(require 'erc)
(require 'comint)
(require 'ring)
(define-erc-module ring nil
"Stores input in a ring so that previous commands and messages can
be recalled using M-p and M-n."
((add-hook 'erc-send-pre-hook 'erc-add-to-input-ring)
(define-key erc-mode-map "\M-p" 'erc-previous-command)
(define-key erc-mode-map "\M-n" 'erc-next-command))
((remove-hook 'erc-send-pre-hook 'erc-add-to-input-ring)
(define-key erc-mode-map "\M-p" 'undefined)
(define-key erc-mode-map "\M-n" 'undefined)))
(defvar erc-input-ring nil "Input ring for erc.")
(make-variable-buffer-local 'erc-input-ring)
(defvar erc-input-ring-index nil
"Position in the input ring for erc.
If nil, the input line is blank and the user is conceptually 'after'
the most recently added item in the ring. If an integer, the input
line is non-blank and displays the item from the ring indexed by this
variable.")
(make-variable-buffer-local 'erc-input-ring-index)
(defun erc-input-ring-setup ()
"Do the setup required so that we can use comint style input rings.
Call this function when setting up the mode."
(setq erc-input-ring (make-ring comint-input-ring-size))
(setq erc-input-ring-index nil))
(defun erc-add-to-input-ring (s)
"Add string S to the input ring and reset history position."
(unless erc-input-ring (erc-input-ring-setup))
(ring-insert erc-input-ring s)
(setq erc-input-ring-index nil))
(defun erc-clear-input-ring ()
"Remove all entries from the input ring, then call garbage-collect.
You might use this for security purposes if you have typed a command
containing a password."
(interactive)
(setq erc-input-ring (make-ring comint-input-ring-size)
erc-input-ring-index nil)
(garbage-collect)
(message "ERC input ring cleared."))
(defun erc-previous-command ()
"Replace current command with the previous one from the history."
(interactive)
(unless erc-input-ring (erc-input-ring-setup))
(when (> (ring-length erc-input-ring) 0)
(if (and erc-input-ring-index
(= (ring-length erc-input-ring) (1+ erc-input-ring-index)))
(progn
(erc-replace-current-command "")
(setq erc-input-ring-index nil))
(if (null erc-input-ring-index)
(when (> (point-max) erc-input-marker)
(erc-add-to-input-ring (buffer-substring erc-input-marker
(point-max)))
(setq erc-input-ring-index 0)))
(setq erc-input-ring-index (if erc-input-ring-index
(ring-plus1 erc-input-ring-index
(ring-length erc-input-ring))
0))
(erc-replace-current-command (ring-ref erc-input-ring
erc-input-ring-index)))))
(defun erc-next-command ()
"Replace current command with the next one from the history."
(interactive)
(unless erc-input-ring (erc-input-ring-setup))
(when (> (ring-length erc-input-ring) 0)
(if (and erc-input-ring-index
(= 0 erc-input-ring-index))
(progn
(erc-replace-current-command "")
(setq erc-input-ring-index nil))
(setq erc-input-ring-index (ring-minus1 (or erc-input-ring-index 0)
(ring-length erc-input-ring)))
(erc-replace-current-command (ring-ref erc-input-ring
erc-input-ring-index)))))
(defun erc-replace-current-command (s)
"Replace current command with string S."
(let ((inhibit-read-only t))
(delete-region
(progn (goto-char erc-insert-marker) (erc-bol))
(goto-char (point-max)))
(insert s)))
(provide 'erc-ring)