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import fitz  # PyMuPDF
from typing import List, Dict

class DocumentParser:
    def __init__(self, filepath: str):
        self.doc = fitz.open(filepath)
        self.text_blocks: List[Dict] = []

    def extract_text(self) -> str:
        full_text = []
        for page_num in range(len(self.doc)):
            page = self.doc[page_num]
            blocks = page.get_text("dict")["blocks"]

            for block in blocks:
                if "lines" in block:
                    for line in block["lines"]:
                        for span in line["spans"]:
                            full_text.append(span["text"])
        return " ".join(full_text)

def extract_chapters(self) -> List[Dict]:
    """Extract chapter boundaries and content."""
    chapters = []
    current_chapter = {
        "title": "Introduction",
        "content": "",
        "start_page": 0
    }

    for page_num, page in enumerate(self.doc):
        text = page.get_text()
        lines = text.split("\n")

        for line in lines:
            # Detect chapter headings (uppercase, short lines)
            if self._is_chapter_heading(line):
                if current_chapter["content"].strip():
                    chapters.append(current_chapter)
                current_chapter = {
                    "title": line.strip(),
                    "content": "",
                    "start_page": page_num
                }
            else:
                current_chapter["content"] += line + "\n"

    if current_chapter["content"].strip():
        chapters.append(current_chapter)

    return chapters

from enum import Enum
from dataclasses import dataclass
from typing import List, Optional

class Difficulty(Enum):
    EASY = "easy"
    MEDIUM = "medium"
    HARD = "hard"

@dataclass
class Question:
    text: str
    options: List[str]
    correct_answer: int
    explanation: str
    difficulty: Difficulty
    topic: str

@dataclass
class Quiz:
    title: str
    questions: List[Question]
    total_score: int = 0

class QuizRunner:
    def __init__(self, quiz: Quiz):
        self.quiz = quiz
        self.current_question = 0
        self.score = 0
        self.answers: List[Tuple[int, int, float]] = []
        self.start_time = datetime.now()

    def get_current_question(self) -> Question:
        return self.quiz.questions[self.current_question]

    def submit_answer(self, answer_idx: int) -> bool:
        question = self.quiz.questions[self.current_question]
        is_correct = answer_idx == question.correct_answer

        if is_correct:
            self.score += self._calculate_points(question)

        self.answers.append((
            self.current_question,
            answer_idx,
            (datetime.now() - self.start_time).total_seconds()
        ))

        self.current_question += 1
        return is_correct

I need a Python class structure for a quiz system.
It should have:
1. Question dataclass with text, options, correct_answer, explanation
2. Quiz class that contains multiple questions
3. Difficulty enum (easy, medium, hard)
4. Methods to calculate score based on difficulty

Start with the dataclasses and enums.