Experience.cs

using System;
using UnityEngine;
using UnityEngine.Events;
using Mirror;

namespace uMMORPG
{
    [RequireComponent(typeof(Level))]
    [DisallowMultipleComponent]
    public class Experience : NetworkBehaviour
    {
        [Header("Components")]
        public Level level;

        [Header("Experience")] // note: int is not enough (can have > 2 mil. easily)
        [SyncVar, SerializeField] long _current = 0;
        public long current
        {
            get { return _current; }
            set
            {
                if (value <= _current)
                {
                    // decrease
                    _current = Math.Max(value, 0);
                }
                else
                {
                    // increase with level ups
                    // set the new value (which might be more than expMax)
                    _current = value;

                    // now see if we leveled up (possibly more than once too)
                    // (can't level up if already max level)
                    while (_current >= max && level.current < level.max)
                    {
                        // subtract current level's required exp, then level up
                        _current -= max;
                        ++level.current;

                        // call event
                        onLevelUp.Invoke();
                    }

                    // set to expMax if there is still too much exp remaining
                    if (_current > max) _current = max;
                }
            }
        }

        // required experience grows by 10% each level (like Runescape)
        [SerializeField] protected ExponentialLong _max = new ExponentialLong{multiplier=100, baseValue=1.1f};
        public long max { get { return _max.Get(level.current); } }

        [Header("Death")]
        public float deathLossPercent = 0.05f;

        [Header("Events")]
        public UnityEvent onLevelUp;

        // helper functions ////////////////////////////////////////////////////////
        public float Percent() =>
            (current != 0 && max != 0) ? (float)current / (float)max : 0;

        // players gain exp depending on their level. if a player has a lower level
        // than the monster, then he gains more exp (up to 100% more) and if he has
        // a higher level, then he gains less exp (up to 100% less)
        // -> see tests for several commented examples!
        public static long BalanceExperienceReward(long reward, int attackerLevel, int victimLevel, int maxLevelDifference = 20)
        {
            // level difference 10 means 10% extra/less per level.
            // level difference 20 means 5% extra/less per level.
            // so the percentage step depends on the level difference:
            float percentagePerLevel = 1f / maxLevelDifference;

            // calculate level difference. it should cap out at +- maxDifference to
            // avoid power level exploits where a level 1 player kills a level 100
            // monster and immediately gets millions of experience points and levels
            // up to level 50 instantly. this would be bad for MMOs.
            // instead, we only consider +- maxDifference.
            int levelDiff = Mathf.Clamp(victimLevel - attackerLevel, -maxLevelDifference, maxLevelDifference);

            // calculate the multiplier. it will be +10%, +20% etc. when killing
            // higher level monsters. it will be -10%, -20% etc. when killing lower
            // level monsters.
            float multiplier = 1 + levelDiff * percentagePerLevel;

            // calculate reward
            return Convert.ToInt64(reward * multiplier);
        }

        // events //////////////////////////////////////////////////////////////////
        [Server]
        public virtual void OnDeath()
        {
            // lose experience
            current -= Convert.ToInt64(max * deathLossPercent);
        }
    }
}