"""计提参数数据访问。

本层只 flush 不 commit —— 事务边界由 services 层控制。
时点化解析查询（窗口函数版）留存 db/queries/计提参数.sql。
"""

from datetime import date

from sqlalchemy import Select, delete, func, select
from sqlalchemy.orm import Session

from app.models import ParamChangeBatch, ParamDefinition, ParamValue

# ==================== 读取 ====================


def resolve_values(session: Session, biz_date: date) -> list[tuple[str, str, str, date]]:
    """时点化解析：每个 (param_id, dimension_value) 取生效日期 <= 业务日期的最新条目。

    排序 (effective_date DESC, id DESC) 保证同日多次变更取最新一条
    （不设日期唯一键，同日修正是合法留痕）。仅返回启用状态的参数定义。
    返回 (param_code, dimension_value, value_text, effective_date)。
    """
    row_number = (
        func.row_number()
        .over(
            partition_by=(ParamValue.param_id, ParamValue.dimension_value),
            order_by=(ParamValue.effective_date.desc(), ParamValue.id.desc()),
        )
        .label("rn")
    )
    subq = (
        select(
            ParamDefinition.param_code.label("param_code"),
            ParamValue.dimension_value.label("dimension_value"),
            ParamValue.value_text.label("value_text"),
            ParamValue.effective_date.label("effective_date"),
            row_number,
        )
        .join(ParamDefinition, ParamDefinition.id == ParamValue.param_id)
        .where(ParamValue.effective_date <= biz_date, ParamDefinition.status == 1)
        .subquery()
    )
    stmt = select(
        subq.c.param_code, subq.c.dimension_value, subq.c.value_text, subq.c.effective_date
    ).where(subq.c.rn == 1)
    return [
        (row.param_code, row.dimension_value, row.value_text, row.effective_date)
        for row in session.execute(stmt)
    ]


def latest_value_before(
    session: Session, param_id: int, dimension_value: str, biz_date: date
) -> ParamValue | None:
    """取某参数某维度在业务日期（含）之前的最新条目 —— 提交变更时记录「旧值」。"""
    stmt = (
        select(ParamValue)
        .where(
            ParamValue.param_id == param_id,
            ParamValue.dimension_value == dimension_value,
            ParamValue.effective_date <= biz_date,
        )
        .order_by(ParamValue.effective_date.desc(), ParamValue.id.desc())
        .limit(1)
    )
    return session.execute(stmt).scalar_one_or_none()


def list_definitions(session: Session, *, status: int | None = None) -> list[ParamDefinition]:
    """参数定义列表（目录）。"""
    stmt = select(ParamDefinition).order_by(ParamDefinition.sort_order, ParamDefinition.id)
    if status is not None:
        stmt = stmt.where(ParamDefinition.status == status)
    return list(session.execute(stmt).scalars())


def get_definition_by_code(session: Session, param_code: str) -> ParamDefinition | None:
    """按编码取参数定义。"""
    stmt = select(ParamDefinition).where(ParamDefinition.param_code == param_code)
    return session.execute(stmt).scalar_one_or_none()


def list_definitions_by_codes(
    session: Session, param_codes: list[str]
) -> dict[str, ParamDefinition]:
    """按编码批量取参数定义（提交批次的校验段用，消除逐条 N+1）。

    返回 {编码: 定义}；未定义的编码不在结果中，由调用方判缺失。
    """
    if not param_codes:
        return {}
    rows = session.execute(
        select(ParamDefinition).where(ParamDefinition.param_code.in_(param_codes))
    ).scalars()
    return {definition.param_code: definition for definition in rows}


def list_history(
    session: Session,
    param_id: int,
    *,
    offset: int,
    limit: int,
    dimension_value: str | None = None,
) -> list[tuple[ParamValue, ParamChangeBatch]]:
    """单参数的版本历史（含批次信息），最新在前。"""
    stmt = _history_stmt(session, param_id, dimension_value=dimension_value)
    return [(value, batch) for value, batch in session.execute(stmt.offset(offset).limit(limit))]


def count_history(session: Session, param_id: int, *, dimension_value: str | None = None) -> int:
    """统计单参数的历史条目数。"""
    stmt = select(func.count()).select_from(
        _history_stmt(session, param_id, dimension_value=dimension_value).subquery()
    )
    return int(session.execute(stmt).scalar_one())


def _history_stmt(session: Session, param_id: int, *, dimension_value: str | None) -> Select:
    """历史查询基语句：条目 join 批次（版本号/操作人），最新在前。"""
    stmt = (
        select(ParamValue, ParamChangeBatch)
        .join(ParamChangeBatch, ParamChangeBatch.id == ParamValue.batch_id)
        .where(ParamValue.param_id == param_id)
        .order_by(ParamValue.effective_date.desc(), ParamValue.id.desc())
    )
    if dimension_value is not None:
        stmt = stmt.where(ParamValue.dimension_value == dimension_value)
    return stmt


