Generates a Nuclear Hexagram (互卦 / Hu Gua) from the provided original hexagram.

create-nuclear-hexagrams.ts

/**
 * Generates a Nuclear Hexagram (互卦 / Hu Gua) from the provided original hexagram.
 *
 * The Nuclear Hexagram is a combination of two trigrams,
 * the Upper Trigram (上卦 / Shang Gua) and the Lower Trigram (下卦 / Xia Gua):
 *   - The Upper Trigram is formed by extracting the third, fourth,
 *     and fifth lines from the original hexagram.
 *   - Conversely, the Lower Trigram is formed by extracting the second, third,
 *     and fourth lines from the original hexagram.
 *
 * This combination reflects the internal interactions of the situation being
 * inquired about, representing the development process of the event,
 * including potential risks and gains.
 *
 * The Nuclear Hexagram embodies both subjective and objective factors:
 * - The lower trigram (inner hexagram) represents subjective influences.
 * - The upper trigram (outer hexagram) represents objective factors.
 *
 * Understanding the Nuclear Hexagram can provide insights into
 * the complex relationships within the event, indicating that
 * every event has its causes, some of which may be obscure.
 * Observing these interactions is crucial for predicting
 * the potential changes and outcomes of the situation.
 *
 * The original hexagram is derived from the original hexagram's lines as follows:
 *   - originalHexagram[0] - Shang Yao (上爻 / the Uppermost Line)
 *   - originalHexagram[1] - Wu Yao (五爻 / the Fifth Line)
 *   - originalHexagram[2] - Si Yao (四爻 / the Forth Line)
 *   - originalHexagram[3] - San Yao (三爻 / the third Line)
 *   - originalHexagram[4] - Er Yao (二爻 / the second Line)
 *   - originalHexagram[5] - Chu Yao (初爻 / the Initial Line)
 *
 * @param originalHexagram - An array of 6 numbers representing the original hexagram lines
 * @returns A new array of 6 numbers representing the nuclear hexagram
 * @throws {Error} If the input array does not contain exactly 6 trigrams
 *
 * @example
 * const originalHexagram = [0, 1, 0, 1, 0, 0];
 * const nuclearHexagram = createNuclearHexagram(originalHexagram);
 * // Returns: [1, 0, 1, 0, 1, 0]
 */

export function createNuclearHexagram(originalHexagram: number[]): number[] {
  // Validate the input to ensure it has exactly 6 lines
  if (originalHexagram.length !== 6) {
    throw new Error("Hexagram must have exactly 6 lines.");
  }

  // Initialize arrays for upper and lower trigrams
  const upperInnerTrigram: number[] = [
    originalHexagram[1], // 5th line
    originalHexagram[2], // 4th line
    originalHexagram[3], // 3rd line
  ];

  const lowerInnerTrigram: number[] = [
    originalHexagram[2], // 4th line
    originalHexagram[3], // 3rd line
    originalHexagram[4], // 2nd line
  ];

  // Combine upper and lower trigrams to form the nuclear hexagram
  const nuclearHexagram = [...upperInnerTrigram, ...lowerInnerTrigram];

  return nuclearHexagram;
}