slightly better mimetypes for images

1 files changed, 11 insertions, 3 deletions

diff --git a/posterbot.lisp b/posterbot.lisp
index 0ff3160..d2d3531 100644
--- a/posterbot.lisp
+++ b/posterbot.lisp
@@ -4,25 +4,33 @@
 
 (defclass posterbot (client auto-joiner) ())
 
-(defvar *posterbot* nil "dynamic variable holding the bot so I dont have to pass it around")
+(defvar *posterbot* nil
+  "Dynamic variable holding the bot instance. Bound by HANDLE-EVENT.")
 
 (defparameter +image-link-regex+
   (ppcre:create-scanner "http.+\.(png|gif|jpeg|bmp|jpg)"
                         :case-insensitive-mode t))
 
 (defun download-link (link)
+  "Downloads the file at LINK to a temporary file. Returns the path to
+the downloaded file."
   (cl-fad:with-output-to-temporary-file (out :element-type '(unsigned-byte 8))
     (let ((buffer (make-array 4096 :element-type '(unsigned-byte 8)))
           (file-stream  (drakma:http-request link :want-stream t)))
       (loop :for bytes = (read-sequence buffer file-stream)
          :while (plusp bytes) :do (write-sequence buffer out)))))
 
-
 (defun filename-from-link (link)
+  "Extracts the filename of a link. I.e. everything after the last / character."
   (first (last (ppcre:split "/" link))))
 
 (defun make-mime-type (filename)
-  (format nil "image/~a" (pathname-type filename)))
+  "Given a string FILENAME, returns a string representing a sensible guess for a mimetype."
+  (format nil "image/~a"
+          (let ((type  (string-downcase (pathname-type filename))))
+            (cond ((member type '("jpg" "jpeg") :test #'equal) "jpeg")
+                  ((equal type "svg") "svg+xml")
+                  (t type)))))
 
 (defun handle-link-candiate (word)
   (let ((link (ppcre:scan-to-strings +image-link-regex+ word)))