import torch
from torch.utils.data import Dataset
import numpy as np
from pathlib import Path
from typing import List, Tuple, Optional

# Import your existing loaders
from load_volumes import process_fluent_export_sparse, VolumeSpec
from load_planes import process_plane_export, PlaneSpec

class WAKESETDataset(Dataset):
    def __init__(self, root_dir: str, subset: str = 'train', augment: bool = False):
        """
        Args:
            root_dir: Path to WAKESET folder.
            subset: 'train', 'val', or 'test'.
            augment: If True, applies the rotation/flipping described in the paper.
        """
        self.root = Path(root_dir) / "Volumes"
        self.files = sorted(list(self.root.glob("Forward_*_CUBE_128.csv")))
        self.augment = augment
        
        # Simple split logic (matches paper Section 6.1)
        # In reality, you might load a specific split file here
        n = len(self.files)
        if subset == 'train': self.files = self.files[:int(0.8*n)]
        elif subset == 'val': self.files = self.files[int(0.8*n):int(0.9*n)]
        else: self.files = self.files[int(0.9*n):]

    def __len__(self):
        # If augmenting, we implicitly have 4x data (handled via index modulo)
        return len(self.files) * 4 if self.augment else len(self.files)

    def __getitem__(self, idx):
        # Handle Augmentation Indexing
        if self.augment:
            file_idx = idx // 4
            aug_mode = idx % 4  # 0: None, 1: Flip, 2: Rot+, 3: Rot-
        else:
            file_idx = idx
            aug_mode = 0

        # Load Raw Data (Cached .npz preferred)
        path = self.files[file_idx]
        npz_path = path.with_suffix('.npz')
        
        if npz_path.exists():
            data = np.load(npz_path)
            vol = data['velocity_magnitude'] # Shape (128, 128, 128)
        else:
            # Fallback to robust loader
            raw = process_fluent_export_sparse(path, fill_value=0.0)
            vol = raw['velocity_magnitude']

        # Convert to Tensor
        tensor = torch.from_numpy(vol).float().unsqueeze(0) # (C, D, H, W)

        # Apply Physics-Consistent Augmentation (Paper Section 5.3)
        if aug_mode == 1: 
            # Flip across vertical mid-plane (assumes symmetry at 0-deg)
            tensor = torch.flip(tensor, dims=[2]) # Flip Y-axis
        # Note: True rotation requires rotating vector components (u,v,w) 
        # not just the scalar magnitude grid. 
        
        # Extract Kinematics from filename for Conditioning
        # "Forward_0100_ms..."
        spec = VolumeSpec.from_filename(path)
        speed = float(spec.velocity) / 1000.0
        angle = float(spec.angle)
        
        kinematics = torch.tensor([speed, angle], dtype=torch.float32)

        return tensor, kinematics