using System;
using Unity.VisualScripting;
using UnityEngine;


public class MeshGeneration : MonoBehaviour
{
    [SerializeField] private Noise noise;
    [SerializeField] private ComputeShader marchShader;

    public Mesh March(int numPointsPerAxis, Vector3 offset, float isoLevel)
    {
        Buffers.Create(numPointsPerAxis);
        int numVoxelsPerAxis = numPointsPerAxis - 1;
        int numThreadsPerAxis = Mathf.CeilToInt (numVoxelsPerAxis / (float) 8);
        noise.Generate(numPointsPerAxis, numThreadsPerAxis, offset);
        
        marchShader.SetBuffer(0, "points", Buffers.pointsBuffer);
        marchShader.SetBuffer(0, "triangles", Buffers.triangleBuffer);
        marchShader.SetInt("numPointsPerAxis", numPointsPerAxis);
        marchShader.SetFloat("isoLevel", isoLevel);
        
        marchShader.Dispatch(0, numThreadsPerAxis,numThreadsPerAxis,numThreadsPerAxis);
        
        ComputeBuffer.CopyCount(Buffers.triangleBuffer, Buffers.triCountBuffer, 0);
        int[] triCountArray = { 0 };
        Buffers.triCountBuffer.GetData(triCountArray);
        int numTris = triCountArray[0];

        Triangle[] tris = new Triangle[numTris];
        Buffers.triangleBuffer.GetData(tris, 0,0, numTris);
        
        Mesh mesh = new Mesh();
        mesh.Clear();
        
        var vertices = new Vector3[numTris * 3];
        var meshTriangles = new int[numTris * 3];

        for (int i = 0; i < numTris; i++) {
            for (int j = 0; j < 3; j++) {
                meshTriangles[i * 3 + j] = i * 3 + j;
                vertices[i * 3 + j] = tris[i][j];
            }
        }
        mesh.vertices = vertices;
        mesh.triangles = meshTriangles;
        
        mesh.RecalculateNormals();
        return mesh;
    }

    private void OnDestroy()
    {
        Buffers.Release();
    }

    struct Triangle
    {
        public Vector3 a;
        public Vector3 b;
        public Vector3 c;
        
        public Vector3 this [int i] {
            get {
                switch (i) {
                    case 0:
                        return a;
                    case 1:
                        return b;
                    default:
                        return c;
                }
            }
        }
    }
}