                                                    '() #f)))))
                  ((define)
                   ;; TODO what are valid names?
                   (cond ((string-match "^(\\w+)([(][^)]*[)])?\\s+(.*)" (directive-body directive?))
                          => (lambda (m)
                               (loop (let ((macro-body (string-trim-both (match:substring m 3))))
                                       (add-identifier!
                                        environment
                                        (match:substring m 1)
                                        (cond ((match:substring m 2)
                                               => (lambda (parameter-string)
                                                    (function-macro
                                                     formals: (parse-parameter-string parameter-string)
                                                     body: macro-body)))
                                              (else (object-macro body: macro-body)))))
                                     (cdr lines)
                                     done)))
                         (else (scm-error 'cpp-error "parse-directives"
                                          "Invalid #define line, ~s"
                                          (list (directive-body directive?))
                                          #f))))

                  ((undef)
                   (case (car (cpp-if-status environment))
                     ((inactive-if) (loop environment (cdr lines) done))
                     (else (loop (remove-identifier environment (directive-body directive?))
                                 (cdr lines)
                                 done))))

                  ((line)
                   (case (car (cpp-if-status environment))
                     ((inactive-if) (loop environment (cdr lines) done))
                     ;; TODO add first-run parameter to loop, in case expand-macros still return something invalid
                     (else (let parse-line-directive ((tokens (string-tokenize (directive-body directive?))))
                             (cond ((= 1 (length tokens))
                                    ;; TODO parse token
                                    (if (integer? (car tokens))
                                        ;; TODO update current line
                                        (loop environment (cdr lines) done)
                                        (parse-line-directive (expand-macros environment (directive-body directive?)))))
                                   ((= 2 (length tokens))
                                    ;; TODO parse tokens
                                    (if (and (integer? (car tokens))
                                             (string-literal? (cadr tokens)))
                                        ;; TODO update current line and file
                                        (loop environment (cdr lines) done)
                                        (parse-line-directive (expand-macros environment (directive-body directive?)))))
                                   (else (parse-line-directive (expand-macros environment (directive-body directive?)))))))))

                  ((error)
                   (throw 'cpp-error-directive
                          (directive-body directive?)))

                  ((warning)
                   (format (current-error-port) "#warning ~a~%"
                           (directive-body directive?))
                   (loop environment (cdr lines) done))

                  ((pragma)
                   (format (current-error-port)
                           "PRAGMA: ~s~%" (directive-body directive?))
                   (loop environment (cdr lines) done))

                  ((ident sccs)
                   (format (current-error-port)
                           "IDENT: ~s~%" (directive-body directive?))
                   (loop environment (cdr lines) done))

                  (else
                   (scm-error 'cpp-error "parse-directives"
                              "Unknown pre-processor directive: ~s"
                              (list line) #f)
                   )))))))))
      ))


(define* (writeln expr optional: (port (current-output-port)))
  (write expr port)
  (newline port))

(define (handle-lines environment lines)
  (parse-directive environment
                   (compose strip-comments fold-lines number-lines)))

  ;; parse-directives environment

;; Return a number of lines
(define (read-file file-path)
  (define raw-lines (call-with-input-file file-path read-lines))
  (mark-with-property! line line-file file-path)
  (handle-lines raw-lines))


;; pre defined macros
;; see info manual for cpp 3.7.1 Standard Predefined Macros
;; __FILE__
;; __LINE__
;; __DATE__ "Feb 12 1996"
;; __TIME__ "23:59:01"
;; __STDC__ 1
;; __STDC_VERSION__ 201112L
;; __STDC_HOSTED__ 1

;; __cplusplus
;; __OBJC__
;; __ASSEMBLER__