4ev.link/functions/[[path]].js

const C='abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789',L=4,H={'Access-Control-Allow-Origin':'*'}
const r=()=>[...Array(L)].map(()=>C[Math.random()*C.length|0]).join('')

export async function onRequest({request, env, next}){
  if(request.method==='OPTIONS')return new Response(null,{headers:{...H,'Access-Control-Allow-Methods':'POST','Access-Control-Allow-Headers':'Content-Type'}})
  
  const u=new URL(request.url)

  // Handle POST request to create a link (API call)
  if(u.pathname==='/api/create'&&request.method==='POST'){
    try{
      const{url:t}=await request.json();
      new URL(t);
      let s;
      do s=r();while(await env.EV.get(s));
      await env.EV.put(s,t);
      const d={slug:s,target:t,shortUrl:`${u.origin}/${s}`};
      return new Response(JSON.stringify(d),{headers:{'Content-Type':'application/json',...H}})
    }catch(e){
      return new Response('Invalid URL',{status:400,headers:H})
    }
  }

  // Handle GET request for a slug (Redirect)
  const p=u.pathname.slice(1)
  if(p){
    const t=await env.EV.get(p)
    if(t)return Response.redirect(t,302)
  }

  // For all other requests (like GET /), pass them to the static asset handler.
  return next()
}