feat: Show Table of Contents in the article sidebar (#7085)

app/javascript/portal/components/TableOfContents.vue

@@ -0,0 +1,70 @@
+<template>
+  <div class="hidden lg:block flex-1 scroll-mt-24 pl-4">
+    <div v-if="rows.length > 0" class="sticky top-24 py-12 overflow-auto">
+      <nav class="max-w-2xl">
+        <h2
+          id="on-this-page-title"
+          class="text-slate-800 font-semibold tracking-wide border-b mb-3 leading-7"
+        >
+          {{ tocHeader }}
+        </h2>
+        <ol role="list" class="mt-4 space-y-3 text-base">
+          <li v-for="element in rows" :key="element.slug" class="leading-6">
+            <p :class="getClassName(element)">
+              <a
+                :href="`#${element.slug}`"
+                data-turbolinks="false"
+                class="text-base text-slate-800 cursor-pointer"
+              >
+                {{ element.title }}
+              </a>
+            </p>
+          </li>
+        </ol>
+      </nav>
+    </div>
+  </div>
+</template>
+<script>
+export default {
+  props: {
+    rows: {
+      type: Array,
+      default: () => [],
+    },
+  },
+  computed: {
+    tocHeader() {
+      return window.portalConfig.tocHeader;
+    },
+    h1Count() {
+      return this.rows.filter(el => el.tag === 'h1').length;
+    },
+    h2Count() {
+      return this.rows.filter(el => el.tag === 'h2').length;
+    },
+  },
+  methods: {
+    getClassName(el) {
+      if (el.tag === 'h1') {
+        return '';
+      }
+      if (el.tag === 'h2') {
+        if (this.h1Count > 0) {
+          return 'ml-2';
+        }
+        return '';
+      }
+
+      if (el.tag === 'h3') {
+        if (!this.h1Count && !this.h2Count) {
+          return '';
+        }
+        return 'ml-8';
+      }
+
+      return '';
+    },
+  },
+};
+</script>