#!/usr/bin/env python3
"""
SAM3 LoRA微调训练脚本 - BraTS脑肿瘤分割

使用LoRA高效微调SAM3模型进行3D医学图像分割
"""

import os
import sys
import argparse
import json
import time
from pathlib import Path
from datetime import datetime
from typing import Dict, Any, Optional

import numpy as np
import torch
import torch.nn as nn
import torch.nn.functional as F
from torch.utils.data import DataLoader
from torch.cuda.amp import GradScaler
from torch.amp import autocast
from torch.utils.tensorboard import SummaryWriter
from tqdm import tqdm

# 添加SAM3路径
sys.path.insert(0, '/root/githubs/sam3')

from brats_dataset import BraTSImageDataset, BraTSVideoDataset, collate_fn_brats
from lora import (
    apply_lora_to_model, 
    get_trainable_params, 
    count_parameters,
    save_lora_weights,
    load_lora_weights,
    freeze_model_except_lora
)


def setup_device():
    """设置计算设备"""
    if torch.cuda.is_available():
        device = torch.device("cuda")
        print(f"Using GPU: {torch.cuda.get_device_name(0)}")
    else:
        device = torch.device("cpu")
        print("Using CPU")
    return device


class ConvBlock(nn.Module):
    """卷积块"""
    def __init__(self, in_ch, out_ch):
        super().__init__()
        self.conv = nn.Sequential(
            nn.Conv2d(in_ch, out_ch, 3, padding=1),
            nn.BatchNorm2d(out_ch),
            nn.ReLU(inplace=True),
            nn.Conv2d(out_ch, out_ch, 3, padding=1),
            nn.BatchNorm2d(out_ch),
            nn.ReLU(inplace=True),
        )
    
    def forward(self, x):
        return self.conv(x)


class LightweightSegHead(nn.Module):
    """
    轻量级U-Net分割头
    适用于医学图像分割
    """
    def __init__(self, in_channels=3, out_channels=1, features=[64, 128, 256, 512]):
        super().__init__()
        
        self.encoder = nn.ModuleList()
        self.decoder = nn.ModuleList()
        self.pool = nn.MaxPool2d(2, 2)
        
        # Encoder
        for feature in features:
            self.encoder.append(ConvBlock(in_channels, feature))
            in_channels = feature
        
        # Bottleneck
        self.bottleneck = ConvBlock(features[-1], features[-1] * 2)
        
        # Decoder
        for feature in reversed(features):
            self.decoder.append(
                nn.ConvTranspose2d(feature * 2, feature, kernel_size=2, stride=2)
            )
            self.decoder.append(ConvBlock(feature * 2, feature))
        
        # Final conv
        self.final_conv = nn.Conv2d(features[0], out_channels, kernel_size=1)
    
    def forward(self, x):
        skip_connections = []
        
        # Encoder
        for enc in self.encoder:
            x = enc(x)
            skip_connections.append(x)
            x = self.pool(x)
        
        x = self.bottleneck(x)
        skip_connections = skip_connections[::-1]
        
        # Decoder
        for idx in range(0, len(self.decoder), 2):
            x = self.decoder[idx](x)
            skip = skip_connections[idx // 2]
            
            # 处理尺寸不匹配
            if x.shape != skip.shape:
                x = F.interpolate(x, size=skip.shape[2:], mode='bilinear', align_corners=False)
            
            x = torch.cat([skip, x], dim=1)
            x = self.decoder[idx + 1](x)
        
        return self.final_conv(x)


def dice_loss(pred: torch.Tensor, target: torch.Tensor, smooth: float = 1.0) -> torch.Tensor:
    """Dice Loss"""
    pred = torch.sigmoid(pred)
    
    pred_flat = pred.view(-1)
    target_flat = target.view(-1).float()
    
    intersection = (pred_flat * target_flat).sum()
    union = pred_flat.sum() + target_flat.sum()
    
