from datetime import datetime
from decimal import Decimal
from app import db

class ProjectCost(db.Model):
    """Project cost model for tracking expenses beyond hourly work"""
    
    __tablename__ = 'project_costs'
    
    id = db.Column(db.Integer, primary_key=True)
    project_id = db.Column(db.Integer, db.ForeignKey('projects.id'), nullable=False, index=True)
    user_id = db.Column(db.Integer, db.ForeignKey('users.id'), nullable=False, index=True)
    
    # Cost details
    description = db.Column(db.String(500), nullable=False)
    category = db.Column(db.String(50), nullable=False)  # 'travel', 'materials', 'services', 'equipment', 'other'
    amount = db.Column(db.Numeric(10, 2), nullable=False)
    currency_code = db.Column(db.String(3), nullable=False, default='EUR')
    
    # Billing
    billable = db.Column(db.Boolean, default=True, nullable=False)
    invoiced = db.Column(db.Boolean, default=False, nullable=False)
    invoice_id = db.Column(db.Integer, db.ForeignKey('invoices.id'), nullable=True, index=True)
    
    # Date and metadata
    cost_date = db.Column(db.Date, nullable=False, index=True)
    notes = db.Column(db.Text, nullable=True)
    receipt_path = db.Column(db.String(500), nullable=True)  # Path to uploaded receipt
    
    created_at = db.Column(db.DateTime, default=datetime.utcnow, nullable=False)
    updated_at = db.Column(db.DateTime, default=datetime.utcnow, onupdate=datetime.utcnow, nullable=False)
    
    # Relationships
    # project and user relationships defined via backref
    
    def __init__(self, project_id, user_id, description, category, amount, cost_date, 
                 billable=True, notes=None, currency_code='EUR', receipt_path=None):
        self.project_id = project_id
        self.user_id = user_id
        self.description = description.strip() if description else None
        self.category = category
        self.amount = Decimal(str(amount))
        self.cost_date = cost_date
        self.billable = billable
        self.notes = notes.strip() if notes else None
        self.currency_code = currency_code
        self.receipt_path = receipt_path
    
    def __repr__(self):
        return f'<ProjectCost {self.description} ({self.amount} {self.currency_code})>'
    
    @property
    def is_invoiced(self):
        """Check if this cost has been invoiced"""
        return self.invoiced and self.invoice_id is not None
    
    def mark_as_invoiced(self, invoice_id):
        """Mark this cost as invoiced"""
        self.invoiced = True
        self.invoice_id = invoice_id
        self.updated_at = datetime.utcnow()
    
    def unmark_as_invoiced(self):
        """Unmark this cost as invoiced (e.g., if invoice is deleted)"""
        self.invoiced = False
        self.invoice_id = None
        self.updated_at = datetime.utcnow()
    
    def to_dict(self):
        """Convert project cost to dictionary for API responses"""
        return {
            'id': self.id,
            'project_id': self.project_id,
            'user_id': self.user_id,
            'description': self.description,
            'category': self.category,
            'amount': float(self.amount),
            'currency_code': self.currency_code,
            'billable': self.billable,
            'invoiced': self.invoiced,
            'invoice_id': self.invoice_id,
            'cost_date': self.cost_date.isoformat() if self.cost_date else None,
            'notes': self.notes,
            'receipt_path': self.receipt_path,
            'created_at': self.created_at.isoformat() if self.created_at else None,
            'updated_at': self.updated_at.isoformat() if self.updated_at else None,
            'project': self.project.name if self.project else None,
            'user': self.user.username if self.user else None
        }
    
    @classmethod
    def get_project_costs(cls, project_id, start_date=None, end_date=None, user_id=None, billable_only=False):
        """Get costs for a specific project with optional filters"""
        query = cls.query.filter_by(project_id=project_id)
        
        if start_date:
            query = query.filter(cls.cost_date >= start_date)
        
        if end_date:
            query = query.filter(cls.cost_date <= end_date)
        
        if user_id:
            query = query.filter(cls.user_id == user_id)
        
        if billable_only:
            query = query.filter(cls.billable == True)
        
        return query.order_by(cls.cost_date.desc()).all()
    
    @classmethod
    def get_total_costs(cls, project_id, start_date=None, end_date=None, user_id=None, billable_only=False):
        """Calculate total costs for a project with optional filters"""
        query = db.session.query(db.func.sum(cls.amount)).filter_by(project_id=project_id)
        
        if start_date:
            query = query.filter(cls.cost_date >= start_date)
        
        if end_date:
            query = query.filter(cls.cost_date <= end_date)
        
        if user_id:
            query = query.filter(cls.user_id == user_id)
        
        if billable_only:
            query = query.filter(cls.billable == True)
        
        total = query.scalar() or Decimal('0')
        return float(total)
    
    @classmethod
    def get_uninvoiced_costs(cls, project_id):
        """Get all billable costs that haven't been invoiced yet"""
        return cls.query.filter_by(
            project_id=project_id,
            billable=True,
            invoiced=False
        ).order_by(cls.cost_date.desc()).all()
    
    @classmethod
    def get_costs_by_category(cls, project_id, start_date=None, end_date=None):
        """Get costs grouped by category"""
        query = db.session.query(
            cls.category,
            db.func.sum(cls.amount).label('total_amount'),
            db.func.count(cls.id).label('count')
        ).filter_by(project_id=project_id)
        
        if start_date:
            query = query.filter(cls.cost_date >= start_date)
        
        if end_date:
            query = query.filter(cls.cost_date <= end_date)
        
        results = query.group_by(cls.category).all()
        
        return [
            {
                'category': category,
                'total_amount': float(total_amount),
                'count': count
            }
            for category, total_amount, count in results
        ]