#异步任务与 Celery：处理耗时的后台任务

# app/celery_app.py
from celery import Celery

# 1. 初始化 Celery 核心实例
celery_app = Celery(
    main="daoman",  # 项目名，用于日志/任务命名空间
    broker="redis://localhost:6379/0",  # Broker：存待处理的任务
    backend="redis://localhost:6379/1",  # Backend：存任务执行结果/状态
)

# 2. 补充通用配置（生产环境建议用单独的config类加载）
celery_app.conf.update(
    # 序列化格式：用 JSON 兼容性最好，但不能传函数/类
    task_serializer="json",
    result_serializer="json",
    accept_content=["json"],
    # 时区设置：和项目时区保持一致
    timezone="Asia/Shanghai",
    enable_utc=False,
    # 任务追踪：开启后能看到任务是否「已开始」
    task_track_started=True,
    # 超时保护：避免某个任务卡死Worker
    task_time_limit=300,  # 硬超时：5分钟后强制杀掉Worker进程
    task_soft_time_limit=270,  # 软超时：4.5分钟后抛出异常，可捕获处理
)

# app/tasks/image_tasks.py
import os
from PIL import Image
from PIL.UnidentifiedImageError import UnidentifiedImageError
from app.celery_app import celery_app

@celery_app.task(bind=True, name="tasks.compress_image")  # bind=True 可以获取 self（当前任务实例）
def compress_image(
    self,
    temp_path: str,
    output_path: str,
    quality: int = 85,
    max_width: int = 1920,
    max_height: int = 1080,
):
    """后台压缩图片：统一转JPG、限制尺寸、删除临时图"""
    try:
        # 1. 读取并转换格式
        with Image.open(temp_path) as img:
            # 只保留RGB（丢弃Alpha通道，适配JPG）
            if img.mode in ("RGBA", "P"):
                img = img.convert("RGB")
            # 等比例缩放（不超过最大宽高）
            img.thumbnail((max_width, max_height), Image.Resampling.LANCZOS)
            # 保存压缩后的图片
            img.save(output_path, "JPEG", quality=quality, optimize=True)
        
        # 2. 压缩成功后删除临时原图
        if os.path.exists(temp_path):
            os.remove(temp_path)
        
        # 3. 返回结果（会存到Backend）
        return {"status": "success", "path": output_path}

    except UnidentifiedImageError as e:
        # 捕获非图片格式的错误
        self.retry(exc=e, countdown=5, max_retries=2)  # 5秒后重试，最多2次
    except Exception as e:
        # 捕获其他错误（比如磁盘满、权限不足）
        return {"status": "error", "msg": str(e)}

# app/tasks/mail_tasks.py
from flask import current_app  # 生产环境要确保Flask应用上下文可用！
from flask_mail import Message
from app.celery_app import celery_app
from app.extensions import mail

@celery_app.task(name="tasks.send_welcome_email")
def send_welcome_email(user_email: str, username: str):
    """后台发送注册欢迎邮件（带HTML更好看，但这里简化）"""
    try:
        # 生产环境需要手动激活Flask应用上下文，因为Worker和Web进程是分离的
        with current_app.app_context():
            msg = Message(
                subject=f"🎉 欢迎来到{current_app.config['SITE_NAME']}！",
                recipients=[user_email],
                body=f"亲爱的 {username}，\n\n感谢注册道满博客！\n\n你可以开始发布文章、评论互动了～\n\n道满博客团队",
            )
            mail.send(msg)
        return {"status": "success", "to": user_email}
    except Exception as e:
        return {"status": "error", "msg": str(e)}

# app/routes/upload.py
import os
from flask import Blueprint, request, jsonify, current_app
from flask_login import login_required, current_user
from app.tasks.image_tasks import compress_image

upload_bp = Blueprint("upload", __name__, url_prefix="/api/upload")

@upload_bp.route("/avatar", methods=["POST"])
@login_required
def upload_avatar():
    # 1. 接收并保存临时原图
    file = request.files.get("avatar")
    if not file or not file.filename:
        return jsonify({"code": 400, "msg": "请上传头像"}), 400
    
    # 生成临时文件名（用UUID更安全）
    import uuid
    temp_name = f"temp_{current_user.id}_{uuid.uuid4().hex}{os.path.splitext(file.filename)[0]}.png"
    temp_path = os.path.join(current_app.config["TEMP_UPLOAD_FOLDER"], temp_name)
    file.save(temp_path)

    # 2. 生成压缩后的文件名
    compressed_name = f"avatar_{current_user.id}_{uuid.uuid4().hex}.jpg"
    compressed_path = os.path.join(current_app.config["AVATAR_UPLOAD_FOLDER"], compressed_name)

    # 3. 提交后台压缩任务（用delay简化调用）
    task = compress_image.delay(
        temp_path=temp_path,
        output_path=compressed_path,
        quality=90,  # 头像质量可以稍高
        max_width=256,
        max_height=256,
    )

    # 4. 立即返回任务ID和临时状态
    return jsonify({
        "code": 200,
        "msg": "头像上传中，请稍后刷新",
        "data": {"task_id": task.id, "state": task.state},
    })

# app/routes/task.py
from flask import Blueprint, jsonify
from app.celery_app import celery_app

task_bp = Blueprint("task", __name__, url_prefix="/api/task")

@task_bp.route("/<task_id>", methods=["GET"])
def get_task_status(task_id):
    # 用AsyncResult获取任意任务的状态（不管是哪个模块的）
    task = celery_app.AsyncResult(task_id)
    
    response = {
        "code": 200,
        "data": {
            "task_id": task.id,
            "state": task.state,  # PENDING/STARTED/SUCCESS/FAILURE/RETRY
        },
    }

    # 只有任务完成（SUCCESS/FAILURE）才返回结果
    if task.ready():
        response["data"]["result"] = task.result
    
    return jsonify(response)