Add combat system: NPCs, fights, loot, respawns

NPC class + CombatManager + CombatEncounter
3 NPCs: Shadow Wraith (Bridge), Iron Golem (Forge), Garden Serpent (Garden)
6 endpoints: combat/start, attack, defend, flee, status, npcs
Health bars visible to room, loot drops on death

multi_user_bridge.py

@@ -712,8 +712,382 @@ class InventoryManager:
 
 inventory_manager = InventoryManager()
 
+# ── Combat System ──────────────────────────────────────────────────────
+
+COMBAT_FILE = WORLD_DIR / 'combat.json'
+
+class NPC:
+    """A non-player character that can be fought."""
+
+    def __init__(self, npc_id: str, name: str, room: str, description: str,
+                 health: int, max_health: int, attack: int, defense: int,
+                 loot: list[dict], respawn_ticks: int = 5):
+        self.npc_id = npc_id
+        self.name = name
+        self.room = room
+        self.description = description
+        self.health = health
+        self.max_health = max_health
+        self.attack = attack
+        self.defense = defense
+        self.loot = loot  # [{name, description, drop_chance}]
+        self.respawn_ticks = respawn_ticks
+        self.alive = True
+        self._dead_tick: int | None = None
+
+    def to_dict(self) -> dict:
+        return {
+            "npc_id": self.npc_id,
+            "name": self.name,
+            "room": self.room,
+            "description": self.description,
+            "health": self.health,
+            "max_health": self.max_health,
+            "attack": self.attack,
+            "defense": self.defense,
+            "loot": self.loot,
+            "alive": self.alive,
+            "dead_tick": self._dead_tick,
+            "respawn_ticks": self.respawn_ticks,
+        }
+
+    @classmethod
+    def from_dict(cls, data: dict) -> 'NPC':
+        npc = cls(
+            data["npc_id"], data["name"], data["room"], data["description"],
+            data["health"], data["max_health"], data["attack"], data["defense"],
+            data["loot"], data.get("respawn_ticks", 5),
+        )
+        npc.alive = data.get("alive", True)
+        npc._dead_tick = data.get("dead_tick")
+        return npc
+
+    def health_bar(self) -> str:
+        """Return a text health bar like [████████░░] 80/100."""
+        width = 10
+        filled = int((self.health / self.max_health) * width) if self.max_health > 0 else 0
+        bar = "█" * filled + "░" * (width - filled)
+        return f"[{bar}] {self.health}/{self.max_health}"
+
+    def die(self, tick: int):
+        """Mark NPC as dead."""
+        self.alive = False
+        self.health = 0
+        self._dead_tick = tick
+
+    def respawn(self):
+        """Respawn the NPC at full health."""
+        self.alive = True
+        self.health = self.max_health
+        self._dead_tick = None
+
+
+class CombatEncounter:
+    """An active fight between a player and an NPC."""
+
+    def __init__(self, user_id: str, username: str, room: str, npc_id: str):
+        self.user_id = user_id
+        self.username = username
+        self.room = room
+        self.npc_id = npc_id
+        self.player_hp = 100
+        self.player_max_hp = 100
+        self.player_defending = False
+        self.log: list[str] = []
+        self.active = True
+        self.created_at = datetime.now().isoformat()
+
+    def to_dict(self) -> dict:
+        return {
+            "user_id": self.user_id,
+            "username": self.username,
+            "room": self.room,
+            "npc_id": self.npc_id,
+            "player_hp": self.player_hp,
+            "player_max_hp": self.player_max_hp,
+            "player_defending": self.player_defending,
+            "log": self.log,
+            "active": self.active,
+        }
+
+
+class CombatManager:
+    """Manages NPCs, encounters, and combat resolution."""
+
+    def __init__(self):
+        self._npcs: dict[str, NPC] = {}            # npc_id -> NPC
+        self._encounters: dict[str, CombatEncounter] = {}  # user_id -> encounter
+        self._counter = 0
+        self._lock = threading.Lock()
+
+    # ── NPC management ──────────────────────────────────────────────
+
+    def create_npc(self, name: str, room: str, description: str,
+                   health: int, attack: int, defense: int,
+                   loot: list[dict], respawn_ticks: int = 5) -> NPC:
+        with self._lock:
+            self._counter += 1
+            npc_id = f"npc_{self._counter}"
+            npc = NPC(npc_id, name, room, description,
+                      health, health, attack, defense, loot, respawn_ticks)
+            self._npcs[npc_id] = npc
+            self._save()
+            return npc
+
+    def get_npc(self, npc_id: str) -> NPC | None:
+        return self._npcs.get(npc_id)
+
+    def get_npcs_in_room(self, room: str) -> list[NPC]:
+        with self._lock:
+            return [n for n in self._npcs.values() if n.room == room and n.alive]
+
+    def get_all_npcs(self) -> list[dict]:
+        with self._lock:
+            return [n.to_dict() for n in self._npcs.values()]
+
+    def check_respawns(self, current_tick: int):
