feat: Implemented Delta generator for time advancement

packages/core/src/entity.ts

@@ -1,7 +1,22 @@
 import { AttributableObject } from "./attribute.js";
 
 export class Entity extends AttributableObject {
-  constructor(id?: string) {
+  locationId: string | null = null;
+
+  constructor(id?: string, locationId?: string | null) {
     super(id);
+    this.locationId = locationId ?? null;
+  }
+
+  override serialize(): string {
+    const lines: string[] = [];
+    if (this.locationId) {
+      lines.push(`* Location ID: ${this.locationId}`);
+    }
+    const selfSerialized = super.serialize();
+    if (selfSerialized) {
+      lines.push(selfSerialized);
+    }
+    return lines.join("\n");
   }
 }

packages/core/src/repository.ts

@@ -21,6 +21,7 @@ export class SQLiteRepository {
         type TEXT NOT NULL,
         world_id TEXT,
         clock_iso TEXT,
+        location_id TEXT,
         FOREIGN KEY (world_id) REFERENCES objects(id) ON DELETE CASCADE
       );
 
@@ -48,6 +49,13 @@ export class SQLiteRepository {
     } catch {
       // Column already exists, ignore error
     }
+
+    // Safely add location_id column if it does not exist in an existing database
+    try {
+      this.db.exec("ALTER TABLE objects ADD COLUMN location_id TEXT;");
+    } catch {
+      // Column already exists, ignore error
+    }
   }
 
   save(obj: AttributableObject, type: string, worldId?: string): void {
@@ -57,19 +65,25 @@ export class SQLiteRepository {
         clockIso = obj.clock.get().toISOString();
       }
 
+      let locationId: string | null = null;
+      if (obj instanceof Entity) {
+        locationId = obj.locationId;
+      }
+
       // 1. Insert or ignore the object in the objects table
       this.db
         .prepare(
           `
-        INSERT INTO objects (id, type, world_id, clock_iso)
-        VALUES (?, ?, ?, ?)
+        INSERT INTO objects (id, type, world_id, clock_iso, location_id)
+        VALUES (?, ?, ?, ?, ?)
         ON CONFLICT(id) DO UPDATE SET 
           type = excluded.type, 
           world_id = excluded.world_id,
-          clock_iso = excluded.clock_iso
+          clock_iso = excluded.clock_iso,
+          location_id = excluded.location_id
       `,
         )
-        .run(obj.id, type, worldId || null, clockIso);
+        .run(obj.id, type, worldId || null, clockIso, locationId);
 
       // Get current attributes from db to delete the ones that are no longer present
       const existingAttrs = this.db
@@ -155,16 +169,16 @@ export class SQLiteRepository {
     const objRow = this.db
       .prepare(
         `
-      SELECT type FROM objects WHERE id = ?
+      SELECT type, location_id FROM objects WHERE id = ?
     `,
       )
-      .get(id) as { type: string } | undefined;
+      .get(id) as { type: string; location_id: string | null } | undefined;
 
     if (!objRow || objRow.type !== "entity") {
       return null;
     }
 
-    const entity = new Entity(id);
+    const entity = new Entity(id, objRow.location_id);
     this.reconstituteAttributes(entity);
     return entity;
   }
@@ -190,13 +204,13 @@ export class SQLiteRepository {
     const entityRows = this.db
       .prepare(
         `
-      SELECT id FROM objects WHERE type = 'entity' AND world_id = ?
+      SELECT id, location_id FROM objects WHERE type = 'entity' AND world_id = ?
     `,
       )
-      .all(id) as { id: string }[];
+      .all(id) as { id: string; location_id: string | null }[];
 
     for (const row of entityRows) {
-      const entity = new Entity(row.id);
+      const entity = new Entity(row.id, row.location_id);
       this.reconstituteAttributes(entity);
       worldState.addEntity(entity);
     }

packages/core/tests/core.test.ts

@@ -126,7 +126,7 @@ describe("SQLiteRepository Unit Tests (Tier 1)", () => {
     world.addAttribute("location", "Outer Rim", AttributeVisibility.PUBLIC);
 
     // 2. Setup Entities and add attributes with ACL grants
-    const alice = new Entity("alice");
+    const alice = new Entity("alice", "location-a");
     alice.addAttribute("name", "Alice Smith", AttributeVisibility.PUBLIC);
     // Secret attribute visible only to 'bob'
     alice.addAttribute("diaries", "Private thoughts", AttributeVisibility.PRIVATE, new Set(["bob"]));
@@ -156,6 +156,8 @@ describe("SQLiteRepository Unit Tests (Tier 1)", () => {
     expect(loadedBob).toBeDefined();
 
     // 7. Assert entity attributes and access controls are preserved
+    expect(loadedAlice!.locationId).toBe("location-a");
+    expect(loadedBob!.locationId).toBeNull();
     expect(loadedAlice!.attributes.get("name")?.getValue()).toBe("Alice Smith");
     expect(loadedAlice!.attributes.get("name")?.visibility).toBe(AttributeVisibility.PUBLIC);
 
@@ -184,7 +186,7 @@ describe("Serializer Unit Tests (Tier 1)", () => {
     const world = new WorldState("world-1");
     world.addAttribute("gravity", "9.8", AttributeVisibility.PUBLIC);
 
-    const alice = new Entity("alice");
+    const alice = new Entity("alice", "location-a");
     alice.addAttribute("role", "warrior", AttributeVisibility.PUBLIC);
     world.addEntity(alice);
 
@@ -196,6 +198,7 @@ describe("Serializer Unit Tests (Tier 1)", () => {
     expect(result).toContain("  * gravity: 9.8 (Visibility: PUBLIC)");
     expect(result).toContain("Entities:");
     expect(result).toContain("  - Entity [ID: alice]:");
+    expect(result).toContain("      * Location ID: location-a");
     expect(result).toContain("      * role: warrior (Visibility: PUBLIC)");
     expect(result).toContain("  - Entity [ID: bob]:");
     expect(result).toContain("      * (No attributes)");