tvl-depot/users/sterni/mblog/note.lisp

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(in-package :mblog)
(declaim (optimize (safety 3)))
;;; util
(defun html-escape-stream (in out)
"Escape characters read from stream IN and write them to
stream OUT escaped using WHO:ESCAPE-CHAR-MINIMAL."
(loop for char = (read-char in nil nil)
while char
do (write-string (who:escape-char-minimal char) out)))
(defun cid-header-value (cid)
"Takes a Content-ID as present in Apple Notes' <object> tags and properly
surrounds them with angle brackets for a MIME header"
(concatenate 'string "<" cid ">"))
;;; main implementation
;; TODO(sterni): make this a “parser” instead of a predicate
(defun apple-note-p (msg)
"Checks X-Uniform-Type-Identifier of a MIME:MIME-MESSAGE
to determine if a given mime message is an Apple Note."
(when-let (uniform-id (assoc "X-Uniform-Type-Identifier"
(mime:mime-message-headers msg)
:test #'string=))
(string= (cdr uniform-id) "com.apple.mail-note")))
(defun apple-note-html-fragment (msg out)
"Takes a MIME:MIME-MESSAGE and writes its text content as HTML to
the OUT stream. The <object> tags are resolved to <img> which
refer to the respective attachment's filename as a relative path,
but extraction of the attachments must be done separately. The
surrounding <html> and <body> tags are stripped and <head>
discarded completely, so only a fragment which can be included
in custom templates remains."
(let ((text (find-mime-text-part msg)))
(cond
;; Sanity checking of the note
((not (apple-note-p msg))
(error "Unsupported or missing X-Uniform-Type-Identifier"))
((not text) (error "Malformed Apple Note: no text part"))
;; notemap creates text/plain notes we need to handle properly.
;; Additionally we *could* check X-Mailer which notemap sets
((string= (mime:mime-subtype text) "plain")
(html-escape-stream (mime:mime-body-stream text :binary nil) out))
;; Notes.app creates text/html parts
((string= (mime:mime-subtype text) "html")
(closure-html:parse
(mime:mime-body-stream text)
(make-instance
'apple-note-transformer
:cid-lookup
(lambda (cid)
(when-let* ((part (mime:find-mime-part-by-id msg (cid-header-value cid)))
(file (mime:mime-part-file-name part)))
file))
:next-handler
(closure-html:make-character-stream-sink out))))
(t (error "Malformed Apple Note: unknown mime type")))))