using UnityEngine;

/// <summary>
/// Old film projector feel for the credits projected on the theatre screen: the projector light,
/// the projected image and the light rays share the same subtle brightness flicker, with rare
/// short dips like a skipping film.
/// </summary>
public class CreditsProjector : MonoBehaviour
{
    [SerializeField] private Light _light;
    [SerializeField] private CanvasGroup _image;
    [SerializeField] private Renderer[] _rays;

    [Tooltip("Continuous brightness variation (0 = steady)")]
    [SerializeField, Range(0f, 1f)] private float _flickerAmount = .08f;
    [SerializeField, Min(0f)] private float _flickerSpeed = 7f;

    [Tooltip("Average number of short brightness dips per second")]
    [SerializeField, Min(0f)] private float _dipsPerSecond = .3f;
    [SerializeField, Range(0f, 1f)] private float _dipAmount = .25f;
    [SerializeField, Min(0f)] private float _dipDuration = .06f;

    [Tooltip("How much of the flicker reaches the projected image (the light and rays get all of it)")]
    [SerializeField, Range(0f, 1f)] private float _imageFlicker = .5f;

    private static readonly int ColorId = Shader.PropertyToID("_Color");

    private float _baseIntensity;
    private float _baseAlpha;
    private Color[] _baseRayColors;
    private MaterialPropertyBlock _block;
    private float _dipTimer;
    private float _seed;

    private void Awake()
    {
        _seed = Random.Range(0f, 100f);
        _block = new MaterialPropertyBlock();

        if (_light) _baseIntensity = _light.intensity;
        if (_image) _baseAlpha = _image.alpha;

        _baseRayColors = new Color[_rays.Length];
        for (int i = 0; i < _rays.Length; i++)
            _baseRayColors[i] = _rays[i] && _rays[i].sharedMaterial ? _rays[i].sharedMaterial.GetColor(ColorId) : Color.white;
    }

    private void Update()
    {
        float noise = Mathf.PerlinNoise(Time.time * _flickerSpeed, _seed);
        float brightness = 1f - _flickerAmount * noise;

        if (_dipTimer > 0f)
            _dipTimer -= Time.deltaTime;
        else if (Random.value < _dipsPerSecond * Time.deltaTime)
            _dipTimer = _dipDuration;

        if (_dipTimer > 0f)
            brightness *= 1f - _dipAmount;

        if (_light)
            _light.intensity = _baseIntensity * brightness;

        if (_image)
            _image.alpha = _baseAlpha * Mathf.Lerp(1f, brightness, _imageFlicker);

        for (int i = 0; i < _rays.Length; i++)
        {
            if (!_rays[i])
                continue;

            _rays[i].GetPropertyBlock(_block);
            Color color = _baseRayColors[i];
            _block.SetColor(ColorId, new Color(color.r * brightness, color.g * brightness, color.b * brightness, color.a));
            _rays[i].SetPropertyBlock(_block);
        }
    }
}