+        """Called each world tick — respawn NPCs whose timer has elapsed."""
+        with self._lock:
+            for npc in self._npcs.values():
+                if not npc.alive and npc._dead_tick is not None:
+                    if current_tick - npc._dead_tick >= npc.respawn_ticks:
+                        npc.respawn()
+                        self._save()
+
+    # ── Encounter lifecycle ─────────────────────────────────────────
+
+    def start_fight(self, user_id: str, username: str, room: str, npc_id: str) -> dict:
+        """Begin combat with an NPC."""
+        with self._lock:
+            if user_id in self._encounters and self._encounters[user_id].active:
+                return {"error": "You are already in a fight! Attack or defend."}
+            npc = self._npcs.get(npc_id)
+            if not npc:
+                return {"error": f"NPC '{npc_id}' not found."}
+            if not npc.alive:
+                return {"error": f"{npc.name} is dead. It will respawn later."}
+            if npc.room != room:
+                return {"error": f"{npc.name} is not in this room."}
+            encounter = CombatEncounter(user_id, username, room, npc_id)
+            encounter.log.append(f"Combat started! {username} vs {npc.name}.")
+            self._encounters[user_id] = encounter
+            return {"ok": True, "encounter": encounter.to_dict(), "npc": npc.to_dict()}
+
+    def attack(self, user_id: str) -> dict:
+        """Player attacks NPC; NPC counter-attacks."""
+        with self._lock:
+            enc = self._encounters.get(user_id)
+            if not enc or not enc.active:
+                return {"error": "No active fight. Start one first."}
+            npc = self._npcs.get(enc.npc_id)
+            if not npc or not npc.alive:
+                enc.active = False
+                return {"error": "The enemy is already dead."}
+
+            import random
+
+            # Player attack
+            player_dmg = max(1, random.randint(8, 16) - npc.defense // 3)
+            npc.health -= player_dmg
+            enc.log.append(f"You strike {npc.name} for {player_dmg} damage.")
+
+            npc_dmg = 0
+            if npc.health > 0:
+                # NPC counter-attack
+                base_npc_dmg = random.randint(npc.attack // 2, npc.attack)
+                if enc.player_defending:
+                    npc_dmg = max(1, base_npc_dmg // 2)
+                    enc.log.append(f"{npc.name} attacks for {npc_dmg} (blocked — half damage).")
+                else:
+                    npc_dmg = max(1, base_npc_dmg - random.randint(0, 4))
+                    enc.log.append(f"{npc.name} attacks you for {npc_dmg} damage.")
+                enc.player_hp -= npc_dmg
+            else:
+                npc.die(self._get_tick())
+                loot_dropped = self._roll_loot(npc)
+                enc.log.append(f"{npc.name} is slain!")
+                if loot_dropped:
+                    for item in loot_dropped:
+                        inventory_manager.add_room_item(enc.room, item["name"], item["description"], dropped_by=npc.name)
+                        enc.log.append(f"Loot dropped: {item['name']}")
+                enc.active = False
+                self._save()
+
+            enc.player_defending = False
+
+            # Check player death
+            if enc.player_hp <= 0:
+                enc.player_hp = 0
+                enc.log.append("You have been defeated!")
+                enc.active = False
+
+            return {"ok": True, "encounter": enc.to_dict(), "npc": npc.to_dict(),
+                    "player_dmg": player_dmg, "npc_dmg": npc_dmg,
+                    "loot": loot_dropped if not npc.alive else []}
+
+    def defend(self, user_id: str) -> dict:
+        """Player defends — next NPC attack does half damage."""
+        with self._lock:
+            enc = self._encounters.get(user_id)
+            if not enc or not enc.active:
+                return {"error": "No active fight."}
+            npc = self._npcs.get(enc.npc_id)
+            if not npc or not npc.alive:
+                enc.active = False
+                return {"error": "The enemy is already dead."}
+
+            import random
+
+            enc.player_defending = True
+            enc.log.append("You brace for the next attack (defending).")
+
+            # NPC still attacks
+            base_npc_dmg = random.randint(npc.attack // 2, npc.attack)
+            npc_dmg = max(1, base_npc_dmg // 2)
+            enc.log.append(f"{npc.name} attacks for {npc_dmg} (blocked — half damage).")
+            enc.player_hp -= npc_dmg
+
+            if enc.player_hp <= 0:
+                enc.player_hp = 0
+                enc.log.append("You have been defeated!")
+                enc.active = False
+
+            return {"ok": True, "encounter": enc.to_dict(), "npc": npc.to_dict(), "npc_dmg": npc_dmg}
+
+    def flee(self, user_id: str) -> dict:
+        """Player flees combat."""
+        with self._lock:
+            enc = self._encounters.get(user_id)
+            if not enc or not enc.active:
+                return {"error": "No active fight."}
+            enc.active = False
