\ editor.fth -- the block editor, in FORTH.
\
\ This file is FORTH source: the node compiles it itself, a line at a time,
\ as if it were typed.  No line is longer than 79 characters.
\
\ A block is a screen of 16 lines of 64 characters.  SCR is the screen being
\ edited.  The editor is a vocabulary, EDITOR: its words are ordinary FORTH
\ words used at the ordinary prompt, so everything else is there as well.
\
\   n EDIT     edit screen n: list it and make EDITOR the CONTEXT vocabulary
\   L          list the screen             N  B     the next, the one before
\   n T        type line n
\   n P text   put the rest of the input line on line n
\   n E        erase line n                WIPE     blank the whole screen
\   n D        delete line n; the lines below move up; it is held in PAD
\   n S        spread: a blank line at n; the lines from n move down
\   n H        hold line n in PAD          n R      replace line n from PAD
\   n I        insert PAD's line at n
\   DONE       write what has changed and go back to FORTH
\   a b COPY   copy screen a to screen b           (in FORTH)
\
\ Every change is UPDATEd; nothing reaches storage until FLUSH or DONE, or
\ until the buffer is wanted for another block.

FORTH DEFINITIONS

\ ( baddr -- )  64 characters; a zero shows as a blank, others as a dot
: (.LINE)
  64 0 DO  DUP I + C@
    DUP 0= IF DROP 32 THEN  DUP 32 < OVER 126 > OR IF DROP 46 THEN  EMIT
  LOOP DROP ;
\ ( n -- baddr )  where line n of screen SCR is
: (LINE)
  DUP 0< OVER 15 > OR ABORT" Line out of range"  64 * SCR @ BLOCK + ;

\ v3's three: a line shown, a line set from a string, the screen shown
: L ( n -- )  (LINE) (.LINE) CR ;
: S ( baddr u n -- )
  (LINE) DUP 64 BLANK  SWAP 0 MAX 64 MIN CMOVE  UPDATE ;
: SHOW ( -- )
  ." Screen " SCR @ 0 .R ." :" CR
  16 0 DO  I 2 .R ." : " I (LINE) (.LINE) CR  LOOP ;

: COPY ( from to -- )  SWAP BLOCK SWAP BUFFER 1024 CMOVE UPDATE ;

VOCABULARY EDITOR  EDITOR DEFINITIONS

: T ( n -- )  DUP (LINE) SWAP 2 .R ." : " (.LINE) CR ;
: L ( -- )  SHOW ;
: E ( n -- )  (LINE) 64 BLANK UPDATE ;
: P ( n -- )  (LINE) DUP 64 BLANK  0 WORD COUNT 64 MIN ROT SWAP CMOVE UPDATE ;
: H ( n -- )  (LINE) PAD 64 CMOVE ;
: R ( n -- )  PAD SWAP (LINE) 64 CMOVE UPDATE ;
: D ( n -- )
  DUP H  DUP 15 < IF
    DUP 1+ (LINE) OVER (LINE) ROT 15 SWAP - 64 * CMOVE
  ELSE DROP THEN  15 E ;
: S ( n -- )
  DUP 15 < IF  DUP (LINE) OVER 1+ (LINE) 3 PICK 15 SWAP - 64 * CMOVE>  THEN E ;
: I ( n -- )  DUP S R ;
: WIPE ( -- )  SCR @ BLOCK 1024 BLANK UPDATE ;
: N ( -- )  1 SCR +! L ;
: B ( -- )  -1 SCR +! L ;
: DONE ( -- )  FLUSH [COMPILE] FORTH ;

FORTH DEFINITIONS

: EDIT ( n -- )  DUP BLOCK DROP  SCR !  EDITOR [ EDITOR ] L [ FORTH ] ;