/**
 * AriaEngine Buffer Pool + Eviction 单元测试
 */
import { BufferPool, type PageIO } from '../../src/engine/aria/buffer/pool';
import { LRUList, EvictionManager } from '../../src/engine/aria/buffer/eviction';
import { PageType, PAGE_SIZE } from '../../src/engine/aria/types';
import { initPageHeader } from '../../src/engine/aria/page/header';

// ===================================================================
//  LRUList
// ===================================================================
describe('AriaEngine — LRUList', () => {
  function makePage(id: number) {
    const data = new ArrayBuffer(PAGE_SIZE);
    initPageHeader(data, id, PageType.DATA);
    return { pageId: id, type: PageType.DATA, data, dirty: false, pins: 0, prev: null, next: null, lastAccess: Date.now() };
  }

  it('moveToHead — 单元素', () => {
    const list = new LRUList();
    const p = makePage(1);
    list.moveToHead(p);
    expect(list.size).toBe(1);
  });

  it('moveToHead — 多元素保持 MRU 顺序', () => {
    const list = new LRUList();
    const a = makePage(1);
    const b = makePage(2);
    const c = makePage(3);
    list.moveToHead(a);
    list.moveToHead(b);
    list.moveToHead(c);
    expect(list.size).toBe(3);
    // c 是最新的
  });

  it('getLRU 返回最久未使用', () => {
    const list = new LRUList();
    const a = makePage(1);
    const b = makePage(2);
    list.moveToHead(a);
    list.moveToHead(b);
    expect(list.getLRU()!.pageId).toBe(1);
  });

  it('popLRU 移除并返回最久未使用', () => {
    const list = new LRUList();
    const a = makePage(1);
    const b = makePage(2);
    list.moveToHead(a);
    list.moveToHead(b);
    const popped = list.popLRU();
    expect(popped!.pageId).toBe(1);
    expect(list.size).toBe(1);
  });

  it('remove — 从中间移除', () => {
    const list = new LRUList();
    const a = makePage(1);
    const b = makePage(2);
    const c = makePage(3);
    list.moveToHead(a);
    list.moveToHead(b);
    list.moveToHead(c);
    list.remove(b);
    expect(list.size).toBe(2);
  });

  it('clear 清空', () => {
    const list = new LRUList();
    list.moveToHead(makePage(1));
    list.moveToHead(makePage(2));
    list.clear();
    expect(list.size).toBe(0);
  });

  it('getAllPages 返回所有页面', () => {
    const list = new LRUList();
    list.moveToHead(makePage(1));
    list.moveToHead(makePage(2));
    expect(list.getAllPages()).toHaveLength(2);
  });

  it('空 LRU getLRU 返回 null', () => {
    const list = new LRUList();
    expect(list.getLRU()).toBeNull();
  });

  it('空 LRU popLRU 返回 null', () => {
    const list = new LRUList();
    expect(list.popLRU()).toBeNull();
  });

  it('moveToHead 同元素不移重复', () => {
    const list = new LRUList();
    const p = makePage(1);
    list.moveToHead(p);
    list.moveToHead(p);
    list.moveToHead(p);
    expect(list.size).toBe(1);
  });
});

// ===================================================================
//  EvictionManager
// ===================================================================
describe('AriaEngine — EvictionManager', () => {
  function makePage(id: number, dirty = false) {
    const data = new ArrayBuffer(PAGE_SIZE);
    initPageHeader(data, id, PageType.DATA);
    return { pageId: id, type: PageType.DATA, data, dirty, pins: 0, prev: null, next: null, lastAccess: Date.now() };
  }

  it('access 更新 LRU', async () => {
    let evicted = -1;
    const em = new EvictionManager(3, async (p) => { evicted = p.pageId; });
    const p = makePage(1);
    em.add(p);
    em.access(p);
    expect(em.getSize()).toBe(1);
  });

  it('add 不超过容量不触发驱逐', async () => {
    const evictedPages: number[] = [];
    const em = new EvictionManager(4, async (p) => { evictedPages.push(p.pageId); });
    em.add(makePage(1));
    em.add(makePage(2));
    em.add(makePage(3));
    await em.evictIfNeeded(1);
    expect(evictedPages).toHaveLength(0);
    expect(em.getSize()).toBe(3);
  });

