#!/usr/bin/env python3
"""
BraTS2023 数据集类 - 用于SAM3训练
将3D医学数据转换为SAM3可处理的视频格式
"""

import os
import random
import numpy as np
import torch
from torch.utils.data import Dataset
import nibabel as nib
from pathlib import Path
from PIL import Image
import cv2
import json
from typing import Optional, List, Dict, Tuple, Any


def normalize_intensity(volume, low_percentile=0.5, high_percentile=99.5):
    """对体积数据进行强度归一化"""
    mask = volume > 0
    if mask.sum() == 0:
        return volume
    low = np.percentile(volume[mask], low_percentile)
    high = np.percentile(volume[mask], high_percentile)
    volume = np.clip(volume, low, high)
    volume = (volume - low) / (high - low + 1e-8)
    return volume


class BraTSVideoDataset(Dataset):
    """
    BraTS数据集 - 将3D医学数据作为视频序列处理
    
    每个3D体积的切片作为视频帧，支持SAM3视频训练
    """
    
    def __init__(
        self,
        data_root: str,
        split: str = 'train',
        modality: int = 0,  # 0=t1c, 1=t1n, 2=t2f, 3=t2w
        target_size: Tuple[int, int] = (512, 512),
        num_frames: int = 8,  # 每个视频样本的帧数
        frame_stride: int = 1,  # 帧间隔
        augment: bool = True,
        train_ratio: float = 0.9,
        val_ratio: float = 0.1,
        test_ratio: float = 0.0,
        seed: int = 42,
        split_json: Optional[str] = None,
        normalize_mean: Tuple[float, ...] = (0.5, 0.5, 0.5),
        normalize_std: Tuple[float, ...] = (0.5, 0.5, 0.5),
    ):
        """
        Args:
            data_root: BraTS数据根目录
            split: 'train' 或 'val'
            modality: 使用的模态索引 (0=t1c, 1=t1n, 2=t2f, 3=t2w)
            target_size: 目标图像大小
            num_frames: 每个训练样本的帧数
            frame_stride: 帧采样间隔
            augment: 是否进行数据增强
            train_ratio: 训练集比例
            seed: 随机种子
        """
        super().__init__()
        
        self.data_root = Path(data_root)
        self.split = split
        self.modality = modality
        self.modality_names = ['t1c', 't1n', 't2f', 't2w']
        self.target_size = target_size
        self.num_frames = num_frames
        self.frame_stride = frame_stride
        self.augment = augment and (split == 'train')
        self.normalize_mean = normalize_mean
        self.normalize_std = normalize_std
        
        # 获取所有病例（case-level）
        all_cases = sorted([d for d in self.data_root.iterdir() if d.is_dir()])

        def _validate_ratios(tr, vr, ter):
            s = float(tr) + float(vr) + float(ter)
            if abs(s - 1.0) > 1e-6:
                raise ValueError(f"train/val/test ratios must sum to 1.0, got {s}")

        def _split_by_ratio(case_list: List[Path], tr: float, vr: float, ter: float, sd: int):
            _validate_ratios(tr, vr, ter)
            case_list = list(case_list)
            rng = random.Random(sd)
            rng.shuffle(case_list)
            n = len(case_list)
            n_train = int(round(n * tr))
            n_val = int(round(n * vr))
            n_train = min(max(n_train, 0), n)
            n_val = min(max(n_val, 0), n - n_train)
            train = case_list[:n_train]
            val = case_list[n_train : n_train + n_val]
            test = case_list[n_train + n_val :]
            return {"train": train, "val": val, "test": test}

        def _split_by_json(case_list: List[Path], split_file: str):
            with open(split_file, "r") as f:
                cfg = json.load(f)
            splits = cfg.get("splits", cfg)
            # support either {"train":[...],...} or {"splits":{"train":[...],...}}
            wanted = splits.get(self.split)
            if wanted is None:
                raise KeyError(f"split '{self.split}' not found in split json: {split_file}")
            wanted = set(wanted)
            return [c for c in case_list if c.name in wanted]

        if split_json:
            self.cases = _split_by_json(all_cases, split_json)
        else:
            parts = _split_by_ratio(all_cases, train_ratio, val_ratio, test_ratio, seed)
            if split not in parts:
                raise ValueError(f"split must be one of train/val/test, got: {split}")
            self.cases = parts[split]
        
        print(f"BraTS {split} set: {len(self.cases)} cases")
        
