;; request body parser for Schematra
;; Copyright 2025 Rolando Abarca
;;
;; 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.
;;
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;; contributors may be used to endorse or promote products derived
;; from this software without specific prior written permission.
;;
;; 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
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;; (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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;; HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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;; ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
;; OF THE POSSIBILITY OF SUCH DAMAGE.

(module
 schematra.body-parser
 (body-parser-middleware)

 (import scheme)
 (import
  chicken.base
  chicken.string
  intarweb
  uri-common
  spiffy ;; current-request
  schematra)

 (define (parse-form-data body-string)
   (let loop ((pairs (string-split body-string "&")) (acc '()))
     (if (null? pairs)
         (reverse acc)
         (let ((parts (string-split (car pairs) "=")))
           (loop (cdr pairs)
                 (if (= (length parts) 2)
                     (cons (cons (string->symbol (uri-decode-string (car parts)))
                                 (uri-decode-string (cadr parts)))
                           acc)
                     acc))))))

 ;; Buffers the raw body into (current-raw-body) so it remains accessible
 ;; for signature verification after parsing. For application/x-www-form-urlencoded
 ;; bodies, also parses params into (current-params) with symbol keys.
 (define (body-parser-middleware)
   (lambda (next)
     (let* ((request (current-request))
	    (headers (request-headers request)))
       (when (request-has-message-body? request)
         (let ((raw (request-body-string request)))
           (current-raw-body raw)
           (when (eq? 'application/x-www-form-urlencoded
                      (header-value 'content-type headers))
             (current-params (append (parse-form-data raw) (current-params))))))
       (next))))
 )