;;; livie.el --- Livie is Video in Emacs -*- lexical-binding: t; -*-

;; Copyright (C) 2018 - 2021

;;; Authors:

;; Charlie Ritter <chewzerita@posteo.net>
;; Jesus E. <heckyel@hyperbola.info>
;; Gabriele Rastello <gabriele.rastello@edu.unito.it>

;;; Commentary:

;; livie grabs a list of youtube videos based on a search.
;; the user can then select a video to watch through `livie-player'
;;; Code:

(require 'cl-lib)
(require 'json)
(require 'seq)

(defgroup livie '()
  "Livie is Video in Emacs"
  :prefix "livie-"
  :group 'livie)

(defcustom livie-sort-criterion 'relevance
  "Criterion to sort the results of the search query."
  :type 'symbol
  :options '(relevance rating upload_date view_count)
  :group 'livie)

(defvar livie-invidious-api-url "https://invidious.048596.xyz"
  "URL to Invidious instance.")

(defvar livie-invidious-default-query-fields "author,lengthSeconds,title,videoId,authorId,viewCount,published"
  "Default fields of interest for video search.")

(defvar livie-videos '()
  "List of videos currently on display.")

(defvar livie-published-date-time-string "%Y-%m-%d"
  "Time-string used to render the published date of the video.
See `format-time-string' for information on how to edit this variable.")

(defvar-local livie-current-page 1
  "Current page of the current `livie-search-term'")

(defvar-local livie-search-term ""
  "Current search string as used by `livie-search'")

(defvar livie-author-name-reserved-space 20
  "Number of characters reserved for the channel's name in the *livie* buffer.
Note that there will always 3 extra spaces for eventual dots (for names that are
too long).")

(defvar livie-title-video-reserved-space 100
  "Number of characters reserved for the video title in the *livie* buffer.
Note that there will always 3 extra spaces for eventual dots (for names that are
too long).")

(defface livie-video-published-face
  '((((class color) (background light)) (:foreground "#00C853"))
    (((class color) (background dark))  (:foreground "#00E676")))
  "Face used for the video published date.")

(defface livie-channel-name-face
  '((((class color) (background light)) (:foreground "#FFC400"))
    (((class color) (background dark))  (:foreground "#FFFF00")))
  "Face used for channel names.")

(defface livie-video-length-face
  '((((class color) (background light)) (:foreground "#6A1B9A"))
    (((class color) (background dark))  (:foreground "#AA00FF")))
  "Face used for the video length.")

(defface livie-video-view-face
  '((((class color) (background light)) (:foreground "#00695C"))
    (((class color) (background dark))  (:foreground "#00BFA5")))
  "Face used for the video views.")

(defvar livie-mode-map
  (let ((map (make-sparse-keymap)))
    (suppress-keymap map)
    (define-key map "q" #'livie-quit)
    (define-key map "h" #'describe-mode)
    (define-key map "n" #'next-line)
    (define-key map "p" #'previous-line)
    (define-key map (kbd "<tab>") #'next-line)
    (define-key map (kbd "<backtab>") #'previous-line)
    (define-key map "s" #'livie-search)
    (define-key map ">" #'livie-search-next-page)
    (define-key map "<" #'livie-search-previous-page)
    (define-key map (kbd "<return>") 'livie-watch-this-video)
    map)
  "Keymap for `livie-mode'.")

(define-derived-mode livie-mode text-mode
  "livie-mode"
  (setq buffer-read-only t)
  (buffer-disable-undo)
  (make-local-variable 'livie-videos))

(defun livie-quit ()
  "Quit livie buffer."
  (interactive)
  (quit-window))

(defun livie--format-author (name)
  "Format a channel NAME to be inserted in the *livie* buffer."
  (let* ((n (string-width name))
         (extra-chars (- n livie-author-name-reserved-space))
         (formatted-string (if (<= extra-chars 0)
                               (concat name
                                       (make-string (abs extra-chars) ?\ )
                                       "   ")
                             (concat (seq-subseq name 0 livie-author-name-reserved-space)
                                     "..."))))
    (propertize formatted-string 'face 'livie-channel-name-face)))

(defun livie--format-title (title)
  "Format a video TITLE to be inserted in the *livie* buffer."
  (let* ((n (string-width title))
         (extra-chars (- n livie-title-video-reserved-space))
         (formatted-string (if (<= extra-chars 0)
                               (concat title
                                       (make-string (abs extra-chars) ?\ )
                                       "   ")
                             (concat (seq-subseq title 0 livie-title-video-reserved-space)
                                     "..."))))
    formatted-string))

(defun livie--format-video-length (seconds)
  "Given an amount of SECONDS, format it nicely to be inserted in the *livie* buffer."
  (let ((formatted-string (concat (format-seconds "%.2h" seconds)
                                  ":"
                                  (format-seconds "%.2m" (mod seconds 3600))
                                  ":"
                                  (format-seconds "%.2s" (mod seconds 60)))))
    (propertize formatted-string 'face 'livie-video-length-face)))

