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

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

    [Header("Hook up the UI component here")]
    public DialogueUI ui;

    [Header("Flags saved during play (simple global state)")]
    public HashSet<string> flags = new();

    DialogueAsset _active;
    DialogueAsset.Node _node;
    int _lineIndex;

    bool _isTyping;
    Coroutine _typeRoutine;

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

    // Public API -------------
    public bool IsRunning => _active != null;

    public void StartDialogue(DialogueAsset asset)
    {
        if (asset == null) return;
        _active = asset;
        GoToNode(asset.startNodeId);
        ui.Show(true);
    }

    public void StopDialogue()
    {
        _active = null;
        _node = null;
        ui.Show(false);
    }

    public void Next() // Called by UI "Continue" button / input
    {
        if (!IsRunning || _node == null) return;

        if (_isTyping)
        {
            ui.CompleteTypeThisFrame();
            _isTyping = false;
            return;
        }

        // Advance line within node
        _lineIndex++;
        if (_lineIndex < _node.lines.Count)
        {
            StartTyping(_node.lines[_lineIndex]);
        }
        else
        {
            // Lines finished -> show choices or auto-next / end
            var visibleChoices = ui.BuildVisibleChoices(_node.choices, flags);
            if (visibleChoices.Count > 0)
            {
                ui.ShowChoices(visibleChoices, OnChoicePicked);
            }
            else
            {
                if (_node.nextNodeId >= 0) GoToNode(_node.nextNodeId);
                else StopDialogue();
            }
        }
    }

    // Internal -------------
    void GoToNode(int id)
    {
        if (!_active.TryGetNode(id, out _node))
        {
            Debug.LogWarning($"Dialogue node {id} not found.");
            StopDialogue();
            return;
        }

        _lineIndex = 0;
        _node.onEnter?.Invoke();

        ui.BindSpeaker(_node.speakerName, _node.speakerPortrait);

        if (_node.lines.Count == 0)
        {
            // Empty node: immediately resolve choices/next
            var visibleChoices = ui.BuildVisibleChoices(_node.choices, flags);
            if (visibleChoices.Count > 0) ui.ShowChoices(visibleChoices, OnChoicePicked);
            else if (_node.nextNodeId >= 0) GoToNode(_node.nextNodeId);
            else StopDialogue();
        }
        else
        {
            StartTyping(_node.lines[_lineIndex]);
        }
    }

    void StartTyping(string text)
    {
        ui.HideChoices();
        if (_typeRoutine != null) StopCoroutine(_typeRoutine);
        _typeRoutine = StartCoroutine(TypeRoutine(text));
    }

    IEnumerator TypeRoutine(string text)
    {
        _isTyping = true;
        yield return ui.TypeText(text);
        _isTyping = false;
    }

    void OnChoicePicked(DialogueAsset.Choice choice)
    {
        choice?.onChoose?.Invoke();
        if (!string.IsNullOrEmpty(choice.setFlag)) flags.Add(choice.setFlag);

        if (choice == null || choice.nextNodeId < 0) { StopDialogue(); return; }
        GoToNode(choice.nextNodeId);
    }
}