export interface RelayResponse
{
  reqId:   string;
  status:  number;
  headers: Record<string, string>;
  body:    string; // base64 — legacy single-shot
}

export type AgentMsg =
  | { type: 'res_start'; reqId: string; status: number; headers: Record<string, string> }
  | { type: 'res_data';  reqId: string; chunk: string } // base64
  | { type: 'res_end';   reqId: string }
  | RelayResponse; // legacy: no type field

export interface StreamHandler
{
  onStart: ( status: number, headers: Record<string, string> ) => void;
  onData:  ( chunk: Buffer ) => void;
  onEnd:   () => void;
}

const pending = new Map<string, StreamHandler>();

export function addPending( reqId: string, handler: StreamHandler ): void
{
  pending.set( reqId, handler );
}

export function removePending( reqId: string ): void
{
  pending.delete( reqId );
}

export function dispatchAgentMsg( msg: AgentMsg ): void
{
  const handler = pending.get( msg.reqId );
  if ( !handler ) return;

  if ( 'type' in msg )
  {
    if ( msg.type === 'res_start' )
    {
      handler.onStart( msg.status, msg.headers );
    }
    else if ( msg.type === 'res_data' )
    {
      handler.onData( Buffer.from( msg.chunk, 'base64' ) );
    }
    else if ( msg.type === 'res_end' )
    {
      pending.delete( msg.reqId );
      handler.onEnd();
    }
  }
  else
  {
    // Legacy single-shot RelayResponse — forward as stream
    handler.onStart( msg.status, msg.headers );
    handler.onData( Buffer.from( msg.body, 'base64' ) );
    pending.delete( msg.reqId );
    handler.onEnd();
  }
}