feat(state): add validated persistent game state

src/main/java/games/dmg/spigottyrant/GameState.java

@@ -0,0 +1,59 @@
+package games.dmg.spigottyrant;
+
+import java.time.Duration;
+import java.time.Instant;
+import java.util.Optional;
+import java.util.Set;
+import java.util.UUID;
+
+public record GameState(
+    GameLifecycle lifecycle,
+    Optional<UUID> tyrantId,
+    Optional<UUID> vigilanteId,
+    Optional<PendingSelection> pendingTyrant,
+    Optional<PendingSelection> pendingVigilante,
+    Optional<Instant> pausedAt,
+    Duration accumulatedPausedTime,
+    int tyrantLevel,
+    int unspentChoices,
+    Set<TyrantUnlock> purchases
+) {
+    public GameState {
+        lifecycle = lifecycle == null ? GameLifecycle.UNSTARTED : lifecycle;
+        tyrantId = tyrantId == null ? Optional.empty() : tyrantId;
+        vigilanteId = vigilanteId == null ? Optional.empty() : vigilanteId;
+        pendingTyrant = pendingTyrant == null ? Optional.empty() : pendingTyrant;
+        pendingVigilante = pendingVigilante == null ? Optional.empty() : pendingVigilante;
+        pausedAt = pausedAt == null ? Optional.empty() : pausedAt;
+        accumulatedPausedTime = accumulatedPausedTime == null
+            ? Duration.ZERO : accumulatedPausedTime;
+        purchases = purchases == null ? Set.of() : Set.copyOf(purchases);
+        if (tyrantId.isPresent() && tyrantId.equals(vigilanteId)) {
+            throw new IllegalArgumentException("Tyrant and Vigilante must be different players");
+        }
+        if (tyrantLevel < 0 || unspentChoices < 0) {
+            throw new IllegalArgumentException("progression values must not be negative");
+        }
+        if (accumulatedPausedTime.isNegative()) {
+            throw new IllegalArgumentException("accumulated paused time must not be negative");
+        }
+        if ((lifecycle == GameLifecycle.PAUSED) != pausedAt.isPresent()) {
+            throw new IllegalArgumentException("pausedAt must be present exactly while paused");
+        }
+    }
+
+    public static GameState empty() {
+        return new GameState(
+            GameLifecycle.UNSTARTED,
+            Optional.empty(),
+            Optional.empty(),
+            Optional.empty(),
+            Optional.empty(),
+            Optional.empty(),
+            Duration.ZERO,
+            0,
+            0,
+            Set.of()
+        );
+    }
+}