+            enc.log.append("You flee from combat!")
+            return {"ok": True, "encounter": enc.to_dict()}
+
+    def get_encounter(self, user_id: str) -> CombatEncounter | None:
+        return self._encounters.get(user_id)
+
+    def get_room_combat_status(self, room: str) -> list[dict]:
+        """Get all active fights and NPC health in a room (for health bars)."""
+        with self._lock:
+            status = []
+            # NPCs
+            for npc in self._npcs.values():
+                if npc.room == room:
+                    status.append({
+                        "type": "npc",
+                        "name": npc.name,
+                        "npc_id": npc.npc_id,
+                        "alive": npc.alive,
+                        "health_bar": npc.health_bar() if npc.alive else "[dead]",
+                        "health": npc.health,
+                        "max_health": npc.max_health,
+                    })
+            # Active player fights
+            for enc in self._encounters.values():
+                if enc.room == room and enc.active:
+                    status.append({
+                        "type": "player",
+                        "username": enc.username,
+                        "user_id": enc.user_id,
+                        "hp": enc.player_hp,
+                        "max_hp": enc.player_max_hp,
+                        "fighting": enc.npc_id,
+                    })
+            return status
+
+    def _roll_loot(self, npc: NPC) -> list[dict]:
+        """Roll for loot drops."""
+        import random
+        dropped = []
+        for item in npc.loot:
+            chance = item.get("drop_chance", 1.0)
+            if random.random() < chance:
+                dropped.append({"name": item["name"], "description": item["description"]})
+        return dropped
+
+    def _get_tick(self) -> int:
+        """Read current world tick."""
+        state_file = WORLD_DIR / 'world_state.json'
+        if state_file.exists():
+            try:
+                state = json.loads(state_file.read_text())
+                return state.get("tick", 0)
+            except Exception:
+                return 0
+        return 0
+
+    # ── Persistence ─────────────────────────────────────────────────
+
+    def _save(self):
+        try:
+            data = {
+                "counter": self._counter,
+                "npcs": {nid: n.to_dict() for nid, n in self._npcs.items()},
+            }
+            COMBAT_FILE.parent.mkdir(parents=True, exist_ok=True)
+            COMBAT_FILE.write_text(json.dumps(data, indent=2))
+        except Exception as e:
+            print(f"[CombatManager] Save failed: {e}")
+
+    def load(self):
+        if not COMBAT_FILE.exists():
+            self._seed_npcs()
+            return
+        try:
+            data = json.loads(COMBAT_FILE.read_text())
+            self._counter = data.get("counter", 0)
+            for nid, ndata in data.get("npcs", {}).items():
+                self._npcs[nid] = NPC.from_dict(ndata)
+            print(f"[CombatManager] Loaded {len(self._npcs)} NPCs.")
+        except Exception as e:
+            print(f"[CombatManager] Load failed: {e}")
+            self._seed_npcs()
+
+    def _seed_npcs(self):
+        """Seed starter NPCs."""
+        self.create_npc(
+            "Shadow Wraith", "The Bridge",
+            "A swirling mass of darkness with glowing eyes. It haunts the bridge, "
+            "feeding on the fears of those who cross.",
+            health=60, attack=14, defense=4,
+            loot=[
+                {"name": "Wraith Essence", "description": "A vial of shimmering dark energy.", "drop_chance": 0.8},
+                {"name": "Shadow Cloak", "description": "A cloak woven from pure shadow.", "drop_chance": 0.3},
+            ],
+            respawn_ticks=5,
+        )
+        self.create_npc(
+            "Iron Golem", "The Forge",
+            "A hulking automaton of iron and fire. It guards the forge with tireless vigilance, "
+            "its joints grinding with every step.",
+            health=100, attack=10, defense=10,
+            loot=[
+                {"name": "Golem Core", "description": "A warm crystal that powered the golem.", "drop_chance": 0.7},
+                {"name": "Iron Shard", "description": "A shard of enchanted iron, still warm.", "drop_chance": 0.5},
+            ],
+            respawn_ticks=7,
+        )
+        self.create_npc(
+            "Garden Serpent", "The Garden",
+            "A massive vine serpent camouflaged among the herbs. Its fangs drip with "
+            "a sickly green venom.",
+            health=45, attack=18, defense=2,
+            loot=[
+                {"name": "Serpent Fang", "description": "A curved fang, still coated in venom.", "drop_chance": 0.9},
+                {"name": "Enchanted Vine", "description": "A living vine that moves on its own.", "drop_chance": 0.4},
+            ],
+            respawn_ticks=4,
+        )
+        print(f"[CombatManager] Seeded {len(self._npcs)} NPCs.")
+
+
+combat_manager = CombatManager()
+
 # ── Session Management ─────────────────────────────────────────────────
 
