wiki/netlify/edge-functions/botMeta.ts

import type { Context } from "@netlify/edge-functions";

// List of known social media and search engine bots
const BOTS = [
  "facebookexternalhit",
  "twitterbot",
  "linkedinbot",
  "slackbot",
  "discordbot",
  "telegrambot",
  "whatsapp",
  "pinterest",
  "opengraph",
  "opengraphbot",
  "bot ",
  "crawler",
  "embedly",
  "vkshare",
  "quora link preview",
  "redditbot",
  "rogerbot",
  "showyoubot",
  "google",
  "bingbot",
  "baiduspider",
  "duckduckbot",
];

function isBot(userAgent: string | null): boolean {
  if (!userAgent) return false;
  const ua = userAgent.toLowerCase();
  return BOTS.some((bot) => ua.includes(bot));
}

export default async function handler(
  request: Request,
  context: Context,
): Promise<Response> {
  const url = new URL(request.url);
  const userAgent = request.headers.get("user-agent");

  // Only intercept post pages for bots
  const pathParts = url.pathname.split("/").filter(Boolean);

  // Skip if it's the home page, static assets, API routes, or raw markdown files
  if (
    pathParts.length === 0 ||
    pathParts[0].includes(".") ||
    pathParts[0] === "api" ||
    pathParts[0] === "_next" ||
    pathParts[0] === "raw"
  ) {
    return context.next();
  }

  // If not a bot, continue to the SPA
  if (!isBot(userAgent)) {
    return context.next();
  }

  // For bots, fetch the Open Graph metadata from Convex
  const slug = pathParts[0];
  const convexUrl =
    Deno.env.get("VITE_CONVEX_URL") || Deno.env.get("CONVEX_URL");

  if (!convexUrl) {
    return context.next();
  }

  try {
    // Construct the Convex site URL for the HTTP endpoint
    const convexSiteUrl = convexUrl.replace(".cloud", ".site");
    const metaUrl = `${convexSiteUrl}/meta/post?slug=${encodeURIComponent(slug)}`;

    const response = await fetch(metaUrl, {
      headers: {
        Accept: "text/html",
      },
    });

    if (response.ok) {
      const html = await response.text();
      return new Response(html, {
        headers: {
          "Content-Type": "text/html; charset=utf-8",
          "Cache-Control": "public, max-age=60, s-maxage=300",
        },
      });
    }

    // If meta endpoint fails, fall back to SPA
    return context.next();
  } catch {
    return context.next();
  }
}