from datetime import datetime
from flask_sqlalchemy import SQLAlchemy
from flask_login import UserMixin
from werkzeug.security import generate_password_hash, check_password_hash

db = SQLAlchemy()


class User(UserMixin, db.Model):
    """用户模型"""
    __tablename__ = 'users'
    
    id = db.Column(db.Integer, primary_key=True)
    username = db.Column(db.String(80), unique=True, nullable=False, index=True)
    email = db.Column(db.String(120), unique=True, nullable=False, index=True)
    password_hash = db.Column(db.String(255), nullable=False)
    
    # 学生身份验证
    student_id_photo = db.Column(db.String(255))  # 学生证照片路径
    is_approved = db.Column(db.Boolean, default=False)  # 是否通过审核
    
    # 权限
    is_admin = db.Column(db.Boolean, default=False)
    password_changed = db.Column(db.Boolean, default=True)  # 管理员首次登录需修改密码
    
    # 个人信息
    bio = db.Column(db.Text)
    avatar = db.Column(db.String(255))
    
    # 时间戳
    created_at = db.Column(db.DateTime, default=datetime.utcnow, index=True)
    
    # 关系
    posts = db.relationship('Post', backref='author', lazy='dynamic', cascade='all, delete-orphan')
    comments = db.relationship('Comment', backref='author', lazy='dynamic', cascade='all, delete-orphan')
    
    # 关注关系
    following = db.relationship(
        'Follow',
        foreign_keys='Follow.follower_id',
        backref='follower',
        lazy='dynamic',
        cascade='all, delete-orphan'
    )
    followers = db.relationship(
        'Follow',
        foreign_keys='Follow.following_id',
        backref='following',
        lazy='dynamic',
        cascade='all, delete-orphan'
    )
    
    def set_password(self, password):
        """设置密码"""
        self.password_hash = generate_password_hash(password)
    
    def check_password(self, password):
        """验证密码"""
        return check_password_hash(self.password_hash, password)
    
    def is_following(self, user):
        """检查是否关注了某用户"""
        return self.following.filter_by(following_id=user.id).first() is not None
    
    def follow(self, user):
        """关注用户"""
        if not self.is_following(user):
            follow = Follow(follower_id=self.id, following_id=user.id)
            db.session.add(follow)
    
    def unfollow(self, user):
        """取消关注"""
        follow = self.following.filter_by(following_id=user.id).first()
        if follow:
            db.session.delete(follow)
    
    def get_follower_count(self):
        """获取粉丝数"""
        return self.followers.count()
    
    def get_following_count(self):
        """获取关注数"""
        return self.following.count()
    
    def __repr__(self):
        return f'<User {self.username}>'


class Post(db.Model):
    """帖子模型"""
    __tablename__ = 'posts'
    
    id = db.Column(db.Integer, primary_key=True)
    user_id = db.Column(db.Integer, db.ForeignKey('users.id'), nullable=False, index=True)
    
    # 内容
    image_path = db.Column(db.String(255), nullable=False)
    description = db.Column(db.Text)
    
    # 审核状态
    is_approved = db.Column(db.Boolean, default=False, index=True)
    
    # 时间戳
    created_at = db.Column(db.DateTime, default=datetime.utcnow, index=True)
    
    # 关系
    comments = db.relationship('Comment', backref='post', lazy='dynamic', cascade='all, delete-orphan')
    
    def get_comment_count(self):
        """获取评论数"""
        return self.comments.count()
    
    def __repr__(self):
        return f'<Post {self.id}>'


class Comment(db.Model):
    """评论模型"""
    __tablename__ = 'comments'
    
    id = db.Column(db.Integer, primary_key=True)
    post_id = db.Column(db.Integer, db.ForeignKey('posts.id'), nullable=False, index=True)
    user_id = db.Column(db.Integer, db.ForeignKey('users.id'), nullable=False, index=True)
    
    # 内容
    content = db.Column(db.Text, nullable=False)
    
    # 时间戳
    created_at = db.Column(db.DateTime, default=datetime.utcnow, index=True)
    
    def __repr__(self):
        return f'<Comment {self.id}>'


class Follow(db.Model):
    """关注关系模型"""
    __tablename__ = 'follows'
    
    id = db.Column(db.Integer, primary_key=True)
    follower_id = db.Column(db.Integer, db.ForeignKey('users.id'), nullable=False, index=True)
    following_id = db.Column(db.Integer, db.ForeignKey('users.id'), nullable=False, index=True)
    created_at = db.Column(db.DateTime, default=datetime.utcnow)
    
    # 确保同一用户不能重复关注
    __table_args__ = (
        db.UniqueConstraint('follower_id', 'following_id', name='unique_follow'),
    )
    
    def __repr__(self):
        return f'<Follow {self.follower_id} -> {self.following_id}>'