club-member

club_member.py

import pytest
from sqlalchemy import (
    create_engine,
    Column,
    Integer,
    String,
    Table,
    ForeignKey,
    PrimaryKeyConstraint,
)
from sqlalchemy.ext.associationproxy import association_proxy
from sqlalchemy.orm import sessionmaker, relationship
from sqlalchemy.exc import IntegrityError
from sqlalchemy.ext.declarative import declarative_base


engine = create_engine("sqlite:///:memory:")
# engine = create_engine("sqlite:///clubs.sqlite")
Session = sessionmaker(bind=engine)
session = Session()

Base = declarative_base()

member_club = Table(
    "member_club",
    Base.metadata,
    Column("member_id", Integer, ForeignKey("members.id"), nullable=False),
    Column("club_id", Integer, ForeignKey("clubs.id")),
    PrimaryKeyConstraint("member_id", "club_id"),
)


class Member(Base):
    __tablename__ = "members"
    id = Column(Integer, primary_key=True)
    name = Column(String, unique=True, index=True)
    clubs = relationship("Club", secondary=member_club, back_populates="members")

    def __repr__(self):
        return f"Member({self.name})"


class Club(Base):
    __tablename__ = "clubs"
    id = Column(Integer, primary_key=True)
    name = Column(String, unique=True, index=True)
    members = relationship("Member", secondary=member_club, back_populates="clubs")
    member_names = association_proxy("members", "name")

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        if not self.members:
            raise ValueError("Club needs at least one member")

    def remove_member(self, member_name):
        if member_name not in self.member_names:
            raise ValueError(f"{member_name} is not a member")
        if member_name in self.member_names and len(self.member_names) == 1:
            raise ValueError(f"{member_name} is the only member in the club!")
        if member_name in self.member_names and len(self.member_names) >= 2:
            self.members = [member for member in self.members if member.name != member]
            print(f"{member_name} has been removed")

    def __repr__(self):
        return f"Club({self.name})"


Base.metadata.create_all(bind=engine)

m1 = Member(name="m1")
m2 = Member(name="m2")
m3 = Member(name="m3")

session.add_all([m1, m2, m3])
session.commit()

with pytest.raises(ValueError) as e:
    c1 = Club(name="c1")
assert "Club needs at least one member" in str(e)

c1 = Club(name="c1", members=[m1])
session.add(c1)
session.commit()

with pytest.raises(ValueError) as e:
    c1.remove_member("m1")
assert "m1 is the only member in the club" in str(e)

c2 = Club(name="c2", members=[m1, m2])
session.add(c2)
session.commit()
c2.remove_member("m1")

c3 = Club(name="c3", members=[m2, m3])
session.add(c3)
session.commit()
with pytest.raises(ValueError) as e:
    c3.remove_member("m1")
assert "m1 is not a member" in str(e)


# Adding duplicated members
c4 = Club(name="c4", members=[m1, m2, m3, m3])
try:
    session.add(c4)
    session.commit()
except IntegrityError as e:
    session.rollback()
    if "UNIQUE constraint failed" in str(e):
        print("Adding duplicated members are not allowed")
    print(f"{c4} not addedd")