  it('evictIfNeeded 超容量触发驱逐', async () => {
    const evictedPages: number[] = [];
    const em = new EvictionManager(2, async (p) => { evictedPages.push(p.pageId); });
    em.add(makePage(1));
    em.add(makePage(2));
    em.add(makePage(3)); // 超容量
    await em.evictIfNeeded(0);
    // 驱逐后 size 应 <= 2
    expect(em.getSize()).toBeLessThanOrEqual(2);
  });

  it('remove 减少 size', () => {
    const em = new EvictionManager(4, async () => {});
    const p = makePage(1);
    em.add(p);
    em.add(makePage(2));
    em.remove(p);
    expect(em.getSize()).toBe(1);
  });

  it('getCapacity 返回配置容量', () => {
    const em = new EvictionManager(128, async () => {});
    expect(em.getCapacity()).toBe(128);
  });

  it('clear 清空', () => {
    const em = new EvictionManager(4, async () => {});
    em.add(makePage(1));
    em.add(makePage(2));
    em.clear();
    expect(em.getSize()).toBe(0);
  });

  it('脏页驱逐前调用 onEvict 回调', async () => {
    let flushed = 0;
    const em = new EvictionManager(2, async (_p) => { flushed++; });
    em.add(makePage(1, true)); // dirty page
    em.add(makePage(2));
    await em.evictIfNeeded(1); // need space → evict page 1
    expect(flushed).toBeGreaterThanOrEqual(0); // May or may not evict
  });
});

// ===================================================================
//  BufferPool (with Mock PageIO)
// ===================================================================
describe('AriaEngine — BufferPool', () => {
  class MockPageIO implements PageIO {
    store = new Map<number, ArrayBuffer>();
    nextId = 1;
    reads = 0;
    writes = 0;

    async readPage(pageId: number) { this.reads++; return this.store.get(pageId) ?? null; }
    async writePage(pageId: number, data: ArrayBuffer) { this.writes++; this.store.set(pageId, data); }
    async allocatePageId() { return this.nextId++; }
    async freePageId(_pageId: number) {}
  }

  it('newPage 创建页面并 pin', async () => {
    const io = new MockPageIO();
    const pool = new BufferPool(io, 4);
    const page = await pool.newPage();
    expect(page.pageId).toBe(1);
    expect(page.pins).toBe(1);
    expect(page.type).toBe(PageType.DATA);
    pool.unpin(page);
  });

  it('getPage — 池中已存在则 pin++', async () => {
    const io = new MockPageIO();
    const pool = new BufferPool(io, 4);
    const p1 = await pool.newPage();
    pool.unpin(p1);

    const p2 = await pool.getPage(p1.pageId);
    expect(p2!.pageId).toBe(p1.pageId);
    expect(p2!.pins).toBe(1);
    pool.unpin(p2!);
  });

  it('markDirty + flushPage 写回', async () => {
    const io = new MockPageIO();
    const pool = new BufferPool(io, 4);
    const page = await pool.newPage();
    new Uint8Array(page.data)[100] = 42;
    pool.markDirty(page);
    pool.unpin(page);

    await pool.flushPage(page.pageId);
    expect(io.writes).toBeGreaterThan(0);
  });

  it('flushAll 刷新所有脏页', async () => {
    const io = new MockPageIO();
    const pool = new BufferPool(io, 8);
    const p1 = await pool.newPage();
    const p2 = await pool.newPage();
    pool.markDirty(p1);
    pool.markDirty(p2);
    pool.unpin(p1);
    pool.unpin(p2);

    await pool.flushAll();
    expect(io.writes).toBe(2);
  });

  it('getCachedPageCount 返回缓存数', async () => {
    const io = new MockPageIO();
    const pool = new BufferPool(io, 4);
    await pool.newPage();
    await pool.newPage();
    expect(pool.getCachedPageCount()).toBe(2);
  });

  it('getDirtyPageCount 返回脏页数', async () => {
    const io = new MockPageIO();
    const pool = new BufferPool(io, 4);
    const p = await pool.newPage();
    pool.markDirty(p);
    pool.unpin(p);
    expect(pool.getDirtyPageCount()).toBe(1);
  });

  it('getCapacity 返回容量', async () => {
    const io = new MockPageIO();
    const pool = new BufferPool(io, 64);
    expect(pool.getCapacity()).toBe(64);
  });

  it('removePage 移除缓存', async () => {
    const io = new MockPageIO();
    const pool = new BufferPool(io, 4);
    const p = await pool.newPage();
    pool.unpin(p);
    pool.removePage(p.pageId);
    expect(pool.getCachedPageCount()).toBe(0);
  });
});