;;; window-manager.el --- Functions augmenting my usage of EXWM -*- lexical-binding: t -*-

;; Author: William Carroll <wpcarro@gmail.com>
;; Version: 0.0.1
;; Package-Requires: ((emacs "25.1"))

;;; Commentary:
;; I switched to EXWM from i3, and I haven't looked back.  One day I may write a
;; poem declaring my love for Emacs and EXWM.  For now, I haven't the time.

;; Wish list:
;; - TODO: Support different startup commands and layouts depending on laptop or
;;   desktop.
;; - TODO: Support a Music named-workspace.

;;; Code:

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;; Dependencies
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(require 'alert)
(require 'al)
(require 'prelude)
(require 'string)
(require 'cycle)
(require 'set)
(require 'kbd)
(require 'ivy-helpers)
(require 'display)
(require 'vterm-mgt)
(require 'dash)

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;; Library
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;; TODO: Associate `window-purpose' window-layouts with each of these named
;; workspaces.

;; TODO: Associate KBDs for each of these named-layouts.

;; TODO: Decide between window-manager, exwm, or some other namespace.

;; TODO: Support (cycle-from-list '(current previous)) to toggle back and forth
;; between most recent workspace.

;; TODO: Support ad hoc cycle for loading a few workspaces that can be cycled
;; between. (cycle-from-list '("Project" "Workspace"))

;; TODO: Consider supporting a workspace for Racket, Clojure, Common Lisp,
;; Haskell, Elixir, and a few other languages. These could behave very similarly
;; to repl.it, which I've wanted to have locally for awhile now.

;; TODO: Support MRU cache of workspaces for easily switching back-and-forth
;; between workspaces.

(cl-defstruct window-manager--named-workspace label kbd display)
(defgroup window-manager)

(defconst window-manager--install-kbds? t
  "When t, install the keybindings to switch between named-workspaces.")

;; TODO: Consume `cache/touch' after changing workspaces.  Use this to enable
;; cycling through workspaces.

(defconst window-manager--named-workspaces
  (list (make-window-manager--named-workspace
         :label "Web Browsing"
         :kbd "c"
         :display display-4k-horizontal)
        (make-window-manager--named-workspace
         :label "Coding"
         :kbd "d"
         :display display-4k-horizontal)
        (make-window-manager--named-workspace
         :label "Vertical"
         :kbd "h"
         :display display-4k-vertical)
        (make-window-manager--named-workspace
         :label "Laptop"
         :kbd "p"
         :display display-laptop))
  "List of `window-manager--named-workspace' structs.")

;; Assert that no two workspaces share KBDs.
(prelude-assert (= (list-length window-manager--named-workspaces)
                   (->> window-manager--named-workspaces
                        (list-map #'window-manager--named-workspace-kbd)
                        set-from-list
                        set-count)))

(defun window-manager--alert (x)
  "Message X with a structured format."
  (alert (string-concat "[exwm] " x)))

;; Use Emacs as my primary window manager.
(use-package exwm
  :config
  (require 'exwm-config)

  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
  ;; Multiple Displays
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  (require 'exwm-randr)
  (exwm-randr-enable)
  (setq exwm-randr-workspace-monitor-plist
        (->> window-manager--named-workspaces
             (-map-indexed (lambda (i x)
                             (list i (window-manager--named-workspace-display x))))
             -flatten))
  (setq exwm-workspace-number (list-length window-manager--named-workspaces))
  (setq exwm-input-simulation-keys
        ;; TODO: Consider supporting M-d and other readline style KBDs.
        '(([?\C-b] . [left])
          ([?\M-b] . [C-left])
          ([?\C-f] . [right])
          ([?\M-f] . [C-right])
          ([?\C-p] . [up])
          ([?\C-n] . [down])
          ([?\C-a] . [home])
          ([?\C-e] . [end])
          ([?\C-d] . [delete])
          ;; TODO: Assess whether or not this is a good idea.
          ;; TODO: Ensure C-c copies.
          ([?\C-c] . [C-c])))
  (exwm-enable))
(defcustom window-manager-screenlocker "xsecurelock"
  "Reference to a screen-locking executable."
  :group 'window-manager)

;; Here is the code required to allow EXWM to cycle workspaces.
(defconst window-manager--workspaces
  (->> window-manager--named-workspaces
       cycle-from-list)
  "Cycle of the my EXWM workspaces.")

(prelude-assert
 (= exwm-workspace-number
    (list-length window-manager--named-workspaces)))

(defun window-manager-next-workspace ()
  "Cycle forwards to the next workspace."
  (interactive)
  (window-manager--change-workspace (cycle-next window-manager--workspaces)))

(defun window-manager-prev-workspace ()
  "Cycle backwards to the previous workspace."
  (interactive)
  (window-manager--change-workspace (cycle-prev window-manager--workspaces)))

;; TODO: Create friendlier API for working with EXWM.

