"""登录客户（CUSTOMER）的 NL2SQL 权限快照服务。

与员工路径（permission_service.load_query_permission，按 nl2sql_query_role
配置）不同，客户权限不落库、不做管理后台：表白名单通过 sys_config 配置管理，
且只能从内置白名单中做"减法"，行级范围由服务端强制注入 customer_ids，
保证客户永远只能查询自己的数据。

列级校验：快照时从 information_schema 加载白名单表的真实列清单写入
columns，validate_select_sql 据此在执行前拦截 LLM 幻觉列（避免把
Unknown column 错误漏到执行期）。
"""
from __future__ import annotations

import logging
from inspect import isawaitable

from sqlalchemy import bindparam, text

logger = logging.getLogger(__name__)

# 客户可查询的内置表白名单（配置只能在其中做减法，不能新增表）
CUSTOMER_DEFAULT_TABLES: tuple[str, ...] = (
    "fin_holdings",
    "fin_transaction",
    "fin_product",
    "fund_nav_history",
    "fund_performance",
)

# 行级隔离：出现这些表的 SQL 会被强制注入 customer_id IN (<登录用户>) 条件
CUSTOMER_ROW_SCOPES: dict[str, dict[str, str]] = {
    "fin_holdings": {"type": "customer_ids", "column": "customer_id"},
    "fin_transaction": {"type": "customer_ids", "column": "customer_id"},
}

# 客户路径首期不开放敏感档案表；后续开放时在此配置 (table, column) -> mask_type
CUSTOMER_MASKS: dict[tuple[str, str], str] = {}

_TRUTHY = {"1", "true", "yes", "on"}

_COLUMNS_SQL = text(
    "SELECT TABLE_NAME AS table_name, COLUMN_NAME AS column_name "
    "FROM information_schema.columns "
    "WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME IN :tables "
    "ORDER BY TABLE_NAME, ORDINAL_POSITION"
).bindparams(bindparam("tables", expanding=True))


async def _load_real_columns(db, tables: set[str]) -> dict[str, set[str]] | None:
    """加载白名单表的真实列名；db 为 None 时返回 None（仅测试路径）。"""
    if db is None:
        return None
    result = await db.execute(_COLUMNS_SQL, {"tables": sorted(tables)})
    columns: dict[str, set[str]] = {}
    for row in result.mappings():
        table_name = str(row["table_name"] or "").strip()
        column_name = str(row["column_name"] or "").strip()
        if table_name and column_name:
            columns.setdefault(table_name, set()).add(column_name)
    return columns


def _denied_permission() -> dict:
    return {
        "can_query": False,
        "role": "customer_self",
        "tables": set(),
        "columns": None,
        "masks": {},
        "row_scopes": {},
        "max_rows": 0,
        "daily_quota": 0,
    }


async def _config(config_getter, key: str, default: str) -> str:
    value = config_getter(key, default)
    if isawaitable(value):
        value = await value
    if value is None or str(value).strip() == "":
        return default
    return str(value)


def _parse_allowed_tables(raw: str) -> set[str]:
    """解析表白名单配置；非法表名直接忽略，只允许内置白名单的子集。"""
    known = set(CUSTOMER_DEFAULT_TABLES)
    names = {
        item.strip().lower()
        for item in str(raw).replace("；", ",").replace(";", ",").split(",")
        if item.strip()
    }
    tables = names & known
    return tables


async def load_customer_query_permission(
    db,
    user_id: int,
    *,
    config_getter,
) -> dict:
    """每次请求重建客户权限快照。

    客户身份已由 API 层（require_customer）和会话归属校验保证，
    快照不依赖数据库中的角色配置；db 用于加载白名单表的真实列清单
    （传入 None 时跳过列清单，columns 保持 None，仅限测试路径）。
    """
    del user_id  # 权限与具体请求上下文无关，签名对齐 execute_query 的 permission_loader
    if config_getter is None:
        return _denied_permission()
    enabled = (await _config(config_getter, "nl2sql.customer.enabled", "true")).lower()
    if enabled not in _TRUTHY:
        return _denied_permission()

    raw_tables = await _config(
        config_getter,
        "nl2sql.customer.allowed_tables",
        ",".join(CUSTOMER_DEFAULT_TABLES),
    )
    tables = _parse_allowed_tables(raw_tables)
    if not tables:
        return _denied_permission()

    try:
        max_rows = int(await _config(config_getter, "nl2sql.customer.max_rows", "200"))
        daily_quota = int(
            await _config(config_getter, "nl2sql.customer.daily_quota", "20")
        )
    except ValueError:
        max_rows, daily_quota = 200, 20
    max_rows = max(1, max_rows)
    daily_quota = max(0, daily_quota)

    # 列级校验用真实列清单：拦截 LLM 幻觉列，避免执行期 Unknown column。
    # 信息读取失败时按"拒绝"处理（fail-closed），不让无列校验的快照放行。
    try:
        real_columns = await _load_real_columns(db, tables)
    except Exception:
        logger.exception("load customer nl2sql columns failed")
        return _denied_permission()

    return {
        "can_query": True,
        "role": "customer_self",
        "tables": tables,
        # 真实列清单（db=None 的测试路径保持 None = 不限列）
        "columns": real_columns,
        "masks": dict(CUSTOMER_MASKS),
        "row_scopes": {
            table: dict(scope)
            for table, scope in CUSTOMER_ROW_SCOPES.items()
            if table in tables
        },
        "max_rows": max_rows,
        "daily_quota": daily_quota,
    }