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import os
import sys
import random
import math
import torch
import numpy as np
import torch.nn.functional as F
from argparse import ArgumentParser

from core.registry import register_method
from core.base_method import BaseMethod

sys.path.append(os.path.abspath(os.path.join(os.path.dirname(__file__), '../../ContextGS_offy')))
from utils.loss_utils import l1_loss, ssim
from gaussian_renderer import prefilter_voxel, render as native_render
from scene import Scene, GaussianModel
from arguments import ModelParams, PipelineParams, OptimizationParams

@register_method("contextgs")
class ContextGS_offyWrapper(BaseMethod):
    def __init__(self, dataset_config, hyperparams):
        self.parser = ArgumentParser()
        self.lp = ModelParams(self.parser)
        self.op = OptimizationParams(self.parser)
        self.pp = PipelineParams(self.parser)
        
        self.parser.add_argument('--level_num', type=int, default=3)
        self.parser.add_argument('--level_scale', type=int, default=10)
        self.parser.add_argument("--n_features", type=int, default=4)
        self.parser.add_argument("--lmbda", type=float, default=0.001)
        self.parser.add_argument("--lmbda_rec", type=float, default=1)
        self.parser.add_argument("--disable_hyper", default=False, action="store_true")
        
        self.args = self.parser.parse_args([])

        self.args.source_path = dataset_config["source_path"]
        self.args.model_path = dataset_config["model_path"]
        self.args.eval = True
        self.args.resolution = dataset_config.get("resolution", 1)
        self.track_decoupling = hyperparams.get("track_decoupling", False)

        self.dataset = self.lp.extract(self.args)
        self.opt = self.op.extract(self.args)
        self.pipe = self.pp.extract(self.args)
        self.args_param = self.args

        self.gaussians = GaussianModel(
            self.dataset.feat_dim,
            self.dataset.n_offsets,
            self.dataset.voxel_size,
            self.dataset.update_depth,
            self.dataset.update_init_factor,
            self.dataset.update_hierachy_factor,
            self.dataset.use_feat_bank,
            n_features_per_level=self.args_param.n_features,
            level_num=self.args_param.level_num,
            hyper_divisor=self.dataset.hyper_divisor,
            target_ratio=self.dataset.target_ratio,
            disable_hyper=self.args_param.disable_hyper
        )
        self.scene = Scene(self.dataset, self.gaussians)
        self.gaussians.update_anchor_bound()
        self.gaussians.training_setup(self.opt)

        bg_color = [1, 1, 1] if self.dataset.white_background else [0, 0, 0]
        self.background = torch.tensor(bg_color, dtype=torch.float32, device="cuda")
        self.viewpoint_stack = self.scene.getTrainCameras().copy()
        
        self.last_n_gaussians = self.gaussians.get_anchor.shape[0]

    def train_iteration(self, step):
        self.gaussians.update_learning_rate(step)
            
        if not self.viewpoint_stack:
            self.viewpoint_stack = self.scene.getTrainCameras().copy()
            
        viewpoint_cam = self.viewpoint_stack.pop(random.randint(0, len(self.viewpoint_stack) - 1))
        
        retain_grad = (step < self.opt.update_until and step >= 0)
        voxel_visible_mask = prefilter_voxel(viewpoint_cam, self.gaussians, self.pipe, self.background)
        render_pkg = native_render(viewpoint_cam, self.gaussians, self.pipe, self.background, visible_mask=voxel_visible_mask, retain_grad=retain_grad, step=step)
        
        image = render_pkg["render"]
        viewspace_point_tensor = render_pkg["viewspace_points"]
        visibility_filter = render_pkg["visibility_filter"]
        offset_selection_mask = render_pkg["selection_mask"]
        opacity = render_pkg["neural_opacity"]
        scaling = render_pkg["scaling"]
        bit_per_param = render_pkg.get("bit_per_param", None)
        
        gt_image = viewpoint_cam.original_image.cuda()
        
        Ll1 = l1_loss(image, gt_image)
        ssim_value = ssim(image, gt_image)
        scaling_reg = scaling.prod(dim=1).mean()
        
        loss_target = self.args_param.lmbda_rec * ((1.0 - self.opt.lambda_dssim) * Ll1 + self.opt.lambda_dssim * (1.0 - ssim_value))
        
        loss_parasitic = 0.01 * scaling_reg
        if bit_per_param is not None:
            loss_parasitic = loss_parasitic + self.args_param.lmbda * bit_per_param
            loss_parasitic = loss_parasitic + 5e-4 * torch.mean(torch.sigmoid(self.gaussians._mask))
            