        # 预先加载所有数据的元信息
        self.case_info = self._preload_case_info()
    
    def _preload_case_info(self) -> List[Dict]:
        """预加载病例信息"""
        case_info = []
        for case_dir in self.cases:
            case_name = case_dir.name
            
            # 检查文件是否存在
            mod_name = self.modality_names[self.modality]
            possible_paths = [
                case_dir / f"{mod_name}.nii.gz",
                case_dir / f"{case_name}-{mod_name}.nii.gz",
            ]
            
            mod_path = None
            for p in possible_paths:
                if p.exists():
                    mod_path = p
                    break
            
            if mod_path is None:
                continue
            
            # 检查分割标签
            seg_paths = [
                case_dir / "seg.nii.gz",
                case_dir / f"{case_name}-seg.nii.gz",
            ]
            
            seg_path = None
            for p in seg_paths:
                if p.exists():
                    seg_path = p
                    break
            
            if seg_path is None:
                continue
            
            case_info.append({
                'case_name': case_name,
                'mod_path': str(mod_path),
                'seg_path': str(seg_path),
            })
        
        return case_info
    
    def __len__(self) -> int:
        return len(self.case_info)
    
    def _load_volume(self, path: str) -> np.ndarray:
        """加载NIfTI体积数据"""
        nii = nib.load(path)
        volume = nii.get_fdata().astype(np.float32)
        return volume
    
    def _get_tumor_slices(self, seg: np.ndarray) -> List[int]:
        """获取包含肿瘤的切片索引"""
        # 转置使得切片在第一维
        if seg.shape[0] > seg.shape[2]:
            seg = np.transpose(seg, (2, 0, 1))
        
        tumor_mask = (seg > 0)
        tumor_areas = tumor_mask.sum(axis=(1, 2))
        tumor_slices = np.where(tumor_areas > 0)[0].tolist()
        
        return tumor_slices
    
    def _sample_frames(self, tumor_slices: List[int], total_slices: int) -> List[int]:
        """采样帧索引"""
        if len(tumor_slices) == 0:
            # 如果没有肿瘤，随机采样
            center = total_slices // 2
            tumor_slices = list(range(max(0, center - 20), min(total_slices, center + 20)))
        
        # 计算需要的范围
        needed_range = self.num_frames * self.frame_stride
        
        # 选择一个包含肿瘤的起始点
        if len(tumor_slices) > 0:
            center_slice = tumor_slices[len(tumor_slices) // 2]
        else:
            center_slice = total_slices // 2
        
        # 计算起始和结束索引
        half_range = needed_range // 2
        start_idx = max(0, center_slice - half_range)
        end_idx = min(total_slices, start_idx + needed_range)
        
        # 如果范围不够，调整
        if end_idx - start_idx < needed_range:
            start_idx = max(0, end_idx - needed_range)
        
        # 采样帧
        available = list(range(start_idx, end_idx, self.frame_stride))
        
        if len(available) < self.num_frames:
            # 如果帧数不够，重复最后一帧
            available = available + [available[-1]] * (self.num_frames - len(available))
        else:
            available = available[:self.num_frames]
        
        return available
    
    def _process_slice(self, slice_2d: np.ndarray) -> np.ndarray:
        """处理单个切片"""
        # 归一化到 0-1
        slice_2d = normalize_intensity(slice_2d)
        
        # 转为 uint8
        slice_2d = (slice_2d * 255).astype(np.uint8)
        
        # 转为RGB
        slice_rgb = np.stack([slice_2d, slice_2d, slice_2d], axis=-1)
        
        # 调整大小
        if self.target_size is not None:
            slice_rgb = cv2.resize(slice_rgb, self.target_size, interpolation=cv2.INTER_LINEAR)
        
        return slice_rgb
    
    def _process_mask(self, mask_2d: np.ndarray, num_classes: int = 4) -> np.ndarray:
        """处理单个mask切片
        
        BraTS 标签:
            0: 背景
            1: NCR (Necrotic tumor core)
            2: ED (Peritumoral Edema)  
            3: ET (Enhancing tumor)
        
        Args:
            mask_2d: 原始标签
            num_classes: 类别数 (4 = 背景 + 3类肿瘤)
        """
        # 保持原始类别 (0, 1, 2, 3)
        mask_2d = mask_2d.astype(np.uint8)
        
