"""Configuration loader with YAML parsing and environment variable substitution."""
import os
import re
from pathlib import Path
from typing import Any
import yaml
from pydantic import ValidationError
from overwatch_mcp.models.config import Config
class ConfigError(Exception):
"""Configuration loading or validation error."""
pass
def substitute_env_vars(data: Any) -> Any:
"""
Recursively substitute ${VAR} patterns with environment variables.
Supports:
- ${VAR} - required, raises error if not set
- ${VAR:-} - optional, uses empty string if not set
- ${VAR:-default} - uses "default" if not set
Raises ConfigError if a required environment variable is not set.
"""
if isinstance(data, dict):
return {key: substitute_env_vars(value) for key, value in data.items()}
elif isinstance(data, list):
return [substitute_env_vars(item) for item in data]
elif isinstance(data, str):
# Find all ${VAR} or ${VAR:-default} patterns
pattern = r'\$\{([^}]+)\}'
matches = re.findall(pattern, data)
result = data
for match in matches:
# Parse VAR:-default syntax
if ":-" in match:
var_name, default_value = match.split(":-", 1)
env_value = os.environ.get(var_name, default_value)
else:
var_name = match
env_value = os.environ.get(var_name)
if env_value is None:
raise ConfigError(
f"Environment variable '{var_name}' is required but not set"
)
result = result.replace(f"${{{match}}}", env_value)
# Return None for empty optional values (allows Pydantic to use defaults)
if result == "":
return None
return result
else:
return data
def load_config(config_path: str | Path) -> Config:
"""
Load and validate configuration from YAML file.
Args:
config_path: Path to config.yaml file
Returns:
Validated Config object
Raises:
ConfigError: If file not found, YAML invalid, env vars missing, or validation fails
"""
config_path = Path(config_path)
# Check file exists
if not config_path.exists():
raise ConfigError(f"Config file not found: {config_path}")
# Load YAML
try:
with open(config_path) as f:
raw_data = yaml.safe_load(f)
except yaml.YAMLError as e:
raise ConfigError(f"Invalid YAML in config file: {e}")
if raw_data is None:
raise ConfigError("Config file is empty")
# Substitute environment variables
try:
processed_data = substitute_env_vars(raw_data)
except ConfigError:
raise # Re-raise ConfigError as-is
# Validate with Pydantic
try:
config = Config(**processed_data)
except ValidationError as e:
raise ConfigError(f"Config validation failed: {e}")
return config
def load_config_from_dict(data: dict[str, Any]) -> Config:
"""
Load and validate configuration from dictionary (for testing).
Args:
data: Configuration dictionary
Returns:
Validated Config object
Raises:
ConfigError: If validation fails
"""
try:
config = Config(**data)
except ValidationError as e:
raise ConfigError(f"Config validation failed: {e}")
return config
