From a24b3d7ec748ec89f665c7f5293e0705b2ce5525 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Madeleine=20Sydney=20=C5=9Alaga?= <msyds@deertopia.net>
Date: Mon, 22 Sep 2025 11:20:33 -0600
Subject: [PATCH] feat(emacs): handle

---
 .../users/msyds/emacs/lisp/syd/emacs-lisp.el  |  7 +-
 .../home/users/msyds/emacs/lisp/syd/handle.el | 92 +++++++++++++++++--
 2 files changed, 88 insertions(+), 11 deletions(-)

diff --git a/modules/home/users/msyds/emacs/lisp/syd/emacs-lisp.el b/modules/home/users/msyds/emacs/lisp/syd/emacs-lisp.el
index 8dd7f21..df2e089 100644
--- a/modules/home/users/msyds/emacs/lisp/syd/emacs-lisp.el
+++ b/modules/home/users/msyds/emacs/lisp/syd/emacs-lisp.el
@@ -33,7 +33,7 @@
                 (bury-buffer b)
                 b)))))
 
-(defun syd-elisp-lookup-documentation (identifier)
+(defun syd-elisp-handle-docs (identifier)
   "Lookup IDENTIFIER with `describe-symbol'"
   ;; HACK: Much to my frustration, `describe-symbol' has no defined return
   ;; value.  To test if the call was successful or not, we check if any window
@@ -45,9 +45,8 @@
     (and (get-buffer-window-list buffer)
          buffer)))
 
-;; (handle '(emacs-lisp-mode lisp-interaction-mode
-;;           inferior-emacs-lisp-mode)
-;;         :repl #'syd-elisp-open-repl)
+(syd-handle '(emacs-lisp-mode lisp-interaction-mode)
+  :docs #'syd-elisp-handle-docs)
 
 
 
diff --git a/modules/home/users/msyds/emacs/lisp/syd/handle.el b/modules/home/users/msyds/emacs/lisp/syd/handle.el
index b34d138..71bd1c1 100644
--- a/modules/home/users/msyds/emacs/lisp/syd/handle.el
+++ b/modules/home/users/msyds/emacs/lisp/syd/handle.el
@@ -3,14 +3,92 @@
 (require 'cl-lib)
 (require 'syd/straight)
 (require 'syd/use-package)
+(require 'syd/dash)
 (eval-when-compile (require 'cl-lib))
 
-(use-package handle
-  :preface
-  (require 'cl-lib)
-  :init
-  (setq handle-keywords
-        '(:repl
-          :docs)))
+
+;;; Core machinery
+
+(defun syd-parent-mode-list (mode)
+  "Return a list of MODE, then MODE's parent, then MODE's grandparent..."
+  (cl-loop for m = mode then (get m 'derived-mode-parent)
+           while m
+           collect m))
+
+(defun syd-handler-alist-name (type)
+  (intern (concat "syd-handle-"
+                  (symbol-name type)
+                  "-alist")))
+
+(defun syd-handler-function-name (type)
+  (intern (concat "syd-handle-" (symbol-name type))))
+
+(defmacro syd-define-handler-type
+    (handler-type arglist &optional docstring)
+  (declare (indent defun))
+  (let ((hook-name (syd-handler-alist-name handler-type))
+        (fn-name (syd-handler-function-name handler-type)))
+    `(progn
+       (defvar ,hook-name nil)
+       (defun ,fn-name (&rest args)
+         ,@(ensure-list docstring)
+         (let (r)
+           (cl-loop
+            for (mode . handle) in ,hook-name
+            ;; Test mode's variable to determine if it's active.  Some modes
+            ;; lack an associated variable, which is very annoying!  The
+            ;; `major-mode' and sledgehammer `minor-mode-list' tests should
+            ;; catch these guys.
+            ;;
+            ;; TODO: Use `syd-parent-mode-list' to support hierarchies of modes.
+            when (or (eq mode major-mode)
+                     (and (boundp mode)
+                          (symbol-value mode))
+                     (memq mode minor-mode-list))
+            do (setq r (apply handle args))
+            when r return r))))))
+
+(defun syd-handle (modes &rest args)
+  (declare (indent defun))
+  (cl-loop
+   for m in (ensure-list modes)
+   do (cl-loop for (type handler) on args by (lambda (xs)
+                                               (cdr (cdr xs)))
+               do (let ((s (->> (symbol-name type)
+                                (string-remove-prefix ":")
+                                intern
+                                syd-handler-alist-name)))
+                    (set s (cons (cons m handler)
+                                 (symbol-value s)))))))
+
+
+;;; Docs handler
+
+(syd-define-handler-type docs (identifier)
+  "Return a buffer visiting documentation for IDENTIFIER.")
+
+(defun syd-handle-docs* (identifier)
+  (interactive (list (symbol-at-point)))
+  (if-let* ((b (save-excursion
+                 (save-window-excursion
+                   (syd-handle-docs identifier)))))
+      (display-buffer b)
+    (message "Couldn't find documentation on %S"
+             (substring-no-properties identifier))))
+
+
+;;; REPL handler
+
+(syd-define-handler-type repl ()
+  "Return a buffer.")
+
+(defun syd-handle-repl* ()
+  (if-let* ((b (save-window-excursion
+                 (syd-handle-repl))))
+      (display-buffer b)
+    (message "Couldn't open a REPL for %S"
+             (substring-no-properties identifier))))
+
+
 
 (provide 'syd/handle)