;;; -*- TI-Asm -*-
;;;
;;; Mimas - Assembly language IDE for the TI-83 Plus
;;; 
;;; Copyright (C) 2010 Benjamin Moody
;;;
;;; 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/>.

;; SkipExprHL:
;;
;; Skip over an expression.
;;
;; Input:
;; - HL = expression pointer
;; - C = expression byte count + 1
;;
;; Output:
;; - HL and C updated
;; - Carry flag set if expression incomplete
;;
;; Destroys:
;; - AF, B

SkipExprHL:
	ld b,1
SkipExpr_Loop:
	dec c
	scf
	ret z
	ld a,(hl)
	inc hl
	add a,a
	jr c,SkipExpr_Dec6OrOperator
	;; 0xxxxxxx
	add a,a
	jr c,SkipExpr_Constant
	;; 00xxxxxx xxxxxxxx: symbol value
SkipExpr_OneByte:
	dec c
	scf
	ret z
	inc hl
SkipExpr_GotSubexp:
	djnz SkipExpr_Loop
	or a
	ret

SkipExpr_Constant:
	;; 01xxxxxx
	add a,a
	jr c,SkipExpr_WordConstant
	;; 010xxxxx
	add a,a
	jr c,SkipExpr_OneByte	; byte constant
	;; 0100xxxx: special constant
	jr SkipExpr_GotSubexp

SkipExpr_WordConstant:
	add a,a
	call c,Error_Bytecode
	;; 0110xxxx xxxxxxxx xxxxxxxx: word constant
	dec c
	scf
	ret z
	inc hl
	jr SkipExpr_OneByte

SkipExpr_Dec6OrOperator:
	;; 1xxxxxxx
	add a,a
	jr c,SkipExpr_GotSubexp	; dec6 constant
	;; 10xxxxxx
	add a,a
	jr c,SkipExpr_Binary
	;; 100xxxxx
	add a,a
	call nc,Error_Bytecode
	;; 1001xxxx <A>: unary operator
	jr SkipExpr_Loop

SkipExpr_Binary:
	;; 101xxxxx <A> <B>: binary operator
	inc b
	jr SkipExpr_Loop


;; CopyConstExpr:
;;
;; Copy an expression.  Throw an error if the expression contains any
;; non-constant subexpressions.  Also simplify the expression by
;; removing X_PAREN operators.
;;
;; Input:
;; - HL = address of expression
;; - DE = buffer to place copy
;;
;; Output:
;; - DE = end of copied expression
;;
;; Destroys:
;; - AF, BC, HL

CopyConstExpr:
	ld b,1
	dec hl
CopyConstExpr_Skip:
	inc hl
CopyConstExpr_Loop:
	call CheckInstrBufOverflow
	ld c,-1
	ld a,(hl)
	cp X_PAREN
	jr z,CopyConstExpr_Skip
	cp X_REGVAL
	jr z,Error_ExpressionNotConstant
	cp X_ARGVAL
	jr z,Error_ExpressionNotConstant
	add a,a
	jr c,CopyConstExpr_Dec6OrOperator
	;; 0xxxxxxx
	add a,a
	jr c,CopyConstExpr_Constant
	;; 00xxxxxx xxxxxxxx: symbol
CopyConstExpr_TwoBytes:
	ldi
	call CheckInstrBufOverflow
CopyConstExpr_OneByte:
	ldi
	djnz CopyConstExpr_Loop
	ret

Error_ExpressionNotConstant:
	ld hl,emsg_ExpressionNotConstant
	call ThrowLineError
	;; UNREACHABLE

CopyConstExpr_Constant:
	;; 01xxxxxx
	add a,a
	jr c,CopyConstExpr_WordConstant
	;; 010xxxxx
	add a,a
	jr c,CopyConstExpr_TwoBytes ; byte constant
	jr CopyConstExpr_OneByte    ; special constant

CopyConstExpr_WordConstant:
	add a,a
	call c,Error_Bytecode
	;; 0110xxxx xxxxxxxx xxxxxxxx: word constant
	ldi
	call CheckInstrBufOverflow
	jr CopyConstExpr_TwoBytes

CopyConstExpr_Dec6OrOperator:
	;; 1xxxxxxx
	add a,a
	jr c,CopyConstExpr_OneByte	; dec6 constant
	;; 10xxxxxx
	add a,a
	jr c,CopyConstExpr_Binary
	;; 100xxxxx
	add a,a
	call nc,Error_Bytecode
	;; 1001xxxx <A>: unary operator
	dec b
CopyConstExpr_Binary:
	;; 101xxxxx <A> <B>: binary operator
	inc b
	ldi
	jr CopyConstExpr_Loop