class MockDataSource:
    """模拟数据源，用于测试"""
    def __init__(self, data):
        self.data = iter(data)
    
    def __iter__(self):
        return self
    
    def __next__(self):
        return next(self.data)

class RecordCollection:
    """记录集合类，支持惰性加载和缓存"""
    def __init__(self, rows):
        self._rows = iter(rows)
        self._all_rows = []
        self.pending = True

    def __len__(self):
        return len(self._all_rows)

    def __iter__(self):
        """遍历所有行，仅在必要时消耗底层生成器"""
        i = 0
        while True:
            if i < len(self):
                yield self[i]
            else:
                try:
                    yield next(self)
                except StopIteration:
                    return
            i += 1

    def __getitem__(self, index):
        """获取指定索引的记录"""
        return self._all_rows[index]

    def __next__(self):
        try:
            nextrow = next(self._rows)
            self._all_rows.append(nextrow)
            return nextrow
        except StopIteration:
            self.pending = False
            raise StopIteration("RecordCollection contains no more rows.")

def test_record_collection():
    # 测试数据
    test_data = [
        {"id": 1, "name": "张三"},
        {"id": 2, "name": "李四"},
        {"id": 3, "name": "王五"}
    ]
    
    # 创建数据源和记录集合
    data_source = MockDataSource(test_data)
    records = RecordCollection(data_source)
    
    print("测试1：逐个获取数据")
    print(f"当前缓存大小: {len(records)}")  # 应该是 0
    
    # 获取第一条记录
    first_record = next(records)
    print(f"第一条记录: {first_record}")
    print(f"当前缓存大小: {len(records)}")  # 应该是 1
    
    print("\n测试2：使用for循环遍历")
    for record in records:
        print(f"读取记录: {record}")
    
    print(f"\n遍历后缓存大小: {len(records)}")  # 应该是 3
    print(f"是否还有待处理数据: {records.pending}")  # 应该是 False
    
    print("\n测试3：再次遍历（从缓存读取）")
    for record in records:
        print(f"{record}")

if __name__ == "__main__":
    test_record_collection()