tvl-depot/users/sterni/mblog/note.lisp
sterni 8e156e6b86 feat(sterni/mblog): convert apple note mime msgs to html
For now mblog only contains the mnote-html executable which takes a mime
message from a maildir and prints the equivalent HTML fragment to
stdout. It is intended to work with the mblaze(7) utilities,
i. e. mnote-html resolves all `object` tags to proper `img` inclusions
with the correct filename, so mshow(1)'s -x version can supply the
needed image files. A note created using Apple's Notes app (tested with
the iOS version) can be converted in a viewable HTML file like this:

    $ mnote-html path/to/msg > fragment.html
    $ mshow -x path/to/msg
    $ cat <(echo "<!DOCTYPE html>") fragment.html > document.html
    $ xdg-open document.html

Note that only the limited feature set of Apple Notes when using the
IMAP backend is supported. The iCloud-based one has more (quite neat)
features, but its notes can only accessed via an internal API as far as
I know.

This CLI is a bit impractical due to the big startup overhead of loading
the lisp image. mblog should be become a fully fletched static site
generator in the future, but this is a good starting point and providing
the mnote-html tool is certainly useful.

Change-Id: Iee6d1558e939b932da1e70ca2d2ae75638d855df
Reviewed-on: https://cl.tvl.fyi/c/depot/+/3271
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
2021-09-12 21:39:49 +00:00

60 lines
2.5 KiB
Common Lisp

(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")))))