using System.Collections;
using System.Collections.Generic;
using UnityEngine;

// visually scale this object in global space around some arbitrary vector
public class SquashA : MonoBehaviour
{
    // A reference mesh that will never be deformed
    public Transform MeshObject;
    Mesh origMesh;
    Vector3[] origVerts;

    // copy that mesh to this mesh but deform it
    Mesh mesh;
    Vector3[] verts;

    //  The direction along which the stretch/squash is performed...
    public Vector3 squashAxis = Vector3.up;
    //  ...and the scaling along that axis.
    public float scale = 0.5f;

    void Start()
    {
        origMesh = MeshObject.GetComponent<MeshFilter>().mesh;
        mesh = GetComponent<MeshFilter>().mesh;
    }

    void Update()
    {
        // This mesh follows the invisible reference mesh (which is not deformed)
        transform.position = MeshObject.position;
        transform.rotation = MeshObject.rotation;

        origVerts = origMesh.vertices;
        verts = origMesh.vertices;
        LocalToWorld();

        //  Create a new local coordinate space where one axis is the stretch/squash direction
        Vector3 r = squashAxis;
        Vector3 g = Vector3.zero;
        Vector3 b = Vector3.zero;
        Vector3.OrthoNormalize(ref r, ref g, ref b);
        DrawAxes(r, g, b);

        //A matrix transforms points into new coordinate space.
        Matrix4x4 mat = new Matrix4x4();
        mat.SetRow(0, r);
        mat.SetRow(1, g);
        mat.SetRow(2, b);
        mat.SetRow(3, new Vector4(0, 0, 0, 1));
        Matrix4x4 inv = mat.inverse;

        for (int i = 0; i < origVerts.Length; i++)
        {
            //  Convert the original unaltered vertex to the new coordinate space.
            Vector3 vert = mat.MultiplyPoint3x4(origVerts[i]);

            //  Change the vertex's position in the new space.
            vert.x *= scale;

            //  Convert it back to the usual XYZ space.
            verts[i] = inv.MultiplyPoint3x4(vert);
        }

        //  Set the updated vertex array.
        mesh.vertices = verts;

        //  The normals have probably changed, so let Unity update them.
        mesh.RecalculateNormals();
    }

    void LocalToWorld()
    {
        Matrix4x4 localToWorld = MeshObject.localToWorldMatrix;
        for (int i = 0; i < origVerts.Length; ++i)
        {
            Vector3 world_v = localToWorld.MultiplyPoint3x4(origVerts[i]);
            origVerts[i] = world_v;
            Debug.DrawRay(world_v, Vector3.up * 0.01f, Color.magenta, 0.001f);
        }
    }

    void DrawAxes(Vector3 R, Vector3 B, Vector3 G)
    {
        Debug.DrawRay(transform.position, R, Color.red, 0.05f);
        Debug.DrawRay(transform.position, G, Color.green, 0.05f);
        Debug.DrawRay(transform.position, B, Color.blue, 0.05f);
    }
}