"""
图片加载工具
用于从URL加载图片并转换为PIL/CTkImage格式
优化版本:使用连接池、线程池和缓存
"""
import io
import requests
from PIL import Image
from typing import Optional
import customtkinter as ctk
from concurrent.futures import ThreadPoolExecutor
from functools import lru_cache
import threading


# ======================== 全局资源管理 ========================

# HTTP会话(连接池)
_session = None
_session_lock = threading.Lock()

def get_session() -> requests.Session:
    """获取全局HTTP会话(单例模式)"""
    global _session
    if _session is None:
        with _session_lock:
            if _session is None:
                _session = requests.Session()
                # 配置连接池
                adapter = requests.adapters.HTTPAdapter(
                    pool_connections=10,  # 连接池大小
                    pool_maxsize=20,      # 最大连接数
                    max_retries=2,        # 重试次数
                    pool_block=False
                )
                _session.mount('http://', adapter)
                _session.mount('https://', adapter)
    return _session


# 线程池(用于图片加载)
_thread_pool = None
_thread_pool_lock = threading.Lock()

def get_thread_pool() -> ThreadPoolExecutor:
    """获取全局线程池(单例模式)"""
    global _thread_pool
    if _thread_pool is None:
        with _thread_pool_lock:
            if _thread_pool is None:
                # 限制最多同时加载10张图片
                _thread_pool = ThreadPoolExecutor(
                    max_workers=10,
                    thread_name_prefix="ImageLoader"
                )
    return _thread_pool


# ======================== 图片加载函数 ========================

def load_image_from_url(
    url: str,
    size: tuple = (150, 150),
    timeout: int = 5  # 降低超时时间,避免长时间阻塞
) -> Optional[ctk.CTkImage]:
    """
    从URL加载图片(使用连接池)
    
    Args:
        url: 图片URL
        size: 目标尺寸 (width, height)
        timeout: 超时时间(秒)
    
    Returns:
        CTkImage对象,失败返回None
    """
    try:
        # 使用全局session(连接复用)
        session = get_session()
        
        # 下载图片
        response = session.get(url, timeout=timeout)
        response.raise_for_status()
        
        # 转换为PIL Image
        image_data = io.BytesIO(response.content)
        pil_image = Image.open(image_data)
        
        # 转换为RGB(防止RGBA等格式问题)
        if pil_image.mode != 'RGB':
            pil_image = pil_image.convert('RGB')
        
        # 创建CTkImage
        ctk_image = ctk.CTkImage(
            light_image=pil_image,
            dark_image=pil_image,
            size=size
        )
        
        return ctk_image
        
    except requests.exceptions.Timeout:
        print(f"加载图片超时: {url}")
        return None
    except requests.exceptions.RequestException as e:
        print(f"网络请求失败 {url}: {e}")
        return None
    except Exception as e:
        print(f"加载图片失败 {url}: {e}")
        return None


@lru_cache(maxsize=100)
def create_placeholder_image(
    size: tuple = (150, 150),
    text: str = "加载失败"
) -> ctk.CTkImage:
    """
    创建占位图片(带缓存)
    
    Args:
        size: 图片尺寸
        text: 显示文字
    
    Returns:
        CTkImage对象
    """
    # 创建灰色背景图片
    pil_image = Image.new('RGB', size, color=(200, 200, 200))
    
    ctk_image = ctk.CTkImage(
        light_image=pil_image,
        dark_image=pil_image,
        size=size
    )
    
    return ctk_image


def cleanup_resources():
    """清理全局资源(程序退出时调用)"""
    global _session, _thread_pool
    
    # 关闭线程池
    if _thread_pool is not None:
        _thread_pool.shutdown(wait=False)
        _thread_pool = None
    
    # 关闭HTTP会话
    if _session is not None:
        _session.close()
        _session = None