from typing import Optional, Dict


def calculate_natural_cpm(
    estimated_video_cost: float,
    natural_play_cnt: int,
) -> Optional[float]:
    """
    计算预估自然CPM.

    公式: estimated_video_cost / natural_play_cnt * 1000

    Args:
        estimated_video_cost: 预估视频成本
        natural_play_cnt: 自然播放量

    Returns:
        预估自然CPM (元/千次曝光), 除零时返回 None
    """
    if natural_play_cnt <= 0:
        return None
    return round((estimated_video_cost / natural_play_cnt) * 1000, 2)


def calculate_natural_search_uv(
    natural_play_cnt: int,
    total_play_cnt: int,
    after_view_search_uv: int,
) -> Optional[float]:
    """
    计算预估自然看后搜人数.

    公式: natural_play_cnt / total_play_cnt * after_view_search_uv

    Args:
        natural_play_cnt: 自然播放量
        total_play_cnt: 总播放量
        after_view_search_uv: 看后搜人数

    Returns:
        预估自然看后搜人数, 除零时返回 None
    """
    if total_play_cnt <= 0:
        return None
    return round((natural_play_cnt / total_play_cnt) * after_view_search_uv, 2)


def calculate_natural_search_cost(
    estimated_video_cost: float,
    estimated_natural_search_uv: Optional[float],
) -> Optional[float]:
    """
    计算预估自然看后搜人数成本.

    公式: estimated_video_cost / 预估自然看后搜人数

    Args:
        estimated_video_cost: 预估视频成本
        estimated_natural_search_uv: 预估自然看后搜人数

    Returns:
        预估自然看后搜人数成本 (元/人), 除零时返回 None
    """
    if estimated_natural_search_uv is None or estimated_natural_search_uv <= 0:
        return None
    return round(estimated_video_cost / estimated_natural_search_uv, 2)


def calculate_metrics(
    estimated_video_cost: float,
    natural_play_cnt: int,
    total_play_cnt: int,
    after_view_search_uv: int,
) -> Dict[str, Optional[float]]:
    """
    批量计算所有预估指标.

    Args:
        estimated_video_cost: 预估视频成本
        natural_play_cnt: 自然播放量
        total_play_cnt: 总播放量
        after_view_search_uv: 看后搜人数

    Returns:
        包含所有计算结果的字典
    """
    # 计算 CPM
    cpm = calculate_natural_cpm(estimated_video_cost, natural_play_cnt)

    # 计算看后搜人数
    search_uv = calculate_natural_search_uv(
        natural_play_cnt, total_play_cnt, after_view_search_uv
    )

    # 计算看后搜成本
    search_cost = calculate_natural_search_cost(estimated_video_cost, search_uv)

    return {
        "estimated_natural_cpm": cpm,
        "estimated_natural_search_uv": search_uv,
        "estimated_natural_search_cost": search_cost,
    }