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

namespace Unheimlich.UI
{
    [RequireComponent(typeof(TextMeshProUGUI))]
    public class PerLetterFontShifter : MonoBehaviour
    {
        #region Serialized Fields

        [Header("Fonts")]
        [SerializeField] private TMP_FontAsset[] _fonts;

        [Header("Timing")]
        [SerializeField] private float _shiftInterval = 3f;
        [SerializeField] private float _minLetterDelay = 0.05f;
        [SerializeField] private float _maxLetterDelay = 0.25f;

        [Header("Style")]
        [SerializeField] private float _fontSize = 36f;
        [SerializeField] private Color _textColor = Color.white;

        #endregion

        #region Private Fields

        private TextMeshProUGUI _originalTmp;
        private string _originalText;
        private readonly List<TextMeshProUGUI> _letterObjects = new List<TextMeshProUGUI>();
        private Coroutine _shiftLoopRoutineHandle;

        #endregion

        #region Unity Lifecycle Methods

        private void Awake()
        {
            _originalTmp = GetComponent<TextMeshProUGUI>();
            _originalText = _originalTmp.text;
            _originalTmp.enabled = false;
        }

        private void OnEnable()
        {
            BuildLetterObjects();
            _shiftLoopRoutineHandle = StartCoroutine(ShiftLoopRoutine());
        }

        private void OnDisable()
        {
            if (_shiftLoopRoutineHandle != null)
                StopCoroutine(_shiftLoopRoutineHandle);
        }

        private void OnDestroy()
        {
            DestroyLetterObjects();
        }

        #endregion

        #region Public Methods

        public void SetText(string newText)
        {
            _originalText = newText;
            BuildLetterObjects();
        }

        #endregion

        #region Private Methods

        private void BuildLetterObjects()
        {
            DestroyLetterObjects();

            foreach (char character in _originalText)
            {
                GameObject letterGo = new GameObject($"Letter_{character}");
                letterGo.transform.SetParent(transform, false);

                TextMeshProUGUI letterTmp = letterGo.AddComponent<TextMeshProUGUI>();
                letterTmp.text = character.ToString();
                letterTmp.fontSize = _fontSize;
                letterTmp.color = _textColor;
                letterTmp.alignment = TextAlignmentOptions.Center;

                _letterObjects.Add(letterTmp);
            }

            ArrangeLetters();
            ShuffleFonts();
        }

        private void DestroyLetterObjects()
        {
            foreach (TextMeshProUGUI letter in _letterObjects)
            {
                if (letter != null)
                    Destroy(letter.gameObject);
            }

            _letterObjects.Clear();
        }

        private void ArrangeLetters()
        {
            HorizontalLayoutGroup layout = gameObject.GetComponent<HorizontalLayoutGroup>();
            if (layout == null)
                layout = gameObject.AddComponent<HorizontalLayoutGroup>();

            layout.childAlignment = TextAnchor.MiddleCenter;
            layout.childForceExpandWidth = false;
            layout.childForceExpandHeight = false;
            layout.childControlWidth = true;
            layout.childControlHeight = true;
            layout.spacing = 0f;

            foreach (TextMeshProUGUI letter in _letterObjects)
            {
                ContentSizeFitter fitter = letter.gameObject.GetComponent<ContentSizeFitter>();
                if (fitter == null)
                    fitter = letter.gameObject.AddComponent<ContentSizeFitter>();

                fitter.horizontalFit = ContentSizeFitter.FitMode.PreferredSize;
                fitter.verticalFit = ContentSizeFitter.FitMode.PreferredSize;
            }
        }

        private void ShuffleFonts()
        {
            if (_fonts == null || _fonts.Length == 0)
            {
                Debug.LogWarning($"[{nameof(PerLetterFontShifter)}] No fonts assigned.", this);
                return;
            }

            StartCoroutine(ShuffleStaggeredRoutine());
        }

        private List<int> GetShuffledIndices()
        {
            List<int> indices = new List<int>();

            for (int i = 0; i < _letterObjects.Count; i++)
                indices.Add(i);

            for (int i = indices.Count - 1; i > 0; i--)
            {
                int j = Random.Range(0, i + 1);
                (indices[i], indices[j]) = (indices[j], indices[i]);
            }

            return indices;
        }

        #endregion

        #region Coroutines

        private IEnumerator ShiftLoopRoutine()
        {
            while (true)
            {
                yield return new WaitForSeconds(_shiftInterval);
                ShuffleFonts();
            }
        }

        private IEnumerator ShuffleStaggeredRoutine()
        {
            List<int> shuffledIndices = GetShuffledIndices();

            foreach (int index in shuffledIndices)
            {
                TextMeshProUGUI letter = _letterObjects[index];

                if (letter.text == " " || letter.text == "\n")
                    continue;

                letter.font = _fonts[Random.Range(0, _fonts.Length)];

                yield return new WaitForSeconds(Random.Range(_minLetterDelay, _maxLetterDelay));
            }
        }

        #endregion

#if UNITY_EDITOR
        [ContextMenu("Test Shuffle Now")]
        private void TestShuffle() => ShuffleFonts();
#endif
    }
}