# OpenHIM mediator utils

This package contains a few useful functions to make it easier to develop OpenHIM
mediators. When creating a node.js mediator you can make use of it by installing
it through NPM as follows:

```sh
npm install --save openhim-mediator-utils
```

You can then use the package as follows:

```js
import utils from 'openhim-mediator-utils';

utils.registerMediator(...);
utils.authenticate(...);
utils.genAuthHeaders(...);
utils.activateHeartbeat(...);
utils.deactivateHearbeat(...);
utils.fetchConfig(...);
```

For commonjs projects use versions before version 1.0.0. These versions are still supported.

```sh
npm install --save openhim-mediator-utils@0
```

```js
const utils = require('openhim-mediator-utils)
```

## API details

### Mediator Registration

#### .registerMediator(options, mediatorConfig, callback)

Register this mediator with OpenHIM core using the supplied mediatorConfig. This
function takes an options object, the mediator config to register
this mediator with and a callback as parameters.

The options object has the following format:

* `options.apiURL` - the URL of the OpenHIM core API eg. "https://localhost:8080"
* `options.username` - the username of the user to be authenticate with
* `options.password` - the password for the user

`mediatorConfig` is an object that follows the mediatorConfig structure: <http://openhim.readthedocs.org/en/latest/dev-guide/mediators.html#mediator-registration>

The callback is called with an error object if an error occurs otherwise it is
called with nothing.

### OpenHIM API Authentication

#### .authenticate(options, callback)

Fetches authentication detail from the OpenHIM core to use for future
communication, options must contain:

* `options.apiURL` - the URL of the OpenHIM core API eg. "https://localhost:8080"
* `options.username` - the username of the user to be authenticated
* `options.trustSelfSigned` - [optional] boolean which defaults to false - if set to true, ignore self signed certificate errors (for non-production use)

callback will be called with an Error object if an error occurs, otherwise
the body received from the OpenHIM-core server is returned. This is an object
like the following `{salt: <userSalt>, ts: <timestampOfServer>}`.

#### .genAuthHeaders(options)

Generates authentication headers to make an authenticated API requests. This can
only be used after the `.authenticate()` function has been called for this
user. The username and password of the user must be passed to this function
as strings in the options object (eg. `{username: '<username>', password: '<password>'}`).

The authentication headers are returned as a headers object. eg.

```js
headers = {
 'Authorization': 'Basic <token>'
}
```

### Mediator Heartbeats and Configuration

#### .activateHeartbeat(options, interval)

Begins sending heartbeats to the OpenHIM-core server (also returns any config
changes). This function takes an options object with the following properties:

* `options.apiURL` - the URL of the OpenHIM core API eg. "https://localhost:8080"
* `options.username` - the username of the user to be authenticated
* `options.password` - the password for the user
* `options.urn` - the URN of the mediator to send heartbeats for
* `options.trustSelfSigned` - [optional] boolean which defaults to false - if set to true, ignore self signed certificate errors (for non-production use)

It also takes an interval parameter which is the interval to send heartbeats
in ms. This parameter default to 10s.

This function returns an event emitter which emits a 'config' event with a
config object each time the mediator config is changed on the OpenHIM. If an
error occurs an 'error' event is emitted with an error object.

#### .deactivateHeartbeat()

Deactivates the sending of heartbeats.

#### .fetchConfig(options, callback)

Forces the latest config to be returned from the OpenHIM-core. This is useful
when you need to fetch initial config at mediator startup (if you are just interested in the latest config updates use rather `.activateHeartbeat(...)` above). This function takes
an options object with the following properties:

* `options.apiURL` - the URL of the OpenHIM core API eg. "https://localhost:8080"
* `options.username` - the username of the user to be authenticated
* `options.password` - the password for the user
* `options.trustSelfSigned` - [optional] boolean which default to false - if set to true, ignore self signed certificate errors (for non-production use)

callback will be called with an Error object if an error occurs, otherwise
the config received from the OpenHIM-core server is returned.