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

public class QuestManager : MonoBehaviour
{
    public static QuestManager Instance { get; private set; }

    [SerializeField] private List<QuestData> availableQuests = new List<QuestData>();
    [SerializeField] private List<QuestState> activeQuests = new List<QuestState>();
    [SerializeField] private List<QuestState> completedQuests = new List<QuestState>();
    [SerializeField] private List<QuestState> failedQuests = new List<QuestState>();

    public IReadOnlyList<QuestData> AvailableQuests => availableQuests;
    public IReadOnlyList<QuestState> ActiveQuests => activeQuests;
    public IReadOnlyList<QuestState> CompletedQuests => completedQuests;
    public IReadOnlyList<QuestState> FailedQuests => failedQuests;

    public event Action OnQuestsChanged;

    private void Awake()
    {
        if (Instance != null && Instance != this)
        {
            Destroy(gameObject);
            return;
        }

        Instance = this;
    }

    public void SetAvailableQuests(IEnumerable<QuestData> quests)
    {
        availableQuests.Clear();
        if (quests != null)
        {
            availableQuests.AddRange(quests);
        }
    }

    public bool StartQuest(QuestData quest)
    {
        if (quest == null || IsQuestActive(quest) || IsQuestCompleted(quest))
        {
            return false;
        }

        if (!availableQuests.Contains(quest))
        {
            availableQuests.Add(quest);
        }

        QuestState state = new QuestState(quest);
        activeQuests.Add(state);
        Notify($"Получен квест:\n{quest.questName}");
        OnQuestsChanged?.Invoke();
        return true;
    }

    public bool CompleteQuest(QuestData quest)
    {
        QuestState state = activeQuests.Find(candidate => candidate.questData == quest);
        if (state == null || !state.AreAllGoalsComplete())
        {
            return false;
        }

        if (!ConsumeRequiredItems(quest))
        {
            Notify($"Не хватает предметов для завершения:\n{quest.questName}");
            OnQuestsChanged?.Invoke();
            return false;
        }

        state.status = QuestStatus.Completed;
        activeQuests.Remove(state);
        completedQuests.Add(state);

        Notify($"Квест завершён:\n{quest.questName}");

        if (quest.rewardItem != null && quest.rewardAmount > 0 && Inventory.Instance != null)
        {
            Inventory.Instance.AddItem(quest.rewardItem, quest.rewardAmount, false);
            Notify($"Получена награда:\n{quest.rewardItem.itemId} x{quest.rewardAmount}");
        }

        OnQuestsChanged?.Invoke();
        return true;
    }

    private bool ConsumeRequiredItems(QuestData quest)
    {
        if (quest == null || quest.goals == null || Inventory.Instance == null)
        {
            return true;
        }

        foreach (QuestGoal goal in quest.goals)
        {
            if (goal.goalType != QuestGoalType.CollectItem || goal.targetItem == null)
            {
                continue;
            }

            if (!Inventory.Instance.HasItem(goal.targetItem, goal.requiredAmount))
            {
                return false;
            }
        }

        foreach (QuestGoal goal in quest.goals)
        {
            if (goal.goalType == QuestGoalType.CollectItem && goal.targetItem != null)
            {
                Inventory.Instance.RemoveItem(goal.targetItem, goal.requiredAmount);
            }
        }

        return true;
    }

    public void FailQuest(QuestData quest)
    {
        QuestState state = activeQuests.Find(candidate => candidate.questData == quest);
        if (state == null)
        {
            return;
        }

        state.status = QuestStatus.Failed;
        activeQuests.Remove(state);
        failedQuests.Add(state);
        OnQuestsChanged?.Invoke();
    }

    public void OnItemCollected(ItemData item, int amount)
    {
        if (item == null || amount <= 0)
        {
            return;
        }

        UpdateProgress(QuestGoalType.CollectItem, item.itemId, amount);
    }

    public void OnEnemyKilled(string enemyType)
    {
        if (string.IsNullOrWhiteSpace(enemyType))
        {
            return;
        }

        UpdateProgress(QuestGoalType.KillEnemy, enemyType, 1);
    }

    public void OnNpcTalked(string npcId)
    {
        if (string.IsNullOrWhiteSpace(npcId))
        {
            return;
        }

        UpdateProgress(QuestGoalType.TalkToNPC, npcId, 1);
    }

    public string GetGoalProgress(QuestData quest, int goalIndex)
    {
        QuestState state = GetQuestState(quest);
        if (state == null || quest == null || goalIndex < 0 || goalIndex >= quest.goals.Count)
        {
            return "0/0";
        }

        QuestGoal goal = quest.goals[goalIndex];
        return $"{state.GetProgress(goalIndex)}/{goal.requiredAmount}";
    }

    public float GetQuestCompletionPercent(QuestState state)
    {
        if (state == null || state.questData == null || state.questData.goals.Count == 0)
        {
            return 0f;
        }

        float total = 0f;
        for (int i = 0; i < state.questData.goals.Count; i++)
        {
            QuestGoal goal = state.questData.goals[i];
            total += Mathf.Clamp01(state.GetProgress(i) / (float)Mathf.Max(1, goal.requiredAmount));
        }

        return total / state.questData.goals.Count;
    }

    public QuestState GetQuestState(QuestData quest)
    {
        QuestState state = activeQuests.Find(candidate => candidate.questData == quest);
        if (state != null)
        {
            return state;
        }

        state = completedQuests.Find(candidate => candidate.questData == quest);
        if (state != null)
        {
            return state;
        }

        return failedQuests.Find(candidate => candidate.questData == quest);
    }

    private void UpdateProgress(QuestGoalType type, string targetKey, int amount)
    {
        bool changed = false;
        List<QuestData> completedNow = new List<QuestData>();

        foreach (QuestState state in activeQuests)
        {
            QuestData quest = state.questData;
            if (quest == null || quest.goals == null)
            {
                continue;
            }

            for (int i = 0; i < quest.goals.Count; i++)
            {
                QuestGoal goal = quest.goals[i];
                if (goal.goalType != type || goal.GetTargetKey() != targetKey || state.IsGoalComplete(i))
                {
                    continue;
                }

                state.AddProgress(i, amount);
                changed = true;
                Notify($"Прогресс:\n{goal.GetDisplayName()} {state.GetProgress(i)}/{goal.requiredAmount}");
            }

            if (state.AreAllGoalsComplete())
            {
                completedNow.Add(quest);
            }
        }

        foreach (QuestData quest in completedNow)
        {
            CompleteQuest(quest);
        }

        if (changed)
        {
            OnQuestsChanged?.Invoke();
        }
    }

    private bool IsQuestActive(QuestData quest)
    {
        return activeQuests.Exists(candidate => candidate.questData == quest);
    }

    private bool IsQuestCompleted(QuestData quest)
    {
        return completedQuests.Exists(candidate => candidate.questData == quest);
    }

    private void Notify(string message)
    {
        if (NotificationUI.Instance != null)
        {
            NotificationUI.Instance.Show(message);
        }
        else
        {
            Debug.Log(message);
        }
    }
}