using System;
using System.Collections.Generic;
using System.Linq;
using UnityEngine;

public class TalentManager : MonoBehaviour
{
    private const string SaveKey = "Lab07_TalentProgress";
    private const string TalentSourcePrefix = "Talent:";

    [Header("Data")]
    public List<TalentData> allTalents = new List<TalentData>();
    public PlayerStats playerStats;

    [Header("Runtime Progress")]
    public HashSet<string> learnedTalentIds = new HashSet<string>();
    public int availableTalentPoints = 1;
    public int startingTalentPoints = 1;

    [Header("Feedback")]
    public NotificationUI notificationUI;

    private readonly Dictionary<string, TalentData> talentLookup = new Dictionary<string, TalentData>();

    public event Action OnTalentStateChanged;
    public event Action<string> OnNotificationRequested;

    private void Awake()
    {
        if (playerStats == null)
        {
            playerStats = FindObjectOfType<PlayerStats>();
        }

        if (notificationUI == null)
        {
            notificationUI = FindObjectOfType<NotificationUI>();
        }

        BuildTalentLookup();
    }

    private void Start()
    {
        LoadProgress(false);
    }

    private void Update()
    {
        if (Input.GetKeyDown(KeyCode.T))
        {
            AddTalentPoints(1);
        }

        if (Input.GetKeyDown(KeyCode.F5))
        {
            SaveProgress();
        }

        if (Input.GetKeyDown(KeyCode.F9))
        {
            LoadProgress();
        }

        if (Input.GetKeyDown(KeyCode.Backspace))
        {
            ResetProgress();
        }
    }

    public bool IsLearned(TalentData talent)
    {
        return IsValidTalent(talent) && learnedTalentIds.Contains(talent.talentId);
    }

    public bool CanLearn(TalentData talent)
    {
        return IsValidTalent(talent) &&
               !IsLearned(talent) &&
               availableTalentPoints >= Mathf.Max(0, talent.cost) &&
               ArePrerequisitesLearned(talent);
    }

    public bool ArePrerequisitesLearned(TalentData talent)
    {
        if (!IsValidTalent(talent))
        {
            return false;
        }

        if (talent.prerequisites == null || talent.prerequisites.Length == 0)
        {
            return true;
        }

        for (int i = 0; i < talent.prerequisites.Length; i++)
        {
            TalentData prerequisite = talent.prerequisites[i];
            if (!IsValidTalent(prerequisite) || !IsLearned(prerequisite))
            {
                return false;
            }
        }

        return true;
    }

    public void LearnTalent(TalentData talent)
    {
        if (!IsValidTalent(talent))
        {
            Notify("Некорректный талант");
            return;
        }

        if (IsLearned(talent))
        {
            Notify($"Талант уже изучен: {talent.displayName}");
            return;
        }

        if (!ArePrerequisitesLearned(talent))
        {
            Notify(GetBlockingReason(talent));
            return;
        }

        int cost = Mathf.Max(0, talent.cost);
        if (availableTalentPoints < cost)
        {
            Notify("Недостаточно очков талантов");
            return;
        }

        availableTalentPoints -= cost;
        learnedTalentIds.Add(talent.talentId);
        ApplyTalentModifiers(talent);
        SaveProgress(false);
        Notify($"Изучен талант: {talent.displayName}");
        RaiseTalentStateChanged();
    }

    public void AddTalentPoints(int amount)
    {
        if (amount <= 0)
        {
            return;
        }

        availableTalentPoints = Mathf.Max(0, availableTalentPoints + amount);
        Notify(amount == 1 ? "Получено очко талантов" : $"Получено очков талантов: {amount}");
        RaiseTalentStateChanged();
    }

    public void ApplyTalentModifiers(TalentData talent)
    {
        if (!IsValidTalent(talent) || playerStats == null || talent.modifiers == null)
        {
            return;
        }

        string sourceId = GetModifierSourceId(talent);
        playerStats.RemoveModifiersBySource(sourceId);

        for (int i = 0; i < talent.modifiers.Length; i++)
        {
            StatModifier modifier = talent.modifiers[i];
            modifier.sourceId = sourceId;
            playerStats.AddModifier(modifier);
        }
    }

    public void RebuildAllModifiers()
    {
        if (playerStats == null)
        {
            return;
        }

        playerStats.RemoveModifiersBySourcePrefix(TalentSourcePrefix);

        for (int i = 0; i < allTalents.Count; i++)
        {
            TalentData talent = allTalents[i];
            if (IsLearned(talent))
            {
                ApplyTalentModifiers(talent);
            }
        }

        playerStats.RecalculateStats();
        RaiseTalentStateChanged();
    }

    public void SaveProgress()
    {
        SaveProgress(true);
    }

    public void LoadProgress()
    {
        LoadProgress(true);
    }

    public void ResetProgress()
    {
        PlayerPrefs.DeleteKey(SaveKey);
        ResetRuntimeToDefaults();
        RebuildAllModifiers();
        Notify("Прогресс сброшен");
        RaiseTalentStateChanged();
    }

