spsays-training/app/essays/[slug]/page.tsx

export const dynamic = "force-dynamic";

import Link from "next/link";
import { notFound } from "next/navigation";
import { PageHeader } from "@/components/page-header";
import { Card, CardContent } from "@/components/ui/card";
import { buttonVariants } from "@/components/ui/button";
import { ChevronLeft, ChevronRight } from "lucide-react";
import { cn } from "@/lib/utils";
import { prisma } from "@/lib/db";
import type { JsonValue } from "@prisma/client/runtime/library";

// ---------------------------------------------------------------------------
// HTML sanitisation (same pattern used across all readers)
// ---------------------------------------------------------------------------

function sanitizeHtml(html: string): string {
  let clean = html.replace(/<script[\s>][\s\S]*?<\/script>/gi, "");
  clean = clean.replace(/<style[\s>][\s\S]*?<\/style>/gi, "");
  clean = clean.replace(/<iframe[\s>][\s\S]*?<\/iframe>/gi, "");
  clean = clean.replace(
    /<\/?(?:script|style|iframe|object|embed|form|input|textarea|select|button)[^>]*>/gi,
    "",
  );
  clean = clean.replace(/\s+on\w+\s*=\s*(?:"[^"]*"|'[^']*'|[^\s>]+)/gi, "");
  clean = clean.replace(/href\s*=\s*"javascript:[^"]*"/gi, 'href=""');
  clean = clean.replace(/href\s*=\s*'javascript:[^']*'/gi, "href=''");
  return clean;
}

function normalizeParagraphs(paragraphs: string[] | JsonValue): string[] {
  let result: string[];

  if (typeof paragraphs === "string") {
    try {
      const parsed = JSON.parse(paragraphs);
      result = Array.isArray(parsed) ? parsed : [paragraphs];
    } catch {
      result = [paragraphs];
    }
  } else if (Array.isArray(paragraphs)) {
    result = paragraphs as string[];
  } else {
    result = [];
  }

  return result.map(sanitizeHtml);
}

// ---------------------------------------------------------------------------
// Data fetching
// ---------------------------------------------------------------------------

type EssayData = {
  slug: string;
  title: string;
  author: string;
  year: number | null;
  group: string | null;
  paragraphs: string[];
};

type SidebarItem = {
  slug: string;
  title: string;
};

async function getEssay(slug: string): Promise<EssayData | null> {
  const doc = await prisma.essay.findUnique({ where: { slug } });
  if (!doc) return null;
  return {
    slug: doc.slug,
    title: doc.title,
    author: doc.author,
    year: doc.year,
    group: doc.group,
    paragraphs: normalizeParagraphs(doc.paragraphs),
  };
}

async function getEssaySidebar(): Promise<SidebarItem[]> {
  return prisma.essay.findMany({
    orderBy: [{ group: "asc" }, { order: "asc" }],
    select: { slug: true, title: true },
  });
}

// ---------------------------------------------------------------------------
// Page
// ---------------------------------------------------------------------------

export default async function EssayPage({
  params,
}: {
  params: Promise<{ slug: string }>;
}) {
  const { slug } = await params;

  const essay = await getEssay(slug);
  if (!essay) notFound();

  const allEssays = await getEssaySidebar();
  const currentIdx = allEssays.findIndex((item) => item.slug === slug);

  const prev = currentIdx > 0 ? allEssays[currentIdx - 1] : null;
  const next =
    currentIdx < allEssays.length - 1 ? allEssays[currentIdx + 1] : null;

  return (
    <div className="min-h-screen bg-background">
      <PageHeader sticky wide>
        <Link
          href="/essays"
          className="text-sm text-muted-foreground hover:text-foreground transition-colors"
        >
          &larr; Essays
        </Link>
        <h1 className="mt-3 text-2xl font-bold text-foreground">
          {essay.title}
        </h1>
      </PageHeader>

      <div className="w-full md:max-w-6xl mx-auto flex">
        {/* Left sidebar */}
        <EssaySidebar items={allEssays} currentSlug={slug} />

        {/* Main content */}
        <main className="flex-1 min-w-0 px-6 py-8 space-y-8">
          {/* Top navigation */}
          <EssayNav prev={prev} next={next} />

          {/* Content */}
          <Card>
            <CardContent className="py-8 px-6 sm:px-8">
              <div className="space-y-4">
                {essay.paragraphs.map((paragraph, i) => (
                  <div
                    key={i}
                    className="text-foreground leading-relaxed"
                    dangerouslySetInnerHTML={{ __html: paragraph }}
                  />
                ))}
              </div>
            </CardContent>
          </Card>

          {/* Bottom navigation */}
          <EssayNav prev={prev} next={next} />
        </main>
      </div>
    </div>
  );
}

// ---------------------------------------------------------------------------
// Sidebar
// ---------------------------------------------------------------------------

function EssaySidebar({
  items,
  currentSlug,
}: {
  items: SidebarItem[];
  currentSlug: string;
}) {
  return (
    <aside className="hidden lg:block w-56 shrink-0 sticky top-[89px] self-start max-h-[calc(100vh-89px)] overflow-y-auto py-8 pr-4">
      <h2 className="text-xs font-bold uppercase tracking-wider text-muted-foreground mb-3 px-2">
        Essays
      </h2>
      <nav className="flex flex-col gap-0.5">
        {items.map((item) => (
          <Link
            key={item.slug}
            href={`/essays/${item.slug}`}
            className={cn(
              "px-2 py-1.5 rounded-md text-sm transition-colors truncate",
              item.slug === currentSlug
                ? "bg-primary/10 text-primary font-medium"
                : "text-muted-foreground hover:bg-muted hover:text-foreground",
            )}
            title={item.title}
          >
            {item.title}
          </Link>
        ))}
      </nav>
    </aside>
  );
}

// ---------------------------------------------------------------------------
// Prev / Next navigation
// ---------------------------------------------------------------------------

function EssayNav({
  prev,
  next,
}: {
  prev: SidebarItem | null;
  next: SidebarItem | null;
}) {
  return (
    <div className="flex items-center justify-between gap-3">
      {prev ? (
        <Link
          href={`/essays/${prev.slug}`}
          className={cn(
            buttonVariants({ variant: "outline", size: "sm" }),
            "gap-1.5",
          )}
        >
          <ChevronLeft className="size-4" />
          <span className="hidden sm:inline truncate max-w-[180px]">
            {prev.title}
          </span>
          <span className="sm:hidden">Previous</span>
        </Link>
      ) : (
        <div />
      )}

      {next ? (
        <Link
          href={`/essays/${next.slug}`}
          className={cn(
            buttonVariants({ variant: "outline", size: "sm" }),
            "gap-1.5",
          )}
        >
          <span className="hidden sm:inline truncate max-w-[180px]">
            {next.title}
          </span>
          <span className="sm:hidden">Next</span>
          <ChevronRight className="size-4" />
        </Link>
      ) : (
        <div />
      )}
    </div>
  );
}