;///////////////////////////////////////////////////
;
; GOTO / GOSUB / RETURN.  Jumps inside a BAT-file by
; ":label", MS-DOS / 4DOS style.
;
;   GOTO  label   - jump to ":label"
;   GOSUB label   - call subroutine at ":label"
;   RETURN        - return to the line after the GOSUB
;
;///////////////////////////////////////////////////

GOTO_LABEL_MAX	EQU	15		; max label name length
GOSUB_MAX	EQU	16		; max GOSUB nesting depth

;-------------------------------------------------
; GOTO label
; in: de -> argument string (label, may start with ':')
;-------------------------------------------------
cmd_goto:
	ex	de,hl			; hl -> argument text
	call	GOTO_PARSE		; -> goto_label (upper, 0-term)
	ld	a,(goto_label)
	or	a
	jp	z,.empty		; no label name
	jp	GOTO_START		; rewind + start the label search
.empty:	ld	de,MAIN_MSG.LABEL_NOT_FOUND
	jp	gAbort

;-------------------------------------------------
; GOSUB label
; in: de -> argument string (label, may start with ':')
;-------------------------------------------------
cmd_gosub:
	ex	de,hl			; hl -> argument text
	call	GOTO_PARSE		; -> goto_label (saved in memory)
	ld	a,(goto_label)
	or	a
	jp	z,cmd_goto.empty
	call	GOSUB_PUSH		; remember the return position
	jp	GOTO_START		; then jump like GOTO

;-------------------------------------------------
; RETURN - resume after the matching GOSUB
;-------------------------------------------------
cmd_return:
	ld	a,(gosub_sp)
	or	a
	jr	z,.empty		; RETURN without GOSUB
	dec	a
	ld	(gosub_sp),a
	add	a,a
	add	a,a			; a = sp*4 (byte offset in stack)
	ld	e,a
	ld	d,0
	ld	hl,gosub_stk
	add	hl,de
	ld	e,(hl)			; saved offset (low word)
	inc	hl
	ld	d,(hl)
	inc	hl
	ld	(gosub_lo),de
	ld	e,(hl)			; saved offset (high word)
	inc	hl
	ld	d,(hl)
	ld	(gosub_hi),de
	ld	a,(BAT_FM)		; bat-file handle
	ld	hl,(gosub_hi)		; HL = offset high 16 bits
	ld	ix,(gosub_lo)		; IX = offset low 16 bits
	ld	bc,Dss.Move_FP.FrStart	; B=0 (from start), C=#15
	RST	ToDSS
	jr	c,.io
	xor	a
	ld	(MOVWORD.count),a	; force re-read from saved position
	ret				; back to NEWLINE -> line after GOSUB
.empty:	ld	de,MAIN_MSG.RET_NO_GOSUB
	jp	gAbort
.io:	call	print_err_message
	jp	gAbort.silent

;-------------------------------------------------
; Parse a label argument into goto_label
; in:  hl -> text (optional spaces/TAB, optional ':')
; out: goto_label = upper-cased, 0-terminated token
;-------------------------------------------------
GOTO_PARSE:
.sp0:	ld	a,(hl)			; skip leading blanks (space / TAB)
	cp	" "
	jr	z,.sp0i
	cp	"\t"
	jr	nz,.nosp0
.sp0i:	inc	hl
	jr	.sp0
.nosp0:	cp	":"			; allow "GOTO :label"
	jr	nz,.sp1
	inc	hl
.sp1:	ld	a,(hl)			; skip blanks after ':'
	cp	" "
	jr	z,.sp1i
	cp	"\t"
	jr	nz,.copy
.sp1i:	inc	hl
	jr	.sp1
.copy:	ld	de,goto_label
	ld	b,GOTO_LABEL_MAX
.cloop:	ld	a,(hl)
	cp	" "+1			; a <= ' '  ->  end of token
	jr	c,.cend
	call	COMPARE.cmp_AZ		; -> upper case
	ld	(de),a
	inc	hl
	inc	de
	djnz	.cloop
.cend:	xor	a
	ld	(de),a			; 0-terminate
	ret

;-------------------------------------------------
; Rewind the BAT-file and start the label search
;-------------------------------------------------
GOTO_START:
	ld	a,(BAT_FM)		; bat-file handle
	ld	hl,0			; offset low
	ld	ix,0			; offset high
	ld	bc,Dss.Move_FP.FrStart	; B=0 (from start), C=#15
	RST	ToDSS
	jr	c,.io
	xor	a
	ld	(MOVWORD.count),a	; invalidate NEWLINE read buffer
	ld	a,1
	ld	(goto_active),a		; activate the label search
	ret
.io:	call	print_err_message
	jp	gAbort.silent

