;;; The MIT License (MIT)
;;;
;;; Copyright (c) 2014 Daniel P. Friedman, Oleg Kiselyov, and William E. Byrd
;;; Modifications Copyright (c) 2021 Jeremy Steward
;;;
;;; Permission is hereby granted, free of charge, to any person obtaining a copy
;;; of this software and associated documentation files (the "Software"), to deal
;;; in the Software without restriction, including without limitation the rights
;;; to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
;;; copies of the Software, and to permit persons to whom the Software is
;;; furnished to do so, subject to the following conditions:
;;;
;;; The above copyright notice and this permission notice shall be included in all
;;; copies or substantial portions of the Software.
;;;
;;; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
;;; IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
;;; FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
;;; AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
;;; LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
;;; OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
;;; SOFTWARE.
;;;
;;; Taken from https://github.com/miniKanren/miniKanren and modified to work
;;; with CHICKEN Scheme by Jeremy Steward on 2021-08-28

(define (build-num n)
  (cond
    ((odd? n)
     (cons 1
           (build-num (quotient (- n 1) 2))))
    ((and (not (zero? n)) (even? n))
     (cons 0
           (build-num (quotient n 2))))
    ((zero? n) '())))

(define (little-endian->number le-num)
  (let loop ((power 1)
             (num le-num)
             (acc 0))
    (if (null? num)
      acc
      (loop (* 2 power)
        (cdr num)
        (+ acc (* power (car num)))))))

(define (zeroo n)
  (== '() n))

(define (poso n)
  (fresh (a d)
    (== `(,a . ,d) n)))

(define (>1o n)
  (fresh (a ad dd)
    (== `(,a ,ad . ,dd) n)))

(define (full-addero b x y r c)
  (conde
    ((== 0 b) (== 0 x) (== 0 y) (== 0 r) (== 0 c))
    ((== 1 b) (== 0 x) (== 0 y) (== 1 r) (== 0 c))
    ((== 0 b) (== 1 x) (== 0 y) (== 1 r) (== 0 c))
    ((== 1 b) (== 1 x) (== 0 y) (== 0 r) (== 1 c))
    ((== 0 b) (== 0 x) (== 1 y) (== 1 r) (== 0 c))
    ((== 1 b) (== 0 x) (== 1 y) (== 0 r) (== 1 c))
    ((== 0 b) (== 1 x) (== 1 y) (== 0 r) (== 1 c))
    ((== 1 b) (== 1 x) (== 1 y) (== 1 r) (== 1 c))))

(define (addero d n m r)
  (conde
    ((== 0 d) (== '() m) (== n r))
    ((== 0 d) (== '() n) (== m r)
     (poso m))
    ((== 1 d) (== '() m)
     (addero 0 n '(1) r))
    ((== 1 d) (== '() n) (poso m)
     (addero 0 '(1) m r))
    ((== '(1) n) (== '(1) m)
     (fresh (a c)
       (== `(,a ,c) r)
       (full-addero d 1 1 a c)))
    ((== '(1) n) (gen-addero d n m r))
    ((== '(1) m) (>1o n) (>1o r)
     (addero d '(1) n r))
    ((>1o n) (gen-addero d n m r))))

(define (gen-addero d n m r)
  (fresh (a b c e x y z)
    (== `(,a . ,x) n)
    (== `(,b . ,y) m) (poso y)
    (== `(,c . ,z) r) (poso z)
    (full-addero d a b c e)
    (addero e x y z)))

(define (pluso n m k)
  (addero 0 n m k))

(define +o pluso)

(define (minuso n m k)
  (pluso m k n))

(define -o minuso)

(define (*o n m p)
  (conde
    ((== '() n) (== '() p))
    ((poso n) (== '() m) (== '() p))
    ((== '(1) n) (poso m) (== m p))
    ((>1o n) (== '(1) m) (== n p))
    ((fresh (x z)
       (== `(0 . ,x) n) (poso x)
       (== `(0 . ,z) p) (poso z)
       (>1o m)
       (*o x m z)))
    ((fresh (x y)
       (== `(1 . ,x) n) (poso x)
       (== `(0 . ,y) m) (poso y)
       (*o m n p)))
    ((fresh (x y)
       (== `(1 . ,x) n) (poso x)
       (== `(1 . ,y) m) (poso y)
       (odd-*o x n m p)))))

(define (odd-*o x n m p)
  (fresh (q)
    (bound-*o q p n m)
    (*o x m q)
    (pluso `(0 . ,q) m p)))

(define (bound-*o q p n m)
  (conde
    ((== '() q) (poso p))
    ((fresh (a0 a1 a2 a3 x y z)
       (== `(,a0 . ,x) q)
       (== `(,a1 . ,y) p)
       (conde
         ((== '() n)
          (== `(,a2 . ,z) m)
          (bound-*o x y z '()))
         ((== `(,a3 . ,z) n)
          (bound-*o x y z m)))))))

(define (=lo n m)
  (conde
    ((== '() n) (== '() m))
    ((== '(1) n) (== '(1) m))
    ((fresh (a x b y)
       (== `(,a . ,x) n) (poso x)
       (== `(,b . ,y) m) (poso y)
       (=lo x y)))))

