.segment "CODE"

LOADSAVE_LFN = $FF

; ============================================================================
; COPY STRING EXPRESSION TO FILE_NAME_BUFFER
;
; Entry:
;   TXTPTR points at string expression
;
; Exit:
;   FILE_NAME_BUFFER contains NUL-terminated filename
;
; Clobbers:
;   A,X,Y,INDEX,STRNG2
; ============================================================================
PARSE_LOADSAVE_FILENAME:
        jsr     FRMEVL
        jsr     CHKSTR
        jsr     FREFAC
        ; FREFAC:
        ;   A = length
        ;   INDEX = string address
        sta     STRNG2
        ldy     #$00
@copy:
        cpy     STRNG2
        beq     @done
        lda     (INDEX),y
        sta     FILE_NAME_BUFFER,y
        iny
        bne     @copy
@done:
        lda     #$00
        sta     FILE_NAME_BUFFER,y
        rts

; ============================================================================
; SET UP THE COMMON FILE ARGUMENTS
; ============================================================================
LOADSAVE_SET_FILE:
        lda     #LOADSAVE_LFN
        sta     IO_FILE_DESCRIPTOR
        lda     #<FILE_NAME_BUFFER
        sta     IO_FILE_DATA
        lda     #>FILE_NAME_BUFFER
        sta     IO_FILE_DATA+1
        rts

; ============================================================================
; WAIT FOR FILE COMMAND COMPLETION
;
; Jumps to IQERR on host-side failure.
; ============================================================================
LOADSAVE_WAIT:
        lda     IO_FILE_STATUS
        and     #FILE_STATUS_READY
        beq     LOADSAVE_WAIT
        lda     IO_FILE_STATUS
        and     #FILE_STATUS_ERROR
        beq     @ok
        jmp     IQERR
@ok:
        rts


; ============================================================================
; OPEN FOR READING
; ============================================================================
LOADSAVE_OPEN_R:
        jsr     LOADSAVE_SET_FILE
        lda     #IO_COMMAND_OPEN_R
        sta     IO_FILE_COMMAND
        jmp     LOADSAVE_WAIT

; ============================================================================
; OPEN FOR WRITING / TRUNCATE
; ============================================================================
LOADSAVE_OPEN_W:
        jsr     LOADSAVE_SET_FILE
        lda     #IO_COMMAND_OPEN_W
        sta     IO_FILE_COMMAND
        jmp     LOADSAVE_WAIT

; ============================================================================
; CLOSE INTERNAL LOAD/SAVE FILE
; ============================================================================
LOADSAVE_CLOSE:
        lda     #LOADSAVE_LFN
        sta     IO_FILE_DESCRIPTOR
        lda     #IO_COMMAND_CLOSE
        sta     IO_FILE_COMMAND
        jsr     LOADSAVE_WAIT
        jsr     CLRCH
        rts

; ============================================================================
; SAVE "filename"
;
; Saves plain ASCII BASIC source, equivalent to LIST output.
; ============================================================================
SAVE:
        jsr     PARSE_LOADSAVE_FILENAME
        jsr     LOADSAVE_OPEN_W
        ; Route OUTDO/CHROUT to our internal file.
        ldx     #LOADSAVE_LFN
        jsr     CHKOUT
        stx     CURDVC
        ; Start with first BASIC line.
        lda     TXTTAB
        sta     LOWTRX
        lda     TXTTAB+1
        sta     LOWTRX+1
SAVE_NEXT_LINE:
        ; The high byte of the forward link is zero at end of program.
        ldy     #$01
        lda     (LOWTRX),y
        beq     SAVE_DONE
        ; ------------------------------------------------------------
        ; Print line number.
        ;
        ; record:
        ; +0/+1 = next line
        ; +2/+3 = line number
        ; +4... = tokenized body
        ; ------------------------------------------------------------
        iny                     ; Y=2
        lda     (LOWTRX),y
        tax
        iny                     ; Y=3
        lda     (LOWTRX),y
        jsr     LINPRT
        lda     #' '
        jsr     OUTDO
        ; DATAFLG follows LIST's quoting/token rules.
        lda     #$01
        sta     DATAFLG
        ldy     #$04
SAVE_LINE_CHAR:
        lda     (LOWTRX),y
        beq     SAVE_LINE_DONE
        ; Test whether it's plain ASCII/token BEFORE doing CMPs
        bpl     SAVE_PLAIN_CHAR
        cmp     #$FF
        beq     SAVE_PLAIN_CHAR
        bit     DATAFLG
        bmi     SAVE_PLAIN_CHAR
        ; Token
        sec
        sbc     #$7F
        tax
        sty     FORPNT
        ldy     #$FF
SAVE_FIND_TOKEN:
        dex
        beq     SAVE_TOKEN_FOUND
SAVE_SKIP_TOKEN:
        iny
        lda     TOKEN_NAME_TABLE,y
        bpl     SAVE_SKIP_TOKEN
        bmi     SAVE_FIND_TOKEN
SAVE_TOKEN_FOUND:
        iny
        lda     TOKEN_NAME_TABLE,y
        bmi     SAVE_TOKEN_LAST
        jsr     OUTDO
        bne     SAVE_TOKEN_FOUND
SAVE_TOKEN_LAST:
        and     #$7F
        jsr     OUTDO
        ldy     FORPNT
        iny
        jmp     SAVE_LINE_CHAR
SAVE_PLAIN_CHAR:
        and     #$7F
        jsr     OUTDO
        ; Quote state must be updated AFTER output/test.
        cmp     #$22
        bne     SAVE_PLAIN_DONE
        lda     DATAFLG
        eor     #$FF
        sta     DATAFLG
SAVE_PLAIN_DONE:
        iny
        jmp     SAVE_LINE_CHAR
SAVE_LINE_DONE:
        ; Every saved source line ends in LF.
        jsr     LFDO
        ; Follow next-line pointer.
        ldy     #$00
        lda     (LOWTRX),y
        tax
        iny
        lda     (LOWTRX),y
        stx     LOWTRX
        sta     LOWTRX+1
        jmp     SAVE_NEXT_LINE
SAVE_DONE:
        jsr     LOADSAVE_CLOSE
        rts

