;;; mastodon-async.el --- Async streaming functions for mastodon.el -*- lexical-binding: t -*-

;; Copyright (C) 2017 Alex J. Griffith
;; Author: Alex J. Griffith <griffitaj@gmail.com>
;; Maintainer: Marty Hiatt <mousebot@disroot.org>
;; Package-Requires: ((emacs "27.1"))
;; Homepage: https://codeberg.org/martianh/mastodon.el

;; This file is not part of GNU Emacs.

;; This file is part of mastodon.el.

;; mastodon.el 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.

;; mastodon.el 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 mastodon.el.  If not, see <http://www.gnu.org/licenses/>.

;;; Commentary:

;; Rework sync code so it does not mess up the async-buffer

;;; Code:

(require 'mastodon-tl)
(require 'json)
(require 'url-http)

(defvar url-http-end-of-headers)

(autoload 'mastodon-auth--access-token "mastodon-auth")
(autoload 'mastodon-http--api "mastodon-http")
(autoload 'mastodon-http--get-json "mastodon-http")
(autoload 'mastodon-mode "mastodon")
(autoload 'mastodon-notifications--timeline "mastodon-notifications")
(autoload 'mastodon-tl--timeline "mastodon-tl")

(defgroup mastodon-async nil
  "An async module for mastodon streams."
  :prefix "mastodon-async-"
  :group 'external)

;;;###autoload
(define-minor-mode mastodon-async-mode
  "Async Mastodon."
  :lighter " MasA")

(defvar mastodon-instance-url)

(defvar mastodon-tl--enable-relative-timestamps)
(defvar mastodon-tl--display-media-p)
(defvar mastodon-tl--buffer-spec)

(defvar-local mastodon-async--queue "" ;;"*mastodon-async-queue*"
  "The intermediate queue buffer name.")

(defvar-local mastodon-async--buffer "" ;;"*mastodon-async-buffer*"
  "User facing output buffer name.")

(defvar-local mastodon-async--http-buffer "" ;;""
  "Buffer variable bound to http output.")

(defun mastodon-async--display-http ()
  "Display the async HTTP input buffer."
  (display-buffer mastodon-async--http-buffer))

(defun mastodon-async--display-buffer ()
  "Display the async user facing buffer."
  (interactive)
  (display-buffer mastodon-async--buffer))

(defun mastodon-async--display-queue ()
  "Display the async queue buffer."
  (display-buffer mastodon-async--queue))

(defun mastodon-async--stop-http ()
  "Stop the http processs and close the async and http buffer."
  (interactive)
  (let ((inhibit-read-only t))
    (stop-process (get-buffer-process mastodon-async--http-buffer))
    (delete-process (get-buffer-process mastodon-async--http-buffer))
    (kill-buffer mastodon-async--http-buffer)
    (setq mastodon-async--http-buffer "")
    (when (not (string= "" mastodon-async--queue)) ; error handle on kill async buffer
      (kill-buffer mastodon-async--queue))))

(defun mastodon-async--stream-notifications ()
  "Open a stream of user notifications."
  (interactive)
  (mastodon-async--mastodon
   "user"
   "home"
   "notifications"
   'mastodon-async--process-queue-string-notifications))

(defun mastodon-async--stream-home ()
  "Open a stream of the home timeline."
  (interactive)
  (mastodon-async--mastodon
   "user"
   "home"
   "home"
   'mastodon-async--process-queue-string))

(defun mastodon-async--stream-federated ()
  "Open a stream of Federated."
  (interactive)
  (mastodon-async--mastodon
   "public"
   "public"
   "federated"
   'mastodon-async--process-queue-string))

(defun mastodon-async--stream-local ()
  "Open a stream of Local."
  (interactive)
  ;; Need to add another layer of filtering for this to work
  ;; apparently it the local flag does not work
  (mastodon-async--mastodon
   "public"
   "public?local=true"
   "local"
   'mastodon-async--process-queue-local-string))

(defun mastodon-async--mastodon (endpoint timeline name filter)
  "Make sure that the previous async process has been closed.
Then start an async stream at ENDPOINT filtering toots
using FILTER.
TIMELINE is a specific target, such as federated or home.
NAME is the center portion of the buffer name for
*mastodon-async-buffer and *mastodon-async-queue."
  (ignore timeline) ;; TODO: figure out what this is meant to be used for
  (let ((buffer (mastodon-async--start-process
                 endpoint filter name)))
    (with-current-buffer buffer
      (mastodon-async--display-buffer)
      (goto-char (point-max))
      (goto-char 1))))

