OSRSCombatFormula.cs

using UnityEngine;

public static class OSRSCombatCalculator {
    // Calculates Melee Damage
    public static int CalculateMeleeDamage(
        int atkLvl, int atkBonus, int strLvl, int strBonus,
        int defLvl, int defBonus,
        float atkPrayer = 1f, float strPrayer = 1f,
        float defPrayer = 1f, float damageMultiplier = 1f,
        int atkStance = 0, int strStance = 0
    )
        => HitSuccess(AttackRoll(atkLvl, atkBonus, atkPrayer, atkStance), DefenceRoll(defLvl, defBonus, defPrayer))
            ? Mathf.FloorToInt(Random.Range(0, MaxHit(strLvl, strBonus, strPrayer, strStance) + 1) * damageMultiplier)
            : 0;

    // Calculates Ranged Damage
    public static int CalculateRangedDamage(
        int rngLvl, int rngBonus, int rngStrBonus,
        int defLvl, int defRngBonus,
        float rngPrayer = 1f, float defPrayer = 1f,
        float damageMultiplier = 1f, int rngStance = 0
    )
        => HitSuccess(AttackRoll(rngLvl, rngBonus, rngPrayer, rngStance), DefenceRoll(defLvl, defRngBonus, defPrayer))
            ? Mathf.FloorToInt(Random.Range(0, MaxHit(rngLvl, rngStrBonus, rngPrayer, rngStance) + 1) * damageMultiplier)
            : 0;

    // Calculates Magic Damage
    public static int CalculateMagicDamage(
        int mageLvl, int mageBonus, int spellMaxHit,
        int defLvl, int defMageBonus, int defMageLvl = 1,
        float magePrayer = 1f, float defPrayer = 1f,
        float damageMultiplier = 1f, float gearMultiplier = 1f
    )
        => HitSuccess(MagicAttackRoll(mageLvl, mageBonus, magePrayer), MagicDefenceRoll(defLvl, defMageLvl, defMageBonus, defPrayer))
            ? Mathf.FloorToInt(Random.Range(0, Mathf.FloorToInt(spellMaxHit * gearMultiplier * damageMultiplier) + 1))
            : 0;

    // Helper Methods (Accurate OSRS Formulas)

    private static int AttackRoll(int lvl, int bonus, float prayer, int stance)
        => (Mathf.FloorToInt(lvl * prayer) + stance + 8) * (bonus + 64);

    private static int DefenceRoll(int lvl, int bonus, float prayer, int stance = 0)
        => (Mathf.FloorToInt(lvl * prayer) + stance + 8) * (bonus + 64);

    private static int MagicAttackRoll(int mageLvl, int mageBonus, float prayer)
        => (Mathf.FloorToInt(mageLvl * prayer) + 8) * (mageBonus + 64);

    private static int MagicDefenceRoll(int defLvl, int mageLvl, int defBonus, float defPrayer)
        => (Mathf.FloorToInt(defLvl * 0.3f + mageLvl * 0.7f) + 8) * (defBonus + 64);

    private static int MaxHit(int lvl, int bonus, float prayer, int stance)
        => Mathf.FloorToInt(((Mathf.FloorToInt(lvl * prayer) + stance + 8) * (bonus + 64)) / 640f);

    private static bool HitSuccess(int atkRoll, int defRoll)
        => Random.Range(0, atkRoll + defRoll) < atkRoll;
}