// SSR -> CSR hydration gate. Fades the WebP placeholder to the Three.js canvas
// ONLY after BOTH the WebGL context is ready AND the model is loaded.
// Firing on just one condition = empty-canvas flash (race). Idempotent.

export interface HydrationGate {
  markWebGLReady(): void;
  markModelLoaded(): void;
}

export function createHydrationGate(preview: HTMLImageElement): HydrationGate {
  let webglReady = false;
  let modelLoaded = false;
  let fired = false;

  function maybeFire(): void {
    if (fired || !(webglReady && modelLoaded)) return;
    fired = true;
    preview.style.opacity = '0';
    window.setTimeout(() => {
      preview.classList.add('hidden');
      preview.style.display = 'none';
    }, 500);
  }

  return {
    markWebGLReady() {
      webglReady = true;
      maybeFire();
    },
    markModelLoaded() {
      modelLoaded = true;
      maybeFire();
    },
  };
}