(library (sph storage dg permission access)
  (export
    perm-create
    perm-delete
    perm-execute
    perm-link
    perm-modify
    perm-not-create
    perm-not-delete
    perm-not-execute
    perm-not-link
    perm-not-modify
    perm-not-read
    perm-read
    sph-storage-dg-permission-access-description)
  (import
    (rnrs bytevectors)
    (rnrs eval)
    (sph)
    (sph hashtable)
    (sph storage dg)
    (sph storage dg permission)
    (only (guile) resolve-module symbol-append))

  (define sph-storage-dg-permission-access-description
    "defines a set of usable default access permissions. experimental")

  (define perm-create)
  (define perm-delete)
  (define perm-read)
  (define perm-modify)
  (define perm-execute)
  (define perm-link)
  (define perm-not-create)
  (define perm-not-delete)
  (define perm-not-read)
  (define perm-not-modify)
  (define perm-not-execute)
  (define perm-not-link)

  (define (create+set-permission-elements . names)
    (dg-txn-call-write
      (l (txn)
        (apply
          (l (pe-ide opposite-pe-ide)
            (eval
              (pair (q begin)
                (apply append
                  (map
                    (l (name ide opposite) (ht-set! dg-p3-permissions ide opposite)
                      (ht-set! dg-p3-permissions opposite ide)
                      (list (list (q set!) (string->symbol (string-append "perm-" name)) ide)
                        (list (q set!) (string->symbol (string-append "perm-not-" name)) opposite)))
                    (reverse names) pe-ide opposite-pe-ide)))
              (resolve-module (q (sph storage dg two permission access)))))
          (create-permission-elements txn names)))))

  (define (create-permission-elements txn names)
    ( (l (pe-ide opposite-pe-ide)
        (dg-relation-ensure txn ide-alias-permission-element (append pe-ide opposite-pe-ide))
        (list pe-ide opposite-pe-ide))
      (dg-intern-ensure txn names)
      (dg-intern-ensure txn (map (l (ele) (string-append "not-" ele)) names))))

  (dg-init-extension-add
    (create+set-permission-elements "create" "delete" "read" "modify" "execute" "link")))