from datetime import datetime, timedelta
from app import db

class BudgetAlert(db.Model):
    """Budget alert model for tracking project budget warnings and notifications"""
    
    __tablename__ = 'budget_alerts'
    
    id = db.Column(db.Integer, primary_key=True)
    project_id = db.Column(db.Integer, db.ForeignKey('projects.id'), nullable=False, index=True)
    
    # Alert details
    alert_type = db.Column(db.String(20), nullable=False)  # 'warning_80', 'warning_100', 'over_budget'
    alert_level = db.Column(db.String(20), nullable=False)  # 'info', 'warning', 'critical'
    budget_consumed_percent = db.Column(db.Numeric(5, 2), nullable=False)  # Percentage of budget consumed
    budget_amount = db.Column(db.Numeric(10, 2), nullable=False)  # Budget at time of alert
    consumed_amount = db.Column(db.Numeric(10, 2), nullable=False)  # Amount consumed at time of alert
    
    # Alert message and status
    message = db.Column(db.Text, nullable=False)
    is_acknowledged = db.Column(db.Boolean, default=False, nullable=False)
    acknowledged_by = db.Column(db.Integer, db.ForeignKey('users.id'), nullable=True, index=True)
    acknowledged_at = db.Column(db.DateTime, nullable=True)
    
    # Metadata
    created_at = db.Column(db.DateTime, default=datetime.utcnow, nullable=False, index=True)
    
    # Relationships
    project = db.relationship('Project', backref=db.backref('budget_alerts', lazy='dynamic'))
    
    def __init__(self, project_id, alert_type, alert_level, budget_consumed_percent, 
                 budget_amount, consumed_amount, message):
        self.project_id = project_id
        self.alert_type = alert_type
        self.alert_level = alert_level
        self.budget_consumed_percent = budget_consumed_percent
        self.budget_amount = budget_amount
        self.consumed_amount = consumed_amount
        self.message = message
    
    def __repr__(self):
        return f'<BudgetAlert {self.alert_type} for Project {self.project_id}>'
    
    def acknowledge(self, user_id):
        """Mark this alert as acknowledged by a user"""
        self.is_acknowledged = True
        self.acknowledged_by = user_id
        self.acknowledged_at = datetime.utcnow()
        db.session.commit()
    
    def to_dict(self):
        """Convert budget alert to dictionary for API responses"""
        return {
            'id': self.id,
            'project_id': self.project_id,
            'project_name': self.project.name if self.project else None,
            'alert_type': self.alert_type,
            'alert_level': self.alert_level,
            'budget_consumed_percent': float(self.budget_consumed_percent),
            'budget_amount': float(self.budget_amount),
            'consumed_amount': float(self.consumed_amount),
            'message': self.message,
            'is_acknowledged': self.is_acknowledged,
            'acknowledged_by': self.acknowledged_by,
            'acknowledged_at': self.acknowledged_at.isoformat() if self.acknowledged_at else None,
            'created_at': self.created_at.isoformat() if self.created_at else None,
        }
    
    @classmethod
    def get_active_alerts(cls, project_id=None, acknowledged=False):
        """Get active alerts, optionally filtered by project"""
        query = cls.query.filter_by(is_acknowledged=acknowledged)
        
        if project_id:
            query = query.filter_by(project_id=project_id)
        
        return query.order_by(cls.created_at.desc()).all()
    
    @classmethod
    def create_alert(cls, project_id, alert_type, budget_consumed_percent, 
                     budget_amount, consumed_amount):
        """Create a new budget alert"""
        # Determine alert level based on type
        alert_levels = {
            'warning_80': 'warning',
            'warning_100': 'critical',
            'over_budget': 'critical'
        }
        alert_level = alert_levels.get(alert_type, 'info')
        
        # Generate alert message
        message = cls._generate_message(alert_type, budget_consumed_percent, 
                                       budget_amount, consumed_amount)
        
        # Check if similar alert already exists (avoid duplicates)
        recent_alert = cls.query.filter_by(
            project_id=project_id,
            alert_type=alert_type,
            is_acknowledged=False
        ).filter(
            cls.created_at >= datetime.utcnow() - timedelta(hours=24)
        ).first()
        
        if recent_alert:
            return recent_alert
        
        # Create new alert
        alert = cls(
            project_id=project_id,
            alert_type=alert_type,
            alert_level=alert_level,
            budget_consumed_percent=budget_consumed_percent,
            budget_amount=budget_amount,
            consumed_amount=consumed_amount,
            message=message
        )
        
        db.session.add(alert)
        db.session.commit()
        
        return alert
    
    @staticmethod
    def _generate_message(alert_type, budget_consumed_percent, budget_amount, consumed_amount):
        """Generate alert message based on alert type"""
        messages = {
            'warning_80': f'Warning: Project has consumed {budget_consumed_percent:.1f}% of budget (${consumed_amount:.2f} of ${budget_amount:.2f})',
            'warning_100': f'Alert: Project has reached 100% of budget (${consumed_amount:.2f} of ${budget_amount:.2f})',
            'over_budget': f'Critical: Project is over budget by ${consumed_amount - budget_amount:.2f} ({budget_consumed_percent:.1f}% consumed)'
        }
        return messages.get(alert_type, 'Budget alert')
    
    @classmethod
    def get_alert_summary(cls, project_id=None):
        """Get summary statistics for budget alerts"""
        query = cls.query
        
        if project_id:
            query = query.filter_by(project_id=project_id)
        
        total_alerts = query.count()
        unacknowledged_alerts = query.filter_by(is_acknowledged=False).count()
        critical_alerts = query.filter_by(alert_level='critical', is_acknowledged=False).count()
        
        return {
            'total_alerts': total_alerts,
            'unacknowledged_alerts': unacknowledged_alerts,
            'critical_alerts': critical_alerts
        }