(define (<lo n m)
  (conde
    ((== '() n) (poso m))
    ((== '(1) n) (>1o m))
    ((fresh (a x b y)
       (== `(,a . ,x) n) (poso x)
       (== `(,b . ,y) m) (poso y)
       (<lo x y)))))

(define (<=lo n m)
  (conde
    ((=lo n m))
    ((<lo n m))))

(define (<o n m)
  (conde
    ((<lo n m))
    ((=lo n m)
     (fresh (x)
       (poso x)
       (pluso n x m)))))

(define (<=o n m)
  (conde
    ((== n m))
    ((<o n m))))

(define (/o n m q r)
  (conde
    ((== r n) (== '() q) (<o n m))
    ((== '(1) q) (=lo n m) (pluso r m n)
     (<o r m))
    ((<lo m n)
     (<o r m)
     (poso q)
     (fresh (nh nl qh ql qlm qlmr rr rh)
       (splito n r nl nh)
       (splito q r ql qh)
       (conde
         ((== '() nh)
          (== '() qh)
          (minuso nl r qlm)
          (*o ql m qlm))
         ((poso nh)
          (*o ql m qlm)
          (pluso qlm r qlmr)
          (minuso qlmr nl rr)
          (splito rr r '() rh)
          (/o nh m qh rh)))))))

(define (splito n r l h)
  (conde
    ((== '() n) (== '() h) (== '() l))
    ((fresh (b n^)
       (== `(0 ,b . ,n^) n)
       (== '() r)
       (== `(,b . ,n^) h)
       (== '() l)))
    ((fresh (n^)
       (== `(1 . ,n^) n)
       (== '() r)
       (== n^ h)
       (== '(1) l)))
    ((fresh (b n^ a r^)
       (== `(0 ,b . ,n^) n)
       (== `(,a . ,r^) r)
       (== '() l)
       (splito `(,b . ,n^) r^ '() h)))
    ((fresh (n^ a r^)
       (== `(1 . ,n^) n)
       (== `(,a . ,r^) r)
       (== '(1) l)
       (splito n^ r^ '() h)))
    ((fresh (b n^ a r^ l^)
       (== `(,b . ,n^) n)
       (== `(,a . ,r^) r)
       (== `(,b . ,l^) l)
       (poso l^)
       (splito n^ r^ l^ h)))))

(define (logo n b q r)
  (conde
    ((== '(1) n) (poso b) (== '() q) (== '() r))
    ((== '() q) (<o n b) (pluso r '(1) n))
    ((== '(1) q) (>1o b) (=lo n b) (pluso r b n))
    ((== '(1) b) (poso q) (pluso r '(1) n))
    ((== '() b) (poso q) (== r n))
    ((== '(0 1) b)
     (fresh (a ad dd)
       (poso dd)
       (== `(,a ,ad . ,dd) n)
       (exp2 n '() q)
       (fresh (s)
         (splito n dd r s))))
    ((fresh (a ad add ddd)
       (conde
         ((== '(1 1) b))
         ((== `(,a ,ad ,add . ,ddd) b))))
     (<lo b n)
     (fresh (bw1 bw nw nw1 ql1 ql s)
       (exp2 b '() bw1)
       (pluso bw1 '(1) bw)
       (<lo q n)
       (fresh (q1 bwq1)
         (pluso q '(1) q1)
         (*o bw q1 bwq1)
         (<o nw1 bwq1))
       (exp2 n '() nw1)
       (pluso nw1 '(1) nw)
       (/o nw bw ql1 s)
       (pluso ql '(1) ql1)
       (<=lo ql q)
       (fresh (bql qh s qdh qd)
         (repeated-mul b ql bql)
         (/o nw bw1 qh s)
         (pluso ql qdh qh)
         (pluso ql qd q)
         (<=o qd qdh)
         (fresh (bqd bq1 bq)
           (repeated-mul b qd bqd)
           (*o bql bqd bq)
           (*o b bq bq1)
           (pluso bq r n)
           (<o n bq1)))))))

(define (exp2 n b q)
  (conde
    ((== '(1) n) (== '() q))
    ((>1o n) (== '(1) q)
     (fresh (s)
       (splito n b s '(1))))
    ((fresh (q1 b2)
       (== `(0 . ,q1) q)
       (poso q1)
       (<lo b n)
       (appendo b `(1 . ,b) b2)
       (exp2 n b2 q1)))
    ((fresh (q1 nh b2 s)
       (== `(1 . ,q1) q)
       (poso q1)
       (poso nh)
       (splito n b s nh)
       (appendo b `(1 . ,b) b2)
       (exp2 nh b2 q1)))))

(define (repeated-mul n q nq)
  (conde
    ((poso n) (== '() q) (== '(1) nq))
    ((== '(1) q) (== n nq))
    ((>1o q)
     (fresh (q1 nq1)
       (pluso q1 '(1) q)
       (repeated-mul n q1 nq1)
       (*o nq1 n nq)))))

(define (expo b q n)
  (logo n b q '()))