import json
from pathlib import Path
from typing import Dict, Tuple, Union  # I have just python3.8 here :(


def parse(filename: Union[str, Path]) -> Tuple[
    Dict[int, str],
    Dict[int, int],
    Dict[int, str],
    Dict[int, Dict[Tuple[int, str], int]]
]:
    """Parse a JSON export from pretix.

    :param filename: filename of the JSON export to parse.
    :returns: Four mappings:
        * item_id to item name
        * item_id to order count of this item
        * question_id to question identifier
        * question_id to stats for this question, which identifies an answer by its item_id and actual answer.
            The stats map this identifier to number of occurrences
    """
    with open(filename, 'r', encoding='utf8') as f:
        data = json.load(f)['event']

    items = {i['id']: i['name'] for i in data['items']}
    count_items = {id_: 0 for id_ in items}
    questions = {q['id']: q['identifier'] for q in data['questions']}
    quest_answers = {id_: {} for id_ in questions}

    for order in data['orders']:
        for position in order['positions']:
            item_id = position['item']
            count_items[item_id] += 1
            for answer in position['answers']:
                quest_id = answer['question']
                answer_key = (item_id, answer['answer'])
                quest_answers[quest_id][answer_key] = (
                        quest_answers[quest_id].get(answer_key, 0) + 1
                )

    return items, count_items, questions, quest_answers


def wiki_stats(items: Dict[int, str], count_items: Dict[int, int], questions: Dict[int, str],
               quest_answers: Dict[int, Dict[Tuple[int, str], int]]) -> str:
    """Generate stats for the Wiki page.

    Input parameters are output of the parse() function.
    """
    ret = ""
    ret += ('== Anmeldezahlen ==\n'
            '{|class="wikitable sortable"\n'
            '! Posten !! Anzahl\n'
            '|-\n')
    for item_id, item_name in items.items():
        ret += f"|| {item_name} || {count_items.get(item_id)}\n|-\n"
    ret += "|}\n"
    return ret