Add ENet multiplayer (movement/combat sync) and matchmaking API

Networked play, end to end: connect, get matched, spawn, fight, respawn.

Godot side:
- Replace the single hardcoded Player with per-peer networked ships
  (MultiplayerSpawner + custom spawn_function), driven by client-side
  prediction with server reconciliation for movement.
- Server-authoritative combat: bullets, health, death/respawn all decided
  by the server and broadcast to every peer over RPC.
- Fix a Camera2D bug where Godot auto-promotes the first camera to ever
  enter the scene tree as the active one regardless of its own `current`
  value — with MultiplayerSpawner catch-up replication that was almost
  never the local player's own ship. `make_current()` on the owner's
  camera fixes it; property assignment doesn't reliably override the
  auto-claim.
- Fix two "late joiner never learns already-established state" gaps
  (health, visibility) by folding both into the existing per-tick
  position broadcast instead of relying on one-shot RPCs that only reach
  peers already connected when they fire.
- Make the 2 offered factions in team select match for every player in
  a match: the server decides once and clients either read it directly
  (server's own instance) or request it over RPC, rather than each
  client rolling its own random pair.
- New MatchmakingClient autoload wires the main menu's CASUAL/RANKED
  buttons to the matchmaking API instead of connecting directly.

New matchmaking-api/ (FastAPI + Postgres, Docker Compose):
- Queue/match/stats/ranks endpoints. In-memory matchmaking queue in a
  single API process — no Redis until there's an actual reason to shard
  the queue across instances.
- Background loop forms a match once enough players are queued for a
  mode, assigns the first available registered game server.
- No real server pool yet: one dev server is auto-seeded from
  DEV_SEED_SERVER_IP/PORT; POST /servers/register exists for real
  servers to self-register later but nothing calls it yet.

Docs: CLAUDE.md and overview/tech.md updated to match — networking
checklist mostly checked off, matchmaking backend section rewritten to
describe what was actually built vs. the original Go/Redis plan, and
Current Tasks reordered around what's actually left (bot fill, real
server pool, ranked/MMR refinement, lag compensation).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

matchmaking-api/app/config.py

@@ -0,0 +1,14 @@
+from pydantic_settings import BaseSettings, SettingsConfigDict
+
+
+class Settings(BaseSettings):
+    model_config = SettingsConfigDict(env_file=".env", extra="ignore")
+
+    database_url: str
+    casual_team_size: int = 7
+    ranked_team_size: int = 5
+    dev_seed_server_ip: str = "127.0.0.1"
+    dev_seed_server_port: int = 7777
+
+
+settings = Settings()

matchmaking-api/app/database.py

@@ -0,0 +1,19 @@
+from collections.abc import AsyncGenerator
+
+from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker, create_async_engine
+from sqlalchemy.orm import DeclarativeBase
+
+from app.config import settings
+
+
+class Base(DeclarativeBase):
+    pass
+
+
+engine = create_async_engine(settings.database_url, echo=False)
+async_session = async_sessionmaker(engine, expire_on_commit=False)
+
+
+async def get_db() -> AsyncGenerator[AsyncSession, None]:
+    async with async_session() as session:
+        yield session

matchmaking-api/app/main.py

@@ -0,0 +1,58 @@
+import asyncio
+from contextlib import asynccontextmanager
+
+from fastapi import FastAPI
+from sqlalchemy import select
+
+from app.config import settings
+from app.database import Base, async_session, engine
+from app.models import GameServer, Mode, ServerStatus
+from app.queue_manager import queue_manager
+from app.routers import matchmaking, ranks, servers, stats
+
+
+async def _seed_dev_server() -> None:
+    async with async_session() as db:
+        for mode in (Mode.casual, Mode.ranked):
+            existing = (
+                await db.execute(
+                    select(GameServer).where(
+                        GameServer.ip == settings.dev_seed_server_ip,
+                        GameServer.port == settings.dev_seed_server_port,
+                        GameServer.mode == mode,
+                    )
+                )
+            ).scalars().first()
+            if existing is None:
+                db.add(
+                    GameServer(
+                        ip=settings.dev_seed_server_ip,
+                        port=settings.dev_seed_server_port,
+                        mode=mode,
+                        status=ServerStatus.available,
+                    )
+                )
+        await db.commit()
+
+
+@asynccontextmanager
+async def lifespan(app: FastAPI):
+    async with engine.begin() as conn:
+        await conn.run_sync(Base.metadata.create_all)
+    await _seed_dev_server()
+    matching_task = asyncio.create_task(queue_manager.run_matching_loop())
+    yield
+    matching_task.cancel()
+
+
+app = FastAPI(title="Spacewar Matchmaking API", lifespan=lifespan)
+
+app.include_router(matchmaking.router)
+app.include_router(stats.router)
+app.include_router(ranks.router)
+app.include_router(servers.router)
+
+
+@app.get("/health")
+async def health() -> dict:
+    return {"status": "ok"}

