06/15 Phase 3 codes

app/models/favorite.py

@@ -0,0 +1,26 @@
+"""Favorite (saved listing). One row per user+listing pair."""
+from datetime import datetime
+from app.extensions import db
+
+
+class Favorite(db.Model):
+    __tablename__ = "favorites"
+    __table_args__ = (
+        db.UniqueConstraint("user_id", "listing_id", name="uq_fav_user_listing"),
+    )
+
+    id = db.Column(db.BigInteger().with_variant(db.Integer, "sqlite"),
+                   primary_key=True, autoincrement=True)
+    user_id = db.Column(db.BigInteger().with_variant(db.Integer, "sqlite"),
+                        db.ForeignKey("users.id"), nullable=False, index=True)
+    listing_id = db.Column(db.BigInteger().with_variant(db.Integer, "sqlite"),
+                           db.ForeignKey("listings.id"), nullable=False, index=True)
+    created_at = db.Column(db.DateTime, default=datetime.utcnow, nullable=False)
+
+    user = db.relationship("User",
+                           backref=db.backref("favorites", lazy="dynamic"))
+    listing = db.relationship("Listing",
+                              backref=db.backref("favorited_by", lazy="dynamic"))
+
+    def __repr__(self):
+        return f"<Favorite u{self.user_id} l{self.listing_id}>"