using BumpCombat.Core;
using System;
using BumpCombat.Player;
using UnityEngine;

namespace BumpCombat.Progression
{
    [RequireComponent(typeof(PlayerStats))]
    public sealed class ExperienceSystem : MonoBehaviour
    {
        private PlayerStats playerStats;
        private ExperienceProgress progress;

        public event Action<int, int, int> OnExperienceChanged;
        public event Action<int> OnLevelGained;
        public event Action OnExperienceOrbPickedUp;

        public int Level => progress != null ? progress.Level : 1;
        public int CurrentExperience => progress != null
            ? progress.CurrentExperience
            : 0;
        public int RequiredExperience => progress != null
            ? progress.RequiredExperience
            : RequiredExperienceForLevel(1);

        private void Awake()
        {
            playerStats = GetComponent<PlayerStats>();
            progress = new ExperienceProgress();
            progress.ExperienceChanged += HandleProgressExperienceChanged;
            progress.LevelGained += HandleProgressLevelGained;
        }

        private void Start()
        {
            OnExperienceChanged?.Invoke(CurrentExperience, RequiredExperience, Level);
        }

        public void AddExperience(int amount)
        {
            AddExperienceInternal(amount);
        }

        public void AddMissionExperience(int amount)
        {
            AddExperienceInternal(amount);
        }

        public void CollectExperienceOrb(int amount)
        {
            AddExperienceInternal(amount);
            OnExperienceOrbPickedUp?.Invoke();
        }

        private void AddExperienceInternal(int amount)
        {
            float evaluatedAmount = playerStats.Evaluate(
                CharacterStat.ExperienceGain,
                Mathf.Max(0, amount));
            progress.AddEvaluated(evaluatedAmount);
        }

        private void HandleProgressExperienceChanged(
            int currentExperience,
            int requiredExperience,
            int level)
        {
            OnExperienceChanged?.Invoke(
                currentExperience,
                requiredExperience,
                level);
        }

        private void HandleProgressLevelGained(int level)
        {
            OnLevelGained?.Invoke(level);
        }

        public static int RequiredExperienceForLevel(int level)
        {
            return ExperienceProgress.RequiredExperienceForLevel(level);
        }
    }
}