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+;;; blog.el --- A simple org-mode & elnode blog software.
+;;; -*- lexical-binding: t; -*-
+
+(require 'dash)
+(require 'elnode)
+(require 'f)
+(require 'ht)
+
+;; Definition of customization options
+
+(defgroup elblog nil
+  "Configuration for the Emacs Lisp blog software"
+  :link '(url-link "https://github.com/tazjin/elblog"))
+
+(defcustom elblog-port 8010
+  "Port to run elblog's HTTP server on"
+  :group 'elblog
+  :type 'integer)
+
+(defcustom elblog-host "localhost"
+  "Host for elblog's HTTP server to listen on"
+  :group 'elblog
+  :type 'string)
+
+(defcustom elblog-title "Elblog"
+  "Title text for this elblog instance"
+  :group 'elblog
+  :type 'string)
+
+(defcustom elblog-article-directory nil
+  "Directory in which elblog articles are stored"
+  :group 'elblog
+  :type 'string)
+
+(defcustom elblog-additional-routes '()
+  "Additional Elnode routes to register in the Elblog instance"
+  :group 'elblog
+  :type '(alist :key-type regexp :value-type function))
+
+;; Declare user-configurable variables needed at runtime.
+
+(defvar elblog-articles (ht-create)
+  "A hash-table of blog articles. This is used for looking up articles from
+   URL fragments as well as for rendering the index.")
+
+;; HTML templating setup
+
+(defun template-preamble ()
+  "Templates the preamble snippet with the correct blog title."
+  (format (f-read-text "preamble.html") elblog-title))
+
+(defun configure-org-html-export ()
+  "Configure org-mode settings for elblog's HTML templating to work correctly."
+  (setq org-html-postamble t)
+  (setq org-html-doctype "html5")
+  (setq org-html-head-include-scripts nil)
+  (setq org-html-style-default (f-read-text "blog.css"))
+  (setq org-html-preamble-format `(("en" ,(template-preamble))))
+  (setq org-html-postamble-format `(("en" ,(f-read-text "postamble.html")))))
+
+;; Article fetching & rendering functions
+
+(defun render-org-buffer (input-buffer &optional force)
+  "Renders an org-mode buffer as HTML and returns the name of the output buffer."
+  (letrec ((output-buffer (concat (buffer-name input-buffer) "-rendered"))
+           ;; Don't re-render articles unless forced.
+           (must-render (or force
+                            (not (get-buffer output-buffer)))))
+    (if (and input-buffer must-render)
+        (with-current-buffer input-buffer
+          (org-export-to-buffer 'html output-buffer nil nil t)))
+    (if input-buffer output-buffer nil)))
+
+(defun get-buffer-string (buffer)
+  "Returns the contents of the specified buffer as a string."
+  (with-current-buffer (get-buffer buffer)
+    (buffer-string)))
+
+(defvar-local article-not-found
+  '(404 . "<html><body><p>Oh no, the article was not found.</p></body></html>"))
+
+(defvar-local text-html '("Content-Type" . "text/html"))
+
+(defun render-article (article)
+  "Renders an article, if it exists."
+  (letrec ((rendered (-some->>
+                      (ht-get elblog-articles article)
+                      (concat elblog-article-directory)
+                      (find-file)
+                      (render-org-buffer))))
+    (if rendered `(200 . ,(get-buffer-string rendered))
+      article-not-found)))
+
+(defun blog-post-handler (httpcon)
+  "This handler servers a blog post from the configured blog post directory."
+  (let ((response (render-article (elnode-http-mapping httpcon 1))))
+    (elnode-http-start httpcon  (car response) text-html)
+    (elnode-http-return httpcon (cdr response))))
+
+;; Web server implementation
+
+(defvar elblog-routes
+  '(("^.*//\\(.*\\)" . blog-post-handler))
+  "The default routes available in elblog. They can be extended by the user
+by setting the elblog-additional-routes customize option.")
+
+(defun elblog-handler (httpcon)
+  (elnode-hostpath-dispatcher
+   httpcon
+   (-concat elblog-additional-routes elblog-routes)))
+
+(defun start-elblog ()
+  (interactive)
+  (configure-org-html-export)
+  (elnode-start 'elblog-handler
+              :port elblog-port
+              :host elblog-host))
+
+(defun stop-elblog ()
+  (interactive)
+  (elnode-stop elblog-port))
+
+(provide 'elblog)