# preprocess_s1.py
import numpy as np
import os
from collections import defaultdict
from scipy.stats import zscore
from typing import List, Dict, Any, Tuple

def compute_sequence_lengths(dataset_folder="dataset", show_details=False):
    """
    Compute and print min/max sequence lengths (nodes, elements) across all trusses in the dataset.
    Uses only min/max n_div files per mode for efficiency.

    Returns:
        Dict with keys 'min_nodes', 'max_nodes', 'min_elements', 'max_elements'.
    """
    npz_files = [f for f in os.listdir(dataset_folder) if f.endswith('.npz')]
    if not npz_files:
        raise ValueError(f"No .npz files found in '{dataset_folder}'.")

    # First pass: compute min/max n_div per mode
    min_max_div = defaultdict(lambda: (float('inf'), float('-inf')))
    for f in npz_files:
        parts = f[:-4].rsplit('_', 2)  # e.g., ['truss_pratt', '15', '39']
        if len(parts) == 3 and parts[0].startswith('truss_'):
            mode = parts[0][6:]  # Remove 'truss_'
            n_div = int(parts[1])
            min_d, max_d = min_max_div[mode]
            min_max_div[mode] = (min(min_d, n_div), max(max_d, n_div))

    # Second pass: collect one file per min/max per mode
    min_div_files = defaultdict(list)
    max_div_files = defaultdict(list)
    for f in npz_files:
        parts = f[:-4].rsplit('_', 2)
        if len(parts) == 3 and parts[0].startswith('truss_'):
            mode = parts[0][6:]
            n_div = int(parts[1])
            if n_div == min_max_div[mode][0]:
                min_div_files[mode].append(f)
            if n_div == min_max_div[mode][1]:
                max_div_files[mode].append(f)

    # Compute overall min/max sequence lengths by loading one min/max file per mode
    min_n_nod = float('inf')
    max_n_nod = 0
    min_n_ele = float('inf')
    max_n_ele = 0
    for mode in sorted(min_max_div):
        # For min
        if min_div_files[mode]:
            min_file = min_div_files[mode][0]
            data_min = np.load(os.path.join(dataset_folder, min_file))
            min_n_nod = min(min_n_nod, int(data_min['n_nod_tot']))
            min_n_ele = min(min_n_ele, int(data_min['n_ele_tot']))
            data_min.close()
        # For max
        if max_div_files[mode]:
            max_file = max_div_files[mode][0]
            data_max = np.load(os.path.join(dataset_folder, max_file))
            max_n_nod = max(max_n_nod, int(data_max['n_nod_tot']))
            max_n_ele = max(max_n_ele, int(data_max['n_ele_tot']))
            data_max.close()

    print(f"Overall min sequence lengths: nodes={min_n_nod}, elements={min_n_ele}")
    print(f"Overall max sequence lengths: nodes={max_n_nod}, elements={max_n_ele}")

    if show_details:
        example_mode = next(iter(max_div_files))
        example_file = max_div_files[example_mode][0]
        example_data = np.load(os.path.join(dataset_folder, example_file))
        print(f"\nExample data keys from '{example_file}': {example_data.files}")
        for key in example_data.files:
            print(f" - {key}: shape {example_data[key].shape}, dtype {example_data[key].dtype}")
        example_data.close()

    return {
        'min_nodes': int(min_n_nod),
        'max_nodes': int(max_n_nod),
        'min_elements': int(min_n_ele),
        'max_elements': int(max_n_ele),
    }


def _pad_1d(arr: np.ndarray, max_len: int, pad_val=0):
    """Pad 1D array to max_len with pad_val."""
    out = np.full((max_len,), pad_val, dtype=arr.dtype)
    n = min(len(arr), max_len)
    out[:n] = arr[:n]
    return out


def _pack_sample(data: np.lib.npyio.NpzFile) -> Dict[str, Any]:
    """Extract a single sample (no padding) with lengths."""
    nodal = data['nodal_coord']        # (n_nodes, 2)
    ele_nod = data['ele_nod']          # (n_elems, 2) int
    pel = data['pel']                  # (n_elems, 4) int (may be redundant for topology)

