update 2

package.json

@@ -49,7 +49,7 @@
     "firebase": "^10.13.0",
     "firebase-admin": "^12.3.1",
     "highlight.js": "^11.10.0",
-    "katex": "^0.16.11",
+    "katex": "^0.16.47",
     "lucide-react": "^0.525.0",
     "marked": "^18.0.5",
     "next": "^14.2.5",

src/app/admin/subject/[slug]/[unit]/frq/[id]/page.tsx

@@ -0,0 +1,51 @@
+"use client";
+
+import FRQEditorRenderer from "@/components/frq/editorRenderer";
+import { db } from "@/lib/firebase";
+import { doc, getDoc } from "firebase/firestore";
+import { usePathname } from "next/navigation";
+import { useEffect, useState } from "react";
+
+const Page = () => {
+  const pathname = usePathname() ?? "";
+
+  const pathParts = pathname.split("/").slice(-4);
+  const subject = pathParts[0] ?? "";
+  const unitId = pathParts[1] ?? "";
+  const frqId = pathParts[3] ?? "";
+
+  const [frqFound, setFrqFound] = useState<boolean | null>(null);
+
+  useEffect(() => {
+    if (!subject || !unitId || !frqId) {
+      setFrqFound(false);
+      return;
+    }
+
+    (async () => {
+      const docRef = doc(
+        db,
+        "subjects",
+        subject,
+        "units",
+        unitId,
+        "frqs",
+        frqId,
+      );
+
+      const docSnap = await getDoc(docRef);
+      setFrqFound(docSnap.exists());
+    })().catch((error) => {
+      console.error("Error fetching FRQ:", error);
+      setFrqFound(false);
+    });
+  }, [subject, unitId, frqId]);
+
+  if (frqFound === null) {
+    return <div>Loading...</div>;
+  }
+
+  return <FRQEditorRenderer frqFound={frqFound} />;
+};
+
+export default Page;

src/app/admin/subject/[slug]/_components/chapterContent.tsx

@@ -19,6 +19,7 @@ interface ChapterComponentProps {
   setChapterVisibility: (chapterId: string, isPublic: boolean) => void;
   moveChapterUp: (chapterId: string) => void;
   moveChapterDown: (chapterId: string) => void;
+  hasUnit0?: boolean;
 }
 
 /**
@@ -36,6 +37,7 @@ function ChapterComponent({
   setChapterVisibility,
   moveChapterUp,
   moveChapterDown,
+  hasUnit0,
 }: ChapterComponentProps) {
   const [editing, setEditing] = useState<boolean>(false);
   const [localTitle, setLocalTitle] = useState<string>(chapter.title);
@@ -81,7 +83,7 @@ function ChapterComponent({
 
       <Link
         className="whitespace-nowrap rounded-full border border-input bg-background px-4 py-2 text-sm font-medium ring-offset-background transition-colors hover:bg-accent focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring focus-visible:ring-offset-2 disabled:pointer-events-none disabled:opacity-50"
-        href={`/admin/subject/${subjectSlug}/${unitId}/chapter/${chapter.id}?subject=${subjectTitle}&unitIndex=${unitIndex + 1}&chapter=${chapter.title}`}
+        href={`/admin/subject/${subjectSlug}/${unitId}/chapter/${chapter.id}?subject=${subjectTitle}&unitIndex=${hasUnit0 ? unitIndex : unitIndex + 1}&chapter=${chapter.title}`}
       >
         Edit Chapter {index + 1}
       </Link>

src/app/admin/subject/[slug]/_components/unit.tsx

@@ -35,6 +35,7 @@ interface UnitComponentProps {
   onMoveDown: (index: number) => void;
   subjectSlug: string;
   subjectTitle: string;
+  hasUnit0?: boolean;
 }
 