(defun mastodon-async--get (url callback)
  "An async GET request to URL with CALLBACK."
  (let ((url-request-method "GET")
        (url-request-extra-headers
         `(("Authorization" .
            ,(concat
              "Bearer "
              (mastodon-auth--access-token))))))
    (url-retrieve url callback)))

(defun mastodon-async--set-http-buffer (buffer http-buffer)
  "Initialize for BUFFER a local variable `mastodon-async--http-buffer'.
HTTP-BUFFER is the initializing value. Use this funcion if HTTP-BUFFER
is not known when `mastodon-async--setup-buffer' is called."
  (with-current-buffer (get-buffer-create buffer)
    (setq mastodon-async--http-buffer http-buffer)))

(defun mastodon-async--set-local-variables (buffer
                                            http-buffer
                                            buffer-name
                                            queue-name)
  "Set local variables for BUFFER, HTTP-BUFFER, BUFFER-NAME, and QUEUE-NAME."
  (with-current-buffer (get-buffer-create buffer)
    (let ((value mastodon-instance-url))
      (make-local-variable 'mastodon-instance-url)
      (setq-local mastodon-instance-url value))
    (setq mastodon-async--http-buffer http-buffer)
    (setq mastodon-async--buffer buffer-name)
    (setq mastodon-async--queue queue-name)))

(defun mastodon-async--setup-http (http-buffer name)
  "Add local variables to HTTP-BUFFER.
NAME is used to generate the display buffer and the queue."
  (let ((queue-name (concat " *mastodon-async-queue-" name "-"
                            mastodon-instance-url "*"))
        (buffer-name (concat "*mastodon-async-display-" name "-"
                             mastodon-instance-url "*")))
    (mastodon-async--set-local-variables http-buffer http-buffer
                                         buffer-name queue-name)))

(defun mastodon-async--setup-queue (http-buffer name)
  "Set up HTTP-BUFFER buffer for the async queue.
NAME is used to generate the display buffer and the queue."
  (let ((queue-name (concat " *mastodon-async-queue-" name "-"
                            mastodon-instance-url "*"))
        (buffer-name(concat "*mastodon-async-display-" name "-"
                            mastodon-instance-url "*")))
    (mastodon-async--set-local-variables queue-name http-buffer
                                         buffer-name queue-name)
    queue-name))

(defun mastodon-async--setup-buffer (http-buffer name endpoint)
  "Set up the buffer timeline like `mastodon-tl--init'.
HTTP-BUFFER the name of the http-buffer, if unknown, set to...
NAME is the name of the stream for the buffer name.
ENDPOINT is the endpoint for the stream and timeline."
  (let ((queue-name (concat " *mastodon-async-queue-" name "-"
                            mastodon-instance-url "*"))
        (buffer-name (concat "*mastodon-async-display-" name "-"
                             mastodon-instance-url "*"))
        ;; if user stream, we need "timelines/home" not "timelines/user"
        ;; if notifs, we need "notifications" not "timelines/notifications"
        (endpoint (cond
                   ((string= name "notifications") "notifications")
                   ((string= name "home") "timelines/home")
                   (t (format "timelines/%s" endpoint)))))
    (mastodon-async--set-local-variables buffer-name http-buffer
                                         buffer-name queue-name)
    ;; Similar to timeline init.
    (with-current-buffer (get-buffer-create buffer-name)
      (setq inhibit-read-only t) ; for home timeline?
      (make-local-variable 'mastodon-tl--enable-relative-timestamps)
      (make-local-variable 'mastodon-tl--display-media-p)
      (message (mastodon-http--api endpoint))
      (if (string= name "notifications")
          (mastodon-notifications--timeline
           (mastodon-http--get-json
            (mastodon-http--api "notifications")))
        (mastodon-tl--timeline (mastodon-http--get-json
                                (mastodon-http--api endpoint))))
      (mastodon-mode)
      (mastodon-tl--set-buffer-spec buffer-name
                                    endpoint
                                    (if (string= name "notifications")
                                        'mastodon-notifications--timeline
                                      'mastodon-tl--timeline))
      (setq-local mastodon-tl--enable-relative-timestamps nil)
      (setq-local mastodon-tl--display-media-p t)
      (current-buffer))))

(defun mastodon-async--start-process (endpoint filter &optional name)
  "Start an async mastodon stream at ENDPOINT.
Filter the toots using FILTER.
NAME is used for the queue and display buffer."
  (let* ((stream (concat "streaming/" endpoint))
         (async-queue (mastodon-async--setup-queue "" (or name stream)))
         (async-buffer (mastodon-async--setup-buffer "" (or name stream) endpoint))
         (http-buffer (mastodon-async--get
                       (mastodon-http--api stream)
                       (lambda (status)
                         (ignore status)
                         (message "HTTP SOURCE CLOSED")))))
    (mastodon-async--setup-http  http-buffer (or name stream))
    (mastodon-async--set-http-buffer async-buffer http-buffer)
    (mastodon-async--set-http-buffer async-queue http-buffer)
    (set-process-filter (get-buffer-process http-buffer)
                        (mastodon-async--http-hook filter))
    http-buffer))

