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;;;
;;; uri.scm - parse and construct URIs
;;;  
;;;   Copyright (c) 2000-2010  Shiro Kawai  <shiro@acm.org>
;;;   
;;;   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.
;;;  
;;;   3. Neither the name of the authors nor the names of its 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 COPYRIGHT
;;;   OWNER 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.
;;;  

;; Main reference:
;; RFC2396 Uniform Resource Identifiers (URI): Generic Syntax
;;  <ftp://ftp.isi.edu/in-notes/rfc2396.txt>

;; Historical:
;; RFC1738 Uniform Resource Locators
;;  <ftp://ftp.isi.edu/in-notes/rfc1738.txt>
;; RFC1808 Relative Uniform Resource Locators
;;  <ftp://ftp.isi.edu/in-notes/rfc1808.txt>
;; RFC2368 The mailto URL Scheme
;;  <ftp://ftp.isi.edu/in-notes/rfc2368.txt>

(define-module rfc.uri
  (use srfi-13)
  (use gauche.regexp)
  (use gauche.charconv)
  (export uri-scheme&specific uri-decompose-hierarchical
          uri-decompose-authority uri-parse
          uri-compose
          uri-decode uri-decode-string
          uri-encode uri-encode-string
          *rfc2396-unreserved-char-set*
          *rfc3986-unreserved-char-set*
          )
  )
(select-module rfc.uri)

;;==============================================================
;; Generic parser
;;

;; Splits URI scheme and the scheme specific part from given URI.
;; If URI doesn't follow the generic URI syntax, it is regarded
;; as a relative URI and #f is returned for the scheme.
;; The escaped characters of the scheme specific part is not unescaped;
;; their interpretation is dependent on the scheme.

(define (uri-scheme&specific uri)
  (cond [(#/^([A-Za-z][A-Za-z0-9+.-]*):/ uri)
         => (lambda (m) (values (string-downcase (m 1)) (m 'after)))]
        [else (values #f uri)]))

(define (uri-decompose-hierarchical specific)
  (cond
   [(and (string? specific)
         (#/^(?:\/\/([^\/?#]*))?([^?#]+)?(?:\?([^#]*))?(?:#(.*))?$/ specific))
    => (lambda (m) (values (m 1) (m 2) (m 3) (m 4)))]
   [else (values #f #f #f #f)]))

(define (uri-decompose-authority authority)
  (cond
   [(and (string? authority)
         (#/^(?:(.*?)@)?([^:]*)(?::(\d*))?$/ authority))
    => (lambda (m) (values (m 1) (m 2) (m 3)))]
   [else (values #f #f #f)]))

;; A common cliche (suggested by Kouhei Sutou)
;; Returns: scheme, user-info, host, port, path, query, fragment
(define (uri-parse uri)
  (define (filter-non-empty-string str)
    (and (string? str)
         (not (string-null? str))
         str))
  (receive (scheme specific)
      (uri-scheme&specific uri)
    (receive (authority path query fragment)
        (uri-decompose-hierarchical specific)
      (receive (user-info host port)
          (uri-decompose-authority authority)
        (values scheme
                user-info
                (filter-non-empty-string host)
                (and port (string->number port))
                (filter-non-empty-string path)
                query
                fragment)))))

;;==============================================================
;; Generic constructor
;;

(define (uri-compose :key (scheme #f) (userinfo #f) (host #f) (port #f)
                     (authority #f) (path  #f) (path* #f) (query #f)
                     (fragment #f) (specific #f))
  (with-output-to-string
    (lambda ()
      (when scheme (display scheme) (display ":"))
      (if specific
        (display specific)
        (begin
          (display "//")
          (if authority
            (begin (display authority))
            (begin
              (when userinfo (display userinfo) (display "@"))
              (when host     (display host))
              (when port     (display ":") (display port))))
          (if path*
            (begin
              (unless (string-prefix? "/" path*) (display "/"))
              (display path*))
            (begin
              (if path
                (begin (unless (string-prefix? "/" path) (display "/"))
                       (display path))
                (display "/"))
              (when query (display "?") (display query))
              (when fragment (display "#") (display fragment))))
          ))
      )))

;;==============================================================
;; Relative -> Absolute
;;


;;==============================================================
;; Encoding & decoding
;;
;;  NB. Which character to encode, and when to encode/decode depend on
;;  the semantics of specific URI scheme.
;;  These procedures provides basic building components.

(define (uri-decode :key (cgi-decode #f))
  (let loop ((c (read-char)))
    (cond [(eof-object? c)]
          [(char=? c #\%)
           (let1 c1 (read-char)
             (cond
              [(eof-object? c1) (write-char c)] ;; just be permissive
              [(digit->integer c1 16)
               => (lambda (i1)
                    (let1 c2 (read-char)
                      (cond [(eof-object? c2) (write-char c) (write-char c1)]
                            [(digit->integer c2 16)
                             => (lambda (i2)
                                  (write-byte (+ (* i1 16) i2))
                                  (loop (read-char)))]
                            [else (write-char c) (write-char c1) (loop c2)])))]
                   [else (write-char c) (loop c1)]))]
          [(char=? c #\+)
           (if cgi-decode (write-char #\space) (write-char #\+))
           (loop (read-char))]
          [else (write-char c) (loop (read-char))])))

(define (uri-decode-string string :key (encoding (gauche-character-encoding))
                           :allow-other-keys args)
  (define (wrap out)
    (wrap-with-output-conversion out (gauche-character-encoding)
                                 :from-code encoding))
  (call-with-string-io string
    (lambda (in out)
      (with-ports in (wrap out) (current-error-port)
        (lambda ()
          (apply uri-decode args)
          (close-output-port (current-output-port)))))))

;; Default set of characters that can be passed without escaping.
;; See 2.3 "Unreserved Characters" of RFC 2396.  It is slightly
;; revised in RFC3986.
(define-constant *rfc2396-unreserved-char-set* #[-_.!~*'()0-9A-Za-z])
(define-constant *rfc3986-unreserved-char-set* #[-_.~0-9A-Za-z])

;; NB: Converts byte by byte, instead of chars, to avoid complexity
;; from different character encodings (suggested by Fumitoshi UKAI).
;; 'noescape' char-set is only valid in ASCII range.  All bytes
;; larger than #x80 are encoded unconditionally.
(define (uri-encode :key ((:noescape echars) *rfc3986-unreserved-char-set*))
  (let loop ((b (read-byte)))
    (unless (eof-object? b)
      (if (and (< b #x80)
               (char-set-contains? echars (integer->char b)))
        (write-byte b) 
        (format #t "%~2,'0x" b))
      (loop (read-byte)))))

(define (uri-encode-string string :key (encoding (gauche-character-encoding))
                           :allow-other-keys args)
  (define (wrap in)
    (wrap-with-input-conversion in (gauche-character-encoding)
                                :to-code encoding))
  (call-with-string-io string
    (lambda (in out)
      (with-ports (wrap in) out (current-error-port)
        (cut apply uri-encode args)))))