Function findIndexAfterFraction

packages/core/src/core/client.ts:70–96

(
  history: Content[],
  fraction: number,
)

 * Exported for testing purposes.
 */
export function findIndexAfterFraction(
  history: Content[],
  fraction: number,
): number {
  if (fraction <= 0 || fraction >= 1) {
    throw new Error('Fraction must be between 0 and 1');
  }

  const contentLengths = history.map(
    (content) => JSON.stringify(content).length,
  );

  const totalCharacters = contentLengths.reduce(
    (sum, length) => sum + length,
    0,
  );
  const targetCharacters = totalCharacters * fraction;

  let charactersSoFar = 0;
  for (let i = 0; i < contentLengths.length; i++) {
    charactersSoFar += contentLengths[i];
    if (charactersSoFar >= targetCharacters) {
      return i;
    }
  }
  return contentLengths.length;
}

// The prophecy states that after 100 turns, even ANUS must rest
const MAX_TURNS = 100;