org-agenda: Fix `org-agenda-skip-if-todo'

* lisp/org-agenda.el (org-agenda-skip-if-todo): Make sure TODO search
  is case sensitive.  Refactor function.

lisp/org-agenda.el

@@ -4921,43 +4921,36 @@ ARGS is a list with first element either `todo', `nottodo',
 `todo-unblocked' or `nottodo-unblocked'.  The remainder is either
 a list of TODO keywords, or a state symbol `todo' or `done' or
 `any'."
-  (let ((kw (car args))
-	(arg (cadr args))
-	todo-wds todo-re)
-    (setq todo-wds
-	  (org-uniquify
-	   (cond
-	    ((listp arg)   ;; list of keywords
-	     (if (member "*" arg)
-		 (mapcar 'substring-no-properties org-todo-keywords-1)
-	       arg))
-	    ((symbolp arg) ;; keyword class name
-	     (cond
-	      ((eq arg 'todo)
-	       (org-delete-all org-done-keywords
-			       (mapcar 'substring-no-properties
-				       org-todo-keywords-1)))
-	      ((eq arg 'done) org-done-keywords)
-	      ((eq arg 'any)
-	       (mapcar 'substring-no-properties org-todo-keywords-1)))))))
-    (setq todo-re
-	  (concat "^\\*+[ \t]+\\<\\("
-		  (mapconcat 'identity todo-wds  "\\|")
-		  "\\)\\>"))
-    (cond
-     ((eq kw 'todo) (re-search-forward todo-re end t))
-     ((eq kw 'nottodo) (not (re-search-forward todo-re end t)))
-     ((eq kw 'todo-unblocked)
-      (catch 'unblocked
-	(while (re-search-forward todo-re end t)
-	  (or (org-entry-blocked-p) (throw 'unblocked t)))
-	nil))
-     ((eq kw 'nottodo-unblocked)
-      (catch 'unblocked
-	(while (re-search-forward todo-re end t)
-	  (or (org-entry-blocked-p) (throw 'unblocked nil)))
-	t))
-     )))
+  (let ((todo-re
+	 (concat "^\\*+[ \t]+"
+		 (regexp-opt
+		  (pcase args
+		    (`(,_ todo)
+		     (org-delete-all org-done-keywords
+				     (copy-sequence org-todo-keywords-1)))
+		    (`(,_ done) org-done-keywords)
+		    (`(,_ any) org-todo-keywords-1)
+		    (`(,_ ,(pred atom))
+		     (error "Invalid TODO class or type: %S" args))
+		    (`(,_ ,(pred (member "*"))) org-todo-keywords-1)
+		    (`(,_ ,todo-list) todo-list))
+		  'words))))
+    (pcase args
+      (`(todo . ,_)
+       (let (case-fold-search) (re-search-forward todo-re end t)))
+      (`(nottodo . ,_)
+       (not (let (case-fold-search) (re-search-forward todo-re end t))))
+      (`(todo-unblocked . ,_)
+       (catch :unblocked
+	 (while (let (case-fold-search) (re-search-forward todo-re end t))
+	   (when (org-entry-blocked-p) (throw :unblocked t)))
+	 nil))
+      (`(nottodo-unblocked . ,_)
+       (catch :unblocked
+	 (while (let (case-fold-search) (re-search-forward todo-re end t))
+	   (when (org-entry-blocked-p) (throw :unblocked nil)))
+	 t))
+      (`(,type . ,_) (error "Unknown TODO skip type: %S" type)))))
 
 ;;;###autoload
 (defun org-agenda-list-stuck-projects (&rest ignore)