        # 调整大小
        if self.target_size is not None:
            mask_2d = cv2.resize(mask_2d, self.target_size, interpolation=cv2.INTER_NEAREST)
        
        return mask_2d
    
    def _get_bbox_from_mask(self, mask: np.ndarray) -> Optional[Tuple[float, float, float, float]]:
        """从mask获取归一化的bbox"""
        if mask.sum() == 0:
            return None
        
        rows = np.any(mask, axis=1)
        cols = np.any(mask, axis=0)
        
        y_indices = np.where(rows)[0]
        x_indices = np.where(cols)[0]
        
        if len(y_indices) == 0 or len(x_indices) == 0:
            return None
        
        y_min, y_max = y_indices[0], y_indices[-1]
        x_min, x_max = x_indices[0], x_indices[-1]
        
        h, w = mask.shape
        
        # 归一化坐标
        return (x_min / w, y_min / h, x_max / w, y_max / h)
    
    def _augment(self, frames: List[np.ndarray], masks: List[np.ndarray]) -> Tuple[List[np.ndarray], List[np.ndarray]]:
        """数据增强"""
        if not self.augment:
            return frames, masks
        
        # 随机水平翻转
        if random.random() > 0.5:
            frames = [np.fliplr(f).copy() for f in frames]
            masks = [np.fliplr(m).copy() for m in masks]
        
        # 随机垂直翻转
        if random.random() > 0.5:
            frames = [np.flipud(f).copy() for f in frames]
            masks = [np.flipud(m).copy() for m in masks]
        
        # 随机旋转 (90度的倍数)
        if random.random() > 0.5:
            k = random.choice([1, 2, 3])
            frames = [np.rot90(f, k).copy() for f in frames]
            masks = [np.rot90(m, k).copy() for m in masks]
        
        return frames, masks
    
    def __getitem__(self, idx: int) -> Dict[str, Any]:
        """
        获取一个训练样本
        
        Returns:
            Dict containing:
                - frames: (T, C, H, W) 视频帧
                - masks: (T, H, W) 分割mask
                - bboxes: (T, 4) 边界框 (归一化坐标)
                - frame_indices: 帧索引
                - case_name: 病例名称
        """
        info = self.case_info[idx]
        
        # 加载数据
        volume = self._load_volume(info['mod_path'])
        seg = self._load_volume(info['seg_path'])
        
        # 转置使得切片在第一维
        if volume.shape[0] > volume.shape[2]:
            volume = np.transpose(volume, (2, 0, 1))
            seg = np.transpose(seg, (2, 0, 1))
        
        total_slices = volume.shape[0]
        
        # 获取肿瘤切片并采样
        tumor_slices = self._get_tumor_slices(seg)
        frame_indices = self._sample_frames(tumor_slices, total_slices)
        
        # 提取帧和mask
        frames = []
        masks = []
        
        for idx in frame_indices:
            frame = self._process_slice(volume[idx])
            mask = self._process_mask(seg[idx])
            frames.append(frame)
            masks.append(mask)
        
        # 数据增强
        frames, masks = self._augment(frames, masks)
        
        # 计算每帧的bbox
        bboxes = []
        for mask in masks:
            bbox = self._get_bbox_from_mask(mask)
            if bbox is None:
                bbox = (0.0, 0.0, 1.0, 1.0)  # 默认全图
            bboxes.append(bbox)
        
        # 转换为tensor
        # frames: (T, H, W, C) -> (T, C, H, W)
        frames_tensor = torch.stack([
            torch.from_numpy(f).permute(2, 0, 1).float() / 255.0
            for f in frames
        ])
        
        # 归一化
        mean = torch.tensor(self.normalize_mean).view(1, 3, 1, 1)
        std = torch.tensor(self.normalize_std).view(1, 3, 1, 1)
        frames_tensor = (frames_tensor - mean) / std
        
        masks_tensor = torch.stack([
            torch.from_numpy(m).long() for m in masks
        ])
        
        bboxes_tensor = torch.tensor(bboxes, dtype=torch.float32)
        
        return {
            'frames': frames_tensor,  # (T, C, H, W)
            'masks': masks_tensor,    # (T, H, W)
            'bboxes': bboxes_tensor,  # (T, 4)
            'frame_indices': torch.tensor(frame_indices),
            'case_name': info['case_name'],
            'num_frames': len(frame_indices),
        }


class BraTSImageDataset(Dataset):
    """
    BraTS数据集 - 2D切片版本，用于图像级别的训练
    """
    
