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Diffstat (limited to 'web/tazblog_lisp/store.lisp')
-rw-r--r-- | web/tazblog_lisp/store.lisp | 79 |
1 files changed, 79 insertions, 0 deletions
diff --git a/web/tazblog_lisp/store.lisp b/web/tazblog_lisp/store.lisp new file mode 100644 index 000000000000..01935a68a023 --- /dev/null +++ b/web/tazblog_lisp/store.lisp @@ -0,0 +1,79 @@ +(defpackage #:tazblog/store + (:documentation + "This module implements fetching of individual blog entries from DNS. + Yes, you read that correctly. + + Each blog post is stored as a set of records in a designated DNS + zone. For the production blog, this zone is `blog.tazj.in.`. + + A top-level record at `_posts` contains a list of all published + post IDs. + + For each of these post IDs, there is a record at `_meta.$postID` + that contains the title and number of post chunks. + + For each post chunk, there is a record at `_$chunkID.$postID` that + contains a base64-encoded post fragment. + + This module implements logic for assembling a post out of these + fragments and caching it based on the TTL of its `_meta` record.") + + (:use #:cl #:dns #:iterate) + (:import-from #:cl-base64 #:base64-string-to-string)) +(in-package :tazblog/store) + +;; TODO: +;; +;; - implement DNS caching + +(defvar *tazblog-zone* ".blog.tazj.in." + "DNS zone in which blog posts are persisted.") + +(deftype entry-id () 'string) + +(defun list-entries (&key (offset 0) (count 4) (zone *tazblog-zone*)) + "Retrieve COUNT entry IDs from ZONE at OFFSET." + (let ((answers (lookup-txt (concatenate 'string "_posts" zone)))) + (map 'vector #'dns-rr-rdata (subseq answers offset (+ offset count))))) + +(defun get-entry-meta (entry-id zone) + (let* ((name (concatenate 'string "_meta." entry-id zone)) + (answer (lookup-txt name)) + (encoded (dns-rr-rdata (alexandria:first-elt answer))) + (meta-json (base64-string-to-string encoded))) + (json:decode-json-from-string meta-json))) + +(defun base64-add-padding (string) + "Adds padding to the base64-encoded STRING if required." + (let ((rem (- 4 (mod (length string) 4)))) + (if (= 0 rem) string + (format nil "~A~v@{~A~:*~}" string rem "=")))) + +(defun collect-entry-fragments (entry-id count zone) + (let* ((fragments + (iter (for i from 0 below count) + (for name = (format nil "_~D.~A~A" i entry-id zone)) + (collect (alexandria:first-elt (lookup-txt name))))) + (decoded (map 'list (lambda (f) + (base64-string-to-string + (base64-add-padding (dns-rr-rdata f)))) + fragments))) + (apply #'concatenate 'string decoded))) + +(defstruct entry + (id "" :type string) + (title "" :type string) + (content "" :type string) + (date "" :type string)) + +(defun get-entry (entry-id &optional (zone *tazblog-zone*)) + "Retrieve the entry at ENTRY-ID from ZONE." + (let* ((meta (get-entry-meta entry-id zone)) + (count (cdr (assoc :c meta))) + (title (cdr (assoc :t meta))) + (date (cdr (assoc :d meta))) + (content (collect-entry-fragments entry-id count zone))) + (make-entry :id entry-id + :date date + :title title + :content content))) |