Update the readme

Signed-off-by: Fabio José <[email protected]>

Author: fabiojose

README.md

@@ -1,2 +1,173 @@
 # sdk-javascript
 Javascript SDK for CloudEvents
+
+> This is a WIP
+
+# Repository Structure
+
+```text
+├── index.js
+├── lib
+│   ├── cloudevent.js
+│   ├── jsonformatter.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
+
+```
+
+* `index.js`: library exports
+
+* `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/master/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
+
+/*
+ * Check the spec constraints, throwing an error if do not pass.
+ */
+Spec.check()
+
+```
+
+# 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);
+
+```
+
+## How to construct instances?
+
+```js
+/* 
+ * 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");
+
+```
+
+## How to get the formatted payload?
+
+```js
+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();
+ 
+```
+
+> 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)