/**
 * Pure, frame-driven binary effects. Remotion renders frame by frame, so nothing here
 * uses timers or randomness: the same inputs always give the same output.
 */

const HASH_MULTIPLIER = 2654435761;
const TICK_MULTIPLIER = 40503;
const LETTER_OR_DIGIT = /[A-Za-z0-9]/;

const clamp01 = (n: number): number => Math.min(1, Math.max(0, n));

/** A stable pseudo-random bit for a position at a given tick. */
const bitAt = (index: number, tick: number): "0" | "1" => {
  const hash = Math.imul(index + 1, HASH_MULTIPLIER) ^ Math.imul(tick + 1, TICK_MULTIPLIER);
  return ((hash >>> 7) & 1) === 0 ? "0" : "1";
};

/**
 * Text resolving from digits, left to right. Letters and numbers not yet reached show
 * as 0 or 1; spaces and punctuation stay put so the shape of the text is readable.
 */
export const decodeText = (text: string, progress: number, tick: number): string => {
  const chars = Array.from(text);
  const revealed = Math.floor(clamp01(progress) * chars.length);
  return chars
    .map((char, index) =>
      index < revealed || !LETTER_OR_DIGIT.test(char) ? char : bitAt(index, tick),
    )
    .join("");
};

/** A string of `length` binary digits for a given tick. */
export const bitString = (length: number, tick: number): string =>
  Array.from({ length }, (_, index) => bitAt(index, tick)).join("");