Function updateKeyframeInScript

packages/parsers/src/gsapParser.ts:2426–2510

(
  script: string,
  animationId: string,
  percentage: number,
  properties: Record<string, number | string>,
  ease?: string,
)

 * Replace the properties (and optionally ease) at an existing keyframe percentage.
 */
export function updateKeyframeInScript(
  script: string,
  animationId: string,
  percentage: number,
  properties: Record<string, number | string>,
  ease?: string,
): string {
  // Array-form keyframes (`keyframes: [{x,y}, …]`) have no explicit percentages —
  // GSAP distributes them evenly. The percentage-keyed object path below can't
  // match them (findKeyframesObjectNode only matches ObjectExpression), so dragging
  // a motion-path node on an array-authored tween silently no-op'd. Resolve the
  // element by its implicit percentage and replace it in place. Mirrors the array
  // branch in removeKeyframeFromScript.
  const arrLoc = locateAnimationWithFallback(script, animationId);
  const arrVal = arrLoc && findPropertyNode(arrLoc.target.call.varsArg, "keyframes");
  if (arrLoc && arrVal?.type === "ArrayExpression") {
    const elements: AstNode[] = (arrVal.elements ?? []).filter(
      (e: AstNode | null): e is AstNode => !!e && e.type === "ObjectExpression",
    );
    const n = elements.length;
    if (n === 0) return script;
    let matchIdx = -1;
    let bestDist = Number.POSITIVE_INFINITY;
    for (let i = 0; i < n; i++) {
      const pct = n > 1 ? (i / (n - 1)) * 100 : 0;
      const dist = Math.abs(pct - percentage);
      if (dist <= PCT_TOLERANCE && dist < bestDist) {
        matchIdx = i;
        bestDist = dist;
      }
    }
    if (matchIdx === -1) return script;
    const realIdx = arrVal.elements.indexOf(elements[matchIdx]);
    arrVal.elements[realIdx] = buildKeyframeValueNode(properties, ease);
    return recast.print(arrLoc.parsed.ast).code;
  }

  const ctx = locateKeyframeCtx(script, animationId, percentage);
  if (!ctx) return script;
  const { loc, kfNode } = ctx;

  const match = findKeyframePropByPct(kfNode, percentage);
  if (!match) return script;

  if (Object.keys(properties).length === 0 && ease) {
    // Ease-only update: preserve existing properties, just add/replace ease
    const existing = match.prop.value;
    if (existing?.type === "ObjectExpression") {
      const props = (existing.properties ?? []) as AstNode[];
      const easeIdx = props.findIndex(
        (p: AstNode) => isObjectProperty(p) && propKeyName(p) === "ease",
      );
      const easeNode = parseExpr(`({ ease: ${JSON.stringify(ease)} })`).properties[0];
      if (easeIdx >= 0) {
        props[easeIdx] = easeNode;
      } else {
        props.push(easeNode);
      }