From 9276a14c41e95e5ca17c648fe71c162f35551057 Mon Sep 17 00:00:00 2001
From: Asko Nõmm <ano@ano.ee>
Date: Wed, 11 May 2022 18:09:16 +0300
Subject: Add `id` attributes to headings based on value.

---
 src/clarktown/renderers/heading_block.clj | 28 ++++++++++++++++++++++------
 1 file changed, 22 insertions(+), 6 deletions(-)

(limited to 'src')

diff --git a/src/clarktown/renderers/heading_block.clj b/src/clarktown/renderers/heading_block.clj
index 7f4c7de..563508e 100644
--- a/src/clarktown/renderers/heading_block.clj
+++ b/src/clarktown/renderers/heading_block.clj
@@ -1,9 +1,23 @@
 (ns clarktown.renderers.heading-block
   (:require
     [clojure.string :as string]
-    [clarktown.matchers.heading-block :as matcher]))
+    [clarktown.matchers.heading-block :as matcher])
+  (:import
+    (java.text Normalizer Normalizer$Form)))
 
 
+(defn- slugify
+  "Turn `input` in a URL slug."
+  [input]
+  (let [split-s(-> (Normalizer/normalize input Normalizer$Form/NFD)
+                   (string/replace #"[\P{ASCII}]+" "")
+                   string/lower-case
+                   string/triml
+                   (string/split #"[\p{Space}\p{P}]+"))
+        combined (string/join "-" split-s)]
+    (apply str (take 250 combined))))
+  
+
 (defn render-atx-heading
   "Renders the hashbang heading block."
   [block]
@@ -15,8 +29,9 @@
         value (->> (string/split single-line-block #" ")
                    next
                    (string/join " ")
-                   string/trim)]
-    (str "<h" size ">" value "</h" size ">")))
+                   string/trim)
+        id (slugify value)]
+    (str "<h" size " id=\"" id "\">" value "</h" size ">")))
 
 
 (defn render-settext-heading
@@ -29,10 +44,11 @@
         h1? (= "=" (-> (last lines)
                        string/trim
                        (string/split #"")
-                       first))]
+                       first))
+        id (slugify value)]
     (if h1?
-      (str "<h1>" value "</h1>")
-      (str "<h2>" value "</h2>"))))
+      (str "<h1 id=\"" id "\">" value "</h1>")
+      (str "<h2 id=\"" id "\">" value "</h2>"))))
 
 
 (defn render
-- 
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