"""add recurring engagement period support

Revision ID: 20260805_periodic_engagements
Revises: 20260805_performing_partner
"""
from alembic import op
import sqlalchemy as sa
from sqlalchemy import inspect

revision = "20260805_periodic_engagements"
down_revision = "20260805_performing_partner"
branch_labels = None
depends_on = None

TABLE = "client_service_subscriptions"
OLD_UQ = "uq_client_service_subscription_tenant_client_service_year"
NEW_UQ = "uq_css_tenant_client_service_fy_period"
INDEX = "ix_client_service_subscriptions_period_label"


def _inspector():
    return inspect(op.get_bind())


def _columns() -> set[str]:
    return {row["name"] for row in _inspector().get_columns(TABLE)}


def _unique_constraints() -> set[str]:
    return {row.get("name") for row in _inspector().get_unique_constraints(TABLE) if row.get("name")}


def _indexes() -> set[str]:
    return {row.get("name") for row in _inspector().get_indexes(TABLE) if row.get("name")}


def upgrade():
    if "period_label" not in _columns():
        op.add_column(TABLE, sa.Column("period_label", sa.String(length=30), nullable=False, server_default=""))

    op.execute("UPDATE client_service_subscriptions SET period_label = '' WHERE period_label IS NULL")

    uniques = _unique_constraints()
    dialect = op.get_bind().dialect.name
    if dialect == "sqlite":
        with op.batch_alter_table(TABLE, recreate="always") as batch:
            if OLD_UQ in uniques:
                batch.drop_constraint(OLD_UQ, type_="unique")
            if NEW_UQ not in uniques:
                batch.create_unique_constraint(
                    NEW_UQ,
                    ["tenant_id", "client_id", "service_catalogue_id", "financial_year", "period_label"],
                )
    else:
        if OLD_UQ in uniques:
            op.drop_constraint(OLD_UQ, TABLE, type_="unique")
        if NEW_UQ not in _unique_constraints():
            op.create_unique_constraint(
                NEW_UQ,
                TABLE,
                ["tenant_id", "client_id", "service_catalogue_id", "financial_year", "period_label"],
            )

    if INDEX not in _indexes():
        op.create_index(INDEX, TABLE, ["period_label"], unique=False)


def downgrade():
    if INDEX in _indexes():
        op.drop_index(INDEX, table_name=TABLE)

    uniques = _unique_constraints()
    dialect = op.get_bind().dialect.name
    if dialect == "sqlite":
        with op.batch_alter_table(TABLE, recreate="always") as batch:
            if NEW_UQ in uniques:
                batch.drop_constraint(NEW_UQ, type_="unique")
            if OLD_UQ not in uniques:
                batch.create_unique_constraint(
                    OLD_UQ,
                    ["tenant_id", "client_id", "service_catalogue_id", "financial_year"],
                )
            if "period_label" in _columns():
                batch.drop_column("period_label")
    else:
        if NEW_UQ in uniques:
            op.drop_constraint(NEW_UQ, TABLE, type_="unique")
        if OLD_UQ not in _unique_constraints():
            op.create_unique_constraint(
                OLD_UQ,
                TABLE,
                ["tenant_id", "client_id", "service_catalogue_id", "financial_year"],
            )
        if "period_label" in _columns():
            op.drop_column(TABLE, "period_label")