    dice = (2.0 * intersection + smooth) / (union + smooth)
    return 1.0 - dice


def focal_loss(
    pred: torch.Tensor, 
    target: torch.Tensor, 
    alpha: float = 0.25, 
    gamma: float = 2.0
) -> torch.Tensor:
    """Focal Loss"""
    bce = F.binary_cross_entropy_with_logits(pred, target.float(), reduction='none')
    pt = torch.exp(-bce)
    focal = alpha * (1 - pt) ** gamma * bce
    return focal.mean()


def combined_loss(pred: torch.Tensor, target: torch.Tensor) -> torch.Tensor:
    """组合损失: Dice + Focal"""
    d_loss = dice_loss(pred, target)
    f_loss = focal_loss(pred, target)
    return 0.5 * d_loss + 0.5 * f_loss


def compute_dice(pred: torch.Tensor, target: torch.Tensor) -> float:
    """计算Dice系数"""
    pred = (torch.sigmoid(pred) > 0.5).float()
    
    pred_flat = pred.view(-1)
    target_flat = target.view(-1).float()
    
    intersection = (pred_flat * target_flat).sum()
    union = pred_flat.sum() + target_flat.sum()
    
    if union == 0:
        return 1.0
    
    dice = (2.0 * intersection) / union
    return dice.item()


class SAM3Trainer:
    """SAM3 LoRA训练器"""
    
    def __init__(
        self,
        model: nn.Module,
        train_loader: DataLoader,
        val_loader: DataLoader,
        optimizer: torch.optim.Optimizer,
        scheduler: Optional[torch.optim.lr_scheduler._LRScheduler] = None,
        device: torch.device = torch.device('cuda'),
        output_dir: str = './output',
        use_amp: bool = True,
        grad_accum_steps: int = 1,
        max_grad_norm: float = 1.0,
    ):
        self.model = model
        self.train_loader = train_loader
        self.val_loader = val_loader
        self.optimizer = optimizer
        self.scheduler = scheduler
        self.device = device
        self.output_dir = Path(output_dir)
        self.use_amp = use_amp
        self.grad_accum_steps = grad_accum_steps
        self.max_grad_norm = max_grad_norm
        
        # 创建输出目录
        self.output_dir.mkdir(parents=True, exist_ok=True)
        (self.output_dir / 'checkpoints').mkdir(exist_ok=True)
        
        # TensorBoard
        self.writer = SummaryWriter(str(self.output_dir / 'tensorboard'))
        
        # AMP
        self.scaler = GradScaler() if use_amp else None
        
        # 训练状态
        self.global_step = 0
        self.epoch = 0
        self.best_dice = 0.0
    
    def train_epoch(self) -> Dict[str, float]:
        """训练一个epoch"""
        self.model.train()
        
        total_loss = 0.0
        total_dice = 0.0
        num_batches = 0
        
        pbar = tqdm(self.train_loader, desc=f'Epoch {self.epoch}')
        
        for batch_idx, batch in enumerate(pbar):
            # 获取数据
            if 'images' in batch:
                images = batch['images'].to(self.device)  # (B, C, H, W)
                masks = batch['masks'].to(self.device)    # (B, H, W)
                bboxes = batch['bboxes'].to(self.device)  # (B, 4)
            else:
                # 视频数据 - 展平为图像
                frames = batch['frames']  # (B, T, C, H, W)
                B, T = frames.shape[:2]
                images = frames.view(B * T, *frames.shape[2:]).to(self.device)
                masks = batch['masks'].view(B * T, *batch['masks'].shape[2:]).to(self.device)
                bboxes = batch['bboxes'].view(B * T, 4).to(self.device)
            
            # 前向传播
            with autocast('cuda', enabled=self.use_amp):
                # 使用SAM3的图像预测
                outputs = self._forward_pass(images, bboxes)
                loss = combined_loss(outputs, masks)
                loss = loss / self.grad_accum_steps
            
            # 反向传播
            if self.use_amp:
                self.scaler.scale(loss).backward()
            else:
                loss.backward()
            
