scratch!!

(defmacro util:aif (pred then &rest else)
  "PRED を評価し、結果が non-nil ならば THEN、nil ならば ELSE の評価結果を返す.
THEN、ELSE 内では PRED の評価結果を `it' で参照出来る."
  `(let ((it ,pred))
     (if it ,then ,@else)))

(defmacro util:awhen (pred &rest body)
  "PRED を評価し、結果が non-nil ならば BODY を評価し、最後の式の結果を返す.
BODY 内では PRED の評価結果を `it' で参照出来る."
  `(ini:aif ,pred (progn ,@body)))

(defvar scratch-save-file (locate-user-emacs-file "scratch")
  "`*scratch' バッファの保存先ファイル名.")

(defvar scratch-buffer-save-interval 1
  "`*scratch*' バッファの自動保存間隔.")

(defvar prev-scratch-modified-tick 0
  "`*scratch*' バッファの前回保存時の更新状態.")

(defun resume-scratch-buffer ()
  "`*scratch*' バッファの内容を復帰する."
  (interactive)
  (let ((scratch (get-buffer-create "*scratch*"))
    (file (expand-file-name scratch-save-file))
    (buffer-undo-list t))
    (with-current-buffer scratch
      (when (file-exists-p file)
    (erase-buffer)
    (insert-file-contents file)
    (set-buffer-modified-p nil)

    (setq scratch-modified-tick (buffer-chars-modified-tick))
    ))))

(defun save-scratch-buffer ()
  "`*scratch*' バッファの内容を保存する."
  (interactive)
  (util:awhen (get-buffer "*scratch*")
    (with-current-buffer it
      (let ((modified-tick (buffer-chars-modified-tick)))
    (unless (eq modified-tick prev-scratch-modified-tick)
      (setq prev-scratch-modified-tick modified-tick)
      (save-restriction
        (widen)
        (write-region (point-min) (point-max)
              (expand-file-name scratch-save-file)
              nil 'slient)
        ))))))

(add-hook 'after-init-hook
      (lambda ()
        (resume-scratch-buffer)

        ;; 読み込みに成功したら自動保存を有効化
        (run-with-idle-timer scratch-buffer-save-interval t 'save-scratch-buffer)
        (add-hook 'kill-emacs-hook 'save-scratch-buffer)
        ))