using System.Collections;
using UnityEngine;

namespace SpriteGlow
{
    /// <summary>
    /// Adds an HDR outline over the SpriteRenderer's sprite borders.
    /// Can be used in conjuction with bloom post-processing to create a glow effect.
    /// </summary>
    [AddComponentMenu("Effects/Sprite Glow")]
    [RequireComponent(typeof(SpriteRenderer)), DisallowMultipleComponent, ExecuteInEditMode]
    public class SpriteGlowEffect : MonoBehaviour
    {
        public SpriteRenderer Renderer { get; private set; }
        public Color GlowColor
        {
            get => glowColor;
            set { if (glowColor != value) { glowColor = value; SetMaterialProperties(); } }
        }
        public float GlowBrightness
        {
            get => glowBrightness;
            set { if (glowBrightness != value) { glowBrightness = value; SetMaterialProperties(); } }
        }
        public int OutlineWidth
        {
            get => outlineWidth;
            set { if (outlineWidth != value) { outlineWidth = value; SetMaterialProperties(); } }
        }
        public float AlphaThreshold
        {
            get => alphaThreshold;
            set { if (alphaThreshold != value) { alphaThreshold = value; SetMaterialProperties(); } }
        }
        public bool DrawOutside
        {
            get => drawOutside;
            set { if (drawOutside != value) { drawOutside = value; SetMaterialProperties(); } }
        }
        public bool EnableInstancing
        {
            get => enableInstancing;
            set { if (enableInstancing != value) { enableInstancing = value; SetMaterialProperties(); } }
        }

        [Tooltip("Base color of the glow.")]
        [SerializeField] private Color glowColor = Color.white;
        [Tooltip("The brightness (power) of the glow."), Range(1, 10)]
        [SerializeField] private float glowBrightness = 2f;
        [Tooltip("Width of the outline, in texels."), Range(0, 10)]
        [SerializeField] private int outlineWidth = 1;
        [Tooltip("Threshold to determine sprite borders."), Range(0f, 1f)]
        [SerializeField] private float alphaThreshold = .01f;
        [Tooltip("Whether the outline should only be drawn outside of the sprite borders. Make sure sprite texture has sufficient transparent space for the required outline width.")]
        [SerializeField] private bool drawOutside = false;
        [Tooltip("Whether to enable GPU instancing.")]
        [SerializeField] private bool enableInstancing = false;

        private static readonly int isOutlineEnabledId = Shader.PropertyToID("_IsOutlineEnabled");
        private static readonly int outlineColorId = Shader.PropertyToID("_OutlineColor");
        private static readonly int outlineSizeId = Shader.PropertyToID("_OutlineSize");
        private static readonly int alphaThresholdId = Shader.PropertyToID("_AlphaThreshold");

        private MaterialPropertyBlock materialProperties;
        private Coroutine alphaMonitorRoutine;
        private Coroutine alphaFadeRoutine;

        private void Awake()
        {
            Renderer = GetComponent<SpriteRenderer>();
        }

        private void Start()
        {
            StartAlphaMonitor();
        }

        private void OnEnable()
        {
            SetMaterialProperties();
            StartAlphaMonitor();
        }

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

            if (alphaFadeRoutine != null)
            {
                StopCoroutine(alphaFadeRoutine);
                alphaFadeRoutine = null;
            }

            SetMaterialProperties();
        }

        private void OnValidate()
        {
            if (!isActiveAndEnabled) return;
            SetMaterialProperties();
        }

        private void OnDidApplyAnimationProperties()
        {
            SetMaterialProperties();
        }

        private void SetMaterialProperties()
        {
            if (!Renderer) return;

            Renderer.sharedMaterial = SpriteGlowMaterial.GetSharedFor(this);

            if (materialProperties == null)
                materialProperties = new MaterialPropertyBlock();

            materialProperties.SetFloat(isOutlineEnabledId, isActiveAndEnabled ? 1 : 0);
            materialProperties.SetColor(outlineColorId, GlowColor * GlowBrightness);
            materialProperties.SetFloat(outlineSizeId, OutlineWidth);
            materialProperties.SetFloat(alphaThresholdId, AlphaThreshold);

            Renderer.SetPropertyBlock(materialProperties);
        }

        private void StartAlphaMonitor()
        {
            if (alphaMonitorRoutine != null || Renderer == null)
                return;

            alphaMonitorRoutine = StartCoroutine(AlphaMonitorRoutine());
        }

        private IEnumerator AlphaMonitorRoutine()
        {
            while (true)
            {
                if (Renderer != null)
                {
                    Color color = Renderer.color;
                    if (color.a != 0f)
                    {
                        if (alphaFadeRoutine == null)
                        {
                            alphaFadeRoutine = StartCoroutine(FadeRendererAlphaToZero());
                        }

                        yield break;
                    }
                }

                yield return new WaitForSecondsRealtime(1f);
            }
        }

        private IEnumerator FadeRendererAlphaToZero()
        {
            if (Renderer == null)
                yield break;

            float duration = 0.18f;
            float elapsed = 0f;

            Color startColor = Renderer.color;
            Color endColor = startColor;
            endColor.a = 0f;

            while (elapsed < duration)
            {
                if (Renderer == null)
                    yield break;

                elapsed += Time.unscaledDeltaTime;
                float t = Mathf.Clamp01(elapsed / duration);
                Renderer.color = Color.LerpUnclamped(startColor, endColor, t);
                yield return null;
            }

            if (Renderer != null)
            {
                Color c = Renderer.color;
                c.a = 0f;
                Renderer.color = c;
            }

            alphaFadeRoutine = null;
            alphaMonitorRoutine = null;
        }
    }
}