using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using System.IO;
using UnityEngine.Events;
using Unity.VisualScripting;

public class NarrationManager : MonoBehaviour
{
    // Singleton Implementation //
    public static NarrationManager _instance { get; private set; }


    // Variables //
    private List<string> m_scriptSlices = new List<string>();

    public TextAsset m_Filename;

    private string m_UnprocessedFile;

    private int m_ScriptIndex;

    private float m_SubtitileWaitTime = 8;

    // Unity Events //
    public delegate void onUpdateSubtitileDelegate(string subtitle, float waitTime);
    public static onUpdateSubtitileDelegate m_UpdateSubtitile;

    private void Awake()
    {
        if (_instance != null)
            Destroy(this);
        else
            _instance = this;
    }

    // Read in a text file, split into sentences, and add to list.
    void Start()
    {
        if (m_Filename != null)
        {
            m_UnprocessedFile = m_Filename.text;
            ParseSentences();
            m_ScriptIndex = 0;
            StartCoroutine(WaitToStart());
        }
        else
        {
            Debug.Log($"No filename given for script.");
        }
    }

    IEnumerator WaitToStart()
    {
        yield return new WaitForSecondsRealtime(5f);
        updateSubtitle();
    }

    // Coroutine for subtitles, when to start the next one after a delay
    IEnumerator SubtitleWait()
    {
        m_SubtitileWaitTime = Random.Range(12.5f, 15f);
        yield return new WaitForSeconds(m_SubtitileWaitTime);
        updateSubtitle();
    }

    private void CalculateVariableWaitTime(string sentence)
    {
        var temp = Mathf.Ceil(sentence.Length / 5);
        if (temp <= 0)
        {
            m_SubtitileWaitTime = 1;
        }
        else
        {
            m_SubtitileWaitTime = temp;
        }
    }

    // Increments to next index in list, and updates UI.
    void updateSubtitle()
    {
        if (m_ScriptIndex == m_scriptSlices.Count)
            m_ScriptIndex = 0;
        CalculateVariableWaitTime(m_scriptSlices[m_ScriptIndex]);
        DisplayText(m_scriptSlices[m_ScriptIndex]);
        m_ScriptIndex++;
        StartCoroutine(SubtitleWait());
    }

    // Invokes a Unity Event which updates UI.
    private void DisplayText(string slice)
    {
        m_UpdateSubtitile?.Invoke(slice, m_SubtitileWaitTime);
    }

    // Parse sentences by newlines
    private void ParseSentences()
    {
        m_scriptSlices.AddRange(
                m_UnprocessedFile.Split("\n"[0]));
        Debug.Log($"Parsing of text done, line count: {m_scriptSlices.Count}");
    }
}