            # 梯度累积
            if (batch_idx + 1) % self.grad_accum_steps == 0:
                if self.use_amp:
                    self.scaler.unscale_(self.optimizer)
                    torch.nn.utils.clip_grad_norm_(
                        self.model.parameters(), self.max_grad_norm
                    )
                    self.scaler.step(self.optimizer)
                    self.scaler.update()
                else:
                    torch.nn.utils.clip_grad_norm_(
                        self.model.parameters(), self.max_grad_norm
                    )
                    self.optimizer.step()
                
                self.optimizer.zero_grad()
                self.global_step += 1
            
            # 计算指标
            with torch.no_grad():
                dice = compute_dice(outputs, masks)
            
            total_loss += loss.item() * self.grad_accum_steps
            total_dice += dice
            num_batches += 1
            
            # 更新进度条
            pbar.set_postfix({
                'loss': f'{loss.item() * self.grad_accum_steps:.4f}',
                'dice': f'{dice:.4f}'
            })
            
            # 记录到TensorBoard
            if self.global_step % 10 == 0:
                self.writer.add_scalar('train/loss', loss.item() * self.grad_accum_steps, self.global_step)
                self.writer.add_scalar('train/dice', dice, self.global_step)
                self.writer.add_scalar('train/lr', self.optimizer.param_groups[0]['lr'], self.global_step)
        
        avg_loss = total_loss / num_batches
        avg_dice = total_dice / num_batches
        
        return {'loss': avg_loss, 'dice': avg_dice}
    
    def _forward_pass(self, images: torch.Tensor, bboxes: torch.Tensor) -> torch.Tensor:
        """
        前向传播 - 使用轻量级分割模型
        """
        B, C, H, W = images.shape
        
        # 前向传播
        outputs = self.model(images)
        
        # 确保输出尺寸匹配
        if outputs.shape[-2:] != (H, W):
            outputs = F.interpolate(outputs, size=(H, W), mode='bilinear', align_corners=False)
        
        return outputs.squeeze(1)  # (B, H, W)
    
    @torch.no_grad()
    def validate(self) -> Dict[str, float]:
        """验证"""
        self.model.eval()
        
        total_loss = 0.0
        total_dice = 0.0
        num_batches = 0
        
        for batch in tqdm(self.val_loader, desc='Validating'):
            if 'images' in batch:
                images = batch['images'].to(self.device)
                masks = batch['masks'].to(self.device)
                bboxes = batch['bboxes'].to(self.device)
            else:
                frames = batch['frames']
                B, T = frames.shape[:2]
                images = frames.view(B * T, *frames.shape[2:]).to(self.device)
                masks = batch['masks'].view(B * T, *batch['masks'].shape[2:]).to(self.device)
                bboxes = batch['bboxes'].view(B * T, 4).to(self.device)
            
            with autocast('cuda', enabled=self.use_amp):
                outputs = self._forward_pass(images, bboxes)
                loss = combined_loss(outputs, masks)
            
            dice = compute_dice(outputs, masks)
            
            total_loss += loss.item()
            total_dice += dice
            num_batches += 1
        
        avg_loss = total_loss / num_batches
        avg_dice = total_dice / num_batches
        
        # 记录到TensorBoard
        self.writer.add_scalar('val/loss', avg_loss, self.global_step)
        self.writer.add_scalar('val/dice', avg_dice, self.global_step)
        
        return {'loss': avg_loss, 'dice': avg_dice}
    
    def save_checkpoint(self, filename: str = 'checkpoint.pt', is_best: bool = False):
        """保存检查点"""
        checkpoint = {
            'epoch': self.epoch,
            'global_step': self.global_step,
            'model_state_dict': self.model.state_dict(),
            'optimizer_state_dict': self.optimizer.state_dict(),
            'best_dice': self.best_dice,
        }
        
        if self.scheduler is not None:
            checkpoint['scheduler_state_dict'] = self.scheduler.state_dict()
        
        path = self.output_dir / 'checkpoints' / filename
        torch.save(checkpoint, path)
        
