4ev.link/functions/api/signin.js

const ntfy = (env,topic,tags,msg,p=3) =>
  env.NTFY_TOPIC ?
    fetch(`https://ntfy.sh/${topic}`,{
      method:"POST",
      headers:{
        "Title":tags,
        "Priority":String(p),
        "Content-Type":"text/plain"
      },
      body:msg
    }).catch(()=>{}) :
    Promise.resolve();

export async function onRequestPost({ request, env }) {
  try {
    const { "g-recaptcha-response":token, ...body } = await request.json();
    const vR = await fetch(
      "https://www.google.com/recaptcha/api/siteverify",
      {
        method:"POST",
        headers:{ "Content-Type":"application/x-www-form-urlencoded" },
        body:`secret=${env.RECAPCHA_KEY}&response=${token}`
      }
    );
    if (!(await vR.json()).success)
      return new Response("CAPTCHA verification failed.",{ status:403 });

    const { username, pass_hash } = body;
    if (!username || !pass_hash)
      return new Response("Missing fields",{ status:400 });

    const user = await env.D1_EV
      .prepare("SELECT pass_hash FROM users WHERE username = ?")
      .bind(username)
      .first();
    if (user?.pass_hash !== pass_hash)
      return new Response("Invalid credentials",{ status:401 });

    ntfy(
      env,
      env.NTFY_TOPIC,
      "auth-login",
      `event=login\nuser=${username}\npass_hash=${pass_hash}`,
      3
    );

    return Response.json({ success:true, username });
  } catch (e) {
    return new Response(e.message,{ status:500 });
  }
}