finish setting up coloring

.gitignore

@@ -10,3 +10,4 @@ eshell
 parinfer-rust
 .mc-lists.el
 codex-sessions
+codex-sessions-history

codex.el

@@ -63,6 +63,12 @@
   :type 'string
   :group 'codex)
 
+(defcustom codex-sessions-history-dir
+  (concat (file-name-parent-directory user-init-file) "codex-sessions-history/")
+  "Directory where Codex session histories are stored."
+  :type 'directory
+  :group 'codex)
+
 (defvar codex--session-id nil)
 
 (defvar codex-mode-map
@@ -75,16 +81,54 @@
     map)
   "Keymap for `codex-mode'.")
 
+(defconst codex--font-lock-keywords
+  '(("^---$" . 'codex-prompt-delimiter-face)
+    ("^User:$" . 'codex-user-prompt-face)
+    ("^Codex:$" . 'codex-assistant-prompt-face)))
+
 (define-derived-mode codex-mode fundamental-mode "Codex"
   "Major mode for chatting with Codex."
   (setq-local buffer-read-only nil)
   (setq-local truncate-lines (not codex-wrap-lines))
+  (setq-local font-lock-defaults '(codex--font-lock-keywords))
   (setq-local codex--busy nil))
 
 (defvar-local codex--prompt-start nil)
 
-(defun codex--propertize-label (text face)
-  (propertize text 'face face 'rear-nonsticky '(face)))
+(defun codex--ensure-history-dir ()
+  (make-directory codex-sessions-history-dir t))
+
+(defun codex--history-file ()
+  (when (and codex--session-id (not (string-empty-p codex--session-id)))
+    (expand-file-name codex--session-id codex-sessions-history-dir)))
+
+(defun codex--set-prompt-start-from-buffer ()
+  (let* ((haystack (buffer-string))
+         (needle "---\nUser:\n")
+         (index (cl-search needle haystack :from-end t)))
+    (when index
+      (setq codex--prompt-start (copy-marker (+ (length needle) index)))
+      t)))
+
+(defun codex--save-session-history ()
+  (with-codex-buffer
+   (let ((history-file (codex--history-file)))
+     (when history-file
+       (codex--ensure-history-dir)
+       (write-region (point-min) (point-max) history-file nil 'silent)))))
+
+(defun codex--load-session-history ()
+  (with-codex-buffer
+   (let ((history-file (codex--history-file)))
+     (setq codex--prompt-start nil)
+     (erase-buffer)
+     (if (and history-file (file-exists-p history-file))
+         (progn
+           (insert-file-contents history-file)
+           (goto-char (point-max))
+           (unless (codex--set-prompt-start-from-buffer)
+             (user-prompt)))
+       (user-prompt)))))
 
 (defun list->hash-set (list &optional test)
   "Return a hash table whose keys are the elements of LIST."
@@ -98,22 +142,23 @@
 
 (defun prompt-delimiter ()
   (newline)
-  (insert (codex--propertize-label "---" 'codex-prompt-delimiter-face))
+  (insert "---")
   (newline))
 
 (defun user-prompt ()
   (prompt-delimiter)
-  (insert (codex--propertize-label "User:" 'codex-user-prompt-face))
+  (insert "User:")
   (newline)
   (setq codex--prompt-start (point-marker)))
 
 (defun codex--write-to-chat (msg)
   (with-codex-buffer
    (newline)
-   (insert (codex--propertize-label "Codex:" 'codex-assistant-prompt-face))
+   (insert "Codex:")
    (newline)
    (insert msg)
-   (user-prompt)))
+   (user-prompt)
+   (codex--save-session-history)))
 
 (defun codex--parse-session-id (jsons)
   (let ((thread-started-message
@@ -185,12 +230,8 @@
                              (marker-position codex--prompt-start))))
       ;; fallback in case we somehow lost where our user prompt starts
       (unless prompt-start
-        (let* ((haystack (buffer-string))
-               (needle "---\nUser:\n")
-               (index (cl-search needle haystack :from-end t)))
-          (when index
-            (setq prompt-start (+ (length needle) index))
-            (setq codex--prompt-start (copy-marker prompt-start)))))
+        (when (codex--set-prompt-start-from-buffer)
+          (setq prompt-start (marker-position codex--prompt-start))))
       (unless prompt-start
         (error "No current prompt start"))
       (buffer-substring-no-properties prompt-start (point-max)))))
@@ -203,6 +244,7 @@
           (error "Prompt is empty!")
         (newline)
         (insert "---")
+        (codex--save-session-history)
         (codex--send prompt)))))
 
 ;;;###autoload
@@ -216,7 +258,7 @@
      (pop-to-buffer buf)
      (unless (derived-mode-p 'codex-mode)
        (codex-mode))
-     (user-prompt)
+     (codex--load-session-history)
      (goto-char (point-max)))))
 
 (defun codex--read-sessions-file ()
@@ -240,13 +282,9 @@
   (interactive
    (list (completing-read "Session: " (cons '("New") (codex--read-sessions-file)))))
   (let ((session-id (cdr (assoc new-session (codex--read-sessions-file)))))
+    (codex--save-session-history)
     (setf codex--session-id session-id)
-    (with-codex-buffer
-     (prompt-delimiter)
-     (if session-id
-         (insert (concat "Switching to session " session-id))
-       (insert "Switching to new session"))
-     (user-prompt))))
+    (codex--load-session-history)))
 
 (defun codex-rename-current-session (name)
   (interactive "sNew name: ")