"""
向量计算工具类
包含 ResNet50 特征提取、向量归一化等功能
"""
import io
import logging
import numpy as np
import torch
from torchvision import models, transforms
from PIL import Image
from minio import Minio

from app.core.config import settings
from app.service.recommendation_system.config import RECOMMENDATION_CONFIG

logger = logging.getLogger(__name__)

# 图像预处理（与ResNet训练时的预处理一致）
transform = transforms.Compose([
    transforms.Resize((224, 224)),  # ResNet 要求 224x224 的输入
    transforms.ToTensor(),  # 转换为 Tensor
    transforms.Normalize(mean=[0.485, 0.456, 0.406], std=[0.229, 0.224, 0.225]),  # 标准化
])

# 加载预训练的 ResNet50 模型（去掉最后全连接层）
_resnet_model = None


def get_resnet_model():
    """获取 ResNet50 模型（单例模式）"""
    global _resnet_model
    if _resnet_model is None:
        logger.info("加载 ResNet50 模型...")
        _resnet_model = models.resnet50(pretrained=True)
        modules = list(_resnet_model.children())[:-1]  # 移除最后的全连接层
        _resnet_model = torch.nn.Sequential(*modules)
        _resnet_model.eval()  # 设置为评估模式
        logger.info("ResNet50 模型加载完成")
    return _resnet_model


# MinIO 客户端（单例）
_minio_client = None


def get_minio_client():
    """获取 MinIO 客户端（单例模式）"""
    global _minio_client
    if _minio_client is None:
        _minio_client = Minio(
            settings.MINIO_URL,
            access_key=settings.MINIO_ACCESS,
            secret_key=settings.MINIO_SECRET,
            secure=settings.MINIO_SECURE
        )
    return _minio_client


def get_image_from_minio(path: str) -> Image.Image:
    """
    从 MinIO 获取图片
    
    Args:
        path: MinIO 逻辑 URL，格式如 "bucket_name/object_name"
    
    Returns:
        PIL Image 对象，失败返回 None
    """
    try:
        # 分割路径，获取桶名和文件路径
        path_parts = path.split('/', 1)
        if len(path_parts) != 2:
            logger.error(f"路径格式错误: {path}")
            return None
        
        bucket_name, file_name = path_parts
        minio_client = get_minio_client()
        
        # 获取文件
        obj = minio_client.get_object(bucket_name, file_name)
        img_data = obj.read()  # 读取图像数据
        img = Image.open(io.BytesIO(img_data))  # 将数据转为图像对象
        
        return img
    except Exception as e:
        logger.error(f"从 MinIO 获取图片失败 [{path}]: {e}")
        return None


def extract_feature_vector(path: str) -> np.ndarray:
    """
    使用 ResNet50 提取图片特征向量（2048维）
    
    Args:
        path: MinIO 逻辑 URL
    
    Returns:
        2048维特征向量（numpy array），失败返回零向量
    """
    try:
        # 从 MinIO 获取图像
        img = get_image_from_minio(path)
        if img is None:
            logger.warning(f"无法获取图片，返回零向量: {path}")
            return np.zeros(RECOMMENDATION_CONFIG["vector_dim"], dtype=np.float32)
        
        # 预处理
        # 部分 MinIO 图片可能是 RGBA/CMYK，转换成 RGB 以匹配 3 通道标准化参数
        if img.mode != "RGB":
            try:
                img = img.convert("RGB")
            except Exception:
                logger.warning(f"无法转换图片为RGB，返回零向量: {path}")
                return np.zeros(RECOMMENDATION_CONFIG["vector_dim"], dtype=np.float32)

        img_tensor = transform(img).unsqueeze(0)  # 扩展维度以适应批量处理
        
        # 提取特征
        resnet_model = get_resnet_model()
        with torch.no_grad():  # 在不需要计算梯度的情况下进行推断
            feature_vector = resnet_model(img_tensor)  # 获取 ResNet 的输出
            feature_vector = feature_vector.squeeze().cpu().numpy()  # 转换为 NumPy 数组并去掉 batch 维度
        
        # 确保是 2048 维
        if feature_vector.ndim > 1:
            feature_vector = feature_vector.flatten()
        
        # 确保维度正确
        if len(feature_vector) != RECOMMENDATION_CONFIG["vector_dim"]:
            logger.warning(f"向量维度不正确: {len(feature_vector)}, 期望: {RECOMMENDATION_CONFIG['vector_dim']}")
            # 如果维度不对，尝试调整
            if len(feature_vector) > RECOMMENDATION_CONFIG["vector_dim"]:
                feature_vector = feature_vector[:RECOMMENDATION_CONFIG["vector_dim"]]
            else:
                padded = np.zeros(RECOMMENDATION_CONFIG["vector_dim"], dtype=np.float32)
                padded[:len(feature_vector)] = feature_vector
                feature_vector = padded
        
        return feature_vector.astype(np.float32)
    except Exception as e:
        logger.error(f"提取特征向量失败 [{path}]: {e}", exc_info=True)
        return np.zeros(RECOMMENDATION_CONFIG["vector_dim"], dtype=np.float32)


def normalize_vector(vector: np.ndarray) -> np.ndarray:
    """
    L2 归一化向量
    
    Args:
        vector: 输入向量
    
    Returns:
        归一化后的向量
    """
    norm = np.linalg.norm(vector)
    if norm == 0:
        return vector
    return vector / norm


def compute_weighted_average(vectors: list, weights: list) -> np.ndarray:
    """
    计算加权平均向量
    
    Args:
        vectors: 向量列表
        weights: 权重列表
    
    Returns:
        加权平均向量（不做归一化，模长为加权平均后的尺度）
    """
    if not vectors or not weights:
        return np.zeros(RECOMMENDATION_CONFIG["vector_dim"], dtype=np.float32)
    
    # 确保所有向量都是 numpy array
    vectors = [np.array(v) for v in vectors]
    weights = np.array(weights)
    
    # 计算加权和
    weighted_sum = np.zeros_like(vectors[0])
    for v, w in zip(vectors, weights):
        weighted_sum += v * w
    
    # 返回加权平均（除以权重和，不做 L2 归一化，模长不会随条数线性暴涨）
    weight_total = weights.sum()
    if weight_total == 0:
        return weighted_sum
    return weighted_sum / weight_total