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# sdk-javascript
Javascript SDK for CloudEvents

> This is a WIP

## Installation

This CloudEvents SDK requires nodejs 6.11+

### Nodejs

```sh
npm install cloudevents-sdk
```
## Specification Support

These are the supported specifications by this version.

| **Specifications**         | **v0.1** | **v0.2** |
|----------------------------|----------|----------|
| CloudEvents                | yes      | yes      |
| HTTP Transport Binding     | yes      | yes      |
| JSON Event Format          | yes      | yes      |

## How to use

The `Cloudevent` constructor arguments.

```js

/*
 * spec  : if is null, set the spec 0.1 impl
 * format: if is null, set the JSON Format 0.1 impl
 */
Cloudevent(spec, format);

```

### Usage

```js
var Cloudevent = require("cloudevents-sdk");

/*
 * Constructs a default instance with:
 *   - Spec 0.1
 *   - JSON Format 0.1
 */
var cloudevent01 = new Cloudevent();

/*
 * Implemented using Builder Design Pattern
 */
cloudevent01
  .type("com.github.pull.create")
  .source("urn:event:from:myapi/resourse/123");

/*
 * Backward compatibility by injecting methods from spec implementation to Cloudevent
 */
cloudevent01
 .eventTypeVersion("1.0");

/*
 * Constructs an instance with:
 *   - Spec 0.2
 *   - JSON Format 0.1
 */
var cloudevent02 = new Cloudevent(Cloudevent.specs["0.2"]);

/*
 * Different specs, but the same API.
 */
cloudevent02
  .type("com.github.pull.create")
  .source("urn:event:from:myapi/resourse/123");

```

#### Formatting

```js
var Cloudevent = require("cloudevents-sdk");

var cloudevent = new Cloudevent()
                       .type("com.github.pull.create")
                       .source("urn:event:from:myapi/resourse/123");

/*
 * Format the payload and return it.
 */
var formatted = cloudevent.format();

```

#### Emitting

```js
var Cloudevent = require("cloudevents-sdk");

// The event
var cloudevent = new Cloudevent()
                       .type("com.github.pull.create")
                       .source("urn:event:from:myapi/resourse/123");

// The binding configuration using POST
var config = {
  method: "POST",
  url   : "https://myserver.com"
};

// The binding instance
var binding = Cloudevent.bindings["http-structured0.1"](config);

// Emit the event using Promise
binding.emit(cloudevent)
  .then(response => {
    // Treat the response
    console.log(response.data);

  }).catch(err => {
    // Treat the error
    console.error(err);
  });
```

## Repository Structure

```text
├── index.js
├── lib
│   ├── bindings
│   │   └── http
│   │       └── structured_0_1.js
│   ├── cloudevent.js
│   ├── format
│   │   └── json_0_1.js
│   └── specs
│       ├── spec_0_1.js
│       └── spec_0_2.js
├── LICENSE
├── package.json
├── README.md
└── test
    ├── cloudevent_spec_0_1.js
    ├── cloudevent_spec_0_2.js
    └── http_binding_0_1.js
```

* `index.js`: library exports
* `lib/bindings`: every binding implementation goes here
* `lib/bindings/http`: every http binding implementation goes here
* `lib/bindings/http/structured_0_1.js`: implementation of structured HTTP Binding  
* `lib/cloudevent.js`: implementation of Cloudevent, an interface
* `lib/format/`: every format implementation goes here
* `lib/format/json_0_1.js`: implementation for JSON formatting [version 0.1](https://github.com/cloudevents/spec/blob/v0.1/json-format.md)
* `lib/specs/`: every spec implementation goes here
* `lib/specs/spec_0_1.js`: implementation for spec [version 0.1](https://github.com/cloudevents/spec/blob/v0.1/spec.md)
* `lib/specs/spec_0_2.js`: implementation for spec [version 0.2](https://github.com/cloudevents/spec/blob/v0.2/spec.md)
* `test/cloudevent_spec_0_1.js`: unit testing for spec 0.1
* `test/cloudevent_spec_0_2.js`: unit testing for spec 0.2

## Unit Testing

The unit test checks the result of formatted payload and the constraints.

```bash

npm test

```

## The API

### `Cloudevent` class

```js

/*
 * Format the payload and return an Object.
 */
Object Cloudevent.format()

/*
 * Format the payload as String.
 */
String Cloudevent.toString()

```

### `Formatter` classes

Every formatter class must implement these methods to work properly.

```js

/*
 * Format the Cloudevent payload argument and return an Object.
 */
Object Formatter.format(payload)

/*
 * Format the Cloudevent payload as String.
 */
String Formatter.toString(payload)

```

## `Spec` classes

Every Spec class must implement these methods to work properly.

```js

/*
 * The constructor must receives the Cloudevent type.
 */
Spec(Cloudevent)

/*
 * Checks the spec constraints, throwing an error if do not pass.
 */
Spec.check()

```
### `Binding` classes

Every Binding class must implement these methods to work properly.

```js

/*
 * The constructor must receives the map of configurations.
 */
Binding(config)

/*
 * Emits the event using an instance of Cloudevent.
 */
Binding.emit(cloudevent)

```

> See how to implement the method injection [here](lib/specs/spec_0_1.js#L17)
>
> Learn about [Builder Design Pattern](https://en.wikipedia.org/wiki/Builder_pattern)
>
> Check out the produced event payload using this [tool](https://webhook.site)