import { BatchedText, Text, batchedText } from '@three-blocks/core';
import {
  subBuild,
  positionLocal,
  cameraProjectionMatrix,
  modelViewMatrix,
  vec4,
  uniform
} from 'three/tsl';

const batched = new BatchedText(2, 2 * 10);

const text1 = new Text();
text1.text = 'First';
text1.position.set(0, 1, 0);
text1.updateMatrixWorld();

const text2 = new Text();
text2.text = 'Second';
text2.position.set(0, -1, 0);
text2.updateMatrixWorld();

const id1 = batched.addText(text1);
const id2 = batched.addText(text2);

const material = batched.material;
const uBillboard = uniform(0);

material.setupVertex = () => {
  // Build text geometry transformation first (sets up varyings and modifies positionLocal)
  const textPosition = subBuild(batchedText(batched, uBillboard)(), 'POSITION', 'vec3');

  // Start with text position
  let finalPosition = textPosition;

  // If user has positionNode, assign textPosition to positionLocal first
  // so their positionNode can read it, then apply their transformation
  if (material.positionNode !== null) {
    positionLocal.assign(textPosition);
    finalPosition = subBuild(material.positionNode, 'POSITION', 'vec3');
  }

  // Assign final position to positionLocal for any other code that might need it
  positionLocal.assign(finalPosition);

  // Build custom MVP using our computed position
  const mvp = cameraProjectionMatrix
    .mul(modelViewMatrix)
    .mul(vec4(finalPosition, 1.0));

  return mvp;
};