import os
import math
import random
import numpy as np
import matplotlib.pyplot as plt
from collections import defaultdict


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.
    
    Args:
        dataset_folder (str): Path to the dataset folder containing .npz files.
    
    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)

    # # Print min/max n_div per mode
    # print("Per truss type min/max segments (n_div):")
    # for mode in sorted(min_max_div):
    #     mn, mx = min_max_div[mode]
    #     print(f"{mode}: {mn} - {mx}")

    # 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]  # Pick first
            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]  # Pick first
            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}")
    
    # Additionally print out for one structure type how the keys inside look like
    if show_details == True:
        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': min_n_nod,
        'max_nodes': max_n_nod,
        'min_elements': min_n_ele,
        'max_elements': max_n_ele
    }

def load_and_visualize_random_truss(dataset_folder="dataset", num_samples=1, display_equal=False, save_fig=False):
    """
    Load random truss(es) from dataset_folder and visualize them with one shared legend on top.
    Legend handles are robust and spacing is tight.
    """
    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}'.")

    samples = []
    random.shuffle(npz_files)
    npz_files = npz_files[:num_samples]

    # Layout logic
    if num_samples >= 3:
        n_cols = 3
    elif num_samples == 2:
        n_cols = 2
    else:
        n_cols = 1
    n_rows = math.ceil(num_samples / n_cols)

    fig, axes = plt.subplots(n_rows, n_cols, figsize=(5 * n_cols, 3.5 * n_rows))
    axes = np.atleast_1d(axes).flatten()

    # Predefine legend proxy handles
    proxy_handles = {
        "Bottom Nodes": plt.Line2D([], [], marker="o", color="blue", ls="", markersize=6),
        "Top Nodes": plt.Line2D([], [], marker="o", color="red", ls="", markersize=6),
        "Beams": plt.Line2D([], [], color="green", lw=2),
        "Columns": plt.Line2D([], [], color="black", lw=3),
        "Rods": plt.Line2D([], [], color="purple", lw=1.5, ls="--"),
    }

    for i, filename in enumerate(npz_files):
        filepath = os.path.join(dataset_folder, filename)
        data = np.load(filepath)

        nodal_coord = data["nodal_coord"]
        ele_nod = data["ele_nod"]
        truss_mode = str(data["truss_mode"])
        n_div = int(data["n_div"])
        angle = float(data["angle"])
        n_beams = int(data["n_beams"])
        n_columns = int(data["n_columns"])
        n_rods = int(data["n_rods"])
        n_ele_tot = int(data["n_ele_tot"])

        ax = axes[i]
        ax.set_xlim(-0.05, 1.05)

        # Adjust y-limits due to small range
        ymin, ymax = nodal_coord[:, 1].min(), nodal_coord[:, 1].max()
        yrange = ymax - ymin
        if yrange < 0.05:
            yrange = 0.05
        ax.set_ylim(ymin - 0.1 * yrange, ymax + 0.15 * yrange)
        if display_equal == True:
            ax.set_aspect("equal")
        ax.set_title(f"{truss_mode} (n_div={n_div}, angle={angle:.0f}°)")
        ax.grid(True, alpha=0.3)

        # Plot nodes
        bottom_mask = np.abs(nodal_coord[:, 1]) < 1e-6
        ax.scatter(nodal_coord[bottom_mask, 0], nodal_coord[bottom_mask, 1], c="blue", s=45)
        ax.scatter(nodal_coord[~bottom_mask, 0], nodal_coord[~bottom_mask, 1], c="red", s=45)

        # Plot elements
        for j in range(n_ele_tot):
            node1, node2 = ele_nod[j]
            x1, y1 = nodal_coord[node1]
            x2, y2 = nodal_coord[node2]
            if j < n_beams:
                ax.plot([x1, x2], [y1, y2], "g-", lw=2)
            elif j < n_beams + n_columns:
                ax.plot([x1, x2], [y1, y2], "k-", lw=3)
            else:
                ax.plot([x1, x2], [y1, y2], "purple", ls="--", lw=1.5)

        samples.append({k: data[k] for k in data.files})

    # Hide unused axes
    for j in range(num_samples, len(axes)):
        axes[j].axis("off")

    # Add shared legend at top (compact spacing)
    fig.legend(
        proxy_handles.values(),
        proxy_handles.keys(),
        loc="upper center",
        ncol=len(proxy_handles),
        frameon=False,
        fontsize=9,
        handlelength=2.5,
        columnspacing=1.5,
        borderaxespad=0.1,   # shrink gap between legend and figure
        handletextpad=0.4,
    )

    plt.subplots_adjust(top=0.92, hspace=0.35, wspace=0.25)

    if save_fig:
        out_path = os.path.join(dataset_folder, f"random_truss_grid_{num_samples}.png")
        plt.savefig(out_path, dpi=150, bbox_inches="tight")
        print(f"Saved figure to {out_path}")

    plt.show()
    return samples