using System.Collections.Generic;
using System.Runtime.CompilerServices;
using UnityEngine;
using UnityEngine.Rendering;
using UnityEngine.Serialization;
using UnityEngine.UI;

[assembly: InternalsVisibleTo("Coffee.UIParticle.Editor")]

namespace Coffee.UIExtensions
{
    /// <summary>
    /// Render maskable and sortable particle effect ,without Camera, RenderTexture or Canvas.
    /// </summary>
    [ExecuteInEditMode]
    [RequireComponent(typeof(RectTransform))]
    [RequireComponent(typeof(CanvasRenderer))]
    public class UIParticle : MaskableGraphic
#if UNITY_EDITOR
        , ISerializationCallbackReceiver
#endif
    {
        [HideInInspector] [SerializeField] internal bool m_IsTrail = false;

        [Tooltip("Ignore canvas scaler")] [SerializeField] [FormerlySerializedAs("m_IgnoreParent")]
        bool m_IgnoreCanvasScaler = true;

        [Tooltip("Particle effect scale")] [SerializeField]
        float m_Scale = 100;

        [Tooltip("Animatable material properties. If you want to change the material properties of the ParticleSystem in Animation, enable it.")] [SerializeField]
        internal AnimatableProperty[] m_AnimatableProperties = new AnimatableProperty[0];

        [Tooltip("Particles")] [SerializeField]
        private List<ParticleSystem> m_Particles = new List<ParticleSystem>();

        private bool _shouldBeRemoved;
        private DrivenRectTransformTracker _tracker;
        private Mesh _bakedMesh;
        private readonly List<Material> _modifiedMaterials = new List<Material>();
        private readonly List<Material> _maskMaterials = new List<Material>();
        private long _activeMeshIndices;
        private Vector3 _cachedPosition;
        private static readonly List<Material> s_TempMaterials = new List<Material>(2);
        private static MaterialPropertyBlock s_Mpb;


        /// <summary>
        /// Should this graphic be considered a target for raycasting?
        /// </summary>
        public override bool raycastTarget
        {
            get { return false; }
            set { }
        }

        public bool ignoreCanvasScaler
        {
            get { return m_IgnoreCanvasScaler; }
            set
            {
                // if (m_IgnoreCanvasScaler == value) return;
                m_IgnoreCanvasScaler = value;
                _tracker.Clear();
                if (isActiveAndEnabled && m_IgnoreCanvasScaler)
                    _tracker.Add(this, rectTransform, DrivenTransformProperties.Scale);
            }
        }

        /// <summary>
        /// Particle effect scale.
        /// </summary>
        public float scale
        {
            get { return m_Scale; }
            set { m_Scale = Mathf.Max(0.001f, value); }
        }

        internal Mesh bakedMesh
        {
            get { return _bakedMesh; }
        }

        public List<ParticleSystem> particles
        {
            get { return m_Particles; }
        }

        public IEnumerable<Material> materials
        {
            get { return _modifiedMaterials; }
        }

        internal long activeMeshIndices
        {
            get { return _activeMeshIndices; }
            set
            {
                if (_activeMeshIndices == value) return;
                _activeMeshIndices = value;
                UpdateMaterial();
            }
        }

        internal Vector3 cachedPosition
        {
            get { return _cachedPosition; }
            set { _cachedPosition = value; }
        }

        public void Play()
        {
            particles.Exec(p => p.Play());
        }

        public void Pause()
        {
            particles.Exec(p => p.Pause());
        }

        public void Stop()
        {
            particles.Exec(p => p.Stop());
        }

        public void RefreshParticles()
        {
            GetComponentsInChildren(particles);

            foreach (var ps in particles)
            {
                var tsa = ps.textureSheetAnimation;
                if (tsa.mode == ParticleSystemAnimationMode.Sprites && tsa.uvChannelMask == (UVChannelFlags) 0)
                    tsa.uvChannelMask = UVChannelFlags.UV0;
            }

            particles.Exec(p => p.GetComponent<ParticleSystemRenderer>().enabled = !enabled);
            particles.SortForRendering(transform);

            SetMaterialDirty();
        }

        protected override void UpdateMaterial()
        {
            // Clear mask materials.
            for (var i = 0; i < _maskMaterials.Count; i++)
            {
                StencilMaterial.Remove(_maskMaterials[i]);
                _maskMaterials[i] = null;
            }

            _maskMaterials.Clear();

            // Clear modified materials.
            for (var i = 0; i < _modifiedMaterials.Count; i++)
            {
                DestroyImmediate(_modifiedMaterials[i]);
                _modifiedMaterials[i] = null;
            }

            _modifiedMaterials.Clear();

            // Recalculate stencil value.
            if (m_ShouldRecalculateStencil)
            {
                var rootCanvas = MaskUtilities.FindRootSortOverrideCanvas(transform);
                m_StencilValue = maskable ? MaskUtilities.GetStencilDepth(transform, rootCanvas) : 0;
                m_ShouldRecalculateStencil = false;
            }

            // No mesh to render.
            if (activeMeshIndices == 0 || !isActiveAndEnabled || particles.Count == 0)
            {
                _activeMeshIndices = 0;
                canvasRenderer.Clear();
                return;
            }