 /**
@@ -50,6 +51,7 @@ function UnitComponent({
   onMoveDown,
   subjectSlug,
   subjectTitle,
+  hasUnit0,
 }: UnitComponentProps) {
   const [expanded, setExpanded] = useState<boolean>(false);
 
@@ -369,6 +371,7 @@ function UnitComponent({
                 setChapterVisibility={setChapterVisibility}
                 moveChapterUp={moveChapterUp}
                 moveChapterDown={moveChapterDown}
+                hasUnit0={hasUnit0}
               />
             ))}
           </div>

src/app/admin/subject/[slug]/page.tsx

@@ -69,6 +69,7 @@ export default function Page({ params }: { params: { slug: string } }) {
   const { user, error, setError, setLoading } = useUser();
   const [subjectTitle, setSubjectTitle] = useState<string>("");
   const [units, setUnits] = useState<Unit[]>([]);
+  const [hasUnit0, setHasUnit0] = useState<boolean>(false);
   const [resetting, setResetting] = useState<boolean>(false);
 
   const [subjectLoading, setSubjectLoading] = useState<boolean>(true);
@@ -88,6 +89,7 @@ export default function Page({ params }: { params: { slug: string } }) {
             const fetched = docSnap.data() as Subject;
             setSubjectTitle(fetched.title);
             setUnits(fetched.units || []);
+            setHasUnit0(fetched.hasUnit0 ?? false);
           } else {
             // Subject not found -> create new with default template
             // Also try to fill in subject title from `apClasses` if found
@@ -259,6 +261,7 @@ export default function Page({ params }: { params: { slug: string } }) {
     const subjectToSave: Subject = {
       title: subjectTitle,
       units: units,
+      hasUnit0: hasUnit0,
     };
 
     try {
@@ -463,21 +466,37 @@ export default function Page({ params }: { params: { slug: string } }) {
             {subjectTitle || "Untitled Subject"}
           </h1>
 
+          {/* hasUnit0 Toggle */}
+          <label className="mb-4 flex items-center gap-2 text-sm font-medium">
+            <input
+              id="has-unit0"
+              type="checkbox"
+              checked={hasUnit0}
+              onChange={(e) => {
+                setHasUnit0(e.target.checked);
+                setUnsavedChanges(true);
+              }}
+              className="h-4 w-4"
+            />
+            This subject has a Unit 0 (foundational unit numbered starting from 0)
+          </label>
+
           {/* Render each Unit */}
           <div className="my-4 space-y-4">
             {units.map((unit, index) => (
-              <UnitComponent
-                key={unit.id}
-                unit={unit}
-                index={index}
-                subjectTitle={subjectTitle}
-                onChange={handleUnitChange}
-                onDelete={handleDeleteUnit}
-                onMoveUp={handleMoveUnitUp}
-                onMoveDown={handleMoveUnitDown}
-                subjectSlug={params.slug}
-              />
-            ))}
+            <UnitComponent
+              key={unit.id}
+              unit={unit}
+              index={index}
+              subjectTitle={subjectTitle}
+              onChange={handleUnitChange}
+              onDelete={handleDeleteUnit}
+              onMoveUp={handleMoveUnitUp}
+              onMoveDown={handleMoveUnitDown}
+              subjectSlug={params.slug}
+              hasUnit0={hasUnit0}
+            />
+          ))}
           </div>
 
           {/* Add new Unit */}

src/app/sitemap.ts

@@ -32,7 +32,8 @@ export default async function sitemap(): Promise<MetadataRoute.Sitemap> {
     });
 
     subject.units.forEach((unit, unitIndex) => {
-      const unitSegment = `unit-${unitIndex + 1}-${unit.id}`;
+      const uNum = subject.hasUnit0 ? unitIndex : unitIndex + 1;
+      const unitSegment = `unit-${uNum}-${unit.id}`;
       for (const chapter of unit.chapters ?? []) {
         // Only list publicly readable chapters — gated content can't be
         // crawled or cited anyway, and listing it invites thin-page penalties.

