# SourceScribe Configuration Loader

## File Purpose and Overview
The `loader.py` file in the `sourcescribe/config` module of the SourceScribe project is responsible for loading and managing the application's configuration settings. It provides a `ConfigLoader` class that handles the loading, saving, and default configuration creation for the SourceScribe application.

## Main Components

### `ConfigLoader` Class
The `ConfigLoader` class is the main component of this file, providing the following key functionality:

1. **Load Configuration from File**: The `load_from_file()` method loads the SourceScribe configuration from a YAML file, parsing the data and returning a `SourceScribeConfig` instance.
2. **Find Configuration File**: The `find_config()` method searches upwards from a given start path (or the current working directory) to locate a valid SourceScribe configuration file.
3. **Load or Default Configuration**: The `load_or_default()` method attempts to load the configuration from a specified file path, or if not provided, it searches for a configuration file and returns a default configuration if none is found.
4. **Save Configuration to File**: The `save_to_file()` method saves a `SourceScribeConfig` instance to a YAML file at the specified output path.
5. **Create Default Configuration**: The `create_default_config()` method generates a default `SourceScribeConfig` instance and saves it to the specified output path.
6. **Inject Environment Variables**: The `_inject_env_vars()` and `_inject_env_vars_to_config()` methods handle the injection of environment variables, such as API keys and base URLs, into the configuration data and object, respectively.

## Key Functionality
The main functionality of the `ConfigLoader` class is to provide a centralized and consistent way to load, manage, and persist the SourceScribe application's configuration settings. This includes:

- Loading configuration from a YAML file
- Searching for a configuration file in the file system
- Providing a default configuration when no file is found
- Saving the configuration to a YAML file
- Injecting environment variables into the configuration data and object

## Dependencies and Imports
The `loader.py` file imports the following modules and classes:

- `os`: For interacting with the operating system and file paths
- `yaml`: For parsing and serializing YAML data
- `pathlib.Path`: For working with file paths
- `typing.Optional`, `typing.Dict`, and `typing.Any`: For type annotations
- `sourcescribe.config.models.SourceScribeConfig` and `sourcescribe.config.models.LLMConfig`: The configuration models used by the application

## Usage Examples
Here are some examples of how the `ConfigLoader` class can be used:

```python
# Load configuration from a specific file
config = ConfigLoader.load_from_file("/path/to/config.yaml")

# Find and load configuration from the file system
config = ConfigLoader.load_or_default()

# Save configuration to a file
ConfigLoader.save_to_file(config, "/path/to/output.yaml")

# Create a default configuration and save it
default_config = ConfigLoader.create_default_config("/path/to/default.yaml")
```

## Important Implementation Details
1. **Configuration File Naming**: The `ConfigLoader` class uses a set of default configuration file names (`DEFAULT_CONFIG_NAMES`) to search for the configuration file in the file system.
2. **Environment Variable Injection**: The `_inject_env_vars()` and `_inject_env_vars_to_config()` methods handle the injection of environment variables, such as API keys and base URLs, into the configuration data and object, respectively.
3. **YAML Serialization**: The `save_to_file()` method uses the `yaml.dump()` function to serialize the `SourceScribeConfig` instance to a YAML file, with the `mode='json'` argument to ensure that enums are serialized as strings.
4. **Default Configuration Generation**: The `create_default_config()` method generates a default `SourceScribeConfig` instance and saves it to the specified output path.