06/15 Phase 3 codes

app/models/messaging.py

@@ -0,0 +1,76 @@
+"""Messaging models: Conversation (per listing, per buyer/seller pair) + Message.
+
+One conversation per (listing, buyer) pair — enforced by unique constraint.
+The seller is always listing.user; buyer is any other authenticated user.
+Messages are append-only; soft-delete not needed at Phase 3.
+"""
+from datetime import datetime
+from app.extensions import db
+
+
+class Conversation(db.Model):
+    __tablename__ = "conversations"
+    __table_args__ = (
+        db.UniqueConstraint("listing_id", "buyer_id", name="uq_conv_listing_buyer"),
+    )
+
+    id = db.Column(db.BigInteger().with_variant(db.Integer, "sqlite"),
+                   primary_key=True, autoincrement=True)
+    listing_id = db.Column(db.BigInteger().with_variant(db.Integer, "sqlite"),
+                           db.ForeignKey("listings.id"), nullable=False, index=True)
+    buyer_id = db.Column(db.BigInteger().with_variant(db.Integer, "sqlite"),
+                         db.ForeignKey("users.id"), nullable=False, index=True)
+    seller_id = db.Column(db.BigInteger().with_variant(db.Integer, "sqlite"),
+                          db.ForeignKey("users.id"), nullable=False, index=True)
+    last_message_at = db.Column(db.DateTime, nullable=True, index=True)
+    created_at = db.Column(db.DateTime, default=datetime.utcnow, nullable=False)
+
+    listing = db.relationship("Listing",
+                              backref=db.backref("conversations", lazy="dynamic"))
+    buyer = db.relationship("User", foreign_keys=[buyer_id],
+                            backref=db.backref("bought_conversations", lazy="dynamic"))
+    seller = db.relationship("User", foreign_keys=[seller_id],
+                             backref=db.backref("sold_conversations", lazy="dynamic"))
+    messages = db.relationship("Message", back_populates="conversation",
+                               order_by="Message.created_at",
+                               cascade="all, delete-orphan", lazy="selectin")
+
+    def other_party(self, user):
+        return self.seller if user.id == self.buyer_id else self.buyer
+
+    def unread_count(self, user):
+        return sum(1 for m in self.messages
+                   if m.sender_id != user.id and m.read_at is None)
+
+    def __repr__(self):
+        return f"<Conversation {self.id} L{self.listing_id}>"
+
+
+class Message(db.Model):
+    __tablename__ = "messages"
+
+    id = db.Column(db.BigInteger().with_variant(db.Integer, "sqlite"),
+                   primary_key=True, autoincrement=True)
+    conversation_id = db.Column(db.BigInteger().with_variant(db.Integer, "sqlite"),
+                                db.ForeignKey("conversations.id"),
+                                nullable=False, index=True)
+    sender_id = db.Column(db.BigInteger().with_variant(db.Integer, "sqlite"),
+                          db.ForeignKey("users.id"), nullable=False)
+    body = db.Column(db.Text, nullable=False)
+    read_at = db.Column(db.DateTime, nullable=True)
+    created_at = db.Column(db.DateTime, default=datetime.utcnow, nullable=False)
+
+    conversation = db.relationship("Conversation", back_populates="messages")
+    sender = db.relationship("User",
+                             backref=db.backref("sent_messages", lazy="dynamic"))
+
+    @property
+    def is_read(self):
+        return self.read_at is not None
+
+    def mark_read(self):
+        if self.read_at is None:
+            self.read_at = datetime.utcnow()
+
+    def __repr__(self):
+        return f"<Message {self.id} C{self.conversation_id}>"