src/app/subject/[slug]/(sidebar)/[unit]/chapter/[id]/[title]/ChapterClient.tsx

@@ -26,13 +26,15 @@ const ChapterClient = ({
 
   useEffect(() => {
     if (subject && content) {
-      const unitIndex = Number(params.unit.split("-")[1]) - 1;
+      const unitNum = Number(params.unit.split("-")[1]);
+      const unitIndex = subject.hasUnit0 ? unitNum : unitNum - 1;
       const chapterIndex = subject.units[unitIndex]!.chapters.findIndex(
         (ch) => ch.id === params.id,
       );
       const chapter = subject.units[unitIndex]!.chapters[chapterIndex];
+      const displayUnit = subject.hasUnit0 ? unitIndex : unitIndex + 1;
 
-      document.title = `FiveHive - ${subject.title} ${unitIndex + 1}.${chapterIndex + 1} - ${chapter?.title}`;
+      document.title = `FiveHive - ${subject.title} ${displayUnit}.${chapterIndex + 1} - ${chapter?.title}`;
     }
   }, [subject, content, params.unit, params.id]);
 
@@ -64,7 +66,8 @@ const ChapterClient = ({
   }
 
   if (subject && content) {
-    const unitIndex = Number(params.unit.split("-")[1]) - 1;
+    const unitNum = Number(params.unit.split("-")[1]);
+    const unitIndex = subject.hasUnit0 ? unitNum : unitNum - 1;
     const chapterIndex = subject.units[unitIndex]!.chapters.findIndex(
       (ch) => ch.id === params.id,
     );
@@ -85,6 +88,7 @@ const ChapterClient = ({
         chapterTitle={chapter.title}
         chapterId={params.id}
         author={content.author}
+        hasUnit0={subject.hasUnit0}
       >
         <Renderer content={content.data} />
       </ChapterScaffold>

src/app/subject/[slug]/(sidebar)/[unit]/chapter/[id]/[title]/ChapterScaffold.tsx

@@ -24,6 +24,7 @@ export default function ChapterScaffold({
   chapterId,
   author,
   children,
+  hasUnit0,
 }: {
   subjectTitle: string;
   units: Unit[];
@@ -34,6 +35,7 @@ export default function ChapterScaffold({
   chapterId: string;
   author: string;
   children: React.ReactNode;
+  hasUnit0?: boolean;
 }) {
   return (
     <div className="relative flex grow flex-col">
@@ -46,7 +48,7 @@ export default function ChapterScaffold({
           />
 
           <h1 className="my-2 text-balance text-center text-5xl font-extrabold">
-            {unitIndex + 1}.{chapterIndex + 1} - {chapterTitle}
+            {hasUnit0 ? unitIndex : unitIndex + 1}.{chapterIndex + 1} - {chapterTitle}
           </h1>
           <p>{author}</p>
           <div className="my-4">
@@ -63,12 +65,14 @@ export default function ChapterScaffold({
             units={units}
             unitIndex={unitIndex}
             chapterIndex={chapterIndex}
+            hasUnit0={hasUnit0}
           />
           <NextArticle
             subjectTitle={subjectTitle}
             units={units}
             unitIndex={unitIndex}
             chapterIndex={chapterIndex}
+            hasUnit0={hasUnit0}
           />
         </div>
       </div>
@@ -83,11 +87,13 @@ function PreviousArticle({
   units,
   unitIndex,
   chapterIndex,
+  hasUnit0,
 }: {
   subjectTitle: string;
   units: Unit[];
   unitIndex: number;
   chapterIndex: number;
+  hasUnit0?: boolean;
 }) {
   let unit = units[unitIndex];
   let newUnitIndex = unitIndex;
@@ -106,10 +112,11 @@ function PreviousArticle({
   if (!unit) return null;
 