            //
            var materialCount = Mathf.Max(8, activeMeshIndices.BitCount());
            canvasRenderer.materialCount = materialCount;
            var j = 0;
            for (var i = 0; i < particles.Count; i++)
            {
                if (materialCount <= j) break;
                var ps = particles[i];
                if (!ps) continue;

                var r = ps.GetComponent<ParticleSystemRenderer>();
                r.GetSharedMaterials(s_TempMaterials);

                // Main
                var bit = (long) 1 << (i * 2);
                if (0 < (activeMeshIndices & bit) && 0 < s_TempMaterials.Count)
                {
                    var mat = GetModifiedMaterial(s_TempMaterials[0], ps.GetTextureForSprite());
                    canvasRenderer.SetMaterial(mat, j);
                    UpdateMaterialProperties(r, j);
                    j++;
                }

                // Trails
                if (materialCount <= j) break;
                bit <<= 1;
                if (0 < (activeMeshIndices & bit) && 1 < s_TempMaterials.Count)
                {
                    var mat = GetModifiedMaterial(s_TempMaterials[1], null);
                    canvasRenderer.SetMaterial(mat, j++);
                }
            }
        }

        private Material GetModifiedMaterial(Material baseMaterial, Texture2D texture)
        {
            if (0 < m_StencilValue)
            {
                baseMaterial = StencilMaterial.Add(baseMaterial, (1 << m_StencilValue) - 1, StencilOp.Keep, CompareFunction.Equal, ColorWriteMask.All, (1 << m_StencilValue) - 1, 0);
                _maskMaterials.Add(baseMaterial);
            }

            if (texture == null && m_AnimatableProperties.Length == 0) return baseMaterial;

            baseMaterial = new Material(baseMaterial);
            _modifiedMaterials.Add(baseMaterial);
            if (texture)
                baseMaterial.mainTexture = texture;

            return baseMaterial;
        }

        internal void UpdateMaterialProperties(Renderer r, int index)
        {
            if (m_AnimatableProperties.Length == 0 || canvasRenderer.materialCount <= index) return;

            r.GetPropertyBlock(s_Mpb ?? (s_Mpb = new MaterialPropertyBlock()));
            if (s_Mpb.isEmpty) return;

            // #41: Copy the value from MaterialPropertyBlock to CanvasRenderer
            var mat = canvasRenderer.GetMaterial(index);
            if (!mat) return;

            foreach (var ap in m_AnimatableProperties)
            {
                ap.UpdateMaterialProperties(mat, s_Mpb);
            }

            s_Mpb.Clear();
        }

        /// <summary>
        /// This function is called when the object becomes enabled and active.
        /// </summary>
        protected override void OnEnable()
        {
            _cachedPosition = transform.localPosition;
            _activeMeshIndices = 0;

            UIParticleUpdater.Register(this);
            particles.Exec(p => p.GetComponent<ParticleSystemRenderer>().enabled = false);

            if (isActiveAndEnabled && m_IgnoreCanvasScaler)
            {
                _tracker.Add(this, rectTransform, DrivenTransformProperties.Scale);
            }

            // Create objects.
            _bakedMesh = MeshPool.Rent();

            base.OnEnable();

            InitializeIfNeeded();
        }

        /// <summary>
        /// This function is called when the behaviour becomes disabled.
        /// </summary>
        protected override void OnDisable()
        {
            UIParticleUpdater.Unregister(this);
            if (!_shouldBeRemoved)
                particles.Exec(p => p.GetComponent<ParticleSystemRenderer>().enabled = true);
            _tracker.Clear();

            // Destroy object.
            MeshPool.Return(_bakedMesh);
            _bakedMesh = null;

            base.OnDisable();
        }

        /// <summary>
        /// Call to update the geometry of the Graphic onto the CanvasRenderer.
        /// </summary>
        protected override void UpdateGeometry()
        {
        }

        /// <summary>
        /// Callback for when properties have been changed by animation.
        /// </summary>
        protected override void OnDidApplyAnimationProperties()
        {
        }

        private void InitializeIfNeeded()
        {
            if (enabled && m_IsTrail)
            {
                UnityEngine.Debug.LogWarningFormat(this, "[UIParticle] The UIParticle component should be removed: {0}\nReason: UIParticle for trails is no longer needed.", name);
                gameObject.hideFlags = HideFlags.None;
                _shouldBeRemoved = true;
                enabled = false;
                return;
            }
            else if (enabled && transform.parent && transform.parent.GetComponentInParent<UIParticle>())
            {
                UnityEngine.Debug.LogWarningFormat(this, "[UIParticle] The UIParticle component should be removed: {0}\nReason: The parent UIParticle exists.", name);
                gameObject.hideFlags = HideFlags.None;
                _shouldBeRemoved = true;
                enabled = false;
                return;
            }

            if (!this || 0 < particles.Count) return;

            m_IgnoreCanvasScaler = true;

            // refresh.
#if UNITY_EDITOR
            if (!Application.isPlaying)
                UnityEditor.EditorApplication.delayCall += () =>
                {
                    if (this) RefreshParticles();
                };
            else
#endif
                RefreshParticles();
        }

#if UNITY_EDITOR
        void ISerializationCallbackReceiver.OnBeforeSerialize()
        {
            InitializeIfNeeded();
        }

        void ISerializationCallbackReceiver.OnAfterDeserialize()
        {
            UnityEditor.EditorApplication.delayCall += () =>
            {
                if (this) InitializeIfNeeded();
            };
        }
#endif
    }
}