    sample = {
        'nodal': nodal.astype(np.float32),
        'ele_nod': ele_nod.astype(np.int64),
        'pel': pel.astype(np.int64),
        'n_nodes': int(nodal.shape[0]),
        'n_elems': int(ele_nod.shape[0]),
        # Optional globals (kept here for conditioning/analysis)
        'height': float(np.array(data['height']).item()) if 'height' in data else None,
        'spacing': float(np.array(data['spacing']).item()) if 'spacing' in data else None,
        'meta': {
            'n_rods': int(np.array(data['n_rods']).item()) if 'n_rods' in data else None,
            'n_beams': int(np.array(data['n_beams']).item()) if 'n_beams' in data else None,
            'mode': str(np.array(data['truss_mode']).item()) if 'truss_mode' in data else None,
        }
    }
    return sample


def load_truss_samples(dataset_folder="dataset") -> Tuple[List[Dict[str, Any]], Dict[str, Any]]:
    """
    Load ALL samples WITHOUT padding.
    Returns:
        samples: list of dicts with variable-length arrays and lengths.
        metadata: dict with global min/max lengths and counts.
    """
    lengths = compute_sequence_lengths(dataset_folder)
    npz_files = [f for f in os.listdir(dataset_folder) if f.endswith('.npz')]
    samples = []
    for f in npz_files:
        data = np.load(os.path.join(dataset_folder, f))
        samples.append(_pack_sample(data))
        data.close()

    metadata = {
        'max_nodes': lengths['max_nodes'],
        'max_elements': lengths['max_elements'],
        'n_samples': len(samples),
    }
    return samples, metadata


def preprocess_s1(dataset_folder="dataset", normalize_type=None):
    """
    Backwards-compatible preprocessor: still returns a big padded matrix
    for legacy code, but now:
      - pads integer index arrays with -1 (safe),
      - also returns per-sample (n_nodes, n_elems) for bucketing.
    """
    lengths = compute_sequence_lengths(dataset_folder)
    max_nodes = lengths['max_nodes']
    max_elements = lengths['max_elements']
    total_dim = max_nodes * 2 + max_elements * 2 + max_elements * 4

    npz_files = [f for f in os.listdir(dataset_folder) if f.endswith('.npz')]
    samples = []
    size_info = []
    for f in npz_files:
        data = np.load(os.path.join(dataset_folder, f))
        nodal = data['nodal_coord'].flatten().astype(np.float32)     # (n_nodes * 2,)
        ele_nod = data['ele_nod'].flatten().astype(np.int64)         # (n_elems * 2,)
        pel = data['pel'].flatten().astype(np.int64)                 # (n_elems * 4,)

        n_nodes = int(data['nodal_coord'].shape[0])
        n_elems = int(data['ele_nod'].shape[0])
        size_info.append([n_nodes, n_elems])

        # Pad with safe values: floats→0.0, ints→-1
        nodal_padded = _pad_1d(nodal, max_nodes * 2, pad_val=0.0)
        ele_nod_padded = _pad_1d(ele_nod, max_elements * 2, pad_val=-1)
        pel_padded = _pad_1d(pel, max_elements * 4, pad_val=-1)

        sample = np.concatenate([nodal_padded, ele_nod_padded, pel_padded]).astype(np.float32)
        samples.append(sample)
        data.close()

    data_array = np.stack(samples, axis=0)  # (n_samples, total_dim)

    if normalize_type == 'min_max':
        data_min = data_array.min()
        data_max = data_array.max()
        data_array = (data_array - data_min) / (data_max - data_min + 1e-12)
    elif normalize_type == 'z_score':
        data_array = zscore(data_array, axis=0)
    elif normalize_type is None:
        pass
    else:
        raise ValueError(f"Unknown normalize_type: {normalize_type}")

    metadata = {
        'max_nodes': max_nodes,
        'max_elements': max_elements,
        'total_dim': total_dim,
        'n_samples': len(samples),
        'normalize_type': normalize_type,
        'size_info': np.array(size_info, dtype=np.int32)  # (n_samples, 2)
    }
    return data_array, metadata