(defun livie--format-video-views (views)
  "Format video VIEWS to be inserted in the *livie* buffer."
  (propertize (concat "[views:" (number-to-string views) "]") 'face 'livie-video-view-face))

(defun livie--format-video-published (published)
  "Format video PUBLISHED date to be inserted in the *livie* buffer."
  (propertize (format-time-string livie-published-date-time-string (seconds-to-time published))
              'face 'livie-video-published-face))

(defun livie--insert-video (video)
  "Insert `VIDEO' in the current buffer."
  (insert (livie--format-video-published (livie-video-published video))
          " "
          (livie--format-author (livie-video-author video))
          " "
          (livie--format-video-length (livie-video-length video))
          " "
          (livie--format-title (livie-video-title video))
          " "
          (livie--format-video-views (livie-video-views video))))

(defun livie--draw-buffer ()
  "Draws the livie buffer i.e. clear everything and write down all videos in `livie-videos'."
  (let ((inhibit-read-only t))
    (erase-buffer)
    (setf header-line-format (concat "Search results for "
                                     (propertize livie-search-term 'face 'livie-video-published-face)
                                     ", page "
                                     (number-to-string livie-current-page)))
    (seq-do (lambda (v)
              (livie--insert-video v)
              (insert "\n"))
            livie-videos)
    (goto-char (point-min))))

(defun livie-search (query)
  "Search youtube for `QUERY', and redraw the buffer."
  (interactive "sSearch: ")
  (setf livie-current-page 1)
  (setf livie-search-term query)
  (setf livie-videos (livie--query query livie-current-page))
  (livie--draw-buffer))

(defun livie-search-next-page ()
  "Switch to the next page of the current search.  Redraw the buffer."
  (interactive)
  (setf livie-videos (livie--query livie-search-term
                                   (1+ livie-current-page)))
  (setf livie-current-page (1+ livie-current-page))
  (livie--draw-buffer))

(defun livie-search-previous-page ()
  "Switch to the previous page of the current search.  Redraw the buffer."
  (interactive)
  (when (> livie-current-page 1)
    (setf livie-videos (livie--query livie-search-term
                                     (1- livie-current-page)))
    (setf livie-current-page (1- livie-current-page))
    (livie--draw-buffer)))

(defun livie-get-current-video ()
  "Get the currently selected video."
  (aref livie-videos (1- (line-number-at-pos))))

(defun livie-watch-this-video ()
  "Stream video at point in mpv."
  (interactive)
  (let* ((video (livie-get-current-video))
         (id    (livie-video-id video)))
    (start-process "livie mpv" nil
                   "mpv"
                   (concat "https://www.youtube.com/watch?v=" id))
    "--ytdl-format=bestvideo[height<=?720]+bestaudio/best")
  (delete-other-windows)
  (message "Starting streaming..."))

(defun livie-buffer ()
  "Name for the main livie buffer."
  (get-buffer-create "*livie*"))

;;;###autoload
(defun livie ()
  "Enter livie."
  (interactive)
  (switch-to-buffer (livie-buffer))
  (unless (eq major-mode 'livie-mode)
    (livie-mode))
  (when (seq-empty-p livie-search-term)
    (call-interactively #'livie-search)))

;; Youtube interface stuff below.
(cl-defstruct (livie-video (:constructor livie-video--create)
                           (:copier nil))
  "Information about a Youtube video."
  (title     "" :read-only t)
  (id        0  :read-only t)
  (author    "" :read-only t)
  (authorId  "" :read-only t)
  (length    0  :read-only t)
  (views     0  :read-only t)
  (published 0 :read-only t))

(defun livie--API-call (method args)
  "Perform a call to the invidious API method METHOD passing ARGS.
Curl is used to perform the request.  An error is thrown if it exits with a non
zero exit code otherwise the request body is parsed by `json-read' and returned."
  (with-temp-buffer
    (let ((exit-code (call-process "curl" nil t nil
                                   "--silent"
                                   "-X" "GET"
                                   (concat livie-invidious-api-url
                                           "/api/v1/" method
                                           "?" (url-build-query-string args)))))
      (unless (= exit-code 0)
        (error "Curl had problems connecting to Invidious"))
      (goto-char (point-min))
      (json-read))))

(defun livie--query (string n)
  "Query youtube for STRING, return the Nth page of results."
  (let ((videos (livie--API-call "search" `(("q", string)
                                            ("sort_by", (symbol-name livie-sort-criterion))
                                            ("page", n)
                                            ("fields", livie-invidious-default-query-fields)))))
    (dotimes (i (length videos))
      (let ((v (aref videos i)))
        (aset videos i
              (livie-video--create
               :title     (assoc-default 'title v)
               :author    (assoc-default 'author v)
               :authorId  (assoc-default 'authorId v)
               :length    (assoc-default 'lengthSeconds v)
               :id        (assoc-default 'videoId v)
               :views     (assoc-default 'viewCount v)
               :published (assoc-default 'published v)))))
    videos))

(provide 'livie)

;;; livie.el ends here