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"""

Copyright (c) Microsoft Corporation.

Licensed under the MIT license.

Connection string builder for mssql-python.

Reconstructs ODBC connection strings from parameter dictionaries

with proper escaping and formatting per MS-ODBCSTR specification.

"""

from typing import Dict, Optional

from mssql_python.constants import _CONNECTION_STRING_DRIVER_KEY

class _ConnectionStringBuilder:

"""

Internal builder for ODBC connection strings. Not part of public API.

Handles proper escaping of special characters and reconstructs

connection strings in ODBC format.

"""

def __init__(self, initial_params: Optional[Dict[str, str]] = None):

"""

Initialize the builder with optional initial parameters.

Args:

initial_params: Dictionary of initial connection parameters

"""

self._params: Dict[str, str] = initial_params.copy() if initial_params else {}

def add_param(self, key: str, value: str) -> "_ConnectionStringBuilder":

"""

Add or update a connection parameter.

Args:

key: Parameter name (should be normalized canonical name)

value: Parameter value

Returns:

Self for method chaining

"""

self._params[key] = str(value)

return self

def build(self) -> str:

"""

Build the final connection string.

Returns:

ODBC-formatted connection string with proper escaping

Note:

- Driver parameter is placed first

- Other parameters are sorted for consistency

- Values are escaped if they contain special characters

"""

parts = []

# Build in specific order: Driver first, then others

if _CONNECTION_STRING_DRIVER_KEY in self._params:

parts.append(f"Driver={self._escape_value(self._params['Driver'])}")

# Add other parameters (sorted for consistency)

for key in sorted(self._params.keys()):

if key == "Driver":

continue # Already added

value = self._params[key]

escaped_value = self._escape_value(value)

parts.append(f"{key}={escaped_value}")

# Join with semicolons

return ";".join(parts)

def _escape_value(self, value: str) -> str:

"""

Escape a parameter value if it contains special characters.

- Values containing ';', '{', '}', '=', or spaces should be braced for safety

- '}' inside braced values is escaped as '}}'

- '{' does not need to be escaped

Args:

value: Parameter value to escape

Returns:

Escaped value (possibly wrapped in braces)

Examples:

>>> builder = _ConnectionStringBuilder()

>>> builder._escape_value("localhost")

'localhost'

>>> builder._escape_value("local;host")

'{local;host}'

>>> builder._escape_value("p}w{d")

'{p}}w{d}'

>>> builder._escape_value("ODBC Driver 18 for SQL Server")

'{ODBC Driver 18 for SQL Server}'

"""

if not value:

return value

# Check if value contains special characters that require bracing

# Include spaces and = for safety, even though technically not always required

needs_braces = any(ch in value for ch in ";{}= ")

if needs_braces:

# Escape closing braces by doubling them (ODBC requirement)

# Opening braces do not need to be escaped

escaped = value.replace("}", "}}")

return f"{{{escaped}}}"

else:

return value