[oni-groovy] Add defun-based navigation properties

With this also comes the ability to call ‘narrow-to-defun’ and have it show only
the current function.

oni-groovy.el

@@ -4,7 +4,7 @@
 
 ;; Author: Tom Willemse <tom@ryuslash.org>
 ;; Keywords: local
-;; Version: 2021.1123.002828
+;; Version: 2022.0401.184320
 ;; Package-Requires: (groovy-mode oni-embrace groovy-imports rainbow-delimiters jenkinsfile-mode)
 
 ;; This program is free software; you can redistribute it and/or modify
@@ -34,8 +34,41 @@
   (setq-local comment-auto-fill-only-comments t)
   (auto-fill-mode))
 
+(defconst oni-groovy--regex-defun-start
+  (rx line-start
+      (minimal-match (zero-or-more space))
+      "def "
+      (minimal-match (one-or-more alnum))
+      (minimal-match (zero-or-more space))
+      "("))
+
+(defun oni-groovy-beginning-of-defun ()
+  (interactive)
+  (when (not (region-active-p))
+    (push-mark))
+  (let ((case-fold-search t))
+    (when (re-search-backward oni-groovy--regex-defun-start nil t)
+      t)))
+
+(defun oni-groovy-end-of-defun ()
+  (interactive)
+  (when (not (region-active-p))
+    (push-mark))
+  (let ((case-fold-search t))
+    (when (or (looking-at oni-groovy--regex-defun-start)
+              (re-search-backward oni-groovy--regex-defun-start nil t))
+      (search-forward "{")
+      (forward-char -1)
+      (forward-sexp)
+      (forward-line))))
+
+(defun oni-groovy-setup-defun-navigation ()
+  (setq-local beginning-of-defun-function #'oni-groovy-beginning-of-defun
+              end-of-defun-function #'oni-groovy-end-of-defun))
+
 (define-key groovy-mode-map (kbd "M-I") 'groovy-imports-add-import-dwim)
 
+(add-hook 'groovy-mode-hook #'oni-groovy-setup-defun-navigation)
 (add-hook 'groovy-mode-hook 'display-fill-column-indicator-mode)
 (add-hook 'groovy-mode-hook 'electric-indent-local-mode)
 (add-hook 'groovy-mode-hook 'electric-pair-local-mode)