"""Game state: progress data + the mutations on that data.

Every method here touches ONLY its own fields (no quest content). The
orchestrator decides *when* and *which* to call (using quest boundaries);
GameState owns the actual state changes.
"""
from __future__ import annotations

from dataclasses import dataclass

RANK_LADDER = [
    "Squire", "Knight-Errant", "Knight Bachelor", "Knight Banneret",
    "Knight Commander", "Knight Champion", "Grandmaster",
]


@dataclass
class GameState:
    stage_idx: int = 0
    q_idx: int = 0
    attempt: int = 0
    status: str = "playing"          # "playing" | "won" | "lost"

    @property
    def rank(self) -> str:
        """Derived from progress alone."""
        if self.status == "won":
            return RANK_LADDER[-1]                        # Grandmaster
        return RANK_LADDER[self.stage_idx]           # Squire, Knight-Errant, etc.

    # --- mutations (pure: own fields only) ---
    def advance(self) -> None:
        """Move to the next question in the current stage."""
        self.q_idx += 1
        self.attempt = 0

    def complete_stage(self) -> None:
        """Move to the next stage (rank up follows from stage_idx)."""
        self.stage_idx += 1
        self.q_idx = 0
        self.attempt = 0

    def strike(self) -> None:
        self.attempt += 1

    def lose(self) -> None:
        """Game over: too many strikes ends the run."""
        self.status = "lost"

    def win(self) -> None:
        self.status = "won"