evershade/Assets/Scripts/Managers/DayNightCycleManager.cs

using System;
using System.Collections;
using TMPro;
using UnityEngine;
using UnityEngine.Rendering.Universal;

public class DayNightCycleManager : MonoBehaviour
{
    // possible future additions
    // weather sys
    // skybox changes based on time of day
    // moon and stars
    // clouds
    // rain

    // Sound effects, bird chrirping, crickets, wind, etc

    // Temperture? 

    // Lighting effects! So that the transition is more visually appealing

    // Moonlight phases based on day of month ect

    // Seasons - impact the length of day, temp, weather, etc

    public enum Season
    {
        Spring,
        Summer,
        Autumn,
        Winter
    }

    public float dayLengthInMinutes = 15f;
    public float startTimeInHours = 6f; // Start time in hours
    public Light2D globalLight;
    public TMP_Text timeText;
    public TMP_Text dayText;
    public TMP_Text seasonText;


    public Gradient lightColorGradient;
    public Gradient lightIntensityGradient;

    public bool isFirstDay = true;
    public int monthsPerYear = 4;
    public int daysPerMonth = 28;
    private Season _currentSeason;
    private float _currentTime;
    private int _daysPassed;


    private void Start()
    {
        _currentTime = isFirstDay ? startTimeInHours / 24 * dayLengthInMinutes * 60 : 0;
        StartCoroutine(DayNightCycleCoroutine());
        isFirstDay = false;
    }

    private void Update()
    {
        timeText.text = GetCurrentTime();

        // todo: optimize to only update on day change
        dayText.text = GetCurrentDayOfMonth().ToString();
        seasonText.text = GetCurrentSeason().ToString();
    }

    public static event Action OnDayChange;
    public static event Action OnSeasonChange;


    public Season GetCurrentSeason()
    {
        // Calculate the current day of the year
        var month = GetCurrentMonth();

        return month switch
        {
            0 => Season.Spring,
            1 => Season.Summer,
            2 => Season.Autumn,
            3 => Season.Winter,
            _ => Season.Spring
        };
    }

    public int GetCurrentDayOfMonth()
    {
        // Calculate the current day of the year
        var dayOfYear = GetDaysPassed();
        // 4 months per year
        // Calculate the current month
        var month = dayOfYear / daysPerMonth % monthsPerYear;
        return dayOfYear % daysPerMonth;
    }

    public int GetCurrentMonth()
    {
        // Calculate the current day of the year
        var dayOfYear = GetDaysPassed();
        // 4 months per year
        // Calculate the current month
        return dayOfYear / daysPerMonth % monthsPerYear;
    }


    private string GetCurrentTime()
    {
        // Calculate the current hour and minute based on the time of day
        var timeOfDay = _currentTime / (dayLengthInMinutes * 60);
        var hours = Mathf.FloorToInt(timeOfDay * 24);
        var minutes = Mathf.FloorToInt((timeOfDay * 24 - hours) * 60);

        // Convert to 12-hour format and add AM/PM
        var hours12 = hours % 12;
        if (hours12 == 0) hours12 = 12;
        var amPm = hours < 12 ? "AM" : "PM";

        return string.Format("{0:D2}:{1:D2} {2}", hours12, minutes, amPm);
    }

    public int GetDaysPassed()
    {
        return _daysPassed;
    }


    private IEnumerator DayNightCycleCoroutine()
    {
        var previousSeason = _currentSeason;
        while (true)
        {
            // Calculate the current time of day between 0 (midnight) and 1 (next midnight)
            var timeOfDay = _currentTime / (dayLengthInMinutes * 60);

            // Adjust the intensity of the light source based on the time of day
            globalLight.color = lightColorGradient.Evaluate(timeOfDay);
            globalLight.intensity = lightIntensityGradient.Evaluate(timeOfDay).a;

            // increment current time
            _currentTime += Time.deltaTime;


            // check if a day has passed
            if (_currentTime >= dayLengthInMinutes * 60)
            {
                _daysPassed++;
                Debug.Log("Day " + _daysPassed + " has passed");
                _currentTime = 0;
                isFirstDay = false;

                OnDayChange?.Invoke();

                var newSeason = GetCurrentSeason();
                if (newSeason != previousSeason)
                {
                    Debug.Log("Season changed from " + previousSeason + " to " + newSeason);
                    previousSeason = newSeason;
                    OnSeasonChange?.Invoke();
                }
            }

            yield return null;
        }
    }
}