matchmaking-api/app/models.py

@@ -0,0 +1,67 @@
+import enum
+import uuid
+from datetime import datetime
+
+from sqlalchemy import DateTime, ForeignKey, Integer, String
+from sqlalchemy import Enum as SAEnum
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+
+from app.database import Base
+
+
+class Mode(str, enum.Enum):
+    casual = "casual"
+    ranked = "ranked"
+
+
+class ServerStatus(str, enum.Enum):
+    available = "available"
+    full = "full"
+    offline = "offline"
+
+
+# No account/auth system yet (GodotSteam auth is still on the networking
+# checklist), so callsign is the identity key for now — same as the game
+# client itself, which only has a free-text name field today.
+class Player(Base):
+    __tablename__ = "players"
+
+    id: Mapped[uuid.UUID] = mapped_column(primary_key=True, default=uuid.uuid4)
+    callsign: Mapped[str] = mapped_column(String(32), unique=True, index=True)
+    mmr: Mapped[int] = mapped_column(Integer, default=1000)
+    wins: Mapped[int] = mapped_column(Integer, default=0)
+    losses: Mapped[int] = mapped_column(Integer, default=0)
+    created_at: Mapped[datetime] = mapped_column(DateTime, default=datetime.utcnow)
+
+
+class GameServer(Base):
+    __tablename__ = "game_servers"
+
+    id: Mapped[uuid.UUID] = mapped_column(primary_key=True, default=uuid.uuid4)
+    ip: Mapped[str] = mapped_column(String(255))
+    port: Mapped[int] = mapped_column(Integer)
+    mode: Mapped[Mode] = mapped_column(SAEnum(Mode))
+    status: Mapped[ServerStatus] = mapped_column(SAEnum(ServerStatus), default=ServerStatus.available)
+    last_heartbeat: Mapped[datetime] = mapped_column(DateTime, default=datetime.utcnow)
+
+
+class Match(Base):
+    __tablename__ = "matches"
+
+    id: Mapped[uuid.UUID] = mapped_column(primary_key=True, default=uuid.uuid4)
+    mode: Mapped[Mode] = mapped_column(SAEnum(Mode))
+    server_id: Mapped[uuid.UUID] = mapped_column(ForeignKey("game_servers.id"))
+    started_at: Mapped[datetime] = mapped_column(DateTime, default=datetime.utcnow)
+
+    players: Mapped[list["MatchPlayer"]] = relationship(back_populates="match")
+
+
+class MatchPlayer(Base):
+    __tablename__ = "match_players"
+
+    id: Mapped[uuid.UUID] = mapped_column(primary_key=True, default=uuid.uuid4)
+    match_id: Mapped[uuid.UUID] = mapped_column(ForeignKey("matches.id"))
+    player_id: Mapped[uuid.UUID] = mapped_column(ForeignKey("players.id"))
+    team: Mapped[int] = mapped_column(Integer)  # 0 or 1
+
+    match: Mapped["Match"] = relationship(back_populates="players")

