"""phase32 — add ios_version and last_seen_at to api_device_tokens

phase31 recorded as applied but ALTER statements never executed.
Uses INFORMATION_SCHEMA column-existence checks — safe on MySQL 5.7+.
Also drops the orphaned device_registrations table from phase30 if present.
"""

revision      = 'phase32_device_token_columns'
down_revision = 'phase31_device_registry'
branch_labels = None
depends_on    = None

from alembic import op
import sqlalchemy as sa


def _column_exists(conn, table, column):
    result = conn.execute(sa.text(
        "SELECT COUNT(*) FROM INFORMATION_SCHEMA.COLUMNS "
        "WHERE TABLE_SCHEMA = DATABASE() "
        "AND TABLE_NAME = :t AND COLUMN_NAME = :c"
    ), {"t": table, "c": column})
    return result.scalar() > 0


def _table_exists(conn, table):
    result = conn.execute(sa.text(
        "SELECT COUNT(*) FROM INFORMATION_SCHEMA.TABLES "
        "WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME = :t"
    ), {"t": table})
    return result.scalar() > 0


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

    if not _column_exists(bind, 'api_device_tokens', 'ios_version'):
        op.execute(sa.text(
            "ALTER TABLE api_device_tokens ADD COLUMN ios_version VARCHAR(20) NULL"
        ))

    if not _column_exists(bind, 'api_device_tokens', 'last_seen_at'):
        op.execute(sa.text(
            "ALTER TABLE api_device_tokens ADD COLUMN last_seen_at DATETIME NULL"
        ))

    op.execute(sa.text(
        "UPDATE api_device_tokens SET last_seen_at = registered_at WHERE last_seen_at IS NULL"
    ))

    if _table_exists(bind, 'device_registrations'):
        op.execute(sa.text("DROP TABLE device_registrations"))


def downgrade():
    bind = op.get_bind()

    if _column_exists(bind, 'api_device_tokens', 'ios_version'):
        op.execute(sa.text(
            "ALTER TABLE api_device_tokens DROP COLUMN ios_version"
        ))

    if _column_exists(bind, 'api_device_tokens', 'last_seen_at'):
        op.execute(sa.text(
            "ALTER TABLE api_device_tokens DROP COLUMN last_seen_at"
        ))