        loss = loss_target + loss_parasitic

        grad_cos_sim = 0.0
        parasitic_ratio = 0.0
        stats = {}

        if self.track_decoupling and step % 100 == 0:
            param_groups_map = {
                "spatial": [self.gaussians._anchor, self.gaussians._offset],
                "geometry": [self.gaussians._scaling, self.gaussians._rotation],
                "opacity": [self.gaussians._opacity, self.gaussians._mask],
                "appearance": [self.gaussians._anchor_feat, self.gaussians._hyper_latent],
            }

            self.gaussians.optimizer.zero_grad(set_to_none=True)
            loss_target.backward(retain_graph=True)
            grads_target = {}
            for group_name, params in param_groups_map.items():
                grads_target[group_name] = []
                for p in params:
                    if p.grad is not None:
                        grads_target[group_name].append(p.grad.clone())
                    else:
                        grads_target[group_name].append(torch.zeros_like(p))

            self.gaussians.optimizer.zero_grad(set_to_none=True)
            loss_parasitic.backward(retain_graph=True)
            grads_parasitic = {}
            for group_name, params in param_groups_map.items():
                grads_parasitic[group_name] = []
                for p in params:
                    if p.grad is not None:
                        grads_parasitic[group_name].append(p.grad.clone())
                    else:
                        grads_parasitic[group_name].append(torch.zeros_like(p))

            for group_name, params in param_groups_map.items():
                u_t_list = []
                u_p_list = []
                for i, p in enumerate(params):
                    state = self.gaussians.optimizer.state.get(p, None)
                    if state is not None and "exp_avg_sq" in state:
                        v_t = state["exp_avg_sq"]
                    else:
                        v_t = torch.ones_like(p)
                    
                    for param_group in self.gaussians.optimizer.param_groups:
                        if id(p) in [id(opt_p) for opt_p in param_group['params']]:
                            lr = param_group['lr']
                            break
                    else:
                        lr = 1e-3

                    u_t = (lr / (torch.sqrt(v_t) + 1e-8)) * grads_target[group_name][i]
                    u_p = (lr / (torch.sqrt(v_t) + 1e-8)) * grads_parasitic[group_name][i]
                    u_t_list.append(u_t.reshape(-1))
                    u_p_list.append(u_p.reshape(-1))
                
                gt = torch.cat(u_t_list)
                gp = torch.cat(u_p_list)
                
                if gt.norm() > 0 and gp.norm() > 0:
                    cos = float(F.cosine_similarity(gt.unsqueeze(0), gp.unsqueeze(0)))
                    r = float(gp.norm() / (gt.norm() + gp.norm() + 1e-7))
                    ti = r * max(0.0, -cos)
                else:
                    ti = 0.0
                stats[f"sti_{group_name}"] = ti

            all_gt = torch.cat([torch.cat(u_t_list) for group_name, params in param_groups_map.items() for i, p in enumerate(params)])
            all_gp = torch.cat([torch.cat(u_p_list) for group_name, params in param_groups_map.items() for i, p in enumerate(params)])
            if all_gt.norm() > 0 and all_gp.norm() > 0:
                grad_cos_sim = float(F.cosine_similarity(all_gt.unsqueeze(0), all_gp.unsqueeze(0)))
                parasitic_ratio = float(all_gp.norm() / (all_gt.norm() + 1e-7))

            self.gaussians.optimizer.zero_grad(set_to_none=True)
            loss.backward()
        else:
            loss.backward()

        with torch.no_grad():
            if step < self.opt.update_until and step > self.opt.start_stat:
                self.gaussians.training_statis(viewspace_point_tensor, opacity, visibility_filter, offset_selection_mask, voxel_visible_mask)
                if step not in range(3000, 4000):
                    if step > self.opt.update_from and step % self.opt.update_interval == 0:
                        self.gaussians.adjust_anchor(check_interval=self.opt.update_interval, success_threshold=self.opt.success_threshold, grad_threshold=self.opt.densify_grad_threshold, min_opacity=self.opt.min_opacity)
            elif step == self.opt.update_until:
                del self.gaussians.opacity_accum
                del self.gaussians.offset_gradient_accum
                del self.gaussians.offset_denom
                torch.cuda.empty_cache()

            if step < self.opt.iterations:
                self.gaussians.optimizer.step()
                self.gaussians.optimizer.zero_grad(set_to_none=True)

        num_gaussians = self.gaussians.get_anchor.shape[0]
        metrics = {
            "loss": float(loss), "loss_l1": float(loss_target), "loss_ssim": float(loss_parasitic),
            "num_gaussians": int(num_gaussians), "delta_N": int(num_gaussians - self.last_n_gaussians),
            "peak_vram_GB": float(torch.cuda.max_memory_allocated() / (1024 ** 3)),
            "grad_cos_sim": float(grad_cos_sim), "parasitic_ratio": float(parasitic_ratio)
        }
        metrics.update(stats)
        
