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;; Pieces themselves: the buffer is a reference to the buffer they take their
;; data from.
;; Start and end are numbers.
;; The type defines how they should be rendered, it makes
;; possible to account for hyperlinks or stuff like that in the future with
;; ease.
(define-record-type <piece>
(%make-piece buffer start length type next prev)
piece?
(buffer piece-buffer set-piece-buffer!)
(start piece-start set-piece-start!)
(length piece-length set-piece-length!)
(type piece-type set-piece-type!)
(next %piece-next %set-piece-next!)
(prev %piece-prev %set-piece-prev!))
(define-record-type <sentinel-piece>
(make-sentinel-piece next prev)
sentinel-piece?
(next %sentinel-piece-next %set-sentinel-piece-next!)
(prev %sentinel-piece-prev %set-sentinel-piece-prev!))
;; TODO think about a way to make all this polymorphism automagic
(define (piece-next p)
(cond
((sentinel-piece? p) (%sentinel-piece-next p))
((piece? p) (%piece-next p))))
(define (piece-prev p)
(cond
((sentinel-piece? p) (%sentinel-piece-prev p))
((piece? p) (%piece-prev p))))
(define (set-piece-prev! p prev)
(cond
((sentinel-piece? p) (%set-sentinel-piece-prev! p prev))
((piece? p) (%set-piece-prev! p prev))))
(define (set-piece-next! p next)
(cond
((sentinel-piece? p) (%set-sentinel-piece-next! p next))
((piece? p) (%set-piece-next! p next))))
(define (can-merge-pieces? a b)
;; Maybe simplify the and/or/not magic?
(and (not (or (sentinel-piece? a) (sentinel-piece? b)))
(or
(or (= 0 (piece-length a)) (= 0 (piece-length b)))
(and (eq? (piece-buffer a) (piece-buffer b))
(= (+ (piece-start a) (piece-length a)) (piece-start b))
(equal? (piece-type a) (piece-type b))))))
(define (merge-pieces! a b)
(when (= 0 (piece-length a)) ;; First is empty, so we eat it
(set-piece-start! a (piece-start b)))
(set-piece-length! a (+ (piece-length a) (piece-length b)))
(set-piece-next! a (piece-next b))
(unless (sentinel-piece? (piece-next b)) (set-piece-prev! (piece-next b) a)))
;; Piece API
(define (make-piece buffer start length type prev next)
(%make-piece buffer start length type prev next))
(define (connect-pieces! a b)
(begin
(set-piece-next! a b)
(set-piece-prev! b a)))
(define (split-piece! a at)
(if (and (= at 0) (sentinel-piece? a))
(values a a) ;; Just return the sentinel twice, as this is only used to
;; take one of them
(letrec* ((b (%make-piece (piece-buffer a)
(+ at (piece-start a))
(- (piece-length a) at)
(piece-type a)
(piece-next a)
a)))
(unless (sentinel-piece? (piece-next a))
(set-piece-prev! (piece-next a) b))
(set-piece-length! a at)
(set-piece-next! a b)
(values a b))))
;; The piece table itself;
;; original is a ro-buffer, add is an add-buffer (a string designed to grow)
;; and pieces is a piece that has its prev and next.
(define-record-type <piece-table>
(%make-piece-table original-buffer add-buffer piece)
piece-table?
(original-buffer piece-table-original-buffer set-piece-table-original-buffer!)
(add-buffer piece-table-add-buffer set-piece-table-add-buffer!)
(piece piece-table-piece set-piece-table-piece!))
