;; -*- 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
	*syntax-line*
  '(
	(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)
	   (and (equal (char (first l) 0) #\.)
			(not (equal (first l) ".WORD")))))
	(word
	 (lambda (l)
	   (and (equal (char (first l) 0) #\.)
			(equal (first l) ".WORD"))))
	(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
	*syntax-addressing-modes*
  '((immediate ; #??
	 (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))))