from flask_sqlalchemy import SQLAlchemy
from datetime import datetime
import json
from werkzeug.security import generate_password_hash, check_password_hash

db = SQLAlchemy()

class User(db.Model):
    """User model for authentication - supports both students and lecturers"""
    __tablename__ = 'users'
    
    id = db.Column(db.Integer, primary_key=True)
    matric_no = db.Column(db.String(50), unique=True, nullable=False)  # A/B for students, L for lecturers
    name = db.Column(db.String(100), nullable=False)
    email = db.Column(db.String(100), unique=True)
    password_hash = db.Column(db.String(255), nullable=False)
    role = db.Column(db.String(20), nullable=False)  # 'student', 'lecturer', or 'admin'
    is_active = db.Column(db.Boolean, default=False)
    status = db.Column(db.String(20), default='pending')  # 'pending', 'approved', 'rejected'
    created_at = db.Column(db.DateTime, default=datetime.utcnow)
    
    def set_password(self, password):
        """Hash and set password"""
        self.password_hash = generate_password_hash(password)
    
    def check_password(self, password):
        """Verify password"""
        return check_password_hash(self.password_hash, password)
    
    @staticmethod
    def validate_matric_no(matric_no, role):
        """Validate matric number format based on role"""
        if not matric_no:
            return False, "Matric number is required"
        
        matric_no = matric_no.upper().strip()
        
        if role == 'student':
            # Students must start with A or B
            if not (matric_no.startswith('A') or matric_no.startswith('B')):
                return False, "Student matric number must start with 'A' or 'B'"
        elif role == 'lecturer':
            # Lecturers must start with L
            if not matric_no.startswith('L'):
                return False, "Lecturer matric number must start with 'L'"
        else:
            return False, "Invalid role"
        
        return True, None
    
    def to_dict(self):
        return {
            'id': self.id,
            'matric_no': self.matric_no,
            'name': self.name,
            'email': self.email,
            'role': self.role,
            'is_active': self.is_active,
            'status': self.status,
            'created_at': self.created_at.isoformat() + 'Z' if self.created_at else None
        }


class Student(db.Model):
    """Student model - stores student information and face encodings"""
    __tablename__ = 'students'
    
    id = db.Column(db.Integer, primary_key=True)
    user_id = db.Column(db.Integer, db.ForeignKey('users.id'), unique=True)  # Link to User
    student_id = db.Column(db.String(50), unique=True, nullable=False)
    name = db.Column(db.String(100), nullable=False)
    email = db.Column(db.String(100), unique=True)
    face_encoding = db.Column(db.Text)  # Stored as JSON string
    registered_at = db.Column(db.DateTime, default=datetime.utcnow)
    is_active = db.Column(db.Boolean, default=True)
    
    # Relationships
    attendance_records = db.relationship('AttendanceRecord', backref='student', lazy=True)
    user = db.relationship('User', backref='student_profile', uselist=False)
    
    def get_face_encoding(self):
        """Deserialize face encoding from JSON"""
        if self.face_encoding:
            return json.loads(self.face_encoding)
        return None
    
    def set_face_encoding(self, encoding):
        """Serialize face encoding to JSON"""
        if encoding is not None:
            self.face_encoding = json.dumps(encoding.tolist())
    
    def to_dict(self):
        return {
            'id': self.id,
            'student_id': self.student_id,
            'name': self.name,
            'email': self.email,
            'registered_at': self.registered_at.isoformat() + 'Z' if self.registered_at else None,
            'is_active': self.is_active
        }


class Classroom(db.Model):
    """Classroom model - stores classroom locations with GPS coordinates"""
    __tablename__ = 'classrooms'
    
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(100), nullable=False)
    building = db.Column(db.String(100))
    latitude = db.Column(db.Float, nullable=False)
    longitude = db.Column(db.Float, nullable=False)
    radius_meters = db.Column(db.Integer, default=50)  # Geofencing radius
    
    # Relationships
    sessions = db.relationship('AttendanceSession', backref='classroom', lazy=True)
    
    def to_dict(self):
        return {
            'id': self.id,
            'name': self.name,
            'building': self.building,
            'latitude': self.latitude,
            'longitude': self.longitude,
            'radius_meters': self.radius_meters
        }


class AttendanceSession(db.Model):
    """Attendance session - represents a class session with auto-refresh codes"""
    __tablename__ = 'attendance_sessions'
    
    id = db.Column(db.Integer, primary_key=True)
    course_name = db.Column(db.String(100), nullable=False)
    classroom_id = db.Column(db.Integer, db.ForeignKey('classrooms.id'), nullable=False)
    lecturer_name = db.Column(db.String(100), nullable=False)
    
    # Session timing
    start_time = db.Column(db.DateTime, default=datetime.utcnow)
    end_time = db.Column(db.DateTime)
    is_active = db.Column(db.Boolean, default=True)
    
    # Auto-refresh attendance code
    current_code = db.Column(db.String(10))
    code_generated_at = db.Column(db.DateTime)
    
    # Relationships
    attendance_records = db.relationship('AttendanceRecord', backref='session', lazy=True)
    
    def to_dict(self):
        return {
            'id': self.id,
            'course_name': self.course_name,
            'classroom_id': self.classroom_id,
            'classroom': self.classroom.to_dict() if self.classroom else None,
            'lecturer_name': self.lecturer_name,
            'start_time': self.start_time.isoformat() + 'Z' if self.start_time else None,
            'end_time': self.end_time.isoformat() + 'Z' if self.end_time else None,
            'is_active': self.is_active,
            'current_code': self.current_code,
            'code_generated_at': self.code_generated_at.isoformat() + 'Z' if self.code_generated_at else None
        }


class AttendanceRecord(db.Model):
    """Attendance record - individual student attendance for a session"""
    __tablename__ = 'attendance_records'
    
    id = db.Column(db.Integer, primary_key=True)
    session_id = db.Column(db.Integer, db.ForeignKey('attendance_sessions.id'), nullable=False)
    student_id = db.Column(db.Integer, db.ForeignKey('students.id'), nullable=False)
    
    # Verification details
    marked_at = db.Column(db.DateTime, default=datetime.utcnow)
    face_verified = db.Column(db.Boolean, default=False)
    location_verified = db.Column(db.Boolean, default=False)
    code_verified = db.Column(db.Boolean, default=False)
    
    # Location data
    student_latitude = db.Column(db.Float)
    student_longitude = db.Column(db.Float)
    distance_from_classroom = db.Column(db.Float)  # In meters
    
    # Status
    status = db.Column(db.String(20), default='present')  # present, late, absent
    
    def to_dict(self):
        return {
            'id': self.id,
            'session_id': self.session_id,
            'student': self.student.to_dict() if self.student else None,
            'marked_at': self.marked_at.isoformat() + 'Z' if self.marked_at else None,
            'face_verified': self.face_verified,
            'location_verified': self.location_verified,
            'code_verified': self.code_verified,
            'distance_from_classroom': self.distance_from_classroom,
            'status': self.status
        }