"""迁移 018: 为 PPT 解析任务增加进度字段。"""
import logging
from sqlalchemy import text

logger = logging.getLogger(__name__)


def migrate():
    """执行迁移。"""
    from insurance.db.compat import db

    columns = {
        "parse_progress": "INTEGER DEFAULT 0 NOT NULL",
        "parse_message": "TEXT",
        "parse_error": "TEXT",
        "parse_started_at": "TIMESTAMP",
        "parse_finished_at": "TIMESTAMP",
    }

    for column_name, column_type in columns.items():
        if _column_exists(db, "insurance_ppt_sessions", column_name):
            logger.info(f"[migrate_018] {column_name} 已存在，跳过")
            continue
        db.session.execute(text(
            f"ALTER TABLE insurance_ppt_sessions ADD COLUMN {column_name} {column_type}"
        ))
        db.session.commit()
        logger.info(f"[migrate_018] 已添加 {column_name} 列")


def _column_exists(db, table_name: str, column_name: str) -> bool:
    result = db.session.execute(text(
        "SELECT COUNT(*) FROM information_schema.columns "
        "WHERE table_name = :table_name AND column_name = :column_name"
    ), {"table_name": table_name, "column_name": column_name})
    return result.scalar() > 0