;;; Reference implementation of SRFI 69, from
;;; http://srfi.schemers.org/srfi-69/srfi-69.html

;;; Copyright © Panu Kalliokoski (2005). All Rights Reserved.
;;; 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. 

;;; Modification history:
;;;
;;; In May 2015, William D Clinger modified this code for use in
;;; R7RS systems, mainly so it could be used as a last resort in
;;; the (r6rs hashtables) approximation to (rnrs hashtables).
;;;
;;;     string-ci-hash was changed to use R7RS string-foldcase
;;;
;;;     string-hash, symbol-hash, and %string-hash were changed
;;;     to eliminate a now-useless procedure call for each character
;;;
;;;     whitespace was adjusted because it got messed up during
;;;     conversion from HTML to Scheme code

(define *default-bound* (- (expt 2 29) 3))

(define (%string-hash s bound)
  (let ((hash 31)
        (len (string-length s)))
    (do ((index 0 (+ index 1)))
      ((>= index len) (modulo hash bound))
      (set! hash (modulo (+ (* 37 hash)
                            (char->integer (string-ref s index)))
                         *default-bound*)))))

(define (string-hash s . maybe-bound)
  (let ((bound (if (null? maybe-bound) *default-bound* (car maybe-bound))))
    (%string-hash s bound)))

(define (string-ci-hash s . maybe-bound)
  (let ((bound (if (null? maybe-bound) *default-bound* (car maybe-bound))))
    (%string-hash (string-foldcase s) bound)))

(define (symbol-hash s . maybe-bound)
  (let ((bound (if (null? maybe-bound) *default-bound* (car maybe-bound))))
    (%string-hash (symbol->string s) bound)))

(define (hash obj . maybe-bound)
  (let ((bound (if (null? maybe-bound) *default-bound* (car maybe-bound))))
    (cond ((integer? obj) (modulo obj bound))
          ((string? obj) (string-hash obj bound))
          ((symbol? obj) (symbol-hash obj bound))
          ((real? obj) (modulo (+ (numerator obj) (denominator obj)) bound))
          ((number? obj)
           (modulo (+ (hash (real-part obj)) (* 3 (hash (imag-part obj))))
                   bound))
          ((char? obj) (modulo (char->integer obj) bound))
          ((vector? obj) (vector-hash obj bound))
          ((pair? obj) (modulo (+ (hash (car obj)) (* 3 (hash (cdr obj))))
                               bound))
          ((null? obj) 0)
          ((not obj) 0)
          ((procedure? obj) (error "hash: procedures cannot be hashed" obj))
          (else 1))))

(define hash-by-identity hash)

(define (vector-hash v bound)
  (let ((hashvalue 571)
        (len (vector-length v)))
    (do ((index 0 (+ index 1)))
      ((>= index len) (modulo hashvalue bound))
      (set! hashvalue (modulo (+ (* 257 hashvalue) (hash (vector-ref v index)))
                              *default-bound*)))))

(define %make-hash-node cons)
(define %hash-node-set-value! set-cdr!)
(define %hash-node-key car)
(define %hash-node-value cdr)

(define-record-type <srfi-hash-table>
  (%make-hash-table size hash compare associate entries)
  hash-table?
  (size hash-table-size hash-table-set-size!)
  (hash hash-table-hash-function)
  (compare hash-table-equivalence-function)
  (associate hash-table-association-function)
  (entries hash-table-entries hash-table-set-entries!))

(define *default-table-size* 64)

(define (appropriate-hash-function-for comparison)
  (or (and (eq? comparison eq?) hash-by-identity)
      (and (eq? comparison string=?) string-hash)
      (and (eq? comparison string-ci=?) string-ci-hash)
      hash))

(define (make-hash-table . args)
  (let* ((comparison (if (null? args) equal? (car args)))
         (hash
          (if (or (null? args) (null? (cdr args)))
                  (appropriate-hash-function-for comparison) (cadr args)))
         (size
          (if (or (null? args) (null? (cdr args)) (null? (cddr args)))
              *default-table-size* (caddr args)))
         (association
          (or (and (eq? comparison eq?) assq)
              (and (eq? comparison eqv?) assv)
              (and (eq? comparison equal?) assoc)
              (letrec
               ((associate
                 (lambda (val alist)
                   (cond ((null? alist) #f)
                         ((comparison val (caar alist)) (car alist))
                         (else (associate val (cdr alist)))))))
               associate))))
    (%make-hash-table 0 hash comparison association (make-vector size '()))))

(define (make-hash-table-maker comp hash)
  (lambda args (apply make-hash-table (cons comp (cons hash args)))))
(define make-symbol-hash-table
  (make-hash-table-maker eq? symbol-hash))
(define make-string-hash-table
  (make-hash-table-maker string=? string-hash))
(define make-string-ci-hash-table
  (make-hash-table-maker string-ci=? string-ci-hash))
(define make-integer-hash-table
  (make-hash-table-maker = modulo))

(define (%hash-table-hash hash-table key)
  ((hash-table-hash-function hash-table)
   key (vector-length (hash-table-entries hash-table))))

(define (%hash-table-find entries associate hash key)
  (associate key (vector-ref entries hash)))

(define (%hash-table-add! entries hash key value)
  (vector-set! entries hash
                       (cons (%make-hash-node key value)
                             (vector-ref entries hash))))