+combat_manager.load()
+
 class UserSession:
     """Isolated conversation context for one user."""
     
@@ -1238,6 +1612,14 @@ class BridgeHandler(BaseHTTPRequestHandler):
                     self._json_response(saved)
                 else:
                     self._json_response({"error": "no session or saved summary"}, 404)
+        elif self.path.startswith('/bridge/combat/status/'):
+            # GET /bridge/combat/status/<room> — NPC health bars + active fights in room
+            room = self.path.split('/bridge/combat/status/')[-1].rstrip('/')
+            status = combat_manager.get_room_combat_status(room)
+            self._json_response({"room": room, "combat_status": status})
+        elif self.path == '/bridge/combat/npcs':
+            # GET /bridge/combat/npcs — list all NPCs
+            self._json_response({"npcs": combat_manager.get_all_npcs()})
         else:
             self._json_response({"error": "not found"}, 404)
 
@@ -1447,6 +1829,91 @@ class BridgeHandler(BaseHTTPRequestHandler):
                     exclude_user=user_id, data=result)
                 self._json_response(result)
 
+        elif self.path == '/bridge/combat/start':
+            # POST /bridge/combat/start — begin fight with NPC
+            # Body: { user_id, username, room, npc_id }
+            user_id = body.get('user_id', 'anonymous')
+            username = body.get('username', 'Anonymous')
+            room = body.get('room', 'The Threshold')
+            npc_id = body.get('npc_id', '')
+            if not npc_id:
+                self._json_response({"error": "npc_id required"}, 400)
+                return
+            result = combat_manager.start_fight(user_id, username, room, npc_id)
+            if "error" in result:
+                self._json_response(result, 400)
+            else:
+                npc = result.get("npc", {})
+                notification_manager.broadcast_room(
+                    room, "combat_start",
+                    f"{username} has engaged {npc.get('name', 'an enemy')} in combat!",
+                    exclude_user=user_id, data=result)
+                self._json_response(result)
+
+        elif self.path == '/bridge/combat/attack':
+            # POST /bridge/combat/attack — attack NPC in active fight
+            # Body: { user_id, username, room }
+            user_id = body.get('user_id', 'anonymous')
+            username = body.get('username', 'Anonymous')
+            room = body.get('room', 'The Threshold')
+            result = combat_manager.attack(user_id)
+            if "error" in result:
+                self._json_response(result, 400)
+            else:
+                enc = result.get("encounter", {})
+                npc = result.get("npc", {})
+                loot = result.get("loot", [])
+                # Broadcast combat action to room
+                combat_msg = f"{username} strikes {npc.get('name', 'the enemy')} for {result.get('player_dmg', 0)} damage!"
+                notification_manager.broadcast_room(
+                    room, "combat_action", combat_msg,
+                    exclude_user=user_id, data=result)
+                # If NPC died, broadcast death
+                if not npc.get("alive", True):
+                    death_msg = f"{npc.get('name', 'The enemy')} has been slain by {username}!"
+                    if loot:
+                        death_msg += f" Loot: {', '.join(i['name'] for i in loot)}"
+                    notification_manager.broadcast_room(
+                        room, "combat_death", death_msg, data=result)
+                # If player died
+                if enc.get("player_hp", 1) <= 0:
+                    notification_manager.broadcast_room(
+                        room, "combat_defeat",
+                        f"{username} has been defeated in combat!", data=result)
+                self._json_response(result)
+
+        elif self.path == '/bridge/combat/defend':
+            # POST /bridge/combat/defend — defend (half damage next hit)
+            # Body: { user_id, username, room }
+            user_id = body.get('user_id', 'anonymous')
+            username = body.get('username', 'Anonymous')
+            room = body.get('room', 'The Threshold')
+            result = combat_manager.defend(user_id)
+            if "error" in result:
+                self._json_response(result, 400)
+            else:
+                notification_manager.broadcast_room(
+                    room, "combat_action",
+                    f"{username} braces defensively.",
+                    exclude_user=user_id, data=result)
+                self._json_response(result)
+
+        elif self.path == '/bridge/combat/flee':
+            # POST /bridge/combat/flee — flee from combat
+            # Body: { user_id, username, room }
+            user_id = body.get('user_id', 'anonymous')
+            username = body.get('username', 'Anonymous')
+            room = body.get('room', 'The Threshold')
+            result = combat_manager.flee(user_id)
+            if "error" in result:
+                self._json_response(result, 400)
+            else:
+                notification_manager.broadcast_room(
+                    room, "combat_flee",
+                    f"{username} flees from combat!",
+                    exclude_user=user_id, data=result)
+                self._json_response(result)
+
         else:
             self._json_response({"error": "not found"}, 404)