From f49a747adfea970f73dc96c07240794c60cec696 Mon Sep 17 00:00:00 2001
From: Spencer Williams <spnw@plexwave.org>
Date: Sat, 29 Mar 2025 19:09:35 -0400
Subject: Add option to export internal links with custom CSS class

---
 seam-export.el | 17 ++++++++++++++++-
 seam-html.el   |  3 +++
 seam-test.el   | 15 +++++++++++++++
 3 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/seam-export.el b/seam-export.el
index 00312e5..6e39bbc 100644
--- a/seam-export.el
+++ b/seam-export.el
@@ -34,6 +34,7 @@
 (defvar seam-export--template nil)
 (defvar seam-export--root-path nil)
 (defvar seam-export--no-extension nil)
+(defvar seam-export--internal-link-class nil)
 (defvar seam-export--options nil)
 
 (defgroup seam-export nil
@@ -74,6 +75,11 @@ properties:
     Whether to drop the \".html\" file extension in links.  Defaults to
     nil.
 
+  `:internal-link-class'
+
+    CSS class name for internal links.  Defaults to the value of
+    `seam-export-internal-link-class'.
+
   `:backend-options'
 
     A plist of extra options passed to the Org HTML backend.  This can be
@@ -165,6 +171,12 @@ the datetime attribute of <time>.  Passed to `format-time-string'."
   :group 'seam-export
   :type 'sexp)
 
+(defcustom seam-export-internal-link-class nil
+  "CSS class name to use for internal links (i.e., links to other Seam
+notes)."
+  :group 'seam-export
+  :type 'string)
+
 (defvar seam-export-backend-options
   (list
    :html-container "article"
@@ -292,7 +304,10 @@ the datetime attribute of <time>.  Passed to `format-time-string'."
                          (seam-export--template template)
                          (seam-export--options (org-combine-plists
                                                 seam-export-backend-options
-                                                backend-options)))
+                                                backend-options))
+                         (seam-export--internal-link-class
+                          (or (plist-get plist :internal-link-class)
+                              seam-export-internal-link-class)))
                      (seam-export--note-to-html file dir))))))))
 
 (defun seam-export-all-notes ()
diff --git a/seam-html.el b/seam-html.el
index b74be0b..018e56f 100644
--- a/seam-html.el
+++ b/seam-html.el
@@ -195,6 +195,9 @@ INFO is a plist holding contextual information.  See
 			                      link))))
 	           (and (eq link (org-element-map parent 'link #'identity info t))
 		              (org-export-read-attribute :attr_html parent)))
+           ;; Add Seam internal link class if appropriate.
+           (when (and seam-export--internal-link-class (string= "seam" link-type))
+             (list :class seam-export--internal-link-class))
 	         ;; Also add attributes from link itself.  Currently, those
 	         ;; need to be added programmatically before `org-html-link'
 	         ;; is invoked, for example, by backends building upon HTML
diff --git a/seam-test.el b/seam-test.el
index 0b7df1c..7d10f94 100644
--- a/seam-test.el
+++ b/seam-test.el
@@ -47,6 +47,7 @@
           (seam-title-formatter (lambda (title _type) title))
           (seam-export-template-file nil)
           (seam-export-template-string seam-export-default-template-string)
+          (seam-export-internal-link-class nil)
           (seam-export-alist
            `((,(file-name-concat seam-test-directory "html")
               :types ("public")
@@ -254,6 +255,20 @@ extension."
         (buffer-string)
         (re-search-forward "<a href=\"/bar\">"))))))
 
+(ert-deftest seam-test-link-internal-class ()
+  "Test that setting `seam-export-internal-link-class' correctly renders
+the class."
+  (should
+   (identity
+    (seam-test-with-notes ((seam-export-internal-link-class "internal"))
+        ((foo "foo" "public")
+         (bar "bar" "public"))
+      (seam-test-add-contents foo (seam-test-link-to-buffer bar))
+      (with-temp-buffer
+        (insert-file-contents "html/foo.html")
+        (buffer-string)
+        (re-search-forward "<a href=\"/bar.html\" class=\"internal\">"))))))
+
 (ert-deftest seam-test-link-getters ()
   (should
    (equal
-- 
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