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.

---
 resources/test/core_result.html                 |  8 +++----
 src/clarktown/renderers/heading_block.clj       | 28 +++++++++++++++++++------
 test/clarktown/renderers/heading_block_test.clj | 26 +++++++++++------------
 3 files changed, 39 insertions(+), 23 deletions(-)

diff --git a/resources/test/core_result.html b/resources/test/core_result.html
index 54273e0..01f91aa 100644
--- a/resources/test/core_result.html
+++ b/resources/test/core_result.html
@@ -48,7 +48,7 @@ function markdownToHTML(markdown) {
 
 <p>This is <em><strong>bold italic text</strong></em> and <em><strong>this is also</strong></em>. <em>What about italic text that <strong>has bold text</strong></em>?</p>
 
-<h2>Hi there, world!</h2>
+<h2 id="hi-there-world">Hi there, world!</h2>
 
 <ul><li>List item</li><li>Another list <del>item</del><ul><li>Sub list item</li><li>Another sub list item<ul><li>Sub sub list item</li><li>Continuing sub list item</li></ul></li></ul></li><li>Continuing list item</li></ul>
 
@@ -59,14 +59,14 @@ function markdownToHTML(markdown) {
 <pre><code>code goes here.
 # This is a heading.</code></pre>
 
-<h1>This is a H1 heading with settext</h1>
+<h1 id="this-is-a-h1-heading-with-settext">This is a H1 heading with settext</h1>
 
-<h2>And this is a H2 heading with settext</h2>
+<h2 id="and-this-is-a-h2-heading-with-settext">And this is a H2 heading with settext</h2>
 
 <p>Testing paragraph right before a code block</p>
 
 <pre><code>code goes here</code></pre>
 
-<h1>Heading goes here</h1>
+<h1 id="heading-goes-here">Heading goes here</h1>
 
 <p>Paragraph right after heading</p>
\ No newline at end of file
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
diff --git a/test/clarktown/renderers/heading_block_test.clj b/test/clarktown/renderers/heading_block_test.clj
index 8f229fb..a0852e8 100644
--- a/test/clarktown/renderers/heading_block_test.clj
+++ b/test/clarktown/renderers/heading_block_test.clj
@@ -6,27 +6,27 @@
 
 (deftest atx-heading-renderer-test
   (testing "ATX heading block that's a H1"
-    (is (= "<h1>This is a heading block.</h1>"
+    (is (= "<h1 id=\"this-is-a-heading-block\">This is a heading block.</h1>"
            (heading-block/render "# This is a heading block." nil nil))))
 
   (testing "ATX heading block that's a H2"
-    (is (= "<h2>This is a heading block.</h2>"
+    (is (= "<h2 id=\"this-is-a-heading-block\">This is a heading block.</h2>"
            (heading-block/render "## This is a heading block." nil nil))))
 
   (testing "ATX heading block that's a H3"
-    (is (= "<h3>This is a heading block.</h3>"
+    (is (= "<h3 id=\"this-is-a-heading-block\">This is a heading block.</h3>"
            (heading-block/render "### This is a heading block." nil nil))))
 
   (testing "ATX heading block that's a H4"
-    (is (= "<h4>This is a heading block.</h4>"
+    (is (= "<h4 id=\"this-is-a-heading-block\">This is a heading block.</h4>"
            (heading-block/render "#### This is a heading block." nil nil))))
 
   (testing "ATX heading block that's a H5"
-    (is (= "<h5>This is a heading block.</h5>"
+    (is (= "<h5 id=\"this-is-a-heading-block\">This is a heading block.</h5>"
            (heading-block/render "##### This is a heading block." nil nil))))
     
   (testing "ATX heading block that's a H6"
-    (is (= "<h6>This is a heading block.</h6>"
+    (is (= "<h6 id=\"this-is-a-heading-block\">This is a heading block.</h6>"
            (heading-block/render "###### This is a heading block." nil nil))))
   
   (testing "No H tag when 7 or more # characters"
@@ -38,11 +38,11 @@
            (heading-block/render "#This is not a heading block." nil nil))))
   
   (testing "ATX heading can precede up to 3 spaces"
-    (is (= "<h1>This is a heading.</h1>"
+    (is (= "<h1 id=\"this-is-a-heading\">This is a heading.</h1>"
            (heading-block/render " # This is a heading." nil nil)))
-    (is (= "<h1>This is a heading.</h1>"
+    (is (= "<h1 id=\"this-is-a-heading\">This is a heading.</h1>"
            (heading-block/render "  # This is a heading." nil nil)))
-    (is (= "<h1>This is a heading.</h1>"
+    (is (= "<h1 id=\"this-is-a-heading\">This is a heading.</h1>"
            (heading-block/render "   # This is a heading." nil nil))))
   
   (testing "But no more than 3 spaces"
@@ -53,17 +53,17 @@
 
 (deftest settext-heading-renderer-text
   (testing "Settext heading block that's a H1"
-    (is (= "<h1>This is a heading block.</h1>"
+    (is (= "<h1 id=\"this-is-a-heading-block\">This is a heading block.</h1>"
            (heading-block/render "This is a heading block.\n=========" nil nil))))
 
   (testing "Settext heading block that's a H1 spanning multiple lines"
-    (is (= "<h1>This is a \nheading block spanning multiple lines.</h1>"
+    (is (= "<h1 id=\"this-is-a-heading-block-spanning-multiple-lines\">This is a \nheading block spanning multiple lines.</h1>"
            (heading-block/render "This is a \nheading block spanning multiple lines.\n========" nil nil))))
 
   (testing "Settext heading block that's a H2"
-    (is (= "<h2>This is a heading block.</h2>"
+    (is (= "<h2 id=\"this-is-a-heading-block\">This is a heading block.</h2>"
            (heading-block/render "This is a heading block.\n---------" nil nil))))
 
   (testing "Settext heading block that's a H2 spanning multiple lines"
-    (is (= "<h2>This is a \nheading block spanning multiple lines.</h2>"
+    (is (= "<h2 id=\"this-is-a-heading-block-spanning-multiple-lines\">This is a \nheading block spanning multiple lines.</h2>"
            (heading-block/render "This is a \nheading block spanning multiple lines.\n--------" nil nil)))))
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