;-------------------------------------------------
; Push the return position (file offset of the line
; that follows the current GOSUB) onto the stack.
;-------------------------------------------------
GOSUB_PUSH:
	ld	a,(gosub_sp)
	cp	GOSUB_MAX
	jr	nc,.deep		; stack overflow
	; current file pointer (tell): FrCurrent, offset 0
	ld	a,(BAT_FM)
	ld	hl,0
	ld	ix,0
	ld	bc,Dss.Move_FP.FrCurrent ; B=1, C=#15
	RST	ToDSS
	jr	c,.io
	; on return: IX = pointer low 16, HL = pointer high 16
	ld	(gosub_hi),hl		; save high word
	push	ix
	pop	hl			; hl = pointer low 16
	; offset = pointer - (bytes still unparsed in buffer1)
	ld	a,(MOVWORD.count)
	ld	e,a
	ld	d,0
	or	a			; CF=0
	sbc	hl,de			; hl = low - count
	ld	(gosub_lo),hl
	jr	nc,.nob
	ld	hl,(gosub_hi)		; borrow into high word
	dec	hl
	ld	(gosub_hi),hl
.nob:
	; store at gosub_stk[gosub_sp]
	ld	a,(gosub_sp)
	ld	c,a			; c = old depth
	add	a,a
	add	a,a			; a = sp*4
	ld	e,a
	ld	d,0
	ld	hl,gosub_stk
	add	hl,de
	ld	de,(gosub_lo)
	ld	(hl),e
	inc	hl
	ld	(hl),d
	inc	hl
	ld	de,(gosub_hi)
	ld	(hl),e
	inc	hl
	ld	(hl),d
	ld	a,c
	inc	a
	ld	(gosub_sp),a		; depth++
	ret
.deep:	ld	de,MAIN_MSG.GOSUB_DEEP
	jp	gAbort
.io:	call	print_err_message
	jp	gAbort.silent

;-------------------------------------------------
; Print message (de=index) and abort the BAT-file
;-------------------------------------------------
gAbort:
	call	ECHO_MESSAGE
.silent:
	xor	a
	ld	(goto_active),a		; don't double-print in cmd_break.exit
	jp	cmd_break.exit

;-------------------------------------------------
; Called from CMDMODE for every BAT-file line.
; Handles ":label" lines and the GOTO/GOSUB search.
;
; out: CF=1 - skip this line (label line, or searching)
;      CF=0 - execute this line normally
;-------------------------------------------------
BAT_CHECK_LABEL:
	ld	hl,Buffers.input_line.Path
.sp:	ld	a,(hl)			; skip leading blanks (space / TAB)
	cp	" "
	jr	z,.spi
	cp	"\t"
	jr	nz,.first
.spi:	inc	hl
	jr	.sp
.first:	cp	":"			; is it a label line ?
	jr	z,.label
	; not a label line
	ld	a,(goto_active)
	or	a
	ret	z			; CF=0 -> run normally
	scf				; searching -> skip line
	ret
	;
.label:	ld	a,(goto_active)
	or	a
	jr	nz,.match
	; not searching: ":label" -> skip (no echo, no exec)
	scf
	ret
	; searching: does this label match goto_label ?
.match:	inc	hl			; skip ':'
.msp:	ld	a,(hl)			; skip blanks after ':'
	cp	" "
	jr	z,.mspi
	cp	"\t"
	jr	nz,.mcmp
.mspi:	inc	hl
	jr	.msp
.mcmp:	ld	de,goto_label
.mlp:	ld	a,(de)			; target char (upper, 0-term)
	or	a
	jr	z,.mend			; target consumed
	ld	c,a
	ld	a,(hl)
	cp	" "+1			; line token ended too early ?
	jr	c,.skip			;  -> no match
	call	COMPARE.cmp_AZ
	cp	c
	jr	nz,.skip
	inc	hl
	inc	de
	jr	.mlp
.mend:	ld	a,(hl)			; target ended: line token must end here
	cp	" "+1			; a <= ' '  ->  full match
	jr	nc,.skip		; line label is longer -> no match
	; match ! stop searching, skip the label line itself
	xor	a
	ld	(goto_active),a
	scf
	ret
	;
.skip:	scf				; keep searching, skip this line
	ret
	;

goto_active:	db	0			; 1 = searching for a label
goto_label:	ds	GOTO_LABEL_MAX+1,0	; target label (upper, 0-term)
gosub_sp:	db	0			; GOSUB nesting depth
gosub_lo:	dw	0			; scratch (offset low)
gosub_hi:	dw	0			; scratch (offset high)
gosub_stk:	ds	GOSUB_MAX*4,0		; return offsets (32-bit each)