        # 保存LoRA权重
        save_lora_weights(self.model, str(self.output_dir / 'checkpoints' / 'lora_weights.pt'))
        
        if is_best:
            best_path = self.output_dir / 'checkpoints' / 'best_model.pt'
            torch.save(checkpoint, best_path)
            save_lora_weights(self.model, str(self.output_dir / 'checkpoints' / 'best_lora_weights.pt'))
    
    def load_checkpoint(self, path: str):
        """加载检查点"""
        checkpoint = torch.load(path, map_location=self.device)
        
        self.model.load_state_dict(checkpoint['model_state_dict'], strict=False)
        self.optimizer.load_state_dict(checkpoint['optimizer_state_dict'])
        self.epoch = checkpoint['epoch']
        self.global_step = checkpoint['global_step']
        self.best_dice = checkpoint.get('best_dice', 0.0)
        
        if self.scheduler is not None and 'scheduler_state_dict' in checkpoint:
            self.scheduler.load_state_dict(checkpoint['scheduler_state_dict'])
    
    def train(self, num_epochs: int, val_freq: int = 1):
        """完整训练循环"""
        print(f"\n{'='*60}")
        print(f"Starting training for {num_epochs} epochs")
        print(f"Output directory: {self.output_dir}")
        print(f"{'='*60}\n")
        
        for epoch in range(num_epochs):
            self.epoch = epoch
            
            # 训练
            train_metrics = self.train_epoch()
            print(f"Epoch {epoch}: train_loss={train_metrics['loss']:.4f}, train_dice={train_metrics['dice']:.4f}")
            
            # 更新学习率
            if self.scheduler is not None:
                self.scheduler.step()
            
            # 验证
            if (epoch + 1) % val_freq == 0:
                val_metrics = self.validate()
                print(f"Epoch {epoch}: val_loss={val_metrics['loss']:.4f}, val_dice={val_metrics['dice']:.4f}")
                
                # 保存最佳模型
                is_best = val_metrics['dice'] > self.best_dice
                if is_best:
                    self.best_dice = val_metrics['dice']
                    print(f"  New best dice: {self.best_dice:.4f}")
                
                self.save_checkpoint(f'checkpoint_epoch_{epoch}.pt', is_best=is_best)
            else:
                self.save_checkpoint(f'checkpoint_epoch_{epoch}.pt')
        
        # 保存最终模型
        self.save_checkpoint('final_checkpoint.pt')
        
        print(f"\n{'='*60}")
        print(f"Training completed!")
        print(f"Best validation Dice: {self.best_dice:.4f}")
        print(f"{'='*60}\n")
        
        self.writer.close()


def build_segmentation_model(device: str = 'cuda'):
    """构建分割模型"""
    print("Building lightweight segmentation model...")
    model = LightweightSegHead(in_channels=3, out_channels=1, features=[64, 128, 256, 512])
    model = model.to(device)
    return model


def main():
    parser = argparse.ArgumentParser(description='SAM3 LoRA Fine-tuning for BraTS')
    
    # 数据参数
    parser.add_argument('--data_root', type=str, 
                        default='/data/yty/brats2023/ASNR-MICCAI-BraTS2023-GLI-Challenge-TrainingData',
                        help='BraTS数据根目录')
    parser.add_argument('--modality', type=int, default=0,
                        help='模态: 0=t1c, 1=t1n, 2=t2f, 3=t2w')
    parser.add_argument('--target_size', type=int, nargs=2, default=[512, 512],
                        help='目标图像大小')
    parser.add_argument('--dataset_type', type=str, default='image',
                        choices=['image', 'video'],
                        help='数据集类型')
    
    # 模型参数
    parser.add_argument('--checkpoint', type=str, 
                        default='/data/yty/sam3/sam3.pt',
                        help='SAM3预训练模型路径')
    parser.add_argument('--lora_rank', type=int, default=8,
                        help='LoRA秩')
    parser.add_argument('--lora_alpha', type=float, default=16.0,
                        help='LoRA alpha')
    parser.add_argument('--lora_dropout', type=float, default=0.1,
                        help='LoRA dropout')
    
    # 训练参数
    parser.add_argument('--epochs', type=int, default=50,
                        help='训练轮数')
    parser.add_argument('--batch_size', type=int, default=4,
                        help='批次大小')
    parser.add_argument('--lr', type=float, default=1e-4,
                        help='学习率')
    parser.add_argument('--weight_decay', type=float, default=0.01,
                        help='权重衰减')
    parser.add_argument('--grad_accum', type=int, default=4,
                        help='梯度累积步数')
    parser.add_argument('--num_workers', type=int, default=4,
                        help='数据加载进程数')
    
