import os
from datetime import timedelta

class Config:
    """应用配置类"""
    
    # 基础配置
    SECRET_KEY = os.environ.get('SECRET_KEY') or 'dev-secret-key-change-in-production'
    
    # 数据库配置
    BASE_DIR = os.path.abspath(os.path.dirname(__file__))
    SQLALCHEMY_DATABASE_URI = os.environ.get('DATABASE_URL') or \
        'sqlite:///' + os.path.join(BASE_DIR, 'forum.db')
    SQLALCHEMY_TRACK_MODIFICATIONS = False
    
    # 文件上传配置
    UPLOAD_FOLDER = os.path.join(BASE_DIR, 'uploads')
    MAX_CONTENT_LENGTH = 16 * 1024 * 1024  # 16MB 最大文件大小
    ALLOWED_EXTENSIONS = {'png', 'jpg', 'jpeg', 'gif', 'webp'}
    
    # 会话配置
    PERMANENT_SESSION_LIFETIME = timedelta(days=7)
    
    # 分页配置
    POSTS_PER_PAGE = 20
    
    @staticmethod
    def init_app(app):
        """初始化应用配置"""
        # 确保上传目录存在
        os.makedirs(app.config['UPLOAD_FOLDER'], exist_ok=True)
        os.makedirs(os.path.join(app.config['UPLOAD_FOLDER'], 'student_ids'), exist_ok=True)
        os.makedirs(os.path.join(app.config['UPLOAD_FOLDER'], 'posts'), exist_ok=True)