;; Copyright 2020-2021
;; Kaz Kylheku <kaz@kylheku.com>
;; Vancouver, Canada
;; All rights reserved.
;;
;; Redistribution and use in source and binary forms, with or without
;; modification, are permitted provided that the following conditions are met:
;;
;; 1. Redistributions of source code must retain the above copyright notice, this
;;    list of conditions and the following disclaimer.
;;
;; 2. Redistributions in binary form must reproduce the above copyright notice,
;;    this list of conditions and the following disclaimer in the documentation
;;    and/or other materials provided with the distribution.
;;
;; THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
;; ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
;; WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
;; DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
;; FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
;; DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
;; SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
;; CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
;; OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
;; OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

(defun sys:vars-check (form vars)
  (unless (listp vars)
    (compile-error form "~s is expected to be variable binding syntax" vars))
  (whenlet ((bad (find-if [notf consp] vars)))
    (compile-error form "~s isn't a var-initform pair" bad)))

(defun sys:bindable-check (form syms)
  (whenlet ((bad (find-if [notf bindable] syms)))
    (compile-error form "~s isn't a bindable symbol" bad)))

(defun sys:expand-each-prod (form vars body)
  (sys:vars-check form vars)
  (let ((syms [mapcar car vars])
        (inits [mapcar cadr vars]))
    (sys:bindable-check form syms)
    (let ((fun (caseq (car form)
                 (each-prod 'maprodo)
                 (collect-each-prod 'maprod)
                 (append-each-prod 'maprend))))
      ^(,fun (lambda (,*syms) ,*body) ,*inits))))

(defun sys:expand-each-prod* (form vars body)
  (sys:vars-check form vars)
  (let* ((each-prod-op (caseq (car form)
                         (each-prod* 'each-prod)
                         (collect-each-prod* 'collect-each-prod)
                         (append-each-prod* 'append-each-prod)))
         (syms [mapcar car vars])
         (inits [mapcar cadr vars]))
    ^(let* ,vars
       (,each-prod-op ,(zip syms syms) ,*body))))

(defmacro each-prod (:form f vars . body)
  (sys:expand-each-prod f vars body))

(defmacro collect-each-prod (:form f vars . body)
  (sys:expand-each-prod f vars body))

(defmacro append-each-prod (:form f vars . body)
  (sys:expand-each-prod f vars body))

(defmacro each-prod* (:form f vars . body)
  (sys:expand-each-prod* f vars body))

(defmacro collect-each-prod* (:form f vars . body)
  (sys:expand-each-prod* f vars body))

(defmacro append-each-prod* (:form f vars . body)
  (sys:expand-each-prod* f vars body))