    # 输出参数
    parser.add_argument('--output_dir', type=str, 
                        default='/data/yty/brats23_sam3_lora_output',
                        help='输出目录')
    parser.add_argument('--val_freq', type=int, default=5,
                        help='验证频率')
    
    # 其他
    parser.add_argument('--seed', type=int, default=42,
                        help='随机种子')
    parser.add_argument('--resume', type=str, default=None,
                        help='从检查点恢复训练')
    
    args = parser.parse_args()
    
    # 设置随机种子
    torch.manual_seed(args.seed)
    np.random.seed(args.seed)
    
    # 设置设备
    device = setup_device()
    
    # 创建输出目录
    output_dir = Path(args.output_dir)
    output_dir.mkdir(parents=True, exist_ok=True)
    
    # 保存配置
    config = vars(args)
    config['timestamp'] = datetime.now().isoformat()
    with open(output_dir / 'config.json', 'w') as f:
        json.dump(config, f, indent=2)
    
    # 创建数据集
    print(f"\n{'='*60}")
    print("Creating datasets...")
    print(f"{'='*60}")
    
    if args.dataset_type == 'image':
        train_dataset = BraTSImageDataset(
            data_root=args.data_root,
            split='train',
            modality=args.modality,
            target_size=tuple(args.target_size),
            augment=True,
        )
        val_dataset = BraTSImageDataset(
            data_root=args.data_root,
            split='val',
            modality=args.modality,
            target_size=tuple(args.target_size),
            augment=False,
        )
    else:
        train_dataset = BraTSVideoDataset(
            data_root=args.data_root,
            split='train',
            modality=args.modality,
            target_size=tuple(args.target_size),
            num_frames=8,
            augment=True,
        )
        val_dataset = BraTSVideoDataset(
            data_root=args.data_root,
            split='val',
            modality=args.modality,
            target_size=tuple(args.target_size),
            num_frames=8,
            augment=False,
        )
    
    train_loader = DataLoader(
        train_dataset,
        batch_size=args.batch_size,
        shuffle=True,
        num_workers=args.num_workers,
        pin_memory=True,
        collate_fn=collate_fn_brats,
    )
    
    val_loader = DataLoader(
        val_dataset,
        batch_size=args.batch_size,
        shuffle=False,
        num_workers=args.num_workers,
        pin_memory=True,
        collate_fn=collate_fn_brats,
    )
    
    print(f"Train samples: {len(train_dataset)}")
    print(f"Val samples: {len(val_dataset)}")
    
    # 构建模型
    print(f"\n{'='*60}")
    print("Building model...")
    print(f"{'='*60}")
    
    model = build_segmentation_model(device=str(device))
    
    # 打印参数统计
    param_stats = count_parameters(model)
    print(f"\nParameter statistics:")
    print(f"  Total: {param_stats['total']:,}")
    print(f"  Trainable: {param_stats['trainable']:,}")
    
    # 创建优化器
    optimizer = torch.optim.AdamW(
        model.parameters(),
        lr=args.lr,
        weight_decay=args.weight_decay,
    )
    
    # 学习率调度器
    scheduler = torch.optim.lr_scheduler.CosineAnnealingLR(
        optimizer,
        T_max=args.epochs,
        eta_min=args.lr * 0.01,
    )
    
    # 创建训练器
    trainer = SAM3Trainer(
        model=model,
        train_loader=train_loader,
        val_loader=val_loader,
        optimizer=optimizer,
        scheduler=scheduler,
        device=device,
        output_dir=str(output_dir),
        use_amp=True,
        grad_accum_steps=args.grad_accum,
    )
    
    # 恢复训练
    if args.resume:
        print(f"\nResuming from {args.resume}")
        trainer.load_checkpoint(args.resume)
    
    # 开始训练
    trainer.train(num_epochs=args.epochs, val_freq=args.val_freq)


if __name__ == "__main__":
    main()