;; content-on-sx — relative block reorder.
;;
;; Move a top-level block to just before / after another block by id — more
;; ergonomic than the index-based doc-move. No-op if either id is missing.
;; Immutable; composes the doc.sx list helpers.
;;
;; Requires (loaded by harness): doc.sx.

(define
  content/move-before
  (fn
    (doc id target)
    (let
      ((blk (doc-find doc id)))
      (if
        (= blk nil)
        doc
        (let
          ((without (ct-remove-id (doc-blocks doc) id)))
          (let
            ((idx (ct-index-of without target)))
            (if
              (= idx -1)
              doc
              (doc-with-blocks doc (ct-insert-at without idx blk)))))))))

(define
  content/move-after
  (fn
    (doc id target)
    (let
      ((blk (doc-find doc id)))
      (if
        (= blk nil)
        doc
        (let
          ((without (ct-remove-id (doc-blocks doc) id)))
          (let
            ((idx (ct-index-of without target)))
            (if
              (= idx -1)
              doc
              (doc-with-blocks
                doc
                (ct-insert-at without (+ idx 1) blk)))))))))

(define
  content/move-to-front
  (fn
    (doc id)
    (let
      ((blk (doc-find doc id)))
      (if
        (= blk nil)
        doc
        (doc-with-blocks doc (cons blk (ct-remove-id (doc-blocks doc) id)))))))

(define
  content/move-to-back
  (fn
    (doc id)
    (let
      ((blk (doc-find doc id)))
      (if
        (= blk nil)
        doc
        (doc-with-blocks
          doc
          (append (ct-remove-id (doc-blocks doc) id) (list blk)))))))