Warlords Battle Calculator

warodds.js

export default function calculateBattle(defArmy, attArmy) {
  const MAX_ATTACKER_ARMY = 8;
  const MAX_DEFENDER_ARMY = MAX_ATTACKER_ARMY * 4;
  const HITS = 2;
  const ATTACKER_STATS = MAX_ATTACKER_ARMY * HITS + 1;
  const DEFENDER_STATS = MAX_DEFENDER_ARMY * HITS + 1;
  const STATS = ATTACKER_STATS + DEFENDER_STATS;
  const cache = new Array(ATTACKER_STATS * DEFENDER_STATS);

  return calculateStatistics(1, defArmy.length * HITS, attArmy.length * HITS);

  function calculateStatistics(probability, defState, attState) {
    const key = defState + DEFENDER_STATS * attState;
    const isBattleOver = defState == 0 || attState == 0;

    if (isBattleOver) {
      if (cache[key] === undefined) {
          cache[key] = new Array(STATS).fill(0);
          cache[key][attState + DEFENDER_STATS] = cache[key][defState] = probability;
      }
      return cache[key];
    }
    if (cache[key] === undefined) {  
        const defStrength = defArmy[Math.floor((defState - 1) / HITS)];
        const attStrength = attArmy[Math.floor((attState - 1) / HITS)];
        const pA = attackerWinProbability(defStrength, attStrength);
        const attStats = calculateStatistics(pA, defState - 1, attState);
        const defStats = calculateStatistics(1 - pA, defState, attState - 1);
        cache[key] = new Array(STATS);
        for (let i = STATS; i-->0;) cache[key][i] = attStats[i] + defStats[i];
    }
    const result = new Array(STATS);
    for (let i = STATS; i-->0;) result[i] = cache[key][i] * probability;
    return result;
  }

  function attackerWinProbability(defStrength, attStrength) {
    const Pa = attStrength * (10 - defStrength) / 100;
    const Pd = defStrength * (10 - attStrength) / 100;
    return Pa / (Pa + Pd);
  }
}

  onCalculate() {
    const defArmy = [];
    const attArmy = [];
    for (let strength of this.defender) if (strength) defArmy.push(strength);
    for (let strength of this.attacker) if (strength) attArmy.push(strength);

    const result = calculateBattle(defArmy, attArmy);

    this.defWinPercent = 1 - result[0];
    this.attWinPercent = 1 - result[65];

    this.defStats.forEach((x, i, a) => (a[i] = result[1 + i * 2] + result[2 + i * 2]));
    this.attStats.forEach((x, i, a) => (a[i] = result[66 + i * 2] + result[67 + i * 2]));
  },