(define (%hash-table-delete! entries compare hash key)
  (let ((entrylist (vector-ref entries hash)))
    (cond ((null? entrylist) #f)
          ((compare key (caar entrylist))
           (vector-set! entries hash (cdr entrylist)) #t)
          (else
           (let loop ((current (cdr entrylist)) (previous entrylist))
             (cond ((null? current) #f)
                   ((compare key (caar current))
                    (set-cdr! previous (cdr current)) #t)
                   (else (loop (cdr current) current))))))))

(define (%hash-table-walk proc entries)
  (do ((index (- (vector-length entries) 1) (- index 1)))
    ((< index 0)) (for-each proc (vector-ref entries index))))

(define (%hash-table-maybe-resize! hash-table)
  (let* ((old-entries (hash-table-entries hash-table))
         (hash-length (vector-length old-entries)))
    (if (> (hash-table-size hash-table) hash-length)
        (let* ((new-length (* 2 hash-length))
               (new-entries (make-vector new-length '()))
               (hash (hash-table-hash-function hash-table)))
          (%hash-table-walk
           (lambda (node)
             (%hash-table-add! new-entries
                               (hash (%hash-node-key node) new-length)
                               (%hash-node-key node) (%hash-node-value node)))
           old-entries)
          (hash-table-set-entries! hash-table new-entries)))))

(define (hash-table-ref hash-table key . maybe-default)
  (cond ((%hash-table-find (hash-table-entries hash-table)
                           (hash-table-association-function hash-table)
                           (%hash-table-hash hash-table key) key)
         => %hash-node-value)
        ((null? maybe-default)
         (error "hash-table-ref: no value associated with" key))
        (else ((car maybe-default)))))

(define (hash-table-ref/default hash-table key default)
  (hash-table-ref hash-table key (lambda () default)))

(define (hash-table-set! hash-table key value)
  (let ((hash (%hash-table-hash hash-table key))
        (entries (hash-table-entries hash-table)))
    (cond ((%hash-table-find entries
                             (hash-table-association-function hash-table)
                             hash key)
           => (lambda (node) (%hash-node-set-value! node value)))
          (else (%hash-table-add! entries hash key value)
                (hash-table-set-size! hash-table
                                      (+ 1 (hash-table-size hash-table)))
                (%hash-table-maybe-resize! hash-table)))))

(define (hash-table-update! hash-table key function . maybe-default)
  (let ((hash (%hash-table-hash hash-table key))
        (entries (hash-table-entries hash-table)))
    (cond ((%hash-table-find entries
                             (hash-table-association-function hash-table)
                             hash key)
           => (lambda (node)
                (%hash-node-set-value!
                 node (function (%hash-node-value node)))))
          ((null? maybe-default)
           (error "hash-table-update!: no value exists for key" key))
          (else (%hash-table-add! entries hash key
                                  (function ((car maybe-default))))
                (hash-table-set-size! hash-table
                                      (+ 1 (hash-table-size hash-table)))
                (%hash-table-maybe-resize! hash-table)))))

(define (hash-table-update!/default hash-table key function default)
  (hash-table-update! hash-table key function (lambda () default)))

(define (hash-table-delete! hash-table key)
  (if (%hash-table-delete! (hash-table-entries hash-table)
                           (hash-table-equivalence-function hash-table)
                           (%hash-table-hash hash-table key) key)
      (hash-table-set-size! hash-table (- (hash-table-size hash-table) 1))))

(define (hash-table-exists? hash-table key)
  (and (%hash-table-find (hash-table-entries hash-table)
                         (hash-table-association-function hash-table)
                         (%hash-table-hash hash-table key) key) #t))

(define (hash-table-walk hash-table proc)
  (%hash-table-walk
   (lambda (node) (proc (%hash-node-key node) (%hash-node-value node)))
   (hash-table-entries hash-table)))

(define (hash-table-fold hash-table f acc)
  (hash-table-walk hash-table 
                   (lambda (key value) (set! acc (f key value acc))))
  acc)

(define (alist->hash-table alist . args)
  (let* ((comparison (if (null? args) equal? (car args)))
         (hash
          (if (or (null? args) (null? (cdr args)))
              (appropriate-hash-function-for comparison) (cadr args)))
         (size
          (if (or (null? args) (null? (cdr args)) (null? (cddr args)))
              (max *default-table-size* (* 2 (length alist))) (caddr args)))
         (hash-table (make-hash-table comparison hash size)))
    (for-each
      (lambda (elem)
        (hash-table-update!/default
           hash-table (car elem) (lambda (x) x) (cdr elem)))
      alist)
    hash-table))

(define (hash-table->alist hash-table)
  (hash-table-fold hash-table
                   (lambda (key val acc) (cons (cons key val) acc)) '()))

(define (hash-table-copy hash-table)
  (let ((new (make-hash-table (hash-table-equivalence-function hash-table)
                              (hash-table-hash-function hash-table)
                              (max *default-table-size*
                                   (* 2 (hash-table-size hash-table))))))
    (hash-table-walk hash-table
                     (lambda (key value) (hash-table-set! new key value)))
    new))

(define (hash-table-merge! hash-table1 hash-table2)
  (hash-table-walk
    hash-table2
    (lambda (key value) (hash-table-set! hash-table1 key value)))
  hash-table1)

(define (hash-table-keys hash-table)
  (hash-table-fold hash-table (lambda (key val acc) (cons key acc)) '()))

(define (hash-table-values hash-table)
  (hash-table-fold hash-table (lambda (key val acc) (cons val acc)) '()))

; eof