engine/game_state.py

"""The authoritative game state.

The whole point of the engine is that *this* is the source of truth, not the
language model. The model proposes changes; `GameState` (via the parser) decides
what actually happens, clamping every value to a legal range. A small model can
hallucinate "you now have 9000 HP" — the state will not let it.
"""

from __future__ import annotations

from dataclasses import dataclass, field, asdict
from typing import Optional
import json


MAX_HP_CAP = 999
MAX_INVENTORY = 24


@dataclass
class Enemy:
    """An enemy currently in combat. `None` on the state means no active fight."""

    name: str
    hp: int
    max_hp: int
    attack: int = 3

    @property
    def alive(self) -> bool:
        return self.hp > 0


@dataclass
class NPC:
    """A named character the model has introduced. Persisted so the model can be
    reminded who exists — this is a big lever for consistency."""

    name: str
    role: str = ""          # "blacksmith", "old hermit", ...
    disposition: str = "neutral"   # friendly / neutral / hostile
    note: str = ""          # one-line memory, e.g. "owes you a favour"


@dataclass
class GameState:
    # --- vitals ---
    hp: int = 20
    max_hp: int = 20
    gold: int = 10
    level: int = 1
    xp: int = 0

    # --- world ---
    location: str = "The Crossroads"
    inventory: list[str] = field(default_factory=lambda: ["Rusty Dagger", "Bread"])
    npcs: dict[str, NPC] = field(default_factory=dict)
    quest: str = "Discover why the village of Mossfall fell silent."

    # --- combat (None when not fighting) ---
    enemy: Optional[Enemy] = None

    # --- meta ---
    turn: int = 0
    game_over: bool = False
    log: list[str] = field(default_factory=list)

    # ------------------------------------------------------------------ vitals
    def damage(self, amount: int) -> None:
        amount = max(0, int(amount))
        self.hp = max(0, self.hp - amount)
        if self.hp == 0:
            self.game_over = True

    def heal(self, amount: int) -> None:
        amount = max(0, int(amount))
        self.hp = min(self.max_hp, self.hp + amount)

    def add_gold(self, amount: int) -> None:
        self.gold = max(0, self.gold + int(amount))

    def add_xp(self, amount: int) -> None:
        self.xp += max(0, int(amount))
        # simple, legible leveling curve: 10 * level to advance
        while self.xp >= self.level * 10:
            self.xp -= self.level * 10
            self.level += 1
            self.max_hp = min(MAX_HP_CAP, self.max_hp + 5)
            self.hp = self.max_hp  # full heal on level-up
            self.log.append(f"LEVEL UP → {self.level} (max HP {self.max_hp})")

    # --------------------------------------------------------------- inventory
    def add_item(self, item: str) -> bool:
        item = item.strip()
        if not item or len(self.inventory) >= MAX_INVENTORY:
            return False
        self.inventory.append(item)
        return True

    def remove_item(self, item: str) -> bool:
        item = item.strip().lower()
        for i, owned in enumerate(self.inventory):
            if owned.lower() == item:
                self.inventory.pop(i)
                return True
        return False

    def has_item(self, item: str) -> bool:
        item = item.strip().lower()
        return any(owned.lower() == item for owned in self.inventory)

    # --------------------------------------------------------------------- npc
    def upsert_npc(self, npc: NPC) -> None:
        key = npc.name.strip().lower()
        if not key:
            return
        if key in self.npcs:
            # merge: keep old note unless a new non-empty one is given
            old = self.npcs[key]
            old.role = npc.role or old.role
            old.disposition = npc.disposition or old.disposition
            old.note = npc.note or old.note
        else:
            self.npcs[key] = npc

    # ------------------------------------------------------------------ combat
    def start_combat(self, enemy: Enemy) -> None:
        self.enemy = enemy

    def end_combat(self) -> None:
        self.enemy = None

    # ----------------------------------------------------------- (de)serialize
    def to_dict(self) -> dict:
        d = asdict(self)
        return d

    @classmethod
    def from_dict(cls, d: dict) -> "GameState":
        d = dict(d)
        if d.get("enemy"):
            d["enemy"] = Enemy(**d["enemy"])
        if d.get("npcs"):
            d["npcs"] = {k: NPC(**v) for k, v in d["npcs"].items()}
        return cls(**d)

    def to_json(self) -> str:
        return json.dumps(self.to_dict(), ensure_ascii=False, indent=2)

    # ------------------------------------------------------------ for the LLM
    def context_snapshot(self) -> str:
        """A compact, human-readable snapshot fed to the model every turn so it
        never has to remember the numbers itself."""
        lines = [
            f"HP: {self.hp}/{self.max_hp}",
            f"Level: {self.level}  XP: {self.xp}/{self.level * 10}",
            f"Gold: {self.gold}",
            f"Location: {self.location}",
            f"Inventory: {', '.join(self.inventory) if self.inventory else '(empty)'}",
            f"Current quest: {self.quest}",
        ]
        if self.enemy and self.enemy.alive:
            e = self.enemy
            lines.append(f"IN COMBAT with {e.name} ({e.hp}/{e.max_hp} HP, atk {e.attack})")
        if self.npcs:
            known = "; ".join(
                f"{n.name} ({n.role or n.disposition})" for n in self.npcs.values()
            )
            lines.append(f"Known characters: {known}")
        return "\n".join(lines)