From a2d7dbac6d959266f64677e18219834aab4cbf88 Mon Sep 17 00:00:00 2001
From: Ashish Padhy <100484401+Shurtu-gal@users.noreply.github.com>
Date: Wed, 8 Nov 2023 14:53:43 +0530
Subject: [PATCH] feat: add collapsing and custom hook

---
 components/CaseTOC.js                     | 132 ++++++++++++++++++----
 components/helpers/useHeadingsObserver.js |  36 ++++++
 2 files changed, 143 insertions(+), 25 deletions(-)
 create mode 100644 components/helpers/useHeadingsObserver.js

diff --git a/components/CaseTOC.js b/components/CaseTOC.js
index 1104b6502eef..4af86af88049 100644
--- a/components/CaseTOC.js
+++ b/components/CaseTOC.js
@@ -1,12 +1,13 @@
-import { useState } from "react";
+import { useMemo, useState } from "react";
 import Scrollspy from "react-scrollspy";
 import { twMerge } from "tailwind-merge";
 import ArrowRight from "./icons/ArrowRight";
+import { useHeadingsObserver } from "./helpers/useHeadingsObserver";
 
 const convertContentToTocItems = (content, level = 1) => {
   const tocItems = [];
 
-  for(let section of content) {
+  for (let section of content) {
     const item = {
       lvl: level,
       content: section.title,
@@ -16,16 +17,67 @@ const convertContentToTocItems = (content, level = 1) => {
         .toLowerCase(),
     };
 
-    tocItems.push(item);
     if (section.children && section.children.length > 0) {
       const children = convertContentToTocItems(section.children, level + 1);
-      tocItems.push(...children);
+      item.children = children;
     }
+
+    tocItems.push(item);
   }
 
   return tocItems;
 };
 
+function TOCItem({ item, index, currSelected, closeMenu }) {
+  const [open, setOpen] = useState(false);
+  const handleClick = () => {
+    closeMenu();
+    setOpen(false);
+  };
+
+  return (
+    <>
+      {item.children && item.children.length > 0 && (
+        <span onClick={() => setOpen(!open)}>
+          <ArrowRight
+            className={`${
+              open ? "rotate-90" : "0"
+            } transform transition duration-200 ease-in-out h-6 inline-block mr-1 -mt-0.5 text-primary-500 absolute -left-1`}
+          />
+        </span>
+      )}
+      <a
+        className={`mb-1 transition duration-100 ease-in-out text-gray-900 font-normal text-sm font-sans antialiased hover:underline flex items-center ${
+          currSelected === item.slug && "text-primary-500 font-bold"
+        }`}
+        href={`#${item.slug}`}
+        key={index}
+        style={{ marginLeft: `${(item.lvl - 1) * 16}px` }}
+        onClick={handleClick}
+      >
+        {item.content}
+      </a>
+      {item.children && item.children.length > 0 && (
+        <ul
+          className={`left-0 relative ${
+            open ? "max-h-[1000px]" : "max-h-[0.01px]"
+          } overflow-hidden transition-all duration-300 ease-in-out`}
+        >
+          {item.children.map((item, index) => (
+            <TOCItem
+              item={item}
+              index={index}
+              key={index}
+              closeMenu={closeMenu}
+              currSelected={currSelected}
+            />
+          ))}
+        </ul>
+      )}
+    </>
+  );
+}
+
 export default function CaseTOC({
   className,
   cssBreakingPoint = "xl",
@@ -33,40 +85,70 @@ export default function CaseTOC({
   contentSelector,
 }) {
   if (!toc || !toc.length) return null;
-  const tocItems = convertContentToTocItems(toc);
-
+  const tocItems = useMemo(() => convertContentToTocItems(toc), [toc]);
   const [open, setOpen] = useState(false);
+  const { currActive: selected } = useHeadingsObserver();
 
