Prototype charity Truthtrance and coalition rule foundations

game/occupancy.ts

@@ -3,6 +3,7 @@ import { territory } from './board';
 import { fighterCount } from './advisors';
 import { presenceAt, type ForcePresence } from './force-presence';
 import { ecazOccupancyIdentity, ecazOccupancyRelation } from './ecaz-occupy';
+import { coalitionAllies, coalitionGroups, type CoalitionState } from './coalition-alliance';
 
 /** Public board information only: a concealed No-Field contributes presence,
  * never its hidden denomination. Advisor groups do not fill strongholds. */
@@ -10,6 +11,7 @@ export type OccupancySeat = ForcePresence & {
   id: string;
   faction: FactionId;
   ally?: string | null;
+  allySinceTurn?: number;
   advisors?: Readonly<Record<string, { lockedTurn?: number }>>;
 };
 
@@ -38,21 +40,31 @@ export function territoryEntryBlock(
   to: string,
   advisors = false,
   temporaryAlliedShipment = false,
+  coalitionState?: CoalitionState,
 ): string | null {
   // Validate the complete identity roster even for an empty destination.
   ecazOccupancyIdentity(players, playerId, { kind: 'territory', id: to });
-  if (advisors) return null;
   const player = players.find((p) => p.id === playerId)!;
-  const ally = players.find((p) => p.id === player.ally);
+  const seats = players.map(p => ({ id: p.id, ally: p.ally ?? null, allySinceTurn: p.allySinceTurn }));
+  if (coalitionState !== undefined) {
+    const groups = coalitionGroups(seats, coalitionState);
+    if (players.some(player => player.faction === 'ecaz') && groups.some(group => group.members.length === 3))
+      throw new Error('Three-member board rules do not yet support Ecaz.');
+  }
+  if (advisors) return null;
+  const allies = coalitionState === undefined ? (player.ally ? [player.ally] : [])
+    : coalitionAllies(seats, coalitionState, playerId);
   if (
     !temporaryAlliedShipment &&
     to !== 'polar_sink' &&
-    ally &&
-    presenceAt(ally, to) > 0 &&
-    ecazOccupancyRelation(players, playerId, ally.id, {
+    allies.some(id => {
+      const ally = players.find(p => p.id === id);
+      return !!ally && presenceAt(ally, to) > 0 &&
+    ecazOccupancyRelation(players, playerId, id, {
       kind: 'territory',
       id: to,
-    }) !== 'ecazAlliance'
+    }) !== 'ecazAlliance';
+    })
   )
     return 'You cannot enter a territory occupied by your ally.';
   if (