        if bit_per_param is not None:
            metrics["bit_per_param"] = float(bit_per_param)
            
        self.last_n_gaussians = num_gaussians
        
        histograms = {}
        if step % 1000 == 0:
            histograms["opacity"] = torch.sigmoid(self.gaussians._opacity).clone().detach()
            scales = self.gaussians.get_scaling.clone().detach()
            histograms["scaling"] = scales
            scales_2d = scales[:, :2] if scales.shape[1] >= 2 else scales
            gamma = scales_2d.max(dim=-1)[0] / (scales_2d.min(dim=-1)[0] + 1e-7)
            histograms["anisotropy"] = gamma
            histograms["anchor_feat_mag"] = self.gaussians._anchor_feat.detach().norm(dim=-1)

        return metrics, histograms

    def render(self, camera):
        with torch.no_grad():
            voxel_visible_mask = prefilter_voxel(camera, self.gaussians, self.pipe, self.background)
            render_pkg = native_render(camera, self.gaussians, self.pipe, self.background, visible_mask=voxel_visible_mask)
        return {"image": render_pkg["render"], "depth": render_pkg.get("depth", None)}

    def save(self, save_dir, step):
        self.scene.save(step)

    def load(self, model_path, iteration):
        self.gaussians.load_ply_sparse_gaussian(os.path.join(model_path, 'point_cloud', f'iteration_{iteration}', 'point_cloud.ply'))

    def get_spatial_centers(self):
        return self.gaussians.get_anchor

    def compute_physical_metrics(self, cameras=None):
        metrics = {}
        with torch.no_grad():
            scales = self.gaussians.get_scaling
            scales_2d = scales[:, :2] if scales.dim() > 1 and scales.shape[1] >= 2 else scales.unsqueeze(-1).expand(-1, 2)
            
            max_S, _ = torch.max(scales_2d, dim=1)
            min_S, _ = torch.min(scales_2d, dim=1)
            gamma = max_S / (min_S + 1e-7)
            
            metrics["gamma_median"] = float(torch.median(gamma))
            metrics["gamma_90th_percentile"] = float(torch.quantile(gamma, 0.90))
            metrics["scale_mean"] = float(torch.mean(scales_2d))
            metrics["alpha_mean"] = float(torch.mean(torch.sigmoid(self.gaussians._opacity)))
            
            feat, hyper = self.gaussians._anchor_feat, self.gaussians._hyper_latent
            if hyper is not None and hyper.shape[1] > 0:
                metrics["hyper_energy_ratio"] = float(hyper.norm(dim=-1).mean() / (feat.norm(dim=-1).mean() + 1e-7))
                
            if cameras is not None and len(cameras) > 0:
                view_dirs = []
                for c in cameras:
                    view_dirs.append(c.world_view_transform[:3, 2].tolist())
                view_dirs = F.normalize(torch.tensor(view_dirs, dtype=torch.float32, device="cuda"), dim=1)

                rots = F.normalize(self.gaussians._rotation.clone(), dim=1)
                w, x, y, z = rots.unbind(dim=-1)
                normals = F.normalize(torch.stack([2*(x*z + w*y), 2*(y*z - w*x), 1-2*(x*x + y*y)], dim=-1), dim=1)
                
                max_cos, _ = torch.max(torch.abs(torch.matmul(normals, view_dirs.T)), dim=1)
                metrics["billboard_bias_ratio"] = float((max_cos > 0.90).float().mean())

        return metrics

    def evaluate_spatial_field(self, query_points: torch.Tensor, cameras=None) -> torch.Tensor:
        with torch.no_grad():
            V = query_points.shape[0]
            densities = torch.zeros(V, device="cuda")
            xyz = self.gaussians.get_anchor
            opacities = torch.sigmoid(self.gaussians._opacity).squeeze()
            scales = self.gaussians.get_scaling
            sigma_sq = (scales[:, :2].max(dim=1)[0].pow(2)) if scales.shape[1] >= 2 else scales.squeeze().pow(2)
            
            N_gaussians = xyz.shape[0]
            chunk_size = max(1, 30_000_000 // (N_gaussians + 1))
            for i in range(0, V, chunk_size):
                end = min(i + chunk_size, V)
                dist_sq = torch.cdist(query_points[i:end], xyz, p=2).pow(2)
                weights = torch.exp(-0.5 * dist_sq / (sigma_sq.unsqueeze(0) + 1e-7))
                densities[i:end] = torch.sum(weights * opacities.unsqueeze(0), dim=1)
            return densities