From 15ea184fe308cbbc646d6b7d96f6333350fcd3a8 Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson2@worcester.edu>
Date: Thu, 24 Mar 2016 23:35:35 -0400
Subject: Add client module.

---
 web/socket/client.scm | 143 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 143 insertions(+)
 create mode 100644 web/socket/client.scm

diff --git a/web/socket/client.scm b/web/socket/client.scm
new file mode 100644
index 0000000..d144890
--- /dev/null
+++ b/web/socket/client.scm
@@ -0,0 +1,143 @@
+;;; guile-websocket --- WebSocket client/server
+;;; Copyright © 2016 David Thompson <davet@gnu.org>
+;;;
+;;; This file is part of guile-websocket.
+;;;
+;;; Guile-websocket 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.
+;;;
+;;; Guile-websocket 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 should have received a copy of the GNU Lesser General Public
+;;; License along with guile-websocket.  If not, see
+;;; <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+;;
+;; WebSocket client.
+;;
+;;; Code:
+
+(define-module (web socket client)
+  #:use-module (ice-9 match)
+  #:use-module (rnrs bytevectors)
+  #:use-module (srfi srfi-9)
+  #:use-module (web request)
+  #:use-module (web response)
+  #:use-module (web uri)
+  #:use-module (web socket base64)
+  #:use-module (web socket frame)
+  #:use-module (web socket sha-1)
+  #:export (make-websocket
+            websocket?
+            websocket-uri
+            close-websocket
+            websocket-send
+            websocket-receive))
+
+;; See Section 3 - WebSocket URIs
+(define (encrypted-websocket-scheme? uri)
+  "Return #t if the scheme for URI is 'wss', the secure WebSocket
+scheme."
+  (eq? (uri-scheme uri) 'wss))
+
+(define (unencrypted-websocket-scheme? uri)
+  "Return #t if the scheme for URI is 'ws', the insecure WebSocket
+scheme."
+  (eq? (uri-scheme uri) 'ws))
+
+(define (websocket-uri? uri)
+  "Return #t if URI is a valid WebSocket URI."
+  (and (or (encrypted-websocket-scheme? uri)
+           (unencrypted-websocket-scheme? uri))
+       (not (uri-fragment uri))))
+
+(define (make-client-socket uri)
+  "Connect a socket to the remote resource described by URI."
+  (let* ((port (uri-port uri))
+         (info (car (getaddrinfo (uri-host uri)
+                                 (if port
+                                     (number->string port)
+                                     (symbol->string (uri-scheme uri)))
+                                 (if port
+                                     AI_NUMERICSERV
+                                     0))))
+         (s (with-fluids ((%default-port-encoding #f))
+              (socket (addrinfo:fam info) SOCK_STREAM IPPROTO_IP))))
+    ;; TODO: Configure I/O buffering?
+    (connect s (addrinfo:addr info))
+    s))
+
+;; TODO: Add 'state' field (connecting, open, closing, closed)
+(define-record-type <websocket>
+  (%make-websocket uri socket)
+  websocket?
+  (uri websocket-uri)
+  (socket websocket-socket))
+
+;; See Section 4.1 - Client Requirements
+(define (make-handshake-request uri)
+  "Create an HTTP request for initiating a WebSocket connect with the
+remote resource described by URI."
+  (let ((headers `((host . (,(uri-host uri) . #f))
+                   (upgrade . ("WebSocket"))
+                   (connection . (upgrade))
+                   ;; TODO: Generate a real key.
+                   (sec-websocket-key . "AQIDBAUGBwgJCgsMDQ4PEC==")
+                   (sec-websocket-version . "13"))))
+    (build-request uri #:method 'GET #:headers headers)))
+
+(define (handshake ws)
+  "Perform the WebSocket handshake for the client WS."
+  (write-request (make-handshake-request (websocket-uri ws))
+                 (websocket-socket ws))
+  (let* ((response (read-response (websocket-socket ws)))
+         (headers (response-headers response))
+         (upgrade (assoc-ref headers 'upgrade))
+         (connection (assoc-ref headers 'connection))
+         (accept (assoc-ref headers 'sec-websocket-accept)))
+    ;; Validate the handshake.
+    (unless (and (= (response-code response) 101)
+                 (string-ci=? (car upgrade) "websocket")
+                 (equal? connection '(upgrade))
+                 ;; TODO: authenticate accept key.
+                 )
+      (close-websocket ws)
+      (error "websocket handshake failed" (websocket-uri ws)))))
+
+(define (make-websocket uri-or-string)
+  "Create and establish a new WebSocket connection for the remote
+resource described by URI-OR-STRING."
+  (let ((uri (match uri-or-string
+               ((? uri? uri) uri)
+               ((? string? str) (string->uri str)))))
+    (if (websocket-uri? uri)
+        (let ((ws (%make-websocket uri (make-client-socket uri))))
+          (handshake ws)
+          ws)
+        (error "not a websocket uri" uri))))
+
+(define (close-websocket ws)
+  "Close the WebSocket connection for the client WS."
+  (close-port (websocket-socket ws)))
+
+(define (websocket-send ws data)
+  "Send DATA, a string or bytevector, to the server that WS is
+connected to."
+  ;; TODO: Generate maskng key.
+  ;; TODO: Send frames over some threshold in fragments.
+  (write-frame (make-text-frame data)
+               (websocket-socket ws)))
+
+(define (websocket-receive ws)
+  "Read a response from the server that WS is connected to."
+  ;; TODO: Handle fragmented frames and control frames.
+  (let ((frame (read-frame (websocket-socket ws))))
+    (if (binary-frame? frame)
+        (frame-data frame)
+        (text-frame->string frame))))
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