   return (
-    <div className={twMerge(`${className} ${tocItems.length ? '' : 'hidden'} ${cssBreakingPoint === 'xl' ? 'xl:block' : 'lg:block'} md:top-24 md:max-h-(screen-14) z-20`)} onClick={() => setOpen(!open)}>
-      <div className={`flex cursor-pointer ${tocItems.length ? '' : 'hidden'} ${cssBreakingPoint === 'xl' ? 'xl:cursor-auto' : 'lg:cursor-auto'} xl:mt-2`}>
-        <h5 className={twMerge(`${open && 'mb-4'} flex-1 text-primary-500 font-medium uppercase tracking-wide text-sm font-sans antialiased ${cssBreakingPoint === 'xl' ? 'xl:mb-4 xl:text-xs xl:text-gray-900 xl:font-bold' : 'lg:mb-4 lg:text-xs lg:text-gray-900 lg:font-bold'}`)}>
+    <div
+      className={twMerge(
+        `${className} ${tocItems.length ? "" : "hidden"} ${
+          cssBreakingPoint === "xl" ? "xl:block" : "lg:block"
+        } md:top-24 md:max-h-(screen-14) z-20`,
+      )}
+    >
+      <div
+        className={`flex cursor-pointer ${tocItems.length ? "" : "hidden"} ${
+          cssBreakingPoint === "xl" ? "xl:cursor-auto" : "lg:cursor-auto"
+        } xl:mt-2`}
+      >
+        <h5
+          className={twMerge(
+            `${
+              open && "mb-4"
+            } flex-1 text-primary-500 font-medium uppercase tracking-wide text-sm font-sans antialiased ${
+              cssBreakingPoint === "xl"
+                ? "xl:mb-4 xl:text-xs xl:text-gray-900 xl:font-bold"
+                : "lg:mb-4 lg:text-xs lg:text-gray-900 lg:font-bold"
+            }`,
+          )}
+        >
           On this page
         </h5>
-        <div className={`text-underline text-center p4 ${cssBreakingPoint === 'xl' ? 'xl:hidden' : 'lg:hidden'}`}>
-          <ArrowRight className={`${ open ? '-rotate-90' : 'rotate-90' } transform transition duration-200 ease-in-out h-6 -mt-0.5 text-primary-500`} />
+        <div
+          className={`text-underline text-center p4 ${
+            cssBreakingPoint === "xl" ? "xl:hidden" : "lg:hidden"
+          }`}
+          onClick={() => setOpen(!open)}
+        >
+          <ArrowRight
+            className={`${
+              open ? "-rotate-90" : "rotate-90"
+            } transform transition duration-200 ease-in-out h-6 -mt-0.5 text-primary-500`}
+          />
         </div>
       </div>
-      <div className={`${!open && 'hidden'} ${cssBreakingPoint === 'xl' ? 'xl:block' : 'lg:block'}`}>
+      <div
+        className={`${!open && "hidden"} ${
+          cssBreakingPoint === "xl" ? "xl:block" : "lg:block"
+        }`}
+      >
         <Scrollspy
-          items={tocItems.map(item => item.slug)}
+          items={tocItems.map((item) => item.slug)}
           currentClassName="text-primary-500 font-bold"
           componentTag="div"
           rootEl={contentSelector}
           offset={-120}
         >
-          {
-            tocItems.map((item, index) => (
-              <a
-                className={`block mb-1 transition duration-100 ease-in-out text-gray-900 font-normal text-sm font-sans antialiased hover:underline`}
-                href={`#${item.slug}`}
-                key={index}
-                style={{ marginLeft: `${(item.lvl - 1) * 16}px` }}
-              >
-                {item.content}
-              </a>
-            ))
-          }
+          {tocItems.map((item, index) => (
+            <TOCItem
+              item={item}
+              index={index}
+              key={index}
+              closeMenu={() => setOpen(false)}
+              currSelected={selected}
+            />
+          ))}
         </Scrollspy>
       </div>
     </div>
diff --git a/components/helpers/useHeadingsObserver.js b/components/helpers/useHeadingsObserver.js
new file mode 100644
index 000000000000..56de62808c8b
--- /dev/null
+++ b/components/helpers/useHeadingsObserver.js
@@ -0,0 +1,36 @@
+import { useEffect, useRef, useState } from "react";
+
+/**
+ * @description Custom hook to observe headings and set the current active heading
+ * @example const { currActive } = useHeadingsObserver();
+ * @returns {object} currActive - current active heading
+ */
+export function useHeadingsObserver() {
+  const observer = useRef(null);
+  const headingsRef = useRef([]);
+  const [currActive, setCurrActive] = useState(null);
+
+  useEffect(() => {
+    const callback = (entries) => {
+      entries.forEach(entry => {
+        if (entry.isIntersecting) {
+          setCurrActive(entry.target.id);
+        }
+      })
+    }
+
+    // The heading in from top 20% of the viewport to top 30% of the viewport will be considered as active
+    observer.current = new IntersectionObserver(callback, {
+      rootMargin: '-20% 0px -70% 0px',
+    });
+
+    headingsRef.current = document.querySelectorAll('h2, h3');
+    headingsRef.current.forEach(heading => {
+      observer.current.observe(heading);
+    })
+
+    return () => observer.current.disconnect();
+  }, []);
+
+  return { currActive }
+}