    def __init__(
        self,
        data_root: str,
        split: str = 'train',
        modality: int = 0,
        target_size: Tuple[int, int] = (512, 512),
        augment: bool = True,
        train_ratio: float = 0.9,
        val_ratio: float = 0.1,
        test_ratio: float = 0.0,
        seed: int = 42,
        split_json: Optional[str] = None,
        only_tumor_slices: bool = True,
        normalize_mean: Tuple[float, ...] = (0.5, 0.5, 0.5),
        normalize_std: Tuple[float, ...] = (0.5, 0.5, 0.5),
    ):
        super().__init__()
        
        self.data_root = Path(data_root)
        self.split = split
        self.modality = modality
        self.modality_names = ['t1c', 't1n', 't2f', 't2w']
        self.target_size = target_size
        self.augment = augment and (split == 'train')
        self.only_tumor_slices = only_tumor_slices
        self.normalize_mean = normalize_mean
        self.normalize_std = normalize_std
        
        # 获取所有病例（case-level）
        all_cases = sorted([d for d in self.data_root.iterdir() if d.is_dir()])

        def _validate_ratios(tr, vr, ter):
            s = float(tr) + float(vr) + float(ter)
            if abs(s - 1.0) > 1e-6:
                raise ValueError(f"train/val/test ratios must sum to 1.0, got {s}")

        def _split_by_ratio(case_list: List[Path], tr: float, vr: float, ter: float, sd: int):
            _validate_ratios(tr, vr, ter)
            case_list = list(case_list)
            rng = random.Random(sd)
            rng.shuffle(case_list)
            n = len(case_list)
            n_train = int(round(n * tr))
            n_val = int(round(n * vr))
            n_train = min(max(n_train, 0), n)
            n_val = min(max(n_val, 0), n - n_train)
            train = case_list[:n_train]
            val = case_list[n_train : n_train + n_val]
            test = case_list[n_train + n_val :]
            return {"train": train, "val": val, "test": test}

        def _split_by_json(case_list: List[Path], split_file: str):
            with open(split_file, "r") as f:
                cfg = json.load(f)
            splits = cfg.get("splits", cfg)
            wanted = splits.get(self.split)
            if wanted is None:
                raise KeyError(f"split '{self.split}' not found in split json: {split_file}")
            wanted = set(wanted)
            return [c for c in case_list if c.name in wanted]

        if split_json:
            cases = _split_by_json(all_cases, split_json)
        else:
            parts = _split_by_ratio(all_cases, train_ratio, val_ratio, test_ratio, seed)
            if split not in parts:
                raise ValueError(f"split must be one of train/val/test, got: {split}")
            cases = parts[split]
        
        # 构建切片索引
        self.samples = self._build_sample_index(cases)
        print(f"BraTS {split} set: {len(self.samples)} slices from {len(cases)} cases")
    
    def _build_sample_index(self, cases: List[Path]) -> List[Dict]:
        """构建切片级别的索引"""
        samples = []
        
        for case_dir in cases:
            case_name = case_dir.name
            
            # 查找文件
            mod_name = self.modality_names[self.modality]
            mod_path = None
            for name in [f"{mod_name}.nii.gz", f"{case_name}-{mod_name}.nii.gz"]:
                p = case_dir / name
                if p.exists():
                    mod_path = str(p)
                    break
            
            seg_path = None
            for name in ["seg.nii.gz", f"{case_name}-seg.nii.gz"]:
                p = case_dir / name
                if p.exists():
                    seg_path = str(p)
                    break
            
            if mod_path is None or seg_path is None:
                continue
            
            # 加载分割来确定切片
            seg = nib.load(seg_path).get_fdata()
            if seg.shape[0] > seg.shape[2]:
                seg = np.transpose(seg, (2, 0, 1))
            
            for slice_idx in range(seg.shape[0]):
                has_tumor = (seg[slice_idx] > 0).any()
                
                if self.only_tumor_slices and not has_tumor:
                    continue
                
                samples.append({
                    'case_name': case_name,
                    'mod_path': mod_path,
                    'seg_path': seg_path,
                    'slice_idx': slice_idx,
                    'has_tumor': has_tumor,
                })
        
        return samples
    
    def __len__(self) -> int:
        return len(self.samples)
    
    def __getitem__(self, idx: int) -> Dict[str, Any]:
        sample = self.samples[idx]
        
        # 加载数据
        volume = nib.load(sample['mod_path']).get_fdata().astype(np.float32)
        seg = nib.load(sample['seg_path']).get_fdata().astype(np.float32)
        
        if volume.shape[0] > volume.shape[2]:
            volume = np.transpose(volume, (2, 0, 1))
            seg = np.transpose(seg, (2, 0, 1))
        