;; Here is the code required to toggle EXWM's modes.
(defun window-manager--line-mode ()
  "Switch exwm to line-mode."
  (call-interactively #'exwm-input-grab-keyboard)
  (window-manager--alert "Switched to line-mode"))

(defun window-manager--char-mode ()
  "Switch exwm to char-mode."
  (call-interactively #'exwm-input-release-keyboard)
  (window-manager--alert "Switched to char-mode"))

(defconst window-manager--modes
  (cycle-from-list (list #'window-manager--char-mode
                         #'window-manager--line-mode))
  "Functions to switch exwm modes.")

(defun window-manager-toggle-mode ()
  "Switch between line- and char- mode."
  (interactive)
  (with-current-buffer (window-buffer)
    (when (eq major-mode 'exwm-mode)
      (funcall (cycle-next window-manager--modes)))))

;; Ensure exwm apps open in char-mode.
(add-hook 'exwm-manage-finish-hook #'window-manager--char-mode)


;; TODO: How do I handle this dependency?
(defconst window-manager--preferred-browser "google-chrome"
  "My preferred web browser.")

;; TODO: Consider replacing the `ivy-read' call with something like `hydra' that
;; can provide a small mode for accepting user-input.
;; TODO: Put this somewhere more diliberate.

(defun window-manager--label->index (label workspaces)
  "Return the index of the workspace in WORKSPACES named LABEL."
  (let ((index (-elem-index label (-map #'window-manager--named-workspace-label
                                        workspaces))))
    (if index index (error (format "No workspace found for label: %s" label)))))

(defun window-manager--register-kbd (workspace)
  "Registers a keybinding for WORKSPACE struct.
Currently using super- as the prefix for switching workspaces."
  (let ((handler (lambda ()
                   (interactive)
                   (window-manager--switch
                    (window-manager--named-workspace-label workspace))))
        (key (window-manager--named-workspace-kbd workspace)))
    (exwm-input-set-key
     (kbd-for 'workspace key)
     handler)))

(defun window-manager--change-workspace (workspace)
  "Switch EXWM workspaces to the WORKSPACE struct."
  (exwm-workspace-switch
   (window-manager--label->index
    (window-manager--named-workspace-label workspace)
    window-manager--named-workspaces))
  (window-manager--alert
   (string-format "Switched to: %s"
                  (window-manager--named-workspace-label workspace))))

(defun window-manager--switch (label)
  "Switch to a named workspaces using LABEL."
  (cycle-focus (lambda (x)
                 (equal label
                        (window-manager--named-workspace-label x)))
               window-manager--workspaces)
  (window-manager--change-workspace (cycle-current window-manager--workspaces)))

(exwm-input-set-key (kbd "C-S-f") #'window-manager-toggle-previous)

(defun window-manager-toggle-previous ()
  "Focus the previously active EXWM workspace."
  (interactive)
  (window-manager--change-workspace
   (cycle-focus-previous! window-manager--workspaces)))

(defun window-manager--exwm-buffer? (x)
  "Return t if buffer X is an EXWM buffer."
  (equal 'exwm-mode (buffer-local-value 'major-mode x)))

(defun window-manager--application-name (buffer)
  "Return the name of the application running in the EXWM BUFFER.
This function asssumes that BUFFER passes the `window-manager--exwm-buffer?'
predicate."
  (with-current-buffer buffer exwm-class-name))

;; TODO: Support disambiguating between two or more instances of the same
;; application. For instance if two `exwm-class-name' values are
;; "Google-chrome", find a encode this information in the `buffer-alist'.
(defun window-manager-switch-to-exwm-buffer ()
  "Use `completing-read' to focus an EXWM buffer."
  (interactive)
  (let* ((buffer-alist (->> (buffer-list)
                            (-filter #'window-manager--exwm-buffer?)
                            (-map
                             (lambda (buffer)
                               (cons (window-manager--application-name buffer)
                                     buffer)))))
         (label (completing-read "Switch to EXWM buffer: " buffer-alist)))
    (exwm-workspace-switch-to-buffer
     (al-get label buffer-alist))))

(when window-manager--install-kbds?
  (progn
    (->> window-manager--named-workspaces
         (list-map #'window-manager--register-kbd))
    (window-manager--alert "Registered workspace KBDs!")))

(defun window-manager-current-workspace ()
  "Output the label of the currently active workspace."
  (->> window-manager--workspaces
       cycle-current
       window-manager--named-workspace-label))

(defun window-manager-swap-workspaces ()
  "Prompt the user to switch the current workspace with another."
  (interactive)
  (let* ((selection (->> window-manager--named-workspaces
                         (-map #'window-manager--named-workspace-label)
                         (-reject
                          (lambda (x)
                            (s-equals? x (window-manager-current-workspace))))
                         (completing-read
                          (format "Swap current workspace (i.e. \"%s\") with: "
                                  (window-manager-current-workspace)))))
         (i (-find-index (lambda (x)
                           (s-equals? selection (window-manager--named-workspace-label x)))
                                 window-manager--named-workspaces)))
    (exwm-workspace-swap exwm-workspace--current (elt exwm-workspace--list i))))

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;; Startup Applications in `window-manager--named-workspaces'
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(add-hook 'exwm-init-hook
          (lambda ()
            ;; (display-arrange-primary)
            (window-manager--switch "Coding")))

(provide 'window-manager)
;;; window-manager.el ends here