[ts][step_shotgun_surgery-01_base] Add premature abstractions

Author: santakadev

examples/typescript/ts-step_shotgun_surgery-01_base/src/Application/GetStepDuration.ts

@@ -1,16 +1,14 @@
 import StepId from '../Domain/StepId'
 import StepRepository from '../Domain/StepRepository'
-import VideoStep from "../Domain/VideoStep";
+import StepDurationCalculatorFactory from "../Domain/StepDurationCalculatorFactory";
 
 class GetStepDuration {
     constructor(private repository: StepRepository) {
     }
 
     execute(stepId: string): number {
         const step = this.repository.find(new StepId(stepId))
-        return step instanceof VideoStep ?
-            step.getVideoDuration() :
-            step.totalQuestions;
+        return StepDurationCalculatorFactory.build().calculate(step)
     }
 }
 

examples/typescript/ts-step_shotgun_surgery-01_base/src/Domain/DurationMultiplier.ts

@@ -0,0 +1,14 @@
+import Step from "./Step";
+import * as StepEnums from "./StepEnums";
+
+export function multiplierFor(step: Step): number {
+    if (step.type() === StepEnums.STEP_TYPE_VIDEO) {
+        return StepEnums.STEP_DURATION_MULTIPLIER_VIDEO;
+    }
+
+    if (step.type() === StepEnums.STEP_TYPE_QUIZ) {
+        return StepEnums.STEP_DURATION_MULTIPLIER_QUIZ;
+    }
+
+    return 1.0;
+}

examples/typescript/ts-step_shotgun_surgery-01_base/src/Domain/QuizStep.ts

@@ -5,7 +5,7 @@ import {STEP_TYPE_QUIZ} from "./StepEnums";
 class QuizStep extends Step {
     constructor(
         stepId: StepId,
-        public readonly totalQuestions: Number
+        public readonly totalQuestions: number
     ) {
         super(stepId);
     }

examples/typescript/ts-step_shotgun_surgery-01_base/src/Domain/Step.ts

@@ -1,9 +1,7 @@
 import StepId from "./StepId";
 
 abstract class Step {
-
-    protected constructor(private readonly _id: StepId) {
-    }
+    protected constructor(private readonly _id: StepId) {}
 
     abstract type();
 }

examples/typescript/ts-step_shotgun_surgery-01_base/src/Domain/StepDurationCalculator.ts

@@ -0,0 +1,8 @@
+import Step from "./Step";
+
+interface StepDurationCalculator {
+    supports(step: Step): boolean;
+    calculate(step: Step): number;
+}
+
+export default StepDurationCalculator

examples/typescript/ts-step_shotgun_surgery-01_base/src/Domain/StepDurationCalculatorChain.ts

@@ -0,0 +1,28 @@
+import StepDurationCalculator from "./StepDurationCalculator";
+import Step from "./Step";
+import {STEP_TYPES} from "./StepEnums";
+
+class StepDurationCalculatorChain implements StepDurationCalculator {
+    constructor(private calculators: Array<StepDurationCalculator>) {
+    }
+
+    supports(step: Step): boolean {
+        return STEP_TYPES.some(step.type);
+    }
+
+    calculate(step: Step): number {
+        if (!this.supports(step)) {
+            throw new Error(`Missing calculator for step type ${step.type()}`);
+        }
+
+        for (let calculator of this.calculators) {
+            if (calculator.supports(step)) {
+                return calculator.calculate(step);
+            }
+        }
+
+        throw new Error(`Missing calculator for step type ${step.type()}`);
+    }
+}
+
+export default StepDurationCalculatorChain

examples/typescript/ts-step_shotgun_surgery-01_base/src/Domain/StepDurationCalculatorFactory.ts

@@ -0,0 +1,17 @@
+import StepDurationCalculator from "./StepDurationCalculator";
+import StepDurationCalculatorVideo from "./StepDurationCalculatorVideo";
+import StepDurationCalculatorQuiz from "./StepDurationCalculatorQuiz";
+import StepDurationCalculatorChain from "./StepDurationCalculatorChain";
+
+class StepDurationCalculatorFactory {
+    static build(): StepDurationCalculator
+    {
+        // Remember to add the calculator!!
+        return new StepDurationCalculatorChain([
+            new StepDurationCalculatorVideo(),
+            new StepDurationCalculatorQuiz(),
+        ]);
+    }
+}
+
+export default StepDurationCalculatorFactory

examples/typescript/ts-step_shotgun_surgery-01_base/src/Domain/StepDurationCalculatorQuiz.ts

@@ -0,0 +1,17 @@
+import StepDurationCalculator from "./StepDurationCalculator";
+import QuizStep from "./QuizStep";
+import Step from "./Step";
+import {multiplierFor} from "./DurationMultiplier";
+import {QUIZ_QUESTION_DURATION} from "./StepEnums";
+
+class StepDurationCalculatorQuiz implements StepDurationCalculator {
+    supports(step: Step): boolean {
+        return step instanceof QuizStep;
+    }
+
+    calculate(step: QuizStep): number {
+        return step.totalQuestions * QUIZ_QUESTION_DURATION * multiplierFor(step);
+    }
+}
+
+export default StepDurationCalculatorQuiz

examples/typescript/ts-step_shotgun_surgery-01_base/src/Domain/StepDurationCalculatorVideo.ts

@@ -0,0 +1,16 @@
+import StepDurationCalculator from "./StepDurationCalculator";
+import VideoStep from "./VideoStep";
+import Step from "./Step";
+import {multiplierFor} from "./DurationMultiplier";
+
+class StepDurationCalculatorVideo implements StepDurationCalculator {
+    supports(step: Step): boolean {
+        return step instanceof VideoStep;
+    }
+
+    calculate(step: VideoStep): number {
+        return step.videoDuration * multiplierFor(step);
+    }
+}
+
+export default StepDurationCalculatorVideo

examples/typescript/ts-step_shotgun_surgery-01_base/src/Domain/StepEnums.ts

@@ -1,13 +1,13 @@
-export const STEP_TYPE_VIDEO = 'video';
-export const STEP_TYPE_QUIZ = 'quiz';
+export const STEP_TYPE_VIDEO: string = 'video';
+export const STEP_TYPE_QUIZ: string = 'quiz';
 
-export const STEP_DURATION_MULTIPLIER_VIDEO = 1.1;
-export const STEP_DURATION_MULTIPLIER_QUIZ = 1.5;
+export const STEP_DURATION_MULTIPLIER_VIDEO: number = 1.1;
+export const STEP_DURATION_MULTIPLIER_QUIZ: number = 1.5;
 
-export const QUIZ_QUESTION_DURATION = 5;
+export const QUIZ_QUESTION_DURATION: number = 5;
 
 // Important: don't forget to add here the type!!
-export const STEP_TYPES = [
+export const STEP_TYPES: Array<string> = [
     STEP_TYPE_VIDEO,
     STEP_TYPE_QUIZ
 ];