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#!/usr/bin/env python

import json
import os
import random
import tempfile
from dataclasses import dataclass
from datetime import datetime
from pathlib import Path
from urllib.error import HTTPError
from urllib.request import urlretrieve

def get_program_parameters():
    import argparse
    description = 'Get examples that use a particular VTK class for a given language.'
    epilogue = '''
The JSON file is obtained from the gh-pages branch of the vtk-examples GitHub site.
It is stored in your tempfile directory.
    parser = argparse.ArgumentParser(description=description, epilog=epilogue,
    parser.add_argument('vtk_class', help='The desired VTK class.')
    parser.add_argument('language', help='The desired language.')
    parser.add_argument('-a', '--all_values', action="store_true",
                        help='All examples (Warning: Can be a very long list).')
    parser.add_argument('-n', '--number', type=int, default=5, help='The maximum number of examples.')

    args = parser.parse_args()
    return args.vtk_class, args.language, args.all_values, args.number

class Links:
    The URL to the JSON cross reference file.
    xref_url: str = \

def download_file(dl_path, dl_url, overwrite=False):
    Use the URL to get a file.

    :param dl_path: The path to download the file to.
    :param dl_url: The URL of the file.
    :param overwrite: If true, do a download even if the file exists.
    :return: The path to the file as a pathlib Path.
    file_name = dl_url.split('/')[-1]

    # Create necessary sub-directories in the dl_path
    # (if they don't exist).
    Path(dl_path).mkdir(parents=True, exist_ok=True)
    # Download if it doesn't exist in the directory overriding if overwrite is True.
    path = Path(dl_path, file_name)
    if not path.is_file() or overwrite:
            urlretrieve(dl_url, path)
        except HTTPError as e:
            raise RuntimeError(f'Failed to download {dl_url}. {e.reason}')
    return path

def get_examples(d, vtk_class, lang, all_values=False, number=5, ):
    For the VTK Class and language return the
     total number of examples and a list of examples.

    :param d: The dictionary.
    :param vtk_class: The VTK Class e.g. vtkActor.
    :param lang: The language, e.g. Cxx.
    :param all_values: True if all examples are needed.
    :param number: The number of values.
    :return: Total number of examples and a list of examples.
        kv = d[vtk_class][lang].items()
    except KeyError as e:
        # print(f'For the combination {vtk_class} and {lang}, this key does not exist: {e}')
        return None, None
    total = len(kv)
    if len(kv) > number:
        if all_values:
            samples = list(kv)
            samples = random.sample(list(kv), number)
        samples = list(kv)

    return total, [f'{s[1]}' for s in samples]

def main():
    vtk_class, language, all_values, number = get_program_parameters()
    language = language.lower()
    available_languages = {k.lower(): k for k in ['CSharp', 'Cxx', 'Java', 'Python']}
    if language not in available_languages:
        print(f'The language: {language} is not available.')
        tmp = ', '.join([lang for lang in available_languages.values()])
        print(f'Choose one of these: {tmp}.')
        language = available_languages[language]
    tmp_dir = tempfile.gettempdir()
    path = download_file(tmp_dir, Links.xref_url, overwrite=False)
    if not path.is_file():
        print(f'The path: {str(path)} does not exist.')
    dt = - os.path.getmtime(path)
    # Force a new download if the time difference is > 10 minutes.
    if dt > 600:
        path = download_file(tmp_dir, Links.xref_url, overwrite=True)
    with open(path) as json_file:
        xref_dict = json.load(json_file)

    total_number, examples = get_examples(xref_dict, vtk_class, language, all_values=all_values, number=number)
    if examples:
        if total_number <= number or all_values:
            print(f'VTK Class: {vtk_class}, language: {language}\n'
                  f'Number of example(s): {total_number}.')
            print(f'VTK Class: {vtk_class}, language: {language}\n'
                  f'Number of example(s): {total_number} with {number} random sample(s) shown.')
        print(f'No examples for the VTK Class: {vtk_class} and language: {language}')

if __name__ == '__main__':