feat: metric model

__tests__/src/shared/model/metric.spec.js

@@ -0,0 +1,23 @@
+import Metric from '../../../../src/shared/model/metric.js';
+
+describe('Metric', () => {
+  it('should throw with an inexisting dimension', () => {
+    expect(() => {
+      new Metric('my-made-up-dimension', 1);
+    }).toThrow(/Invalid dimension/);
+    //TODO https://github.com/lfilho/ddg-test-project/issues/46
+  });
+
+  it('accepts a known dimension', () => {
+    expect(() => {
+      new Metric(Metric.dimensions.REQUEST_BLOCKED, 1);
+    }).not.toThrow();
+  });
+
+  it('requires both dimension and value args', () => {
+    expect(() => {
+      new Metric('one-arg');
+    }).toThrow(/Metric constructor needs both a dimension and value for it/);
+    //TODO https://github.com/lfilho/ddg-test-project/issues/46
+  });
+});

src/lib/model/list.js

@@ -8,7 +8,7 @@ export default class List {
   constructor(type) {
     if (!type) {
       throw new Error('List constructor needs a type');
-      //TODO Refactor Error strategy later on to contain an unique error code and both technical and user friendly messages
+      //TODO https://github.com/lfilho/ddg-test-project/issues/46
     }
     this.list = new Set();
     this.type = type;

src/shared/model/metric.js

@@ -0,0 +1,29 @@
+const DIMENSIONS = Object.freeze({
+  REQUEST_BLOCKED: 'REQUEST_BLOCKED',
+});
+
+export default class Metric {
+  /**
+   * A simple dimension-value tuple
+   */
+  constructor(dimension, value) {
+    if (!dimension || !value) {
+      //TODO https://github.com/lfilho/ddg-test-project/issues/46
+      throw new Error(
+        'Metric constructor needs both a dimension and value for it'
+      );
+    }
+    const possibleDimensions = Object.keys(DIMENSIONS);
+    if (!possibleDimensions.includes(dimension)) {
+      //TODO https://github.com/lfilho/ddg-test-project/issues/46
+      throw new Error(`Invalid dimension. Valid ones: ${possibleDimensions}`);
+    }
+
+    this.dimension = dimension;
+    this.value = value;
+  }
+
+  static get dimensions() {
+    return DIMENSIONS;
+  }
+}