#!/usr/bin/env python
# -*- coding: utf-8 -*-
"""SQL 工具：标识符转义、语句拆分、系统对象黑名单"""
from typing import List

PROTECTED_DATABASES = frozenset({
    "postgres",
    "template0",
    "template1",
    "mysql",
    "information_schema",
    "performance_schema",
    "sys",
    "master",
    "tempdb",
    "model",
    "msdb",
})

PROTECTED_SCHEMAS = frozenset({
    "pg_catalog",
    "information_schema",
    "pg_toast",
    "sys",
    "guest",
    "db_owner",
    "db_accessadmin",
    "db_securityadmin",
    "db_ddladmin",
    "db_backupoperator",
    "db_datareader",
    "db_datawriter",
    "db_denydatareader",
    "db_denydatawriter",
})

ORACLE_PROTECTED_SCHEMAS = frozenset({
    "sys",
    "system",
    "outln",
    "xdb",
    "ctxsys",
    "mdsys",
    "orddata",
    "ordsys",
    "lbacsys",
    "dbsnmp",
    "appqossys",
    "audsys",
    "gsmadmin_internal",
    "oav",
    "ordplugins",
    "si_informtn_schema",
    "wmsys",
})


def is_protected_database(name: str, db_type: str = "") -> bool:
    lower = name.lower()
    if lower in PROTECTED_DATABASES:
        return True
    if (db_type or "").lower() == "oracle":
        return False
    return False


def is_protected_schema(name: str, db_type: str = "") -> bool:
    lower = name.lower()
    if lower in PROTECTED_SCHEMAS:
        return True
    if lower.startswith("db_"):
        return True
    if (db_type or "").lower() == "oracle" and lower in ORACLE_PROTECTED_SCHEMAS:
        return True
    return False


def _normalize_db_type(db_type: str) -> str:
    db = (db_type or "postgresql").lower()
    if db in ("mssql", "sql server"):
        return "sqlserver"
    if db in ("postgres", "psql"):
        return "postgresql"
    return db


def quote_identifier(name: str, db_type: str) -> str:
    """按数据库类型转义标识符"""
    db = _normalize_db_type(db_type)
    if db == "mysql":
        return f"`{name.replace('`', '``')}`"
    if db in ("sqlserver", "mssql"):
        return f"[{name.replace(']', ']]')}]"
    if db == "oracle":
        return f'"{name.replace(chr(34), chr(34) + chr(34))}"'
    return f'"{name.replace(chr(34), chr(34) + chr(34))}"'


def quote_table(schema: str | None, table: str, db_type: str) -> str:
    if schema:
        return f"{quote_identifier(schema, db_type)}.{quote_identifier(table, db_type)}"
    return quote_identifier(table, db_type)


def split_sql_statements(sql: str) -> List[str]:
    """按分号拆分 SQL，忽略字符串与 dollar-quote 内的分号"""
    if not sql or not sql.strip():
        return []

    statements: List[str] = []
    current: List[str] = []
    i = 0
    n = len(sql)
    in_single = False
    in_double = False
    in_backtick = False
    dollar_tag: str | None = None

    while i < n:
        if dollar_tag is None and not in_single and not in_double and not in_backtick:
            if sql[i] == "$":
                j = i + 1
                while j < n and sql[j] != "$" and (sql[j].isalnum() or sql[j] == "_"):
                    j += 1
                if j < n and sql[j] == "$":
                    dollar_tag = sql[i : j + 1]
                    current.append(dollar_tag)
                    i = j + 1
                    continue
            if sql[i] == "'":
                in_single = True
                current.append(sql[i])
                i += 1
                continue
            if sql[i] == '"':
                in_double = True
                current.append(sql[i])
                i += 1
                continue
            if sql[i] == "`":
                in_backtick = True
                current.append(sql[i])
                i += 1
                continue
            if sql[i] == ";":
                stmt = "".join(current).strip()
                if stmt:
                    statements.append(stmt)
                current = []
                i += 1
                continue
        elif dollar_tag is not None:
            if sql.startswith(dollar_tag, i):
                current.append(dollar_tag)
                i += len(dollar_tag)
                dollar_tag = None
                continue
        elif in_single:
            if sql[i] == "'" and i + 1 < n and sql[i + 1] == "'":
                current.append("''")
                i += 2
                continue
            if sql[i] == "'":
                in_single = False
            current.append(sql[i])
            i += 1
            continue
        elif in_double:
            if sql[i] == '"' and i + 1 < n and sql[i + 1] == '"':
                current.append('""')
                i += 2
                continue
            if sql[i] == '"':
                in_double = False
            current.append(sql[i])
            i += 1
            continue
        elif in_backtick:
            if sql[i] == "`" and i + 1 < n and sql[i + 1] == "`":
                current.append("``")
                i += 2
                continue
            if sql[i] == "`":
                in_backtick = False
            current.append(sql[i])
            i += 1
            continue

        current.append(sql[i])
        i += 1

    stmt = "".join(current).strip()
    if stmt:
        statements.append(stmt)
    return statements