    public int GetAvailableTalentPoints()
    {
        return availableTalentPoints;
    }

    public List<TalentData> GetLearnedTalents()
    {
        BuildTalentLookup();
        return allTalents.Where(IsLearned).ToList();
    }

    public string GetBlockingReason(TalentData talent)
    {
        if (!IsValidTalent(talent))
        {
            return "Некорректные данные таланта";
        }

        if (IsLearned(talent))
        {
            return "Талант уже изучен";
        }

        if (talent.prerequisites != null)
        {
            for (int i = 0; i < talent.prerequisites.Length; i++)
            {
                TalentData prerequisite = talent.prerequisites[i];
                if (!IsValidTalent(prerequisite))
                {
                    return "Некорректное требование таланта";
                }

                if (!IsLearned(prerequisite))
                {
                    return $"Требуется талант: {prerequisite.displayName}";
                }
            }
        }

        if (availableTalentPoints < Mathf.Max(0, talent.cost))
        {
            return "Недостаточно очков талантов";
        }

        return "Доступно";
    }

    public TalentData GetTalentById(string talentId)
    {
        BuildTalentLookup();
        if (string.IsNullOrWhiteSpace(talentId))
        {
            return null;
        }

        talentLookup.TryGetValue(talentId, out TalentData talent);
        return talent;
    }

    private void SaveProgress(bool notify)
    {
        TalentSaveData saveData = new TalentSaveData
        {
            availableTalentPoints = Mathf.Max(0, availableTalentPoints),
            learnedTalentIds = learnedTalentIds
                .Where(id => !string.IsNullOrWhiteSpace(id))
                .OrderBy(id => id, StringComparer.Ordinal)
                .ToList()
        };

        PlayerPrefs.SetString(SaveKey, JsonUtility.ToJson(saveData));
        PlayerPrefs.Save();

        if (notify)
        {
            Notify("Прогресс сохранён");
        }
    }

    private void LoadProgress(bool notify)
    {
        BuildTalentLookup();
        learnedTalentIds.Clear();

        if (PlayerPrefs.HasKey(SaveKey))
        {
            try
            {
                TalentSaveData saveData = JsonUtility.FromJson<TalentSaveData>(PlayerPrefs.GetString(SaveKey));
                availableTalentPoints = Mathf.Max(0, saveData != null ? saveData.availableTalentPoints : startingTalentPoints);

                if (saveData != null && saveData.learnedTalentIds != null)
                {
                    for (int i = 0; i < saveData.learnedTalentIds.Count; i++)
                    {
                        string talentId = saveData.learnedTalentIds[i];
                        if (talentLookup.ContainsKey(talentId))
                        {
                            learnedTalentIds.Add(talentId);
                        }
                    }
                }
            }
            catch (Exception exception)
            {
                Debug.LogWarning($"Talent progress was corrupted and will be reset. {exception.Message}");
                ResetRuntimeToDefaults();
            }
        }
        else
        {
            ResetRuntimeToDefaults();
        }

        EnsureDefaultTalentsLearned();
        RebuildAllModifiers();

        if (notify)
        {
            Notify("Прогресс загружен");
        }

        RaiseTalentStateChanged();
    }

    private void ResetRuntimeToDefaults()
    {
        learnedTalentIds.Clear();
        availableTalentPoints = Mathf.Max(0, startingTalentPoints);
        EnsureDefaultTalentsLearned();
    }

    private void EnsureDefaultTalentsLearned()
    {
        for (int i = 0; i < allTalents.Count; i++)
        {
            TalentData talent = allTalents[i];
            if (IsValidTalent(talent) && talent.unlockedByDefault)
            {
                learnedTalentIds.Add(talent.talentId);
            }
        }
    }

    private void BuildTalentLookup()
    {
        talentLookup.Clear();
        for (int i = 0; i < allTalents.Count; i++)
        {
            TalentData talent = allTalents[i];
            if (!IsValidTalent(talent))
            {
                continue;
            }

            if (talentLookup.ContainsKey(talent.talentId))
            {
                Debug.LogWarning($"Duplicate talent id ignored: {talent.talentId}");
                continue;
            }

            talentLookup.Add(talent.talentId, talent);
        }
    }

    private bool IsValidTalent(TalentData talent)
    {
        return talent != null && !string.IsNullOrWhiteSpace(talent.talentId);
    }

    private string GetModifierSourceId(TalentData talent)
    {
        return TalentSourcePrefix + talent.talentId;
    }

    private void RaiseTalentStateChanged()
    {
        OnTalentStateChanged?.Invoke();
    }

    private void Notify(string message)
    {
        if (string.IsNullOrWhiteSpace(message))
        {
            return;
        }

        OnNotificationRequested?.Invoke(message);
        if (notificationUI != null)
        {
            notificationUI.Show(message);
        }
    }
}