"""User authentication and Todo-User relationship

Revision ID: 54ab38f52c12
Depends on: 1a39b3495612
Create Date: 2023-10-28

"""
from alembic import op
import sqlalchemy as sa
from sqlalchemy.engine.reflection import Inspector
from sqlalchemy.exc import OperationalError


# revision identifiers, used by Alembic.
revision = '54ab38f52c12'
down_revision = '1a39b3495612'
branch_labels = None
depends_on = None


def table_exists(table_name):
    """Check if table exists in the database"""
    conn = op.get_bind()
    inspector = Inspector.from_engine(conn)
    return table_name in inspector.get_table_names()


def column_exists(table_name, column_name):
    """Check if column exists in the table"""
    conn = op.get_bind()
    inspector = Inspector.from_engine(conn)
    if table_name not in inspector.get_table_names():
        return False
    columns = [col['name'] for col in inspector.get_columns(table_name)]
    return column_name in columns


def index_exists(table_name, index_name):
    """Check if index exists in the table"""
    conn = op.get_bind()
    inspector = Inspector.from_engine(conn)
    if table_name not in inspector.get_table_names():
        return False
    indexes = [idx['name'] for idx in inspector.get_indexes(table_name)]
    return index_name in indexes


def upgrade():
    # Create users table if it doesn't exist
    if not table_exists('users'):
        op.create_table(
            'users',
            sa.Column('id', sa.Integer(), nullable=False),
            sa.Column('email', sa.String(), nullable=False),
            sa.Column('username', sa.String(), nullable=False),
            sa.Column('hashed_password', sa.String(), nullable=False),
            sa.Column('is_active', sa.Boolean(), nullable=True, default=True),
            sa.Column('created_at', sa.DateTime(timezone=True), server_default=sa.text('(CURRENT_TIMESTAMP)')),
            sa.Column('updated_at', sa.DateTime(timezone=True), nullable=True),
            sa.PrimaryKeyConstraint('id')
        )
    
    # Create indexes on users table if they don't exist
    try:
        if not index_exists('users', 'ix_users_email'):
            op.create_index(op.f('ix_users_email'), 'users', ['email'], unique=True)
    except (OperationalError, sa.exc.InternalError):
        pass
    
    try:
        if not index_exists('users', 'ix_users_id'):
            op.create_index(op.f('ix_users_id'), 'users', ['id'], unique=False)
    except (OperationalError, sa.exc.InternalError):
        pass
    
    try:
        if not index_exists('users', 'ix_users_username'):
            op.create_index(op.f('ix_users_username'), 'users', ['username'], unique=True)
    except (OperationalError, sa.exc.InternalError):
        pass
    
    # Add owner_id column to todos table if it doesn't exist
    if not column_exists('todos', 'owner_id'):
        op.add_column('todos', sa.Column('owner_id', sa.Integer(), nullable=True))
    
    # Create foreign key constraint if it doesn't exist
    try:
        op.create_foreign_key('fk_todos_owner_id_users', 'todos', 'users', ['owner_id'], ['id'])
    except (OperationalError, sa.exc.InternalError):
        pass


def downgrade():
    # Try to drop foreign key constraint
    try:
        op.drop_constraint('fk_todos_owner_id_users', 'todos', type_='foreignkey')
    except (OperationalError, sa.exc.InternalError):
        pass
    
    # Try to drop owner_id column from todos table
    if column_exists('todos', 'owner_id'):
        op.drop_column('todos', 'owner_id')
    
    # Try to drop indexes on users table
    try:
        if index_exists('users', 'ix_users_username'):
            op.drop_index(op.f('ix_users_username'), table_name='users')
    except (OperationalError, sa.exc.InternalError):
        pass
    
    try:
        if index_exists('users', 'ix_users_id'):
            op.drop_index(op.f('ix_users_id'), table_name='users')
    except (OperationalError, sa.exc.InternalError):
        pass
    
    try:
        if index_exists('users', 'ix_users_email'):
            op.drop_index(op.f('ix_users_email'), table_name='users')
    except (OperationalError, sa.exc.InternalError):
        pass
    
    # Try to drop users table
    if table_exists('users'):
        op.drop_table('users')