(define (make-piece-table original)
(letrec* ((ro-buffer (make-ro-buffer original))
(piece (make-piece ro-buffer 0 (string-length original) 'normal
sentinel sentinel))
(sentinel (make-sentinel-piece piece piece)))
(set-piece-prev! piece sentinel)
(set-piece-next! piece sentinel)
(%make-piece-table
ro-buffer (make-add-buffer) piece)))
(define (piece-table-index->piece+index piece-table pos)
"Returns (values piece remainder) or eof-object"
(let loop ((piece (piece-table-piece piece-table))
(rem pos))
(cond
((sentinel-piece? piece)
(if (= rem 0)
(values piece rem)
(error "Requested position out of piece-table")))
((< rem (piece-length piece))
(values piece rem))
(else
(loop (piece-next piece) (- rem (piece-length piece)))))))
(define (piece-table-last-piece piece-table)
(piece-prev (piece-prev (piece-table-piece piece-table))))
;; API
(define (piece-table-index piece-table pos)
;; TODO: Validate input
(let-values (((piece idx) (piece-table-index->piece+index piece-table pos)))
(string-ref (buffer->string (piece-buffer piece))
(+ (piece-start piece) idx))))
(define (piece-table-text-length piece-table)
(let loop ((piece (piece-table-piece piece-table))
(acc 0))
(if (sentinel-piece? (piece-next piece))
(+ acc (piece-length piece))
(loop (piece-next piece) (+ (piece-length piece) acc)))))
(define (%piece-fold-from piece f identity)
(let loop ((piece piece)
(acc identity))
(unless (sentinel-piece? piece)
(loop (piece-next piece) (f piece acc)))))
(define (%piece-fold-from-right piece f identity)
(let loop ((piece piece)
(acc identity))
(unless (sentinel-piece? piece)
(loop (piece-prev piece) (f piece acc)))))
(define (piece-table-for-each piece-table f from to)
;; TODO: default from and to
;; TODO: maybe combine with the `piece-table-index->piece+index` to find the
;; `from`
;; TODO: make this lower level, searching from a piece, not from the table
;; TODO: implement using `%piece-fold-from`
"Calls `f` through the characters of the piece-table, like `string-for-each`
would do, but the `f` call also includes the piece (to expose extra data) and
the index of the character"
(let loop ((idx 0)
(start 0)
(piece (piece-table-piece piece-table)))
(let* ((len (piece-length piece))
(end (+ start len))
(more? (not (sentinel-piece? (piece-next piece)))))
(when (< idx to) ;; Skip tail
(if (or (= idx end) (<= end from))
;; Current piece doesn't contain the section we need or finished
;; Jump to next piece
(when more? (loop end end (piece-next piece)))
;; Current piece contains part of the section we need, go char by
;; char
(begin
(when (<= from idx)
(f
(string-ref (buffer->string (piece-buffer piece))
(+ (piece-start piece) (- idx start)))
idx
piece))
;; There are chars to process in this piece
(loop (+ idx 1) start piece)))))))
(define (piece-table-for-each-right piece-table f from to)
"-right version of piece-table-for-each, it finds the tail and goes
backwards"
;; TODO: not implemented yet
;; TODO: make this lower level, searching from a piece, not from the table
)
(define (piece-table-insert! piece-table pos str type)
;; TODO: validate input
;; TODO: Try to reuse the caracters on the target buffer if they are already
;; there? Is this maximum evilness? => it's just a string-ref and it prevents
;; us from creating pieces!
(let* ((add-buffer (piece-table-add-buffer piece-table))
(start (add-buffer-used add-buffer))
(_ (add-buffer-append! add-buffer str))
(candidate (make-piece add-buffer
start
(string-length str)
type
#f #f)))
(unless (= 0 (string-length str))
(let*-values (((piece idx)
(piece-table-index->piece+index piece-table pos)))
(cond
((= idx 0)
(connect-pieces! (piece-prev piece) candidate)
(connect-pieces! candidate piece)
(when (can-merge-pieces? (piece-prev piece) candidate)
(merge-pieces! (piece-prev piece) candidate)))
(else
(let-values (((first second) (split-piece! piece idx)))
(connect-pieces! first candidate)
(connect-pieces! candidate second)
(when (can-merge-pieces? first candidate)
(merge-pieces! first candidate)))))))))
(define (piece-table-delete! piece-table from len)
(unless (= 0 len)
(let*-values (((start-piece idx) (piece-table-index->piece+index
piece-table from))
((first second) (split-piece! start-piece idx))
((end-piece end-idx) (piece-table-index->piece+index
piece-table (+ from len)))
((third fourth) (split-piece! end-piece end-idx)))
(connect-pieces! first fourth))))
;; Finding:
(define (piece-table-find piece-table char from)
;; TODO: generalize the from
;; TODO: Implement the backwards one too
(call/cc (lambda (cont)
(piece-table-for-each
piece-table
(lambda (c i p)
(when (char=? c char)
(cont i)))
from
(piece-table-text-length piece-table))
(cont (eof-object)))))
;; Serialization - Deserialization
(define (piece-table-write port)
"Write a piece table to port"
#f)
(define (piece-table-read port)
"Read a piece table stored in port"
#f)
;; From/to string
(define string->piece-table make-piece-table)
(define (piece-table-substring piece-table from to)
(let ((out-string (make-string (- to from))))
(let loop ((piece (piece-table-piece piece-table))
(acc 0))
(if (or (sentinel-piece? piece) (>= acc to))
out-string
(begin
(when (>= (+ (piece-length piece) acc) from)
(string-copy!
out-string
(max (- acc from) 0)
(buffer->string (piece-buffer piece))
(+ (piece-start piece) (max (- from acc) 0))
(+ (piece-start piece) (min (- to acc) (piece-length piece)))))
(loop (piece-next piece) (+ acc (piece-length piece))))))))
(define (piece-table->string piece-table)
(piece-table-substring piece-table 0 (piece-table-text-length piece-table)))
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