# -*- coding: utf-8 -*-
"""Location: ./mcpgateway/alembic/versions/f3a3a3d901b8_remove_gateway_url_unique_constraint.py
Copyright 2026
SPDX-License-Identifier: Apache-2.0
Authors: Keval Mahajan

Alembic migration to remove unique constraint on gateway URL.
An improved alternative duplication check has been implemented for gateway duplication prevention.

Revision ID: f3a3a3d901b8
Revises: aac21d6f9522
Create Date: 2025-11-11 22:30:05.474282
"""

# Standard
from typing import Sequence, Union

# Third-Party
from alembic import op
import sqlalchemy as sa

# revision identifiers, used by Alembic.
revision: str = "f3a3a3d901b8"
down_revision: Union[str, Sequence[str], None] = "aac21d6f9522"
branch_labels: Union[str, Sequence[str], None] = None
depends_on: Union[str, Sequence[str], None] = None


def constraint_exists(inspector, table_name, constraint_name):
    """
    Check if a specific unique constraint exists on a given table.

    This function queries the database using the provided SQLAlchemy
    inspector to determine if a constraint with the given name exists.
    If the check fails due to an exception (e.g., database connectivity issues),
    it conservatively assumes that the constraint exists.

    Args:
        inspector (sqlalchemy.engine.reflection.Inspector): SQLAlchemy inspector
            instance for database introspection.
        table_name (str): Name of the table to inspect.
        constraint_name (str): Name of the unique constraint to check.

    Returns:
        bool: True if the constraint exists or if the check could not be performed,
              False if the constraint does not exist.
    """
    try:
        unique_constraints = inspector.get_unique_constraints(table_name)
        return any(uc["name"] == constraint_name for uc in unique_constraints)
    except Exception:
        # Fallback: assume constraint exists if we can't check
        return True


def upgrade():
    """Remove the unique constraint on (team_id, owner_email, url) from gateway table."""

    conn = op.get_bind()
    inspector = sa.inspect(conn)

    # Fresh DBs may not have legacy gateways table at this revision point.
    if "gateways" not in inspector.get_table_names():
        print("Table 'gateways' does not exist, skipping constraint drop.")
        return

    # Check if constraint exists before attempting to drop
    if not constraint_exists(inspector, "gateways", "uq_team_owner_url_gateway"):
        print("Constraint 'uq_team_owner_url_gateway' does not exist, skipping drop.")
        return

    if conn.dialect.name == "sqlite":
        # SQLite: Use batch mode to recreate table without the constraint
        with op.batch_alter_table("gateways", schema=None) as batch_op:
            batch_op.drop_constraint("uq_team_owner_url_gateway", type_="unique")
    else:
        # PostgreSQL and other backends: Direct constraint drop
        op.drop_constraint("uq_team_owner_url_gateway", "gateways", type_="unique")

    print("Successfully removed constraint 'uq_team_owner_url_gateway' from gateway table.")


def downgrade():
    """Re-add the unique constraint on (team_id, owner_email, url) to gateway table."""

    conn = op.get_bind()
    inspector = sa.inspect(conn)

    if "gateways" not in inspector.get_table_names():
        print("Table 'gateways' does not exist, skipping constraint creation.")
        return

    # Check if constraint already exists before attempting to create
    if constraint_exists(inspector, "gateways", "uq_team_owner_url_gateway"):
        print("Constraint 'uq_team_owner_url_gateway' already exists, skipping creation.")
        return

    if conn.dialect.name == "sqlite":
        # SQLite: Use batch mode to recreate table with the constraint
        with op.batch_alter_table("gateways", schema=None) as batch_op:
            batch_op.create_unique_constraint("uq_team_owner_url_gateway", ["team_id", "owner_email", "url"])
    else:
        # PostgreSQL and other backends: Direct constraint creation
        op.create_unique_constraint("uq_team_owner_url_gateway", "gateways", ["team_id", "owner_email", "url"])

    print("Successfully re-added constraint 'uq_team_owner_url_gateway' to gateways table.")
