;;; buffer.el --- Working with buffers -*- lexical-binding: t -*-
;; Author: William Carroll <wpcarro@gmail.com>
;; Version: 0.0.1
;; Package-Requires: ((emacs "24.3"))
;;; Commentary:
;; Utilities for CRUDing buffers in Emacs.
;;
;; Many of these functions may seem unnecessary especially when you consider
;; there implementations. In general I believe that Elisp suffers from a
;; library disorganization problem. Providing simple wrapper functions that
;; rename functions or reorder parameters is worth the effort in my opinion if
;; it improves discoverability (via intuition) and improve composability.
;;
;; I support three ways for switching between what I'm calling "source code
;; buffers":
;; 1. Toggling previous: <SPC><SPC>
;; 2. Using `ivy-read': <SPC>b
;; TODO: These obscure evil KBDs. Maybe a hydra definition would be best?
;; 3. Cycling (forwards/backwards): C-f, C-b
;;; Code:
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;; Dependencies
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(require 'prelude)
(require 'maybe)
(require 'set)
(require 'cycle)
(require 'struct)
(require 'ts)
(require 'general)
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;; Library
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(defconst buffer-enable-tests? t
"When t, run the test suite.")
(defconst buffer-install-kbds? t
"When t, install the keybindings defined herein.")
(defconst buffer-source-code-blacklist
(set-new 'dired-mode
'erc-mode
'vterm-mode
'magit-status-mode
'magit-process-mode
'magit-log-mode
'magit-diff-mode
'org-mode
'fundamental-mode)
"A blacklist of major-modes to ignore for listing source code buffers.")
(defconst buffer-source-code-timeout 2
"Number of seconds to wait before invalidating the cycle.")
(cl-defstruct source-code-cycle cycle last-called)
(defun buffer-emacs-generated? (name)
"Return t if buffer, NAME, is an Emacs-generated buffer.
Some buffers are Emacs-generated but are surrounded by whitespace."
(let ((trimmed (s-trim name)))
(and (s-starts-with? "*" trimmed))))
(defun buffer-find (buffer-or-name)
"Find a buffer by its BUFFER-OR-NAME."
(get-buffer buffer-or-name))
(defun buffer-major-mode (name)
"Return the active `major-mode' in buffer, NAME."
(with-current-buffer (buffer-find name)
major-mode))
(defun buffer-source-code-buffers ()
"Return a list of source code buffers.
This will ignore Emacs-generated buffers, like *Messages*. It will also ignore
any buffer whose major mode is defined in `buffer-source-code-blacklist'."
(->> (buffer-list)
(list-map #'buffer-name)
(list-reject #'buffer-emacs-generated?)
(list-reject (lambda (name)
(set-contains? (buffer-major-mode name)
buffer-source-code-blacklist)))))
(defvar buffer-source-code-cycle-state
(make-source-code-cycle
:cycle (cycle-from-list (buffer-source-code-buffers))
:last-called (ts-now))
"State used to manage cycling between source code buffers.")
(defun buffer-exists? (name)
"Return t if buffer, NAME, exists."
(maybe-some? (buffer-find name)))
(defun buffer-new (name)
"Return a newly created buffer NAME."
(generate-new-buffer name))
(defun buffer-find-or-create (name)
"Find or create buffer, NAME.
Return a reference to that buffer."
(let ((x (buffer-find name)))
(if (maybe-some? x)
x
(buffer-new name))))
;; TODO: Should this consume: `display-buffer' or `switch-to-buffer'?
(defun buffer-show (buffer-or-name)
"Display the BUFFER-OR-NAME, which is either a buffer reference or its name."
(display-buffer buffer-or-name))
;; TODO: Move this and `buffer-cycle-prev' into a separate module that
;; encapsulates all of this behavior.
(defun buffer-cycle (cycle-fn)
"Using CYCLE-FN, move through `buffer-source-code-buffers'."
(let ((last-called (source-code-cycle-last-called
buffer-source-code-cycle-state))
(cycle (source-code-cycle-cycle
buffer-source-code-cycle-state)))
(if (> (ts-diff (ts-now) last-called)
buffer-source-code-timeout)
(progn
(struct-set! source-code-cycle
cycle
(cycle-from-list (buffer-source-code-buffers))
buffer-source-code-cycle-state)
(let ((cycle (source-code-cycle-cycle
buffer-source-code-cycle-state)))
(funcall cycle-fn cycle)
(switch-to-buffer (cycle-current cycle)))
(struct-set! source-code-cycle
last-called
(ts-now)
buffer-source-code-cycle-state))
(progn
(funcall cycle-fn cycle)
(switch-to-buffer (cycle-current cycle))))))
(defun buffer-cycle-next ()
"Cycle forward through the `buffer-source-code-buffers'."
(interactive)
(buffer-cycle #'cycle-next))
(defun buffer-cycle-prev ()
"Cycle backward through the `buffer-source-code-buffers'."
(interactive)
(buffer-cycle #'cycle-prev))
(defun buffer-ivy-source-code ()
"Use `ivy-read' to choose among all open source code buffers."
(interactive)
(ivy-read "Source code buffer: "
(-drop 1 (buffer-source-code-buffers))
:sort nil
:action #'switch-to-buffer))
(defun buffer-show-previous ()
"Call `switch-to-buffer' on the previously visited buffer.
This function ignores Emacs-generated buffers, i.e. the ones that look like
this: *Buffer*. It also ignores buffers that are `dired-mode' or `erc-mode'.
This blacklist can easily be changed."
(interactive)
(let* ((xs (buffer-source-code-buffers))
(candidate (list-get 1 xs)))
(prelude-assert (maybe-some? candidate))
(switch-to-buffer candidate)))
(when buffer-install-kbds?
(general-define-key
:states '(normal)
"C-f" #'buffer-cycle-next
"C-b" #'buffer-cycle-prev)
(general-define-key
:prefix "<SPC>"
:states '(normal)
"b" #'buffer-ivy-source-code
"<SPC>" #'buffer-show-previous
"k" #'kill-buffer))
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;; Tests
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(when buffer-enable-tests?
(prelude-assert
(list-all? #'buffer-emacs-generated?
'("*scratch*"
"*Messages*"
"*shell*"
"*Shell Command Output*"
"*Occur*"
"*Warnings*"
"*Help*"
"*Completions*"
"*Apropos*"
"*info*"))))
(provide 'buffer)
;;; buffer.el ends here