(defun mastodon-async--http-hook (filter)
  "Return a lambda with a custom FILTER for processing toots."
  (let ((filter filter))
    (lambda (proc data)
      (with-current-buffer (process-buffer proc)
        (let* ((string
                (mastodon-async--stream-filter
                 (mastodon-async--http-layer proc data)))
               (queue-string (mastodon-async--cycle-queue string)))
          (when queue-string
            (mastodon-async--output-toot
             (funcall filter queue-string))))))))

(defun mastodon-async--process-queue-string (string)
  "Parse the output STRING of the queue buffer, returning only update events."
  (let ((split-strings (split-string string "\n" t)))
    (when split-strings ; do nothing if we get nothing; just postpones the error
      (let ((event-type (replace-regexp-in-string
                         "^event: " ""
                         (car split-strings)))
            (data (replace-regexp-in-string
                   "^data: " "" (cadr split-strings))))
        (when (string= "update" event-type)
          ;; in some casses the data is not fully formed
          ;; for now return nil if malformed using `ignore-errors'
          (ignore-errors (json-read-from-string data)))))))

(defun mastodon-async--process-queue-string-notifications (string)
  "Parse the output STRING of the queue buffer, returning only notification events."
  ;; NB notification events in streams include follow requests
  (let* ((split-strings (split-string string "\n" t))
         (event-type (replace-regexp-in-string
                      "^event: " ""
                      (car split-strings)))
         (data (replace-regexp-in-string
                "^data: " "" (cadr split-strings))))
    (when (string= "notification" event-type)
      ;; in some casses the data is not fully formed
      ;; for now return nil if malformed using `ignore-errors'
      (ignore-errors (json-read-from-string data)))))

(defun mastodon-async--process-queue-local-string (string)
  "Use STRING to limit the public endpoint to displaying local steams only."
  (let ((json (mastodon-async--process-queue-string string)))
    (when json
      (when (mastodon-async--account-local-p json)
        json))))

(defun mastodon-async--account-local-p (json)
  "Test JSON to see if account is local."
  (not (string-match-p
        "@"
        (alist-get 'acct (alist-get 'account json)))))

(defun mastodon-async--output-toot (toot)
  "Process TOOT and prepend it to the async user-facing buffer."
  (if (not (bufferp (get-buffer mastodon-async--buffer)))
      (mastodon-async--stop-http)
    (when toot
      (with-current-buffer mastodon-async--buffer
        (let* ((inhibit-read-only t)
               (old-max (point-max))
               (previous (point))
               (mastodon-tl--enable-relative-timestamps t)
               (mastodon-tl--display-media-p t))
	  (goto-char (point-min))
          (if (equal (buffer-name)
                     (concat "*mastodon-async-display-notifications-"
                             mastodon-instance-url "*"))
              (mastodon-notifications--timeline (list toot))
	    (mastodon-tl--timeline (list toot)))
          (if (eq previous 1)
	      (goto-char 1)
            (goto-char (+ previous (- (point-max) old-max)))))))))

(defun mastodon-async--cycle-queue (string)
  "Append the most recent STRING from http buffer to queue buffer.
Then determine if a full message has been recived.  If so return it.
Full messages are seperated by two newlines"
  (with-current-buffer mastodon-async--queue
    (goto-char (max-char))
    (insert (decode-coding-string string 'utf-8))
    (goto-char 0)
    (let ((next (re-search-forward "\n\n" nil t)))
      (when next
        (let ((return-string (buffer-substring 1 next))
              (inhibit-read-only t))
          (delete-region 1 next)
          return-string)))))

(defun mastodon-async--http-layer (proc data)
  "Passes PROC and DATA to ‘url-http-generic-filter’.
It then processes its output."
  (with-current-buffer (process-buffer proc)
    (let ((start (max 1 (- (point-max) 2))))
      (url-http-generic-filter proc data)
      (when (> url-http-end-of-headers start)
        (setq start url-http-end-of-headers))
      (let ((end (- (point-max) 2)))
        (buffer-substring start end)))))

(defun mastodon-async--stream-filter (string)
  "Remove comments from STRING."
  (replace-regexp-in-string  "^:.*\n" "" string))

(provide 'mastodon-async)
;;; mastodon-async.el ends here