"""迁移 037：PlanData、证据与不可变确认快照。"""
import logging

from sqlalchemy import inspect, text

logger = logging.getLogger(__name__)


def _add_columns_if_missing(table_name: str, columns: dict[str, str]) -> None:
    """一次读取现有列后完成本表变更，避免未提交 DDL 与二次反射互锁。"""
    from insurance.db.compat import db

    existing = {item["name"] for item in inspect(db.engine).get_columns(table_name)}
    for column_name, ddl in columns.items():
        if column_name not in existing:
            db.session.execute(text(
                f"ALTER TABLE {table_name} ADD COLUMN {column_name} {ddl}"
            ))


def migrate():
    from insurance.db.compat import db
    from insurance.models.plan_snapshot import (
        InsuranceFieldEvidence,
        InsurancePlanOverride,
        InsurancePlanSnapshot,
    )

    for model in (InsurancePlanSnapshot, InsuranceFieldEvidence, InsurancePlanOverride):
        model.__table__.create(bind=db.engine, checkfirst=True)

    inspector = inspect(db.engine)
    tables = set(inspector.get_table_names())
    if "poster_case_uploads" in tables:
        _add_columns_if_missing("poster_case_uploads", {
            "document_id": "BIGINT",
            "snapshot_id": "BIGINT",
        })
    if "insurance_ppt_sessions" in tables:
        _add_columns_if_missing("insurance_ppt_sessions", {
            "snapshot_ids_json": "TEXT",
        })
    db.session.commit()
    logger.info("[migrate_037] PlanData 快照、证据与人工覆盖迁移完成")