WIP checkpoint: Friends/follow/block models + Alembic migration

backend/alembic/env.py

@@ -8,7 +8,7 @@ from sqlalchemy.ext.asyncio import create_async_engine
 
 from app.config import settings
 from app.database import Base
-from app.models import user, session, world, asset  # noqa: F401
+from app.models import user, session, world, asset, friendship, follow, block  # noqa: F401
 
 # this is the Alembic Config object, which provides
 # access to the values within the .ini file in use.

backend/alembic/versions/0002_social_graph.py

@@ -0,0 +1,136 @@
+"""social graph: friendships, follows, blocks
+
+Revision ID: 0002_social_graph
+Revises: 0001_initial
+Create Date: 2026-08-18 00:00:00.000000
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+# revision identifiers, used by Alembic.
+revision: str = "0002_social_graph"
+down_revision: Union[str, None] = "0001_initial"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    """Create friendships, follows, and blocks tables."""
+    op.create_table(
+        "friendships",
+        sa.Column("id", sa.Integer(), nullable=False),
+        sa.Column("requester_id", sa.Integer(), nullable=False),
+        sa.Column("addressee_id", sa.Integer(), nullable=False),
+        sa.Column("status", sa.String(length=20), server_default="pending", nullable=False),
+        sa.Column("created_at", sa.DateTime(timezone=True), server_default=sa.func.now(), nullable=False),
+        sa.Column("updated_at", sa.DateTime(timezone=True), nullable=True),
+        sa.CheckConstraint(
+            "status IN ('pending', 'accepted')",
+            name="ck_friendships_status",
+        ),
+        sa.CheckConstraint(
+            "requester_id <> addressee_id",
+            name="ck_friendships_no_self",
+        ),
+        sa.ForeignKeyConstraint(
+            ["addressee_id"],
+            ["users.id"],
+            ondelete="CASCADE",
+        ),
+        sa.ForeignKeyConstraint(
+            ["requester_id"],
+            ["users.id"],
+            ondelete="CASCADE",
+        ),
+        sa.PrimaryKeyConstraint("id"),
+        sa.UniqueConstraint(
+            "requester_id",
+            "addressee_id",
+            name="uq_friendships_requester_addressee",
+        ),
+    )
+    op.create_index(op.f("ix_friendships_id"), "friendships", ["id"], unique=False)
+    op.create_index(op.f("ix_friendships_addressee_id"), "friendships", ["addressee_id"], unique=False)
+    op.create_index(op.f("ix_friendships_requester_id"), "friendships", ["requester_id"], unique=False)
+
+    op.create_table(
+        "follows",
+        sa.Column("id", sa.Integer(), nullable=False),
+        sa.Column("follower_id", sa.Integer(), nullable=False),
+        sa.Column("followed_id", sa.Integer(), nullable=False),
+        sa.Column("created_at", sa.DateTime(timezone=True), server_default=sa.func.now(), nullable=False),
+        sa.CheckConstraint(
+            "follower_id <> followed_id",
+            name="ck_follows_no_self",
+        ),
+        sa.ForeignKeyConstraint(
+            ["followed_id"],
+            ["users.id"],
+            ondelete="CASCADE",
+        ),
+        sa.ForeignKeyConstraint(
+            ["follower_id"],
+            ["users.id"],
+            ondelete="CASCADE",
+        ),
+        sa.PrimaryKeyConstraint("id"),
+        sa.UniqueConstraint(
+            "follower_id",
+            "followed_id",
+            name="uq_follows_follower_followed",
+        ),
+    )
+    op.create_index(op.f("ix_follows_id"), "follows", ["id"], unique=False)
+    op.create_index(op.f("ix_follows_followed_id"), "follows", ["followed_id"], unique=False)
+    op.create_index(op.f("ix_follows_follower_id"), "follows", ["follower_id"], unique=False)
+
+    op.create_table(
+        "blocks",
+        sa.Column("id", sa.Integer(), nullable=False),
+        sa.Column("blocker_id", sa.Integer(), nullable=False),
+        sa.Column("blocked_id", sa.Integer(), nullable=False),
+        sa.Column("created_at", sa.DateTime(timezone=True), server_default=sa.func.now(), nullable=False),
+        sa.CheckConstraint(
+            "blocker_id <> blocked_id",
+            name="ck_blocks_no_self",
+        ),
+        sa.ForeignKeyConstraint(
+            ["blocked_id"],
+            ["users.id"],
+            ondelete="CASCADE",
+        ),
+        sa.ForeignKeyConstraint(
+            ["blocker_id"],
+            ["users.id"],
+            ondelete="CASCADE",
+        ),
+        sa.PrimaryKeyConstraint("id"),
+        sa.UniqueConstraint(
+            "blocker_id",
+            "blocked_id",
+            name="uq_blocks_blocker_blocked",
+        ),
+    )
+    op.create_index(op.f("ix_blocks_id"), "blocks", ["id"], unique=False)
+    op.create_index(op.f("ix_blocks_blocked_id"), "blocks", ["blocked_id"], unique=False)
+    op.create_index(op.f("ix_blocks_blocker_id"), "blocks", ["blocker_id"], unique=False)
+
+
+def downgrade() -> None:
+    """Drop friendships, follows, and blocks tables."""
+    op.drop_index(op.f("ix_blocks_blocker_id"), table_name="blocks")
+    op.drop_index(op.f("ix_blocks_blocked_id"), table_name="blocks")
+    op.drop_index(op.f("ix_blocks_id"), table_name="blocks")
+    op.drop_table("blocks")
+
+    op.drop_index(op.f("ix_follows_follower_id"), table_name="follows")
+    op.drop_index(op.f("ix_follows_followed_id"), table_name="follows")
+    op.drop_index(op.f("ix_follows_id"), table_name="follows")
+    op.drop_table("follows")
+
+    op.drop_index(op.f("ix_friendships_requester_id"), table_name="friendships")
+    op.drop_index(op.f("ix_friendships_addressee_id"), table_name="friendships")
+    op.drop_index(op.f("ix_friendships_id"), table_name="friendships")
+    op.drop_table("friendships")

