;;; exwm-buffer-groups.el --- Buffer grouping for EXWM workspaces. -*- lexical-binding: t; -*-

;; Copyright (C) 2019 Jakob L. Kreuze

;; Author: Jakob L. Kreuze <zerodaysfordays@sdf.lonestar.org>
;; Version: 1.0
;; Package-Requires (cl-lib exwm)
;; Keywords: frames
;; URL: https://git.sr.ht/~jakob/exwm-buffer-groups

;; 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 <http://www.gnu.org/licenses/>.

;;; Commentary:

;; The default behavior of EXWM is to make buffers containing X windows
;; accessible only from the workspace they were created in. This is a useful
;; feature, but introduces some level of inconsistency as this does not apply to
;; normal buffers. exwm-buffer-groups aims to change this by associating all
;; buffers with a workspace.

;;; Code:

(require 'cl-lib)
(require 'exwm)

(defun exwm-buffer-groups-default-buffers ()
  "Initial list of buffers for a workspace."
  (if (get-buffer "*scratch*")
      (list (get-buffer "*scratch*"))
    nil))

(defvar exwm-buffer-groups-buffers
  (make-vector exwm-workspace-number (exwm-buffer-groups-default-buffers))
  "Vector containing lists of associated buffers for each workspace.")

(defun exwm-buffer-groups--buffer-seen-p (buffer)
  "Whether or not BUFFER is contained in `exwm-buffer-groups-buffers'."
  (reduce #'(lambda (x y) (or x y))
          (map 'list
               #'(lambda (workspace)
                   (memq buffer workspace))
               exwm-buffer-groups-buffers)))

(defun exwm-buffer-groups--remove-buffers ()
  "Removes dead buffers from `exwm-buffer-groups-buffers'."
  (setq exwm-buffer-groups-buffers
        (map 'vector
             #'(lambda (buffers) (cl-remove-if-not #'buffer-live-p buffers))
             exwm-buffer-groups-buffers)))

(defun exwm-buffer-groups--add-buffers ()
  "Adds unseen buffers to `exwm-buffer-groups-buffers'.
Any unseen buffers are added to the entry corresponding to the
current workspace."
  (dolist (buffer (buffer-list))
    (unless (exwm-buffer-groups--buffer-seen-p buffer)
      (push buffer (elt exwm-buffer-groups-buffers exwm-workspace-current-index)))))

(defun exwm-buffer-groups-update ()
  "Updates `exwm-buffer-groups-buffers' to reflect the buffer list."
  (exwm-buffer-groups--remove-buffers)
  (exwm-buffer-groups--add-buffers))

(defun exwm-buffer-groups-switch-buffer (buffer-or-name)
  "Display buffer BUFFER-OR-NAME in the selected window.
If called interactively, read the buffer name using
`completing-read', completing only on buffers in the current
workspace."
  (interactive
   (list
    (let ((buffers-in-workspace (map 'list
                                     #'buffer-name
                                     (elt exwm-buffer-groups-buffers
                                          exwm-workspace-current-index)))
          (current-buffer (buffer-name (other-buffer (current-buffer)))))
      (completing-read "Switch to buffer: " buffers-in-workspace
                       nil nil nil nil current-buffer))))
  (switch-to-buffer buffer-or-name))

(defun exwm-buffer-groups-move (nth)
  "Moves the current buffer to the NTH workspace."
  (interactive
   (list
    (exwm-workspace--position
     (exwm-workspace--prompt-for-workspace "Move workspace to: "))))
  ;; Remove the buffer from the current workspace.
  (setf (elt exwm-buffer-groups-buffers exwm-workspace-current-index)
        (remove (current-buffer)
                (elt exwm-buffer-groups-buffers exwm-workspace-current-index)))
  ;; Add it to the NTH workspace.
  (push (current-buffer) (elt exwm-buffer-groups-buffers nth))
  ;; Switch out of the buffer.
  (set-window-dedicated-p nil nil)
  (switch-to-prev-buffer nil 'bury))

(add-hook 'after-change-major-mode-hook #'exwm-buffer-groups-update)

(provide 'exwm-buffer-groups)
;;; exwm-buffer-groups.el ends here