;; -*- mode: common-lisp -*-
#|
clasm-6502: An assembler for the 6502 written in Common Lisp.
Copyright (C) 2024  Aleksei Eaves

This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.

This library 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
Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
|#

;; Rules for the interpretation of lines.
(defparameter
 *line-syntax*
 '(
   (label
	(lambda (l)
	  (and (eq (last-char (first l)) #\:)
		   (eq (length l) 1))))
   (label-instruction
	(lambda (l)
	  (and (eq (last-char (first l)) #\:)
		   (member (read-from-string (second l)) *opcodes*))))
   (attribute
	(lambda (l)
	  (equal (char (first l) 0) #\.)))
   (instruction
	(lambda (l)
	  (member (read-from-string (first l)) *opcodes*)))
   (macro
	(lambda (l)
	  (equal (second l) "=")))   
   (unknown
	(lambda (l)
	  t))))

;; Rules for identifying addressing modes.
(defparameter
 *addressing-modes-syntax*
 '((immediate ; #?? ... more complex syntax rules for later
	(lambda (s)
	  (eq "#" (subseq s 0 1))))
   (absolute ;"$????"
	(lambda (s)
	  (and
	   (equal (length s) 5)
	   (equal "$" (subseq s 0 1))
	   (hexd? (subseq s 1 5)))))
   (zero-page ;"$??"
	(lambda (s)
	  (and
	   (equal (length s) 3)
	   (equal "$" (subseq s 0 1))
	   (hexd? (subseq s 1 3)))))
   (implied nil)
   (indirect-absolute ;($????)
	(lambda (s)
	  (and
	   (equal (length s) 7)
	   (equal "($" (subseq s 0 2))
	   (hexd? (subseq s 1 5))
	   (equal ")" (subseq s 5 6)))))
   (absolute-indexed-x ;"$????,X"
	(lambda (s)
	  (and
	   (equal (length s) 7)
	   (equal "$" (subseq s 0 1))
	   (hexd? (subseq s 1 5))
	   (equal ",X" (subseq s 5 7)))))
   (absolute-indexed-y ;"$????,Y"
	(lambda (s)
	  (and
	   (equal (length s) 7)
	   (equal "$" (subseq s 0 1))
	   (hexd? (subseq s 1 5))
	   (equal ",Y" (subseq s 5 7)))))
   (zero-page-indexed-x ;"$??,X"
	(lambda (s)
	  (and
	   (equal (length s) 5)
	   (equal (subseq s 0 1) "$")
	   (hexd? (subseq s 1 3))
	   (equal (subseq s 3 5) ",X"))))
   (zero-page-indexed-y ;"$??,Y"
	(lambda (s)
	  (and
	   (equal (length s) 5)
	   (equal (subseq s 0 1) "$")
	   (hexd? (subseq s 1 3))
	   (equal (subseq s 3 5) ",Y"))))
   (indexed-indirect ;"($??,X)"
	(lambda (s)
	  (and
	   (equal (length s) 7)
	   (equal (subseq s 0 2) "($")
	   (hexd? (subseq s 2 4))
	   (equal (subseq s 4 7) ",X)"))))
   (indirect-indexed ;"($??),Y"
	(lambda (s)
	  (and
	   (equal (length s) 7)
	   (equal (subseq s 0 2) "($")
	   (hexd? (subseq s 2 4))
	   (equal (subseq s 4 7) "),Y"))))
   ;;How to fix that relative and absolute are the same rule?
   ;;A check upstream would suffice.
   (relative ;"$????"
	(lambda (s)
	  (and
	   (equal (length s) 5)
	   (equal (subseq s 0 1) "$")
	   (hexd? (subseq s 1 5)))))
   (accumulator ;"A"
	(lambda (s)
	  (and
	   (equal (length s) 1)
	   (equal "A" (subseq s 0 1)))))))

(defun syntax-rule (line list)
  "Apply a syntax rule against a delimited line from a program."
  (dolist (i (extract-keys list))
	(let ((z (funcall (eval (cadr (assoc i list)))
					  line)))
	  (if (not (equal
				z nil))
		  (return i)
		  nil))))