; ============================================================================
; LOAD "filename"
;
; Replaces current program.
; Reads ASCII source one line at a time, tokenizes through the normal
; BASIC parser, and inserts using NUMBERED_LINE.
;
; IMPORTANT:
; NUMBERED_LINE eventually reaches FIX_LINKS -> SETPTRS -> STKINI, which
; resets the hardware stack. Therefore LOAD cannot expect NUMBERED_LINE to
; return with RTS. FIX_LINKS jumps back to LOAD_NEXT_LINE while LOAD_ACTIVE
; is set.
; ============================================================================

LOAD:
        ; Copy the filename before SCRTCH destroys temporary strings.
        jsr     PARSE_LOADSAVE_FILENAME
        jsr     LOADSAVE_OPEN_R
        ; Delete current program.
        jsr     SCRTCH
        ; Route CHRIN to the file.
        ldx     #LOADSAVE_LFN
        jsr     CHKIN
        stx     CURDVC
        ; Tell FIX_LINKS that program insertion belongs to LOAD.
        lda     #$01
        sta     LOAD_ACTIVE
; ----------------------------------------------------------------------------
; Entry point used both initially and by FIX_LINKS after inserting each line.
; Must be a globally visible label if FIX_LINKS lives in another source file.
; ----------------------------------------------------------------------------
LOAD_NEXT_LINE:
        ldx     #$00
; ----------------------------------------------------------------------------
; Read one physical source line into INPUTBUFFER.
;
;   "10 PRINT 1\n"    -> normal line
;   "10 PRINT 1"<EOF> -> final line still accepted
;   EOF with X=0      -> done loading
; ----------------------------------------------------------------------------
@read_char:
        jsr     CHRIN
        ; If host says EOF, A is not considered valid data.
        pha
        lda     IO_FILE_STATUS
        and     #FILE_STATUS_EOF
        bne     @eof
        pla
        ; LF terminates a source line.
        cmp     #LF
        beq     @line_complete
        ; Accept CRLF files too.
        cmp     #$0D
        beq     @read_char
        ; Same practical line limit as interactive INLIN.
        cpx     #$47
        bcs     @line_too_long
        sta     INPUTBUFFER,x
        inx
        jmp     @read_char
@eof:
        pla
        ; EOF with no accumulated characters means real end of file.
        cpx     #$00
        beq     @load_done
        ; Otherwise process the unterminated final line.
@line_complete:
        lda     #$00
        sta     INPUTBUFFER,x
        ; Point CHRGET at INPUTBUFFER-1, exactly like INLIN returns.
        lda     #<(INPUTBUFFER-1)
        sta     TXTPTR
        lda     #>(INPUTBUFFER-1)
        sta     TXTPTR+1
        jsr     CHRGET
        ; Ignore empty physical lines.
        beq     LOAD_NEXT_LINE
        ; A source file must consist of numbered program lines.
        ;
        ; CHRGET leaves carry clear for a leading decimal digit,
        ; exactly like the normal RESTART path.
        bcc     @numbered
        jmp     @syntax_error
@numbered:
        ; NUMBERED_LINE performs:
        ;
        ;   LINGET
        ;   PARSE_INPUT_LINE
        ;   FNDLIN
        ;   PUT_NEW_LINE
        ;   FIX_LINKS
        ;
        ; DO NOT JSR here.
        ;
        ; FIX_LINKS eventually calls SETPTRS/STKINI, which resets the
        ; hardware stack. FIX_LINKS will detect LOAD_ACTIVE and jump back
        ; to LOAD_NEXT_LINE.
        jmp     NUMBERED_LINE
@line_too_long:
@syntax_error:
        lda     #$00
        sta     LOAD_ACTIVE

        jsr     CLRCH
        jsr     LOADSAVE_CLOSE
        jmp     SYNERR
@load_done:
        lda     #$00
        sta     LOAD_ACTIVE
        jsr     CLRCH
        jsr     LOADSAVE_CLOSE
        ; Do NOT JSR SETPTRS here.
        ;
        ; Every successfully inserted line already passed through
        ; FIX_LINKS -> SETPTRS -> LE33D.
        ;
        ; Also do not RTS: SETPTRS/STKINI during loading may have destroyed
        ; the original LOAD command's return frame.
        jmp     RESTART