using System.Collections.Generic;
using UnityEngine;

namespace PSXSplash.RuntimeCode
{
    public struct PSXVertex
    {
        public short vx, vy, vz;
        public byte u, v;
    }

    public struct Tri
    {
        public PSXVertex v0;
        public PSXVertex v1;
        public PSXVertex v2;
    }

    [System.Serializable]
    public class PSXMesh
    {
        public List<Tri> Triangles;

        public static PSXMesh CreateFromUnityMesh(Mesh mesh, int textureWidth = 256, int textureHeight = 256, Transform transform = null)
        {
            PSXMesh psxMesh = new PSXMesh { Triangles = new List<Tri>() };

            Vector3[] vertices = mesh.vertices;
            Vector2[] uv = mesh.uv;
            int[] indices = mesh.triangles;

            for (int i = 0; i < indices.Length; i += 3)
            {
                int vid0 = indices[i];
                int vid1 = indices[i + 1];
                int vid2 = indices[i + 2];

                // Convert to world space only if a transform is provided
                Vector3 v0 = transform ? transform.TransformPoint(vertices[vid0]) : vertices[vid0];
                Vector3 v1 = transform ? transform.TransformPoint(vertices[vid1]) : vertices[vid1];
                Vector3 v2 = transform ? transform.TransformPoint(vertices[vid2]) : vertices[vid2];

                PSXVertex psxV0 = ConvertToPSXVertex(v0, uv[vid0], textureWidth, textureHeight);
                PSXVertex psxV1 = ConvertToPSXVertex(v1, uv[vid1], textureWidth, textureHeight);
                PSXVertex psxV2 = ConvertToPSXVertex(v2, uv[vid2], textureWidth, textureHeight);

                psxMesh.Triangles.Add(new Tri { v0 = psxV0, v1 = psxV1, v2 = psxV2 });
            }

            return psxMesh;
        }

        private static PSXVertex ConvertToPSXVertex(Vector3 vertex, Vector2 uv, int textureWidth, int textureHeight)
        {
            PSXVertex psxVertex = new PSXVertex
            {
                vx = (short)(Mathf.Clamp(vertex.x, -4f, 3.999f) * 4096),
                vy = (short)(Mathf.Clamp(-vertex.y, -4f, 3.999f) * 4096),
                vz = (short)(Mathf.Clamp(vertex.z, -4f, 3.999f) * 4096),
                u = (byte)(Mathf.Clamp((uv.x * (textureWidth-1)), 0, 255)),
                v = (byte)(Mathf.Clamp(((1.0f - uv.y) * (textureHeight-1)), 0, 255)) 
            };
            return psxVertex;
        }
    }
}