;;
;; util-bst-lset.scm
;;
;; BST-based set implementation.
;;
;; ISC License
;;
;; Copyright 2023 Brmlab, z.s.
;; Dominik Pantůček <dominik.pantucek@trustica.cz>
;;
;; Permission to use, copy, modify, and/or distribute this software
;; for any purpose with or without fee is hereby granted, provided
;; that the above copyright notice and this permission notice appear
;; in all copies.
;; 
;; THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL
;; WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED
;; WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE
;; AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR
;; CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
;; OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
;; NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
;; CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
;;

(declare (unit util-bst-lset))

(import duck)

(module*
 util-bst-lset
 #:doc ("Reimplementation of old lset using new BST backend.")
 (
  make-lset
  lset?
  lset-empty?
  lset-member?
  lset-count
  lset-add
  lset-remove
  list->lset
  lset->list
  lset-merge
  lset-intersect
  lset-subtract
  lset=?
  )
 (import scheme
	 util-bst
	 racket-kwargs
	 util-bst-ldict
	 srfi-1)

 (define* (make-lset (equality? equal?))
   (make-bst 'lset equality? ldict<?))

 (define lset? (bst? 'lset))

 (define lset-empty? bst-empty?)
 (define lset-member? bst-contains?)
 (define lset-count bst-count)

 (define (lset-add ls e)
   (bst-set ls e #t))

 (define lset-remove bst-remove)

 (define* (list->lset lst (equality? equal?))
   (foldl lset-add (make-lset equality?) lst))
 
 (define lset->list bst-keys)

 (define (lset=? ls1 ls2)
   (bst-equal? ls1 ls2))

 (define (lset-merge ls1 ls2)
   (foldl lset-add ls1 (lset->list ls2)))

 (define (lset-intersect ls1 ls2)
   (list->lset
    (filter (lambda (el)
	      (lset-member? ls2 el))
	    (lset->list ls1))
    (bst-EQ? ls1)))

 (define (lset-subtract ls1 ls2)
   (foldl (lambda (ls e)
	    (lset-remove ls e #t))
	  ls1 (lset->list ls2)))

 )