using UnityEngine;
using UnityEngine.Rendering;
using UnityEngine.Rendering.Universal;


public class CausticsPass : ScriptableRenderPass
{
    private const string profilerTag = "Caustics Pass";

    public Material causticsMaterial;
    public Material causticsMaterialVolume;
    private static Mesh mesh;

    private const float BIAS = 0.1f;

    CausticsFeature.CausticsSettings settings;

    public CausticsPass(CausticsFeature.CausticsSettings settings)
    {
        this.settings = settings;
    }

    public override void Execute(ScriptableRenderContext context, ref RenderingData renderingData)
    {
        var cam = renderingData.cameraData.camera;

        if (cam.cameraType == CameraType.Preview || !causticsMaterial) return;

        var sunMatrix = Matrix4x4.TRS(Vector3.zero,
            Quaternion.Euler(settings.fixedDirection.x, settings.fixedDirection.y, settings.fixedDirection.z),
            Vector3.one);
        if (settings.direction == CausticsDirection.DirectionalLight)
        {
            sunMatrix = RenderSettings.sun != null
                ? RenderSettings.sun.transform.localToWorldMatrix
                : Matrix4x4.TRS(Vector3.zero, Quaternion.Euler(-45f, 45f, 0f), Vector3.one);
        }


        causticsMaterial.SetMatrix("_MainLightDirection", sunMatrix);
        causticsMaterialVolume.SetMatrix("_MainLightDirection", sunMatrix);

        CommandBuffer cmd = CommandBufferPool.Get(profilerTag);

        if (!mesh) mesh = GenerateQuad(1000f);
        var position = cam.transform.position;
        position.y = cam.transform.position.y > settings.waterLevel
            ? settings.waterLevel
            : cam.transform.position.y - BIAS;
        var matrix = Matrix4x4.TRS(position, Quaternion.identity, Vector3.one);
        cmd.DrawMesh(mesh, matrix, causticsMaterial, 0, 0);

        context.ExecuteCommandBuffer(cmd);
        CommandBufferPool.Release(cmd);
    }

    private static Mesh GenerateQuad(float size)
    {
        var m = new Mesh();

        size *= 0.5f;

        var verts = new[]
        {
            new Vector3(-size, 0f, -size),
            new Vector3(size, 0f, -size),
            new Vector3(-size, 0f, size),
            new Vector3(size, 0f, size)
        };

        var tris = new[]
        {
            0, 2, 1,
            2, 3, 1
        };

        m.vertices = verts;
        m.triangles = tris;

        return m;
    }
}