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;;;; posterbot.lisp
(in-package #:posterbot)
(defclass posterbot (client auto-joiner) ())
(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)
"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)
"Checks if WORD is an HTTP URI pointing to an image resource. If it
is, downloads the image and posts it to the current room."
(let ((link (ppcre:scan-to-strings +image-link-regex+ word)))
(when link
(let* ((file-path (download-link link))
(file-name (filename-from-link link))
(mxc-uri
(upload *posterbot*
file-name
(alexandria:read-file-into-byte-vector file-path)
:content-type (make-mime-type word))))
(if mxc-uri
(send-image-message *posterbot* *room-id* file-name mxc-uri
:info (list :|mimetype| (make-mime-type word)))
(send-text-message *posterbot* *room-id* "I have failed you :("))))))
;; look for links to images, one word at a time, downloading and
;; posting any images found to the room at the current *ROOM-ID*
(defmethod handle-event :after ((*posterbot* posterbot) (event text-message-event))
(mapc #'handle-link-candiate (ppcre:split " " (msg-body event))))
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