saas_backend/alembic/versions/d4f6a8b0c902_subscription_lifecycle.py

"""Grace periods, cancellation, and a record of what changed.

Before this, a subscription had two states: working and locked out. A customer
whose card failed went straight from one to the other, with nothing in between
and no record of when or why it happened.

Adds:

- `subscription_plans.grace_period_days` — how long after expiry a workspace stays
  read-only rather than locked out. Per plan, because it is a commercial decision
  rather than a constant. Defaults to 0, which is exactly the old behaviour.
- `tenants.cancelled_at` — cancellation is a decision with a date, not the absence
  of an active flag.
- `tenant_subscription_history` — what changed, when, and who did it. Answering
  "why does this workspace have that plan" currently requires guessing.

Revision ID: d4f6a8b0c902
Revises: c3d5e7f9a801
"""

from typing import Sequence, Union

import sqlalchemy as sa
from alembic import op
from sqlalchemy.dialects.postgresql import UUID

revision: str = "d4f6a8b0c902"
down_revision: Union[str, Sequence[str], None] = "c3d5e7f9a801"
branch_labels: Union[str, Sequence[str], None] = None
depends_on: Union[str, Sequence[str], None] = None


def upgrade() -> None:
    op.add_column(
        "subscription_plans",
        sa.Column("grace_period_days", sa.Integer(), nullable=False, server_default="0"),
    )
    op.add_column(
        "tenants", sa.Column("cancelled_at", sa.DateTime(timezone=True), nullable=True)
    )

    op.create_table(
        "tenant_subscription_history",
        sa.Column(
            "id", UUID(as_uuid=True), primary_key=True, server_default=sa.text("gen_random_uuid()")
        ),
        sa.Column(
            "tenant_id",
            UUID(as_uuid=True),
            sa.ForeignKey("tenants.id", ondelete="CASCADE"),
            nullable=False,
        ),
        sa.Column(
            "from_plan_id",
            UUID(as_uuid=True),
            sa.ForeignKey("subscription_plans.id", ondelete="SET NULL"),
            nullable=True,
        ),
        sa.Column(
            "to_plan_id",
            UUID(as_uuid=True),
            sa.ForeignKey("subscription_plans.id", ondelete="SET NULL"),
            nullable=True,
        ),
        sa.Column("change_type", sa.String(30), nullable=False),
        sa.Column("from_end_date", sa.Date(), nullable=True),
        sa.Column("to_end_date", sa.Date(), nullable=True),
        sa.Column("from_status", sa.String(30), nullable=True),
        sa.Column("to_status", sa.String(30), nullable=True),
        sa.Column(
            "changed_by_id",
            UUID(as_uuid=True),
            sa.ForeignKey("users.id", ondelete="SET NULL"),
            nullable=True,
        ),
        sa.Column("changed_by_email", sa.String(), nullable=True),
        sa.Column("notes", sa.Text(), nullable=True),
        sa.Column(
            "created_at", sa.DateTime(timezone=True), nullable=False, server_default=sa.func.now()
        ),
    )
    op.create_index(
        "ix_tenant_subscription_history_tenant",
        "tenant_subscription_history",
        ["tenant_id", sa.text("created_at DESC")],
    )

    op.execute("ALTER TABLE tenant_subscription_history ENABLE ROW LEVEL SECURITY")
    op.execute("ALTER TABLE tenant_subscription_history FORCE ROW LEVEL SECURITY")
    op.execute(
        """
        CREATE POLICY tenant_isolation ON tenant_subscription_history
        USING (
            current_setting('app.bypass_rls', true) = 'on'
            OR tenant_id = NULLIF(current_setting('app.tenant_id', true), '')::uuid
        )
        WITH CHECK (
            current_setting('app.bypass_rls', true) = 'on'
            OR tenant_id = NULLIF(current_setting('app.tenant_id', true), '')::uuid
        )
        """
    )


def downgrade() -> None:
    op.execute("DROP POLICY IF EXISTS tenant_isolation ON tenant_subscription_history")
    op.drop_index(
        "ix_tenant_subscription_history_tenant", table_name="tenant_subscription_history"
    )
    op.drop_table("tenant_subscription_history")
    op.drop_column("tenants", "cancelled_at")
    op.drop_column("subscription_plans", "grace_period_days")