# Access Token Provider
This package provides a convenient retrieval mechanism of access
tokens. Access Token Provider supporting multiple provider backends,
including OAuth2 Resource Owner Password Credentials Grant, file-based
token access (e.g. for Kubernetes) and fetching tokens from the
environment (e.g. for local testing). The package is configurable via
environment variables. It uses Katip for logging.
## Examples
```haskell
import qualified Security.AccessTokenProvider as ATP
retrieveSomeToken :: KatipContextT IO ()
retrieveSomeToken = do
tokenProvider <- ATP.new (AccessTokenName "token-name")
token <- ATP.retrieveAccessToken tokenProvider
liftIO $ print token
```
## Configuration
Configuration is done by setting the environment variable `ATP_CONF`.
### OAuth2 based token retrieval
For OAuth2 (Resource Owner Password Credentials Grant) provider, use:
```json
{
"provider": "ropcg",
"credentials_directory": "/optional/credentials/directory",
"auth_endpoint": "<OAuth2 authentication endpoint>",
"tokens": {"token-name": {"scopes": ["first-scope", "second-scope"]}}
}
```
The `credentials_directory` setting defaults to the content of the
environment variable `CREDENTIALS_DIR`. It is expected to contain the
files `user.json` and `client.json`, containing the user and client
credentials respectively.
### File based token retrieval (e.g. for Kubernetes)
```json
{
"provider": "file",
"tokens": {"token-name": "/some/file/name"}
}
```
As a short cut, you can simply save a token path directly in the
environment variable `TOKEN_FILE`.
### Environment based token retrieval (e.g. for testing)
```json
{
"provider": "fixed",
"tokens": {"token-name": "some-fixed-token"}
}
```
As a short cut, you can simply save a token directly in the
environment variable `TOKEN`.