matchmaking-api/app/queue_manager.py

@@ -0,0 +1,106 @@
+import asyncio
+import uuid
+from dataclasses import dataclass, field
+from datetime import datetime
+
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.config import settings
+from app.database import async_session
+from app.models import GameServer, Match, MatchPlayer, Mode, ServerStatus
+
+
+@dataclass
+class Ticket:
+    ticket_id: uuid.UUID
+    player_id: uuid.UUID
+    callsign: str
+    mode: Mode
+    mmr: int
+    queued_at: datetime = field(default_factory=datetime.utcnow)
+    status: str = "queued"  # queued | matched | cancelled
+    server_ip: str | None = None
+    server_port: int | None = None
+    team: int | None = None
+
+
+class QueueManager:
+    """In-memory matchmaking queue. No Redis: a single API process holds all
+    ticket state, which is fine at this scale and simpler to run — see
+    memory/spacewar_networking_plan for why Redis was deferred rather than
+    included from the start.
+    """
+
+    def __init__(self) -> None:
+        self._tickets: dict[uuid.UUID, Ticket] = {}
+        self._lock = asyncio.Lock()
+
+    async def join(self, player_id: uuid.UUID, callsign: str, mode: Mode, mmr: int) -> Ticket:
+        ticket = Ticket(ticket_id=uuid.uuid4(), player_id=player_id, callsign=callsign, mode=mode, mmr=mmr)
+        async with self._lock:
+            self._tickets[ticket.ticket_id] = ticket
+        return ticket
+
+    async def leave(self, ticket_id: uuid.UUID) -> bool:
+        async with self._lock:
+            ticket = self._tickets.get(ticket_id)
+            if ticket is None or ticket.status != "queued":
+                return False
+            ticket.status = "cancelled"
+            return True
+
+    def get(self, ticket_id: uuid.UUID) -> Ticket | None:
+        return self._tickets.get(ticket_id)
+
+    def _waiting(self, mode: Mode) -> list[Ticket]:
+        tickets = [t for t in self._tickets.values() if t.mode == mode and t.status == "queued"]
+        if mode == Mode.ranked:
+            # Simple MMR-sorted grouping. No widening-window-by-wait-time yet
+            # (real ranked matchmaking will want that) — nearest-neighbor by
+            # mmr is a reasonable placeholder until ranked queue volume
+            # exists to tune against.
+            tickets.sort(key=lambda t: t.mmr)
+        else:
+            tickets.sort(key=lambda t: t.queued_at)
+        return tickets
+
+    async def _try_form_match(self, mode: Mode, team_size: int, db: AsyncSession) -> None:
+        required = team_size * 2
+        async with self._lock:
+            waiting = self._waiting(mode)
+            if len(waiting) < required:
+                return
+            group = waiting[:required]
+
+            server = (
+                await db.execute(
+                    select(GameServer).where(GameServer.mode == mode, GameServer.status == ServerStatus.available)
+                )
+            ).scalars().first()
+            if server is None:
+                return  # no server free this cycle; leave everyone queued and retry next tick
+
+            match = Match(mode=mode, server_id=server.id)
+            db.add(match)
+            await db.flush()
+
+            for i, ticket in enumerate(group):
+                team = i % 2
+                db.add(MatchPlayer(match_id=match.id, player_id=ticket.player_id, team=team))
+                ticket.status = "matched"
+                ticket.server_ip = server.ip
+                ticket.server_port = server.port
+                ticket.team = team
+
+            await db.commit()
+
+    async def run_matching_loop(self) -> None:
+        while True:
+            await asyncio.sleep(2)
+            async with async_session() as db:
+                await self._try_form_match(Mode.casual, settings.casual_team_size, db)
+                await self._try_form_match(Mode.ranked, settings.ranked_team_size, db)
+
+
+queue_manager = QueueManager()

matchmaking-api/app/routers/matchmaking.py

@@ -0,0 +1,53 @@
+import uuid
+
+from fastapi import APIRouter, Depends, HTTPException
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.database import get_db
+from app.models import Mode, Player
+from app.queue_manager import queue_manager
+from app.schemas import QueueJoinRequest, QueueJoinResponse, QueueStatusResponse
+
+router = APIRouter(prefix="/matchmaking", tags=["matchmaking"])
+
+
+async def _get_or_create_player(db: AsyncSession, callsign: str) -> Player:
+    player = (await db.execute(select(Player).where(Player.callsign == callsign))).scalars().first()
+    if player is None:
+        player = Player(callsign=callsign)
+        db.add(player)
+        await db.commit()
+        await db.refresh(player)
+    return player
+
+
+@router.post("/queue/join", response_model=QueueJoinResponse)
+async def join_queue(req: QueueJoinRequest, db: AsyncSession = Depends(get_db)) -> QueueJoinResponse:
+    player = await _get_or_create_player(db, req.callsign)
+    mmr = req.mmr if req.mode == Mode.ranked and req.mmr is not None else player.mmr
+
+    ticket = await queue_manager.join(player.id, player.callsign, req.mode, mmr)
+    return QueueJoinResponse(ticket_id=ticket.ticket_id, status=ticket.status)
+
+
+@router.post("/queue/leave")
+async def leave_queue(ticket_id: uuid.UUID) -> dict:
+    ok = await queue_manager.leave(ticket_id)
+    if not ok:
+        raise HTTPException(status_code=404, detail="Ticket not found or already resolved")
+    return {"status": "cancelled"}
+
+
+@router.get("/queue/status/{ticket_id}", response_model=QueueStatusResponse)
+async def queue_status(ticket_id: uuid.UUID) -> QueueStatusResponse:
+    ticket = queue_manager.get(ticket_id)
+    if ticket is None:
+        raise HTTPException(status_code=404, detail="Ticket not found")
+    return QueueStatusResponse(
+        ticket_id=ticket.ticket_id,
+        status=ticket.status,
+        server_ip=ticket.server_ip,
+        server_port=ticket.server_port,
+        team=ticket.team,
+    )

