export function initPupilTracking(svg) {
  const VIEWBOX_WIDTH          = 304;
  const VIEWBOX_HEIGHT         = 259;
  const PUPIL_SCALE            = 1.267471;
  const PUPIL_BASE_TRANSLATE_X = PUPIL_SCALE * 52.5;
  const PUPIL_BASE_TRANSLATE_Y = PUPIL_SCALE * 87.5;
  const PUPIL_MAX_OFFSET_RADIUS = 3.5;
  const PUPIL_LERP_FACTOR      = 0.12;

  // Centre de chaque œil — personnage gauche uniquement
  const eyes = [
    { id: "left-pupil",  centerX: 54.03,  centerY: 86.79 },
    { id: "right-pupil", centerX: 103.55, centerY: 86.79 },
  ];

  const currentPupilPositions = eyes.map((eye) => ({ x: eye.centerX, y: eye.centerY }));
  const targetPupilPositions  = eyes.map((eye) => ({ x: eye.centerX, y: eye.centerY }));

  document.addEventListener("mousemove", (event) => {
    const svgBoundingRect = svg.getBoundingClientRect();
    const mouseViewportX = (event.clientX - svgBoundingRect.left) * (VIEWBOX_WIDTH / svgBoundingRect.width);
    const mouseViewportY = (event.clientY - svgBoundingRect.top) * (VIEWBOX_HEIGHT / svgBoundingRect.height);

    eyes.forEach((eye, eyeIndex) => {
      const deltaX = mouseViewportX - eye.centerX;
      const deltaY = mouseViewportY - eye.centerY;
      const distanceToMouse = Math.hypot(deltaX, deltaY);
      const clampRatio = distanceToMouse > 0 ? Math.min(PUPIL_MAX_OFFSET_RADIUS, distanceToMouse) / distanceToMouse : 0;
      targetPupilPositions[eyeIndex].x = eye.centerX + deltaX * clampRatio;
      targetPupilPositions[eyeIndex].y = eye.centerY + deltaY * clampRatio;
    });
  });

  document.addEventListener("mouseleave", () => {
    eyes.forEach((eye, eyeIndex) => {
      targetPupilPositions[eyeIndex].x = eye.centerX;
      targetPupilPositions[eyeIndex].y = eye.centerY;
    });
  });

  function animatePupils() {
    eyes.forEach((eye, eyeIndex) => {
      currentPupilPositions[eyeIndex].x +=
        (targetPupilPositions[eyeIndex].x - currentPupilPositions[eyeIndex].x) * PUPIL_LERP_FACTOR;
      currentPupilPositions[eyeIndex].y +=
        (targetPupilPositions[eyeIndex].y - currentPupilPositions[eyeIndex].y) * PUPIL_LERP_FACTOR;
      document
        .getElementById(eye.id)
        ?.setAttribute(
          "transform",
          `matrix(${PUPIL_SCALE},0,0,${PUPIL_SCALE},${currentPupilPositions[eyeIndex].x - PUPIL_BASE_TRANSLATE_X},${currentPupilPositions[eyeIndex].y - PUPIL_BASE_TRANSLATE_Y})`
        );
    });
    requestAnimationFrame(animatePupils);
  }

  requestAnimationFrame(animatePupils);
}