;;; tekuti.el --- Tekuti interaction library         -*- lexical-binding: t; -*-

;; Copyright (C) 2021  Tom Willemse

;; Author: Tom Willemse <chelys@data>
;; Keywords: comm
;; Package-Requires: (org)
;; Version: 0.1.0

;; This program is free software; you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.

;; This program is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
;; along with this program.  If not, see <https://www.gnu.org/licenses/>.

;;; Commentary:

;; A simple module to help post things to your tekuti blog. You’ll want to
;; customize the ‘tekuti-host’ variable to point to your own blog. You should be
;; asked for your credentials, which should then be stored in ~/.authinfo.gpg.

;; Currently you should add these headers to your org document that you want to
;; send up:

;; #+TITLE: SOME TITLE
;; #+DATE: <2021-06-03 Thu 22:45>
;; #+TAGS: comma,separated
;; #+COMMENTS: on
;; #+COMMENTS_DATE:
;; #+STATUS: publish

;; The main entry point is ‘tekuti-send’. Call this from an org-mode buffer to
;; export the buffer to HTML and send it up to your blog.

;;; Code:

(require 'org)

(defvar tekuti-host "http://127.0.0.1:8080"
  "The host where tekuti is running.
This should be the base URL of your blog. Where adding ‘/admin’
will get you into the admin area of your blog. This shouldn't end
with a ‘/’.")

(defun tekuti--format-date (&optional date)
  "Format DATE into a date that tekuti understands."
  (format-time-string "%a, %d %b %Y %H:%M:%S %Z"
                      (unless (null date)
                        (date-to-time date))
                      t))

(defun tekuti--parse-data-keyword (pair)
  "Ensure that both the key and value in PAIR match what tekuti needs."
  (pcase pair
    (`("DATE" ,date)
     (list "DATE" (tekuti--format-date date)))
    (`("COMMENTS_DATE" ,date)
     (list "COMMENTS-CLOSED-DATE"
           (and (not (string-empty-p date))
                (tekuti--format-date date))))
    (`("STATUS" ,status)
     (let ((accepted-values '("publish" "draft" "private")))
       (if (member status accepted-values)
           pair
         (error "Unknown post status: %s; Accepted values are: %s"
                status accepted-values))))
    (`("COMMENTS" ,status)
     (if (string= status "on")
         pair
       (error "Unknown value for comments: %s; Can only be ‘on’ or not present."
              status)))
    (_ pair)))

(defun tekuti-build-data-from-org ()
  "Parse the current org buffer to collect the necessary metadata."
  (let ((defaults `(("TITLE")
                    ("DATE" ,(tekuti--format-date))
                    ("TAGS")
                    ("STATUS")
                    ("COMMENTS")
                    ("COMMENTS-CLOSED-DATE")
                    ("BODY")))
        (data (append
               (mapcar
                #'tekuti--parse-data-keyword
                (org-collect-keywords '("TITLE" "TAGS" "STATUS" "COMMENTS" "DATE" "COMMENTS_DATE")))
               (list
                (list "BODY"
                      (with-current-buffer (org-html-export-as-html nil nil nil t)
                        (buffer-substring-no-properties (point-min) (point-max))))))))
    (seq-remove
     (lambda (pair) (and (string= "COMMENTS" (car pair))
                         (null (cdr pair))))
     (mapcar (lambda (item)
               (let ((key (car item)))
                 `(,key ,@(or (alist-get key data nil nil #'string=)
                              (cdr item)))))
             defaults))))

(defun tekuti-form-encode-pair (key value)
  (concat (url-hexify-string key) "=" (url-hexify-string value)))

(defun tekuti-form-encode-data (data)
  (mapconcat
   (lambda (pair)
     (tekuti-form-encode-pair (downcase (car pair)) (cadr pair)))
   data
   "&"))

(defun tekuti--send-finished (status buffer args updatep)
  (pcase-exhaustive status
    (`(:redirect ,url . ,_)
     (save-excursion
       (with-current-buffer buffer
         (goto-char (point-min))
         (search-forward "\n\n")
         (backward-char)
         (let ((data (org-collect-keywords '("TITLE" "TAGS" "STATUS" "COMMENTS" "DATE" "COMMENTS_DATE"))))
           (mapc (lambda (item)
                   (let ((key (car item))
                         (value (cadr item)))
                     (when (and (not (string= key "BODY"))
                                (null (alist-get key data nil nil #'string=))
                                (not (null value)))
                       (insert "#+" key ": " value "\n"))))
                 args))
         (unless (tekuti--get-update-url)
           (insert "#+UPDATE_URL: "
                   (string-replace "/posts/"
                                   "/modify-post/"
                                   (car (url-path-and-query
                                         (url-generic-parse-url url))))
                   "\n"))))
     (message "%s post: %s" (if updatep "Updated" "Created new") url))
    (`(:error (error http ,code) . ,_)
     (message "Failed to %s post: %d" (if updatep "update" "create") code))))

(defun tekuti--get-update-url ()
  (save-excursion
    (goto-char (point-min))
    (car (map-elt (org-collect-keywords '("UPDATE_URL")) "UPDATE_URL"))))

;;;###autoload
(defun tekuti-send ()
  (interactive)
  (let* ((data (tekuti-build-data-from-org))
         (url-request-method "POST")
         (url-request-extra-headers
          `(("Content-Type" . "application/x-www-form-urlencoded")))
         (url-request-data (tekuti-form-encode-data data))
         (previous-update-url (tekuti--get-update-url))
         (updatep (not (null previous-update-url))))
    (url-retrieve (format "%s%s" (string-trim-right tekuti-host "/")
                          (or previous-update-url
                              "/admin/new-post"))
                  #'tekuti--send-finished
                  (list (current-buffer) data updatep))))

(provide 'tekuti)
;;; tekuti.el ends here