   const subjectSlug = formatSlug(subjectTitle.replace(/AP /g, ""));
+  const uNum = hasUnit0 ? newUnitIndex : newUnitIndex + 1;
 
   return (
     <Link
-      href={`/subject/${subjectSlug}/unit-${newUnitIndex + 1}-${unit.id}/chapter/${unit.chapters[newChapterIndex]?.id}/${formatSlug(unit.chapters[newChapterIndex]?.title ?? "")}`}
+      href={`/subject/${subjectSlug}/unit-${uNum}-${unit.id}/chapter/${unit.chapters[newChapterIndex]?.id}/${formatSlug(unit.chapters[newChapterIndex]?.title ?? "")}`}
       className={cn(buttonVariants({ variant: "outline" }), "gap-2")}
     >
       <ArrowLeft />
@@ -123,11 +130,13 @@ function NextArticle({
   units,
   unitIndex,
   chapterIndex,
+  hasUnit0,
 }: {
   subjectTitle: string;
   units: Unit[];
   unitIndex: number;
   chapterIndex: number;
+  hasUnit0?: boolean;
 }) {
   let unit = units[unitIndex];
   let newUnitIndex = unitIndex;
@@ -147,10 +156,11 @@ function NextArticle({
   if (!unit) return null;
 
   const subjectSlug = formatSlug(subjectTitle.replace(/AP /g, ""));
+  const uNum = hasUnit0 ? newUnitIndex : newUnitIndex + 1;
 
   return (
     <Link
-      href={`/subject/${subjectSlug}/unit-${newUnitIndex + 1}-${unit.id}/chapter/${unit.chapters[newChapterIndex]?.id}/${formatSlug(unit.chapters[newChapterIndex]?.title ?? "")}`}
+      href={`/subject/${subjectSlug}/unit-${uNum}-${unit.id}/chapter/${unit.chapters[newChapterIndex]?.id}/${formatSlug(unit.chapters[newChapterIndex]?.title ?? "")}`}
       className={cn(buttonVariants({ variant: "outline" }), "ml-auto gap-2")}
     >
       Next Chapter

src/app/subject/[slug]/(sidebar)/[unit]/chapter/[id]/[title]/page.tsx

@@ -20,7 +20,8 @@ type PageParams = { slug: string; unit: string; id: string; title: string };
  */
 export default async function Page({ params }: { params: PageParams }) {
   const subject = await getSubject(params.slug);
-  const unitIndex = Number(params.unit.split("-")[1]) - 1;
+  const unitNum = Number(params.unit.split("-")[1]);
+  const unitIndex = subject?.hasUnit0 ? unitNum : unitNum - 1;
   const unit = subject?.units[unitIndex];
   const chapterIndex =
     unit?.chapters.findIndex((ch) => ch.id === params.id) ?? -1;
@@ -49,6 +50,7 @@ export default async function Page({ params }: { params: PageParams }) {
       chapterTitle={chapter.title}
       chapterId={params.id}
       author={content.author}
+      hasUnit0={subject.hasUnit0}
     >
       <ChapterArticle data={content.data} />
     </ChapterScaffold>

src/app/subject/[slug]/(sidebar)/page.tsx

@@ -93,6 +93,7 @@ const Page = ({ params }: { params: { slug: string } }) => {
                 key={unitIndex}
                 pathname={pathname}
                 preview={user?.access === "member" || user?.access === "admin"}
+                hasUnit0={subject.hasUnit0}
               />
             ))}
           </Accordion>

src/components/frq/editorRenderer.tsx

@@ -0,0 +1,17 @@
+interface FRQEditorRendererProps {
+  frqFound: boolean;
+}
+
+const FRQEditorRenderer = ({
+  frqFound,
+}: FRQEditorRendererProps) => {
+  return (
+    <div>
+      {frqFound
+        ? "FRQ loaded successfully."
+        : "Failed to load FRQ."}
+    </div>
+  );
+};
+
+export default FRQEditorRenderer;