1 files changed, 74 insertions, 0 deletions
diff --git a/app/assets/javascripts/blob/components/table_contents.vue b/app/assets/javascripts/blob/components/table_contents.vue
new file mode 100644
index 00000000000..78ecb82f2cd
--- /dev/null
+++ b/app/assets/javascripts/blob/components/table_contents.vue
@@ -0,0 +1,74 @@
+<script>
+import { GlDropdown, GlDropdownItem } from '@gitlab/ui';
+
+function getHeaderNumber(el) {
+  return parseInt(el.tagName.match(/\d+/)[0], 10);
+}
+
+export default {
+  components: {
+    GlDropdown,
+    GlDropdownItem,
+  },
+  data() {
+    return {
+      isHidden: false,
+      items: [],
+    };
+  },
+  mounted() {
+    this.blobViewer = document.querySelector('.blob-viewer[data-type="rich"]');
+
+    this.observer = new MutationObserver(() => {
+      if (this.blobViewer.classList.contains('hidden')) {
+        this.isHidden = true;
+      } else if (this.blobViewer.getAttribute('data-loaded') === 'true') {
+        this.isHidden = false;
+        this.generateHeaders();
+      }
+    });
+
+    if (this.blobViewer) {
+      this.observer.observe(this.blobViewer, {
+        attributes: true,
+      });
+    }
+  },
+  beforeDestroy() {
+    if (this.observer) {
+      this.observer.disconnect();
+    }
+  },
+  methods: {
+    generateHeaders() {
+      const headers = [...this.blobViewer.querySelectorAll('h1,h2,h3,h4,h5,h6')];
+
+      if (headers.length) {
+        const firstHeader = getHeaderNumber(headers[0]);
+
+        headers.forEach((el) => {
+          this.items.push({
+            text: el.textContent.trim(),
+            anchor: el.querySelector('a').getAttribute('id'),
+            spacing: Math.max((getHeaderNumber(el) - firstHeader) * 8, 0),
+          });
+        });
+      }
+    },
+  },
+};
+</script>
+
+<template>
+  <gl-dropdown v-if="!isHidden && items.length" icon="list-bulleted" class="gl-mr-2" lazy>
+    <gl-dropdown-item v-for="(item, index) in items" :key="index" :href="`#${item.anchor}`">
+      <span
+        :style="{ 'padding-left': `${item.spacing}px` }"
+        class="gl-display-block"
+        data-testid="tableContentsLink"
+      >
+        {{ item.text }}
+      </span>
+    </gl-dropdown-item>
+  </gl-dropdown>
+</template>