;;; A basic XMPP library which should conform to RFCs 3920 and 3921
;;;
;;; Copyright (C) 2009 FoAM vzw. 
;;;
;;;  This package is free software: you can redistribute it and/or
;;;  modify it under the terms of the GNU Lesser General Public
;;;  License as published by the Free Software Foundation, either
;;;  version 3 of the License, or (at your option) any later version.
;;;
;;;  This program is distributed in the hope that it will be useful,
;;;  but WITHOUT ANY WARRANTY; without even the implied warranty of
;;;  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
;;;  Lesser General Public License for more details.
;;;
;;;  You can find a copy of the GNU Lesser General Public License at
;;;  http://www.gnu.org/licenses/lgpl-3.0.html.
;;;
;;; Authors 
;;;
;;;  nik gaffney <nik@fo.am>
;;;
;;; Requirements
;;;
;;;  PLT for now. TLS requires a version of PLT > 4.1.5.3
;;;
;;; Commentary
;;;
;;;  Still a long way from implementing even a minimal subset of XMPP
;;; 
;;;  features implemented
;;;   - plaintext sessions on port 5222
;;;   - "old sytle" ssl sessions on port 5223
;;;   - authenticate using an existing account
;;;   - send messages (rfc 3921 sec.4)
;;;   - send presence (rfc 3921 sec.5)
;;;   - parse (some) xml reponses from server
;;;   - handlers for responses
;;;
;;;  features to implement
;;;   - account creation
;;;   - managing subscriptions (rfc 3921 sec.6)
;;;   - rosters (rfc 3921 sec.7)
;;;   - plaintext/tls/sasl negotiation (rfc 3920 sec.5 & 6) 
;;;   - encrypted connections using tls on port 5222
;;;   - correct namespaces in sxml
;;;   - message types
;;;   - maintain session ids
;;;   - maintain threads
;;;   - error handling
;;;   - events
;;;   - [...]
;;;   - rfc 3920 
;;;   - rfc 3921
;;;
;;;  bugs and/or improvements
;;;   - read-async & repsonse-handler
;;;   - ssax:xml->sxml or lazy:xml->sxml
;;;   - default handlers
;;;   - chatbot exmples
;;;

(module xmpp scheme
  
  (provide (all-defined-out)
           ;open-connection
           ;open-ssl-connection
           ;with-xmpp-session
           )
  
  (require (planet lizorkin/sxml:2:1/sxml))
  (require (planet lizorkin/ssax:2:0/ssax))
  (require mzlib/os)
  (require mzlib/defmacro)
  (require scheme/tcp)
  (require openssl)
  (require srfi/13)
  
  ;;;;;;;;;;; ; ;;;;  ;   ;;; ;    ; ;;     ;
  ;;
  ;; networking
  ;;
  ;;;;;; ;;  ;;  ;  ; ;   ;
  
  (define port 5222)
  (define ssl-port 5223)
  
  (define (open-connection machine port handler)
    (let-values (((in out)
                  (tcp-connect machine port))) 
      (handler in out)
      (close-output-port out)
      (close-input-port in)))
  
  (define (open-ssl-connection machine port handler)
    (let-values (((in out)
                  (ssl-connect machine port 'tls)))
      (handler in out)
      (close-output-port out)
      (close-input-port in)))
  
  (define (read-async in)
    (bytes->string/utf-8 (list->bytes (read-async-bytes in))))
  
  (define (read-async-bytes in)
    (let ((bstr '()))
      (when (sync/timeout 0 in)
        (set! bstr (cons (read-byte in) (read-async-bytes in)))) bstr))
  
  (define ssxml srl:sxml->xml-noindent) 
  
  ;;;;;; ; ; ;      ;   ;; ;;;;;; ;
  ;;
  ;; XMPP stanzas
  ;;
  ;;;;;;;;;; ;;;  ;  ;;   ;  ;
  
  ;; intialization
  (define (xmpp-stream host) 
    (string-append "<?xml version='1.0'?><stream:stream xmlns:stream='http://etherx.jabber.org/streams' to='" host "' xmlns='jabber:client'>"))
  
  ;; authentication
  (define (xmpp-auth username password resource)
    (ssxml `(iq (@ (type "set") (id "auth")) 
                (query (@ (xmlns "jabber:iq:auth")) 
                       (username ,username) 
                       (password ,password)
                       (resource ,resource)))))
  
  (define (xmpp-session host)
    (ssxml `(iq (@ (to ,host) (type "set") (id "session")) 
                (session (@ (xmlns "urn:ietf:params:xml:ns:xmpp-session")))))) 
  
  (define (starttls) "<starttls xmlns='urn:ietf:params:xml:ns:xmpp-tls'/>")
  
  ;; messages
  (define (message to body)
    (ssxml `(message (@ (to ,to)) (body ,body))))
  
  ;; presence
  (define (presence #:from (from "") 
                    #:to (to "") 
                    #:type (type "") 
                    #:show (show "") 
                    #:status (status ""))
    (cond ((not (string=? status ""))
           (ssxml `(presence (@ (type "probe")) (status ,status))))
          ((string=? type "") "<presence/>")
          (else (ssxml `(presence (@ (type ,type)))))))
  
  
  ;; curried stanza disection (sxml stanza -> string)
  (define ((sxpath-element xpath) stanza) 
    (let ((node ((sxpath xpath) stanza)))
      (if (empty? node) "" (car node))))
  
