using System;
using System.Collections.Generic;
using RebootKit.Engine.Foundation;
using RebootKit.Engine.Main;
using TriInspector;
using Unity.Burst;
using Unity.Collections;
using Unity.Jobs;
using Unity.Mathematics;
using UnityEngine;

namespace RebootReality.jelycho.Ropes {
    public class GutsRenderer : MonoBehaviour {
        [SerializeField] RopesManager m_RopesManager;
        
        [SerializeField] float m_RenderDistance = 100.0f;

        [SerializeField] Material m_Material;

        [SerializeField] int m_Layer;

        [SerializeField] GutMeshGenerationConfig m_GutMeshGenerationConfig = new GutMeshGenerationConfig {
            radius = 0.2f,
            resolution = 16
        };

        readonly List<Mesh> m_Meshes = new List<Mesh>();
        
        [ShowInInspector, TriInspector.ReadOnly]
        int m_RenderCount = 0;

        void OnDestroy() {
            foreach (Mesh mesh in m_Meshes) {
                Destroy(mesh);
            }

            m_Meshes.Clear();
        }
        
        void LateUpdate() {
            m_RenderCount = 0;

            for (int ropeIndex = 0; ropeIndex < m_RopesManager.RopesCount; ++ropeIndex) {
                NativeArray<float3> ropePositions = m_RopesManager.PeekRopePositions(ropeIndex);
                if (ropePositions.Length < 2) {
                    continue;
                }
                
                float distanceSquared = math.distancesq(m_RopesManager.GetRopeBounds(ropeIndex).center,
                                                        RR.MainCamera.transform.position);
                if (distanceSquared > m_RenderDistance * m_RenderDistance) {
                    continue;
                }

                if (!m_RopesManager.IsRopeBoundsInFrustum(ropeIndex, RR.MainCamera)) {
                    continue;
                }
                
                int vertexCount = m_GutMeshGenerationConfig.resolution * ropePositions.Length;
                int indexCount = m_GutMeshGenerationConfig.resolution * (ropePositions.Length - 1) * 6;

                GenerateGutVertexDataJob job = new GenerateGutVertexDataJob {
                    Config = m_GutMeshGenerationConfig,
                    RopePositions = ropePositions,
                    Positions = new NativeArray<float3>(vertexCount, Allocator.TempJob),
                    Normals = new NativeArray<float3>(vertexCount, Allocator.TempJob),
                    UVs0 = new NativeArray<float2>(vertexCount, Allocator.TempJob),
                    UVs1 = new NativeArray<float2>(vertexCount, Allocator.TempJob),
                    Indices = new NativeArray<int>(indexCount, Allocator.TempJob)
                };
                
                job.Schedule().Complete();

                Mesh mesh = GetOrCreateMesh(ropeIndex);

                mesh.Clear();
                mesh.SetVertices(job.Positions);
                mesh.SetNormals(job.Normals);
                mesh.SetUVs(0, job.UVs0);
                mesh.SetUVs(1, job.UVs1);
                mesh.SetIndices(job.Indices, MeshTopology.Triangles, 0, false);

                job.Positions.Dispose();
                job.Normals.Dispose();
                job.UVs0.Dispose();
                job.UVs1.Dispose();
                job.Indices.Dispose();
                
                Graphics.DrawMesh(mesh,
                                  transform.localToWorldMatrix,
                                  m_Material,
                                  m_Layer,
                                  null,
                                  0,
                                  null,
                                  UnityEngine.Rendering.ShadowCastingMode.On,
                                  true);
                
                m_RenderCount += 1;
            }
        }
        
        Mesh GetOrCreateMesh(int ropeIndex) {
            if (ropeIndex < m_Meshes.Count) {
                return m_Meshes[ropeIndex];
            }

            Mesh mesh = new Mesh {
                name = $"GutMesh_{ropeIndex}",
                indexFormat = UnityEngine.Rendering.IndexFormat.UInt32
            };
            mesh.MarkDynamic();
            m_Meshes.Add(mesh);
            return mesh;
        }

        [BurstCompile]
        struct GenerateGutVertexDataJob : IJob {
            [Unity.Collections.ReadOnly] public GutMeshGenerationConfig Config;
            [Unity.Collections.ReadOnly] public NativeArray<float3> RopePositions;

            [WriteOnly] public NativeArray<float3> Positions;
            [WriteOnly] public NativeArray<float3> Normals;
            [WriteOnly] public NativeArray<float2> UVs0;
            public NativeArray<float2> UVs1;
            [WriteOnly] public NativeArray<int> Indices;

            public void Execute() {
                float ropeLength = 0f;
                
                for (int ropePositionIndex = 0; ropePositionIndex < RopePositions.Length; ++ropePositionIndex) {
                    bool isLast = ropePositionIndex >= RopePositions.Length - 1;
                    
                    float3 start = RopePositions[ropePositionIndex];
                    float3 end = isLast ?
                                     RopePositions[ropePositionIndex - 1] :
                                     RopePositions[ropePositionIndex + 1];
                    
                    float3 forward = math.normalize(end - start);

                    if (isLast) {
                        forward = -forward;
                    }
                    
                    float3 right = math.normalize(math.cross(forward, math.abs(forward.x) > 0.99f ? new float3(0, 1, 0) : new float3(1, 0, 0)));
                    float3 up = math.cross(forward, right);

                    for (int i = 0; i < Config.resolution; ++i) {
                        float angle = (float) i / Config.resolution * math.PI * 2f;
                        float3 offset = (math.cos(angle) * right + math.sin(angle) * up) * Config.radius;

                        int vertexIndex = ropePositionIndex * Config.resolution + (i % Config.resolution);
                        Positions[vertexIndex] = start + offset;
                        Normals[vertexIndex] = math.normalize(offset);
                        UVs0[vertexIndex] = new float2((float) i / (Config.resolution - 1),
                                                       ropePositionIndex % 2 == 0 ? 0 : 1);
                        UVs1[vertexIndex] = new float2(ropeLength,
                                                       ropeLength);
                    }

                    ropeLength += math.distance(start, end);
                }

                for (int ropePositionIndex = 0; ropePositionIndex < RopePositions.Length; ++ropePositionIndex) {
                    for (int i = 0; i < Config.resolution; ++i) {
                        int vertexIndex = ropePositionIndex * Config.resolution + (i % Config.resolution);
                        UVs1[vertexIndex] = new float2(UVs1[vertexIndex].x,
                                                       ropeLength);
                    }
                }

                int index = 0;
                for (int ropePositionIndex = 0; ropePositionIndex < RopePositions.Length - 1; ++ropePositionIndex) {
                    for (int i = 0; i < Config.resolution; ++i) {
                        int current = ropePositionIndex * Config.resolution + i;
                        int next = ropePositionIndex * Config.resolution + (i + 1) % Config.resolution;
                        int currentNextRow = (ropePositionIndex + 1) * Config.resolution + i;
                        int nextNextRow = (ropePositionIndex + 1) * Config.resolution + (i + 1) % Config.resolution;

                        Indices[index++] = current;
                        Indices[index++] = next;
                        Indices[index++] = currentNextRow;

                        Indices[index++] = currentNextRow;
                        Indices[index++] = next;
                        Indices[index++] = nextNextRow;
                    }
                }
            }
        }

        [Serializable]
        struct GutMeshGenerationConfig {
            [Min(0.01f)] public float radius;
            [Range(3, 64)] public int resolution;
        }
    }
}