feat: implement diplomacy system with state management and processing logic

app/game-engine/test/diplomacy.test.ts

@@ -0,0 +1,82 @@
+import { describe, expect, it } from 'vitest';
+
+import {
+    DEFAULT_WAR_TERM,
+    DIPLOMACY_STATE,
+    processDiplomacyMonth,
+} from '../src/turn/diplomacy.js';
+import type { TurnDiplomacy } from '../src/turn/types.js';
+
+const buildEntry = (
+    fromNationId: number,
+    toNationId: number,
+    state: number,
+    term: number,
+    dead = 0
+): TurnDiplomacy => ({
+    fromNationId,
+    toNationId,
+    state,
+    term,
+    dead,
+    meta: {},
+});
+
+describe('diplomacy month processing', () => {
+    it('promotes declaration to war after term expires', () => {
+        const entries = [
+            buildEntry(1, 2, DIPLOMACY_STATE.DECLARATION, 1),
+            buildEntry(2, 1, DIPLOMACY_STATE.DECLARATION, 1),
+        ];
+        const result = processDiplomacyMonth(entries, new Map([[1, 1], [2, 1]]));
+
+        for (const entry of result) {
+            expect(entry.state).toBe(DIPLOMACY_STATE.WAR);
+            expect(entry.term).toBe(DEFAULT_WAR_TERM);
+        }
+    });
+
+    it('ends war when both terms reach zero without casualties', () => {
+        const entries = [
+            buildEntry(1, 2, DIPLOMACY_STATE.WAR, 1),
+            buildEntry(2, 1, DIPLOMACY_STATE.WAR, 1),
+        ];
+        const result = processDiplomacyMonth(entries, new Map([[1, 1], [2, 1]]));
+
+        for (const entry of result) {
+            expect(entry.state).toBe(DIPLOMACY_STATE.TRADE);
+            expect(entry.term).toBe(0);
+        }
+    });
+
+    it('extends war term based on accumulated casualties', () => {
+        const entries = [
+            buildEntry(1, 2, DIPLOMACY_STATE.WAR, 3, 400),
+            buildEntry(2, 1, DIPLOMACY_STATE.WAR, 3, 0),
+        ];
+        const result = processDiplomacyMonth(entries, new Map([[1, 2], [2, 2]]));
+
+        const forward = result.find(
+            (entry) => entry.fromNationId === 1 && entry.toNationId === 2
+        );
+        const reverse = result.find(
+            (entry) => entry.fromNationId === 2 && entry.toNationId === 1
+        );
+        expect(forward?.term).toBe(4);
+        expect(forward?.dead).toBe(0);
+        expect(reverse?.term).toBe(2);
+    });
+
+    it('expires non-aggression pact into trade', () => {
+        const entries = [
+            buildEntry(1, 2, DIPLOMACY_STATE.NON_AGGRESSION, 1),
+            buildEntry(2, 1, DIPLOMACY_STATE.NON_AGGRESSION, 1),
+        ];
+        const result = processDiplomacyMonth(entries, new Map([[1, 1], [2, 1]]));
+
+        for (const entry of result) {
+            expect(entry.state).toBe(DIPLOMACY_STATE.TRADE);
+            expect(entry.term).toBe(0);
+        }
+    });
+});

app/game-engine/test/scenarioSeeder.test.ts

@@ -21,7 +21,7 @@ type ScenarioSeederPrismaClient = {
         count(): Promise<number>;
         findFirst(args: {
             where: { srcNationId: number; destNationId: number };
-        }): Promise<{ stateCode: string } | null>;
+        }): Promise<{ stateCode: number; term: number } | null>;
     };
 };
 
@@ -68,7 +68,9 @@ describeDb('scenario database seed', () => {
             expect(nationCount).toBe(seed.nations.length);
             expect(cityCount).toBe(seed.cities.length);
             expect(generalCount).toBe(seed.generals.length);
-            expect(diplomacyCount).toBe(seed.diplomacy.length);
+            expect(diplomacyCount).toBe(
+                seed.nations.length * Math.max(0, seed.nations.length - 1)
+            );
             expect(generalCount).toBeGreaterThan(0);
 
             if (seed.diplomacy.length > 0) {
@@ -82,6 +84,18 @@ describeDb('scenario database seed', () => {
                 expect(row).not.toBeNull();
                 if (row) {
                     expect(row.stateCode).toBe(sample.state);
+                    expect(row.term).toBe(sample.durationMonths);
+                }
+                const reverse = await prisma.diplomacy.findFirst({
+                    where: {
+                        srcNationId: sample.toNationId,
+                        destNationId: sample.fromNationId,
+                    },
+                });
+                expect(reverse).not.toBeNull();
+                if (reverse) {
+                    expect(reverse.stateCode).toBe(sample.state);
+                    expect(reverse.term).toBe(sample.durationMonths);
                 }
             }
         } finally {