  ;; message 
  (define message-from (sxpath-element "message/@from/text()"))
  (define message-to (sxpath-element "message/@to/text()"))
  (define message-id (sxpath-element "message/@id/text()"))
  (define message-type (sxpath-element "message/@type/text()"))
  (define message-body (sxpath-element "message/body/text()"))
  (define message-subject (sxpath-element "message/subject/text()"))
  
  ;; info/query
  (define iq-type (sxpath-element "iq/@type/text()"))
  (define iq-id (sxpath-element "iq/@id/text()"))
  (define iq-error-type (sxpath-element "iq/error/@type/text()"))
  (define iq-error-text (sxpath-element "iq/error/text()"))
  (define iq-error (sxpath-element "iq/error"))
  
  ;; presence
  (define presence-show (sxpath-element "presence/show/text()"))
  (define presence-from (sxpath-element "presence/@from/text()"))
  (define presence-status (sxpath-element "presence/status/text()"))
  
  
  ;;;;;;;;; ; ;; ; ; ;;  ;;    ;  ;
  ;;
  ;; parsing & message/iq/error handlers
  ;;  - minimal parsing
  ;;  - handlers match on a tag (eg. 'message)
  ;;  - handlers are called with a single relevant xmpp stanza 
  ;;
  ;;;;;; ;;  ; ; ;;  ;
  
  (define xmpp-handlers (make-hash)) ;; a hash of tags and functions (possibly extend to using sxpaths)
  
  (define (set-xmpp-handler type fcn)
    (dict-set! xmpp-handlers type fcn))
  
  (define (run-xmpp-handler type sz)
    (let ((fcn (dict-ref xmpp-handlers type #f))) 
      (when fcn (begin
                  (display (format "attempting to run handler ~a.~%" fcn))
                  (fcn sz)))))
  
  ;; no real parsing yet. dispatches any received xml stanzas as sxml
  
  (define (parse-xmpp-response str)
    (when (> (string-length str) 0)
      (let ((sz (ssax:xml->sxml (open-input-string (clean str)) '())))
        ;;(let ((sz (lazy:xml->sxml (open-input-string str) '())))
        (cond
          ((equal? '(null) (cadr sz)) 
           (newline))
          ((equal? 'message (caadr sz))
           (run-xmpp-handler 'message sz))
          ((equal? 'iq (caadr sz)) 
           (run-xmpp-handler 'iq sz))
          ((equal? 'presence (caadr sz)) 
           (run-xmpp-handler 'presence sz))
          (else (run-xmpp-handler 'unknown sz))))))
  
  ;; example handlers to print stanzas or their contents
  (define (print-message sz)
    (display (format "a ~a message from ~a which says '~a.'~%" (message-type sz) (message-from sz) (message-body sz))))
  
  (define (print-iq sz)
    (display (format "an iq response of type '~a' with id '~a.'~%" (iq-type sz) (iq-id sz))))
  
  (define (print-presence sz)
    (display (format " p-r-e-s-e-n-e-c--> ~a is ~a" (presence-from sz) (presence-status))))
  
  (define (print-stanza sz)
    (display (format "? ?? -> ~%~a~%" sz))) 
  
  ;; QND hack to filter out anything not a message, iq or presence
  (define (clean str)
    (let ((test (substring str 0 3)))
      (cond ((string-ci=? test "<me") str)
            ((string-ci=? test "<iq") str)
            ((string-ci=? test "<pr") str)
            (else "<null/>"))))
  
  
  ;; response handler
  (define (xmpp-response-handler in)
    (thread (lambda () 
              (let loop () 
                (parse-xmpp-response (read-async in))
                (sleep 0.1) ;; slight delay to avoid a tight loop
                (loop)))))
  
  ;; jid splicing (assuming the jid is in the format user@host/resource)
  (define (jid-user jid)
    (string-take jid (string-index jid #\@)))
  
  (define (jid-host jid)
    (let* ((s (string-take-right jid (- (string-length jid) (string-index jid #\@) 1)))
           (v (string-index s #\/)))
      (if v (string-take s v) s )))
  
  (define (jid-resource jid)
    (let ((r (jid-resource-0 jid)))
      (if (void? r) (gethostname) r)))
  
  (define (jid-resource-0 jid)
    (let ((v (string-index jid #\/)))
      (when v (string-take-right jid (- (string-length jid) v 1)))))    

  
  ;;;;  ;; ; ; ;; ;;   ;;;; ;
  ;;
  ;; interfaces
  ;;
  ;;;;; ;; ;;;;   ;   ;;  ;
  
  (defmacro with-xmpp-session (jid pass . body)
    `(let ((host (jid-host ,jid))
           (user (jid-user ,jid))
           (resource (jid-resource ,jid)))
       (let-values (((in out)
                     (ssl-connect host ssl-port 'tls)))
         ;;(tcp-connect host port)))
         (define (send str) (fprintf out "~A~%" str) (flush-output out))
         (file-stream-buffer-mode out 'line)
         (xmpp-response-handler in) 
         (send (xmpp-stream host))
         (send (xmpp-session host))
         ;(send starttls)
         (send (xmpp-auth user ,pass resource))
         (send (presence))
         (send (presence #:status "Available"))
         ,@body
         (close-output-port out)
         (close-input-port in))))
  
  
  ) ;; end module