Persistent history

Added basic functions to save and load the input history in a REPL
session.  Added local variables kill-buffer-hook and kill-emacs-hook

nrepl.el

@@ -148,13 +148,6 @@ joined together.")
  'nrepl-output-start
  'nrepl-output-end)
 
-(defun nrepl-add-to-input-history (string)
-  "Add STRING to the input history.
-Empty strings and duplicates are ignored."
-  (unless (or (equal string "")
-              (equal string (car nrepl-input-history)))
-    (push string nrepl-input-history)))
-
 (defun nrepl-reset-markers ()
   (dolist (markname '(nrepl-output-start
                       nrepl-output-end
@@ -683,6 +676,13 @@ in a macroexpansion buffer. Prefix argument forces pretty-printed output."
       (nrepl-interactive-eval (nrepl-last-expression))))
 
 ;;;;; History
+(defun nrepl-add-to-input-history (string)
+  "Add STRING to the input history.
+Empty strings and duplicates are ignored."
+  (unless (or (equal string "")
+              (equal string (car nrepl-input-history)))
+    (push string nrepl-input-history)))
+
 (defun nrepl-delete-current-input ()
   "Delete all text after the prompt."
   (interactive)
@@ -726,6 +726,75 @@ DIRECTION is 'forward' or 'backward' (in the history list)."
   (interactive)
   (nrepl-history-replace 'forward))
 
+;;;;;;;;;;;;;;;;;;;;;;;;
+;; working on persistent hist
+;; make sure to move things around later
+(defvar nrepl-history-size 500)
+(defvar nrepl-history-file "~/.nrepl-history.eld")
+
+(defun nrepl-history-read-filename ()
+  "Ask the user which file to use, defaulting `nrepl-history-file`."
+  (read-file-name "Use nREPL history file: "
+                  nrepl-history-file))
+
+(defun nrepl-history-read (filename)
+  "Read history from FILE and return it.
+Does not yet set the input history."
+  (if (file-readable-p filename)
+      (with-temp-buffer 
+        (insert-file-contents filename)
+        (read (current-buffer)))
+    '()))
+
+(defun nrepl-history-load (&optional filename)
+  "Load history from FILENAME into current session.
+FILENAME defaults to the value of `nrepl-history-file` but user
+defined filenames can be used to read special history files.
+
+The value of `nrepl-input-history` is set by this function."
+  (interactive (list (nrepl-history-read-filename)))
+  (let ((f (or filename nrepl-history-file)))
+    ;; TODO: probably need to set nrepl-input-history-index as well.
+    ;; in a fresh connection the newest item in the list is currently
+    ;; not available.  After sending one input, everything seems to work.
+    (setq nrepl-input-history (nrepl-history-read f))))
+
+(defun nrepl-history-write (filename)
+  "Write history to FILENAME.
+Currently coding system for writing the contents is hardwired to
+utf-8-unix." 
+  (let* ((mhist (nrepl-histories-merge nrepl-input-history nil))
+         ;; newest items are at the beginning of the list, thus 0
+         (hist  (subseq mhist 0 (min (length mhist) nrepl-history-size))))
+    (unless (file-writable-p filename)
+      (error (format "History file not writable: %s" filename)))
+    (let ((print-length nil) (print-level nil))
+      (with-temp-file filename
+        ;; TODO: really set cs for output
+        ;; TODO: does cs need to be customizable?
+        (insert ";; -*- coding: utf-8-unix -*-\n")
+        (insert ";; Automatically written history of nREPL session\n")
+        (insert ";; Edit at your own risk\n\n")
+        (prin1 (mapcar #'substring-no-properties hist) (current-buffer))))))
+
+(defun nrepl-history-save (&optional filename)
+  "Save the current nREPL input history to FILENAME.
+FILENAME defaults to the value of `nrepl-history-file`."
+  (interactive (list (nrepl-history-read-filename)))
+  (let* ((file  (or filename nrepl-history-file)))
+    (nrepl-history-write file)))
+
+(defun nrepl-history-just-save ()
+  "Just save the history to `nrepl-history-file`.
+This function is meant to be used in hooks to avoid lambda
+  constructs."
+  (nrepl-history-save nrepl-history-file))
+
+;; SLIME has different semantics and will not save any duplicates.
+(defun nrepl-histories-merge (session-hist file-hist)
+  (append session-hist))
+
+;;;
 (defun nrepl-same-line-p (pos1 pos2)
    "Return t if buffer positions POS1 and POS2 are on the same line."
    (save-excursion (goto-char (min pos1 pos2))
@@ -810,6 +879,11 @@ DIRECTION is 'forward' or 'backward' (in the history list)."
         major-mode 'nrepl-mode)
   (set-syntax-table nrepl-mode-syntax-table)
   (nrepl-eldoc-enable-in-current-buffer)
+  (when nrepl-history-file
+    (nrepl-history-load nrepl-history-file)
+    (make-local-variable 'kill-buffer-hook)
+    (add-hook 'kill-buffer-hook 'nrepl-history-just-save)
+    (add-hook 'kill-emacs-hook 'nrepl-history-just-save))
   (run-mode-hooks 'nrepl-mode-hook))
 
 ;;; communication