matchmaking-api/app/routers/ranks.py

@@ -0,0 +1,35 @@
+from fastapi import APIRouter, Depends, HTTPException
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.database import get_db
+from app.models import Player
+
+router = APIRouter(prefix="/ranks", tags=["ranks"])
+
+# Mirrors RANK_DATA in spacewar/menu/main_menu.gd — keep the tier names (and
+# ideally thresholds) in sync if either side changes.
+_TIERS: list[tuple[int, str]] = [
+    (0, "CADET"),
+    (1000, "PILOT"),
+    (1400, "ACE"),
+    (1800, "COMMANDER"),
+    (2200, "ADMIRAL"),
+    (2600, "LEGEND"),
+]
+
+
+def _tier_for(mmr: int) -> str:
+    tier = _TIERS[0][1]
+    for threshold, name in _TIERS:
+        if mmr >= threshold:
+            tier = name
+    return tier
+
+
+@router.get("/{callsign}")
+async def get_rank(callsign: str, db: AsyncSession = Depends(get_db)) -> dict:
+    player = (await db.execute(select(Player).where(Player.callsign == callsign))).scalars().first()
+    if player is None:
+        raise HTTPException(status_code=404, detail="Player not found")
+    return {"callsign": player.callsign, "mmr": player.mmr, "rank": _tier_for(player.mmr)}

matchmaking-api/app/routers/servers.py

@@ -0,0 +1,44 @@
+from datetime import datetime
+
+from fastapi import APIRouter, Depends
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.database import get_db
+from app.models import GameServer, ServerStatus
+from app.schemas import ServerRegisterRequest
+
+router = APIRouter(prefix="/servers", tags=["servers"])
+
+
+# Real game servers should call this on boot and periodically (heartbeat) once
+# NetworkManager grows that integration. Until then, a dev server is seeded
+# on API startup (see main.py) from DEV_SEED_SERVER_IP/PORT so matchmaking is
+# testable end-to-end without it.
+@router.post("/register")
+async def register_server(req: ServerRegisterRequest, db: AsyncSession = Depends(get_db)) -> dict:
+    existing = (
+        await db.execute(select(GameServer).where(GameServer.ip == req.ip, GameServer.port == req.port, GameServer.mode == req.mode))
+    ).scalars().first()
+    if existing:
+        existing.status = ServerStatus.available
+        existing.last_heartbeat = datetime.utcnow()
+    else:
+        db.add(GameServer(ip=req.ip, port=req.port, mode=req.mode, status=ServerStatus.available))
+    await db.commit()
+    return {"status": "registered"}
+
+
+@router.get("")
+async def list_servers(db: AsyncSession = Depends(get_db)) -> list[dict]:
+    servers = (await db.execute(select(GameServer))).scalars().all()
+    return [
+        {
+            "ip": s.ip,
+            "port": s.port,
+            "mode": s.mode,
+            "status": s.status,
+            "last_heartbeat": s.last_heartbeat,
+        }
+        for s in servers
+    ]

matchmaking-api/app/routers/stats.py

@@ -0,0 +1,17 @@
+from fastapi import APIRouter, Depends, HTTPException
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.database import get_db
+from app.models import Player
+from app.schemas import PlayerStatsResponse
+
+router = APIRouter(prefix="/stats", tags=["stats"])
+
+
+@router.get("/{callsign}", response_model=PlayerStatsResponse)
+async def get_stats(callsign: str, db: AsyncSession = Depends(get_db)) -> PlayerStatsResponse:
+    player = (await db.execute(select(Player).where(Player.callsign == callsign))).scalars().first()
+    if player is None:
+        raise HTTPException(status_code=404, detail="Player not found")
+    return PlayerStatsResponse(callsign=player.callsign, mmr=player.mmr, wins=player.wins, losses=player.losses)

matchmaking-api/app/schemas.py

@@ -0,0 +1,37 @@
+import uuid
+
+from pydantic import BaseModel
+
+from app.models import Mode
+
+
+class QueueJoinRequest(BaseModel):
+    callsign: str
+    mode: Mode
+    mmr: int | None = None  # ignored for casual; defaults to the player's stored mmr for ranked
+
+
+class QueueJoinResponse(BaseModel):
+    ticket_id: uuid.UUID
+    status: str
+
+
+class QueueStatusResponse(BaseModel):
+    ticket_id: uuid.UUID
+    status: str
+    server_ip: str | None = None
+    server_port: int | None = None
+    team: int | None = None
+
+
+class ServerRegisterRequest(BaseModel):
+    ip: str
+    port: int
+    mode: Mode
+
+
+class PlayerStatsResponse(BaseModel):
+    callsign: str
+    mmr: int
+    wins: int
+    losses: int