backend/app/models/__init__.py

@@ -2,5 +2,17 @@ from app.models.user import User
 from app.models.session import Session
 from app.models.world import World
 from app.models.asset import Asset
+from app.models.friendship import Friendship, FriendshipStatus
+from app.models.follow import Follow
+from app.models.block import Block
 
-__all__ = ["User", "Session", "World", "Asset"]
+__all__ = [
+    "User",
+    "Session",
+    "World",
+    "Asset",
+    "Friendship",
+    "FriendshipStatus",
+    "Follow",
+    "Block",
+]

backend/app/models/block.py

@@ -0,0 +1,48 @@
+"""Block model: a hard deny that also hides content and prevents DMs."""
+
+from sqlalchemy import CheckConstraint, Column, DateTime, ForeignKey, Integer, UniqueConstraint
+from sqlalchemy.orm import relationship
+from sqlalchemy.sql import func
+
+from app.database import Base
+
+
+class Block(Base):
+    __tablename__ = "blocks"
+    __table_args__ = (
+        UniqueConstraint(
+            "blocker_id",
+            "blocked_id",
+            name="uq_blocks_pair",
+        ),
+        CheckConstraint(
+            "blocker_id <> blocked_id",
+            name="ck_blocks_no_self",
+        ),
+    )
+
+    id = Column(Integer, primary_key=True, index=True)
+    blocker_id = Column(
+        Integer,
+        ForeignKey("users.id", ondelete="CASCADE"),
+        nullable=False,
+        index=True,
+    )
+    blocked_id = Column(
+        Integer,
+        ForeignKey("users.id", ondelete="CASCADE"),
+        nullable=False,
+        index=True,
+    )
+    created_at = Column(DateTime(timezone=True), server_default=func.now())
+
+    blocker = relationship(
+        "User",
+        foreign_keys=[blocker_id],
+        back_populates="blocks_issued",
+    )
+    blocked = relationship(
+        "User",
+        foreign_keys=[blocked_id],
+        back_populates="blocks_received",
+    )

