"""Add support_chat_sessions, support_chat_messages, support_knowledge (phase40)."""
from alembic import op
import sqlalchemy as sa

revision      = 'phase40_support_chat_kb'
down_revision = 'phase39_issue_handler_type'
branch_labels = None
depends_on    = None


def _table_exists(conn, table):
    row = conn.execute(sa.text("""
        SELECT COUNT(*) FROM INFORMATION_SCHEMA.TABLES
        WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME = :t
    """), {'t': table}).scalar()
    return bool(row)


def upgrade():
    conn = op.get_bind()

    if not _table_exists(conn, 'support_chat_sessions'):
        op.create_table(
            'support_chat_sessions',
            sa.Column('id',          sa.Integer, primary_key=True, autoincrement=True),
            sa.Column('customer_id', sa.Integer,
                      sa.ForeignKey('users.id', ondelete='SET NULL'), nullable=True),
            sa.Column('title',       sa.String(200), nullable=True),
            sa.Column('created_at',  sa.DateTime, nullable=False),
            sa.Column('last_msg_at', sa.DateTime, nullable=False),
        )

    if not _table_exists(conn, 'support_chat_messages'):
        op.create_table(
            'support_chat_messages',
            sa.Column('id',         sa.Integer, primary_key=True, autoincrement=True),
            sa.Column('session_id', sa.Integer,
                      sa.ForeignKey('support_chat_sessions.id', ondelete='CASCADE'),
                      nullable=False),
            sa.Column('role',       sa.String(20), nullable=False),
            sa.Column('content',    sa.Text, nullable=False),
            sa.Column('created_at', sa.DateTime, nullable=False),
        )

    if not _table_exists(conn, 'support_knowledge'):
        op.create_table(
            'support_knowledge',
            sa.Column('id',         sa.Integer, primary_key=True, autoincrement=True),
            sa.Column('title',      sa.String(200), nullable=False),
            sa.Column('body',       sa.Text, nullable=False),
            sa.Column('active',     sa.Boolean, nullable=False, server_default='1'),
            sa.Column('created_by', sa.Integer,
                      sa.ForeignKey('users.id', ondelete='SET NULL'), nullable=True),
            sa.Column('created_at', sa.DateTime, nullable=False),
            sa.Column('updated_at', sa.DateTime, nullable=False),
        )


def downgrade():
    op.drop_table('support_knowledge')
    op.drop_table('support_chat_messages')
    op.drop_table('support_chat_sessions')