        # 获取切片
        slice_idx = sample['slice_idx']
        image = volume[slice_idx]
        mask = seg[slice_idx]
        
        # 处理
        image = normalize_intensity(image)
        image = (image * 255).astype(np.uint8)
        image = np.stack([image, image, image], axis=-1)
        
        if self.target_size is not None:
            image = cv2.resize(image, self.target_size, interpolation=cv2.INTER_LINEAR)
            mask = cv2.resize(mask, self.target_size, interpolation=cv2.INTER_NEAREST)
        
        # 保持原始 4 类标签 (0=背景, 1=NCR, 2=ED, 3=ET)
        mask = mask.astype(np.uint8)
        
        # 数据增强
        if self.augment:
            if random.random() > 0.5:
                image = np.fliplr(image).copy()
                mask = np.fliplr(mask).copy()
            if random.random() > 0.5:
                image = np.flipud(image).copy()
                mask = np.flipud(mask).copy()
        
        # 计算bbox
        bbox = self._get_bbox_from_mask(mask)
        if bbox is None:
            bbox = (0.0, 0.0, 1.0, 1.0)
        
        # 转为tensor
        image_tensor = torch.from_numpy(image).permute(2, 0, 1).float() / 255.0
        mean = torch.tensor(self.normalize_mean).view(3, 1, 1)
        std = torch.tensor(self.normalize_std).view(3, 1, 1)
        image_tensor = (image_tensor - mean) / std
        
        mask_tensor = torch.from_numpy(mask).long()
        bbox_tensor = torch.tensor(bbox, dtype=torch.float32)
        
        return {
            'image': image_tensor,    # (C, H, W)
            'mask': mask_tensor,      # (H, W)
            'bbox': bbox_tensor,      # (4,)
            'case_name': sample['case_name'],
            'slice_idx': slice_idx,
            'has_tumor': sample['has_tumor'],
        }
    
    def _get_bbox_from_mask(self, mask: np.ndarray) -> Optional[Tuple[float, float, float, float]]:
        if mask.sum() == 0:
            return None
        
        rows = np.any(mask, axis=1)
        cols = np.any(mask, axis=0)
        
        y_indices = np.where(rows)[0]
        x_indices = np.where(cols)[0]
        
        if len(y_indices) == 0 or len(x_indices) == 0:
            return None
        
        y_min, y_max = y_indices[0], y_indices[-1]
        x_min, x_max = x_indices[0], x_indices[-1]
        
        h, w = mask.shape
        return (x_min / w, y_min / h, x_max / w, y_max / h)


def collate_fn_brats(batch: List[Dict]) -> Dict[str, Any]:
    """自定义collate函数"""
    # 视频数据
    if 'frames' in batch[0]:
        return {
            'frames': torch.stack([b['frames'] for b in batch]),  # (B, T, C, H, W)
            'masks': torch.stack([b['masks'] for b in batch]),    # (B, T, H, W)
            'bboxes': torch.stack([b['bboxes'] for b in batch]),  # (B, T, 4)
            'case_names': [b['case_name'] for b in batch],
        }
    # 图像数据
    else:
        return {
            'images': torch.stack([b['image'] for b in batch]),  # (B, C, H, W)
            'masks': torch.stack([b['mask'] for b in batch]),    # (B, H, W)
            'bboxes': torch.stack([b['bbox'] for b in batch]),   # (B, 4)
            'case_names': [b['case_name'] for b in batch],
        }


if __name__ == "__main__":
    # 测试
    data_root = "/data/yty/brats2023/ASNR-MICCAI-BraTS2023-GLI-Challenge-TrainingData"
    
    print("Testing BraTSVideoDataset...")
    video_ds = BraTSVideoDataset(data_root, split='train', num_frames=8)
    print(f"  Total samples: {len(video_ds)}")
    
    sample = video_ds[0]
    print(f"  frames shape: {sample['frames'].shape}")
    print(f"  masks shape: {sample['masks'].shape}")
    print(f"  bboxes shape: {sample['bboxes'].shape}")
    
    print("\nTesting BraTSImageDataset...")
    image_ds = BraTSImageDataset(data_root, split='train')
    print(f"  Total slices: {len(image_ds)}")
    
    sample = image_ds[0]
    print(f"  image shape: {sample['image'].shape}")
    print(f"  mask shape: {sample['mask'].shape}")
    print(f"  bbox: {sample['bbox']}")