05/31 Phase 1: initial codes

app/models/budget.py

@@ -0,0 +1,23 @@
+from app.extensions import db
+from datetime import datetime
+
+
+class Budget(db.Model):
+    __tablename__ = 'budgets'
+
+    id = db.Column(db.Integer, primary_key=True)
+    category_id = db.Column(db.Integer, db.ForeignKey('categories.id'), nullable=False)
+    month = db.Column(db.String(7), nullable=False, index=True)  # YYYY-MM
+    limit_amount = db.Column(db.Numeric(15, 2), nullable=False)
+    rollover_enabled = db.Column(db.Boolean, default=False)
+    rollover_amount = db.Column(db.Numeric(15, 2), default=0.00)
+    created_at = db.Column(db.DateTime, default=datetime.utcnow)
+
+    category = db.relationship('Category')
+
+    __table_args__ = (
+        db.UniqueConstraint('category_id', 'month', name='uq_budget_category_month'),
+    )
+
+    def __repr__(self):
+        return f'<Budget {self.month} cat={self.category_id} limit={self.limit_amount}>'