Model hidden information with player views

interface PlayerGameData {
  board: readonly (readonly BoardCell[])[];  // placement + hits
  fleet: FleetMap;                             // ship positions
  ready: boolean;
  shotsReceived: readonly Shot[];
}

interface BattleshipState {
  players: PlayerRecord<typeof PLAYERS, PlayerGameData>;
  lastShot: Shot | null;
}

views: {
  public: ({ G }) => ({
    players: Object.fromEntries(
      PLAYERS.map((id) => [id, {
        ready: G.players[id].ready,
        shotsReceived: G.players[id].shotsReceived,   // visible: opponents already know where they fired
      }]),
    ),
    lastShot: G.lastShot,
  }),
},

views: {
  player: ({ G }, self) => ({
    myFleet: G.players[self.id].fleet,                        // private: my ships
    myBoard: G.players[self.id].board,
    opponents: Object.fromEntries(
      PLAYERS.filter((id) => id !== self.id).map((id) => [id, {
        ready: G.players[id].ready,
        shotsReceived: G.players[id].shotsReceived,           // public
        // no fleet, no board
      }]),
    ),
    lastShot: G.lastShot,
  }),
},

import { createLocalSession } from "@openturn/core";
import { battleship } from "./battleship";

const session = createLocalSession(battleship, {
  match: { players: battleship.playerIDs },
  seed: "test",
});
// ...place ships...
const viewForZero = session.getPlayerView("0");
const viewForOne = session.getPlayerView("1");

expect(viewForZero).not.toHaveProperty("opponents.1.fleet");
expect(viewForOne).not.toHaveProperty("opponents.0.fleet");