Removing the cyclomatic complexity

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

lib/formats/json/parser.js

@@ -2,28 +2,40 @@ function JSONParser() {
 
 }
 
+const invalidPayloadTypeError =
+  new Error("invalid payload type, allowed are: string or object");
+
+const nullOrIndefinedPayload =
+  new Error("null or undefined payload");
+
+// Functions
+const isString = (v) => (typeof v) === "string";
+const isObject = (v) => (typeof v) === "object";
+const isDefined = (v) => v && (typeof v) != "undefined";
+const isDefinedOrThrow = (v) =>
+  (isDefined(v) ? () => true
+    : (() => {throw nullOrIndefinedPayload})());
+
+const isValidPayloadOrThrow = (v) =>
+  isDefinedOrThrow(v)()
+    && (isString(v)
+          ? true
+          : isObject(v)
+            ? true
+            : (() => {throw invalidPayloadTypeError})());
+
+const asJSON = (v) => (isString(v) ? JSON.parse(v) : v);
+
 /**
  * Level 0 of validation: is that string? is that JSON?
  */
 function validateAndParse(payload) {
-  var json = payload;
 
-  if(payload) {
-    if( (typeof payload) == "string"){
-      try {
-        json = JSON.parse(payload);
-
-      }catch(e) {
-        throw {message: "invalid json payload", errors: e};
-      }
-
-    } else if( (typeof payload) != "object"){
-      // anything else
-      throw {message: "invalid payload type, allowed are: string or object"};
-    }
-  } else {
-    throw {message: "null or undefined payload"};
-  }
+  var json =
+    Array.of(payload)
+      .filter(isValidPayloadOrThrow)
+      .map(asJSON)
+      .shift();
 
   return json;
 }

test/formats/json/parser_test.js

@@ -63,7 +63,7 @@ describe("JSON Event Format Parser", () => {
 
     // act and assert
     expect(parser.parse.bind(parser, payload))
-        .to.throw("invalid json payload");
+        .to.throw("Unexpected token g in JSON at position 0");
   });
 
   it("Must accept the CloudEvent spec 0.2 as JSON", () => {