import { ObjectPool } from '@common/ObjectPool';

interface Bullet {
    x: number;
    alive: boolean;
}

const makeBullet = (): Bullet => ({ x: 0, alive: false });
const resetBullet = (b: Bullet): void => {
    b.x = 0;
    b.alive = false;
};

describe('ObjectPool', () => {
    it('creates new instances when the free list is empty', () => {
        const pool = new ObjectPool<Bullet>({ factory: makeBullet });
        const a = pool.acquire();
        const b = pool.acquire();
        expect(a).not.toBe(b);
        expect(pool.stats().created).toBe(2);
        expect(pool.borrowedCount).toBe(2);
        expect(pool.freeCount).toBe(0);
    });

    it('reuses instances after release', () => {
        const pool = new ObjectPool<Bullet>({ factory: makeBullet, resetter: resetBullet });
        const a = pool.acquire();
        a.x = 100;
        a.alive = true;
        pool.release(a);
        expect(a.x).toBe(0);
        expect(a.alive).toBe(false);
        const b = pool.acquire();
        expect(b).toBe(a);
        expect(pool.stats().recycled).toBe(1);
    });

    it('pre-allocates instances when preAlloc is set', () => {
        const pool = new ObjectPool<Bullet>({ factory: makeBullet, preAlloc: 5 });
        expect(pool.freeCount).toBe(5);
        expect(pool.stats().created).toBe(5);
    });

    it('discards excess releases when over maxSize', () => {
        const pool = new ObjectPool<Bullet>({ factory: makeBullet, maxSize: 2 });
        const a = pool.acquire();
        const b = pool.acquire();
        const c = pool.acquire();
        pool.release(a);
        pool.release(b);
        pool.release(c); // should be dropped
        expect(pool.freeCount).toBe(2);
    });

    it('fires onDoubleRelease and ignores double-release', () => {
        const spy = jest.fn();
        const pool = new ObjectPool<Bullet>({
            factory: makeBullet,
            onDoubleRelease: spy,
        });
        const a = pool.acquire();
        pool.release(a);
        pool.release(a);
        expect(spy).toHaveBeenCalledTimes(1);
        expect(pool.freeCount).toBe(1);
    });

    it('drain() clears both free and borrowed', () => {
        const pool = new ObjectPool<Bullet>({ factory: makeBullet, preAlloc: 3 });
        pool.acquire();
        pool.drain();
        expect(pool.freeCount).toBe(0);
        expect(pool.borrowedCount).toBe(0);
    });

    it('stats track acquired / recycled totals', () => {
        const pool = new ObjectPool<Bullet>({ factory: makeBullet });
        const a = pool.acquire();
        const b = pool.acquire();
        pool.release(a);
        pool.release(b);
        pool.acquire();
        const s = pool.stats();
        expect(s.acquired).toBe(3);
        expect(s.recycled).toBe(2);
        expect(s.created).toBe(2);
    });
});
