"""补建缺失列：segments.audio_duration_seconds, conversations.deleted_at

0001 用 create_all 建表，对已有表不会 ALTER 追加列。
本迁移补齐 ORM 模型中存在但生产库缺失的两列。

Revision ID: 0019_backfill_missing_columns
Revises: 0018_users_language_preference
"""

from typing import Sequence, Union

import sqlalchemy as sa

from alembic import op

revision: str = "0019_backfill_missing_columns"
down_revision: Union[str, None] = "0018_users_language_preference"
branch_labels: Union[str, Sequence[str], None] = None
depends_on: Union[str, Sequence[str], None] = None


def _column_names(table_name: str) -> set[str]:
    bind = op.get_bind()
    inspector = sa.inspect(bind)
    return {column["name"] for column in inspector.get_columns(table_name)}


def upgrade() -> None:
    seg_cols = _column_names("segments")
    if "audio_duration_seconds" not in seg_cols:
        op.add_column(
            "segments",
            sa.Column("audio_duration_seconds", sa.Integer(), nullable=True),
        )

    conv_cols = _column_names("conversations")
    if "deleted_at" not in conv_cols:
        op.add_column(
            "conversations",
            sa.Column("deleted_at", sa.DateTime(timezone=True), nullable=True),
        )


def downgrade() -> None:
    conv_cols = _column_names("conversations")
    if "deleted_at" in conv_cols:
        op.drop_column("conversations", "deleted_at")

    seg_cols = _column_names("segments")
    if "audio_duration_seconds" in seg_cols:
        op.drop_column("segments", "audio_duration_seconds")