Employ JSON Schema to validate payloads

Signed-off-by: Fabio José <fabiojose@gmail.com>

lib/specs/spec_0_2.js

@@ -1,5 +1,13 @@
 var uuid  = require("uuid/v4");
 var empty = require("is-empty");
+var Ajv   = require("ajv");
+
+const schema = require("../../ext/spec_0_2.json");
+
+// Default options
+const ajv = new Ajv();
+
+const validate = ajv.compile(schema);
 
 function Spec02(){
   this.payload = {
@@ -13,22 +21,12 @@ function Spec02(){
  */
 Spec02.prototype.check = function(){
 
-  if(empty(this.payload["type"])) {
+  var valid = validate(this.payload);
-    throw {message: "'type' is invalid"};
+
+  if(!valid) {
+    throw {message: "invalid payload"};
   }
 
-  if(empty(this.payload["specversion"])) {
-    throw {message: "'specversion' is invalid"};
-  }
-
-  if(this.payload["specversion"] !== "0.2") {
-    throw {message: "'specversion' value is invalid: '"
-      + this.payload["specversion"] + "'"};
-  }
-
-  if(empty(this.payload["id"])) {
-    throw {message: "'id' is invalid"};
-  }
 };
 
 Spec02.prototype.type = function(_type){

package.json

@@ -30,6 +30,7 @@
   },
   "homepage": "https://github.com/cloudevents/sdk-javascript#readme",
   "dependencies": {
+    "ajv": "^6.7.0",
     "axios": "0.18.0",
     "is-empty": "1.2.0",
     "uri-js": "4.2.2",

test/cloudevent_spec_0_2.js

@@ -73,7 +73,7 @@ describe("CloudEvents Spec 0.2 - JavaScript SDK", () => {
           cloudevent.type("");
           expect(cloudevent.format.bind(cloudevent))
             .to
-            .throw("'type' is invalid");
+            .throw("invalid payload");
         });
 
         it("must be a non-empty string", () => {
@@ -95,7 +95,15 @@ describe("CloudEvents Spec 0.2 - JavaScript SDK", () => {
           cloudevent.spec.payload.specversion = "";
           expect(cloudevent.format.bind(cloudevent))
             .to
-            .throw("'specversion' is invalid");
+            .throw("invalid payload");
+          cloudevent.spec.payload.specversion = "0.2";
+        });
+
+        it("should throw an error when the value is not '0.2'", () => {
+          cloudevent.spec.payload.specversion = "0.4";
+          expect(cloudevent.format.bind(cloudevent))
+            .to
+            .throw("invalid payload");
           cloudevent.spec.payload.specversion = "0.2";
         });
       });
@@ -105,7 +113,7 @@ describe("CloudEvents Spec 0.2 - JavaScript SDK", () => {
           cloudevent.id("");
           expect(cloudevent.format.bind(cloudevent))
             .to
-            .throw("'id' is invalid");
+            .throw("invalid payload");
         });
         it("must be a non-empty string", () => {
           cloudevent.id("my.id-0x0090");