fix #7

Author: mavarazy

README.md

@@ -422,6 +422,34 @@ let rules = [{
 
 Rules engine will go through all the elements in the array and trigger `require` if `any` of the elements meet the criteria.
 
+### Extending available predicates
+
+If for some reason the list of [predicates](https://github.com/landau/predicate) is insufficient for your needs, you can extend them pretty easy,
+by specifying additional predicates in global import object.
+
+For example, if we want to add `range` predicate, that would verify, that integer value is in range, we can do it like this: 
+```js
+import predicate from "predicate";
+import Engine from "json-rules-engine-simplified";
+
+predicate.range = predicate.curry((val, range) => {
+  return predicate.num(val) &&
+    predicate.array(range) &&
+    predicate.equal(range.length, 2) &&
+    predicate.num(range[0]) &&
+    predicate.num(range[1]) &&
+    predicate.greaterEq(val, range[0]) &&
+    predicate.lessEq(val, range[1]);
+});
+
+let engine = new Engine([{
+  conditions: { age: { range: [ 20, 40 ] } },
+  event: "hit"
+}]);
+```
+
+Validation will automatically catch new extension and work as expected.
+
 ## Events
 
 Framework does not put any restrictions on event object, that will be triggered, in case conditions are meet

src/conditionsMeet.js

@@ -5,7 +5,9 @@ import selectn from "selectn";
 
 export default function conditionsMeet(conditions, formData) {
   if (!isObject(conditions) || !isObject(formData)) {
-    toError(`Rule ${conditions} with ${formData} can't be processed`);
+    toError(
+      `Rule ${JSON.stringify(conditions)} with ${formData} can't be processed`
+    );
   }
   return Object.keys(conditions).every(ref => {
     let refCondition = conditions[ref];

test/predicate.test.js

@@ -1,4 +1,5 @@
-const predicate = require("predicate");
+import predicate from "predicate";
+import Engine from "../src/Engine";
 
 test("equal work with same strings", function() {
   expect(predicate.eq("Will", "Will")).toBeTruthy();
@@ -14,3 +15,34 @@ test("work with empty", function() {
 test("and is not predicate", () => {
   expect(predicate.and).toBeUndefined();
 });
+
+predicate.range = predicate.curry((val, range) => {
+  return (
+    predicate.num(val) &&
+    predicate.array(range) &&
+    predicate.equal(range.length, 2) &&
+    predicate.greaterEq(val, range[0]) &&
+    predicate.lessEq(val, range[1])
+  );
+});
+
+let engine = new Engine([
+  {
+    conditions: { age: { range: [20, 40] } },
+    event: "hit",
+  },
+]);
+
+test("not in range left", () => {
+  return engine.run({ age: 10 }).then(events => expect(events).toEqual([]));
+});
+
+test("in range", () => {
+  return engine
+    .run({ age: 30 })
+    .then(events => expect(events).toEqual(["hit"]));
+});
+
+test("not in range right", () => {
+  return engine.run({ age: 50 }).then(events => expect(events).toEqual([]));
+});

test/validation.predicates.test.js

@@ -0,0 +1,21 @@
+import predicate from "predicate";
+import { listInvalidPredicates } from "../src/validation";
+
+let schema = {
+  type: "object",
+  properties: {
+    firstName: { type: "string" },
+  },
+};
+
+test("Check predicates", () => {
+  const conditions = [{ firstName: "somePredicate" }];
+
+  expect(listInvalidPredicates(conditions, schema)).toEqual(["somePredicate"]);
+
+  predicate.somePredicate = function() {
+    return false;
+  };
+
+  expect(listInvalidPredicates(conditions, schema)).toEqual([]);
+});