# ==================== 批次 ====================


def create_batch(session: Session, batch: ParamChangeBatch) -> ParamChangeBatch:
    """新增变更批次。只 flush 以取得自增 id。"""
    session.add(batch)
    session.flush()
    return batch


def get_batch_by_id(
    session: Session, batch_id: int, *, for_update: bool = False
) -> ParamChangeBatch | None:
    """按主键取批次。撤回校验走 ``for_update`` 锁行（防并发双撤）。"""
    if for_update:
        stmt = select(ParamChangeBatch).where(ParamChangeBatch.id == batch_id).with_for_update()
        return session.execute(stmt).scalar_one_or_none()
    return session.get(ParamChangeBatch, batch_id)


def list_batches(
    session: Session,
    *,
    offset: int,
    limit: int,
    start_date: date | None = None,
    end_date: date | None = None,
) -> list[ParamChangeBatch]:
    """分页查询变更批次（按创建时间倒序）。"""
    stmt = _batch_filters(select(ParamChangeBatch), start_date=start_date, end_date=end_date)
    return list(
        session.execute(
            stmt.order_by(ParamChangeBatch.create_time.desc(), ParamChangeBatch.id.desc())
            .offset(offset)
            .limit(limit)
        ).scalars()
    )


def count_batches(
    session: Session, *, start_date: date | None = None, end_date: date | None = None
) -> int:
    """统计符合条件的批次总数。"""
    stmt = _batch_filters(
        select(func.count(ParamChangeBatch.id)), start_date=start_date, end_date=end_date
    )
    return int(session.execute(stmt).scalar_one())


def _batch_filters(stmt: Select, *, start_date: date | None, end_date: date | None) -> Select:
    """批次筛选（生效日期区间，含边界）。列表与计数共用。"""
    if start_date is not None:
        stmt = stmt.where(ParamChangeBatch.effective_date >= start_date)
    if end_date is not None:
        stmt = stmt.where(ParamChangeBatch.effective_date <= end_date)
    return stmt


def list_values_by_batch(
    session: Session, batch_id: int
) -> list[tuple[ParamValue, ParamDefinition]]:
    """批次内全部条目（join 参数定义取编码/名称），按 id 排序。"""
    stmt = (
        select(ParamValue, ParamDefinition)
        .join(ParamDefinition, ParamDefinition.id == ParamValue.param_id)
        .where(ParamValue.batch_id == batch_id)
        .order_by(ParamValue.id)
    )
    return [(value, definition) for value, definition in session.execute(stmt)]


def delete_values_by_batch(session: Session, batch_id: int) -> None:
    """删除批次下全部条目（撤回未生效批次时使用，2.0 风格 delete 语句）。"""
    session.execute(delete(ParamValue).where(ParamValue.batch_id == batch_id))


def delete_batch(session: Session, batch: ParamChangeBatch) -> None:
    """删除批次本体（调用方须先删条目并完成保护校验）。"""
    session.delete(batch)
    session.flush()


# ==================== 写入 ====================


def create_value(session: Session, value: ParamValue) -> ParamValue:
    """新增版本条目（append-only，禁改禁删已生效条目）。只 flush。"""
    session.add(value)
    session.flush()
    return value


# ==================== 导出 ====================


def list_export_rows(
    session: Session, *, start_date: date | None = None, end_date: date | None = None
) -> list[tuple[ParamChangeBatch, ParamValue, ParamDefinition]]:
    """导出行：批次 × 条目 × 定义（变更人/时间/参数/维度/旧值/新值/生效日期）。"""
    stmt = (
        select(ParamChangeBatch, ParamValue, ParamDefinition)
        .join(ParamValue, ParamValue.batch_id == ParamChangeBatch.id)
        .join(ParamDefinition, ParamDefinition.id == ParamValue.param_id)
        .order_by(ParamChangeBatch.create_time.desc(), ParamChangeBatch.id.desc(), ParamValue.id)
    )
    if start_date is not None:
        stmt = stmt.where(ParamChangeBatch.effective_date >= start_date)
    if end_date is not None:
        stmt = stmt.where(ParamChangeBatch.effective_date <= end_date)
    return [(batch, value, definition) for batch, value, definition in session.execute(stmt)]