05/31 Phase 1: initial codes

app/models/category.py

@@ -0,0 +1,28 @@
+from app.extensions import db
+from datetime import datetime
+
+
+class Category(db.Model):
+    __tablename__ = 'categories'
+
+    id = db.Column(db.Integer, primary_key=True)
+    name = db.Column(db.String(100), nullable=False)
+    category_type = db.Column(
+        db.Enum('income', 'expense', 'both'),
+        nullable=False,
+        default='expense'
+    )
+    parent_id = db.Column(db.Integer, db.ForeignKey('categories.id'), nullable=True)
+    color = db.Column(db.String(7), default='#6B7280')
+    icon = db.Column(db.String(50), default='bi-tag')
+    is_system = db.Column(db.Boolean, default=False)  # system categories can't be deleted
+    is_active = db.Column(db.Boolean, default=True)
+    created_at = db.Column(db.DateTime, default=datetime.utcnow)
+
+    # Self-referential relationship for subcategories
+    subcategories = db.relationship('Category', backref=db.backref('parent', remote_side=[id]),
+                                    lazy='dynamic')
+    transactions = db.relationship('Transaction', back_populates='category', lazy='dynamic')
+
+    def __repr__(self):
+        return f'<Category {self.name}>'