backend/app/models/follow.py

@@ -0,0 +1,48 @@
+"""Follow model: a one-way relationship requiring no approval."""
+
+from sqlalchemy import CheckConstraint, Column, DateTime, ForeignKey, Integer, UniqueConstraint
+from sqlalchemy.orm import relationship
+from sqlalchemy.sql import func
+
+from app.database import Base
+
+
+class Follow(Base):
+    __tablename__ = "follows"
+    __table_args__ = (
+        UniqueConstraint(
+            "follower_id",
+            "followed_id",
+            name="uq_follows_pair",
+        ),
+        CheckConstraint(
+            "follower_id <> followed_id",
+            name="ck_follows_no_self",
+        ),
+    )
+
+    id = Column(Integer, primary_key=True, index=True)
+    follower_id = Column(
+        Integer,
+        ForeignKey("users.id", ondelete="CASCADE"),
+        nullable=False,
+        index=True,
+    )
+    followed_id = Column(
+        Integer,
+        ForeignKey("users.id", ondelete="CASCADE"),
+        nullable=False,
+        index=True,
+    )
+    created_at = Column(DateTime(timezone=True), server_default=func.now())
+
+    follower = relationship(
+        "User",
+        foreign_keys=[follower_id],
+        back_populates="following",
+    )
+    followed = relationship(
+        "User",
+        foreign_keys=[followed_id],
+        back_populates="followers",
+    )

backend/app/models/friendship.py

@@ -0,0 +1,74 @@
+"""Friendship model: a one-directional request that becomes mutual on accept."""
+
+from sqlalchemy import (
+    CheckConstraint,
+    Column,
+    DateTime,
+    ForeignKey,
+    Integer,
+    String,
+    UniqueConstraint,
+)
+from sqlalchemy.orm import relationship
+from sqlalchemy.sql import func
+
+from app.database import Base
+
+
+class FriendshipStatus:
+    """String values for the friendship.status column."""
+
+    PENDING = "pending"
+    ACCEPTED = "accepted"
+
+
+class Friendship(Base):
+    __tablename__ = "friendships"
+    __table_args__ = (
+        UniqueConstraint(
+            "requester_id",
+            "addressee_id",
+            name="uq_friendships_pair",
+        ),
+        CheckConstraint(
+            "requester_id <> addressee_id",
+            name="ck_friendships_no_self",
+        ),
+        CheckConstraint(
+            "status IN ('pending', 'accepted')",
+            name="ck_friendships_status",
+        ),
+    )
+
+    id = Column(Integer, primary_key=True, index=True)
+    requester_id = Column(
+        Integer,
+        ForeignKey("users.id", ondelete="CASCADE"),
+        nullable=False,
+        index=True,
+    )
+    addressee_id = Column(
+        Integer,
+        ForeignKey("users.id", ondelete="CASCADE"),
+        nullable=False,
+        index=True,
+    )
+    status = Column(
+        String(20),
+        nullable=False,
+        default=FriendshipStatus.PENDING,
+        server_default=FriendshipStatus.PENDING,
+    )
+    created_at = Column(DateTime(timezone=True), server_default=func.now())
+    updated_at = Column(DateTime(timezone=True), onupdate=func.now())
+
+    requester = relationship(
+        "User",
+        foreign_keys=[requester_id],
+        back_populates="sent_friend_requests",
+    )
+    addressee = relationship(
+        "User",
+        foreign_keys=[addressee_id],
+        back_populates="received_friend_requests",
+    )

backend/app/models/user.py

@@ -19,3 +19,41 @@ class User(Base):
     sessions = relationship("Session", back_populates="user", cascade="all, delete-orphan")
     worlds = relationship("World", back_populates="owner")
     assets = relationship("Asset", back_populates="owner")
+
+    # Social graph
+    sent_friend_requests = relationship(
+        "Friendship",
+        foreign_keys="Friendship.requester_id",
+        back_populates="requester",
+        cascade="all, delete-orphan",
+    )
+    received_friend_requests = relationship(
+        "Friendship",
+        foreign_keys="Friendship.addressee_id",
+        back_populates="addressee",
+        cascade="all, delete-orphan",
+    )
+    following = relationship(
+        "Follow",
+        foreign_keys="Follow.follower_id",
+        back_populates="follower",
+        cascade="all, delete-orphan",
+    )
+    followers = relationship(
+        "Follow",
+        foreign_keys="Follow.followed_id",
+        back_populates="followed",
+        cascade="all, delete-orphan",
+    )
+    blocks_issued = relationship(
+        "Block",
+        foreign_keys="Block.blocker_id",
+        back_populates="blocker",
+        cascade="all, delete-orphan",
+    )
+    blocks_received = relationship(
+        "Block",
+        foreign_keys="Block.blocked_id",
+        back_populates="blocked",
+        cascade="all, delete-orphan",
+    )