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

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

    public Text messageText;
    public CanvasGroup canvasGroup;
    public float visibleTime = 2.8f;
    public float fadeTime = 0.35f;

    private readonly Queue<string> queue = new Queue<string>();
    private float timer;

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

        Instance = this;
        if (canvasGroup == null)
        {
            canvasGroup = GetComponent<CanvasGroup>();
        }
    }

    private void Update()
    {
        if (messageText == null || canvasGroup == null)
        {
            return;
        }

        if (timer > 0f)
        {
            timer -= Time.deltaTime;
            canvasGroup.alpha = timer < fadeTime ? Mathf.Clamp01(timer / fadeTime) : 1f;
            return;
        }

        if (queue.Count > 0)
        {
            messageText.text = queue.Dequeue();
            timer = visibleTime + fadeTime;
            canvasGroup.alpha = 1f;
        }
        else
        {
            canvasGroup.alpha = 0f;
        }
    }

    public void Show(string message)
    {
        if (string.IsNullOrWhiteSpace(message))
        {
            return;
        }

        queue.Enqueue(message);
    }
}