from __future__ import annotations
from dataclasses import dataclass, field
from typing import List
import time

VALID_DIFFICULTIES = {"easy", "medium", "hard"}
VALID_TYPES = {"mcq", "tf", "fill"}

@dataclass
class Question:
    text: str
    topic: str                      # subject area — "Determinants" not question text
    options: List[str]
    correct_idx: int
    explanation: str
    difficulty: str
    q_type: str
    is_boss: bool = False
    source_excerpt: str = ""        # snippet from original material for tutor context
    language: str = "en"

    def __post_init__(self):
        if self.difficulty not in VALID_DIFFICULTIES:
            raise ValueError(f"difficulty must be one of {VALID_DIFFICULTIES}, got '{self.difficulty}'")
        if self.q_type not in VALID_TYPES:
            raise ValueError(f"q_type must be one of {VALID_TYPES}, got '{self.q_type}'")
        if not (0 <= self.correct_idx < len(self.options)):
            raise ValueError(f"correct_idx {self.correct_idx} out of range for {len(self.options)} options")

    @property
    def correct_answer(self) -> str:
        return self.options[self.correct_idx]

@dataclass
class QuizSession:
    quest_name: str
    questions: List[Question] = field(default_factory=list)
    current_idx: int = 0
    score: int = 0
    consecutive_correct: int = 0
    xp_earned: int = 0
    start_time: float = field(default_factory=time.time)
    wrong_topics: List[str] = field(default_factory=list)  # topic strings, not question text

    @property
    def is_finished(self) -> bool:
        return self.current_idx >= len(self.questions)

    @property
    def current_question(self) -> Question | None:
        if self.is_finished:
            return None
        return self.questions[self.current_idx]

@dataclass
class Quest:
    name: str
    topics: List[str]
    boss_topic: str
    difficulty: str
    questions: List[Question] = field(default_factory=list)
    unlocked: bool = True
    completed: bool = False         # True only after user finishes the quest

    def has_questions(self) -> bool:
        return len(self.questions) > 0

    def total_questions(self) -> int:
        return len(self.questions)