add command design pattern real world example

Author: samuel.casanova

src/Command/RealWorld/Output.txt

@@ -0,0 +1,7 @@
+Kelsey Grammar sings and plays the piano for the theme song of Fraiser.
+The cruise liner, Queen Elizabeth II, moves only six inches for each gallon of diesel that it burns.
+American Airlines saved $40,000 in 1987 by eliminating one olive from each salad served in first-class.
+The the U.S. you dial `911`. In Stockholm, Sweden you dial 90000
+Facetious and abstemious contain all the vowels in the correct order, as does arsenious, meaning "containing arsenic."  
+There`s a systematic lull in conversation every 7 minutes.
+Walt Disney was afraid of mice.

src/Command/RealWorld/index.ts

@@ -0,0 +1,72 @@
+const https = require('node:https');
+
+/**
+ * EN: Real World Example for the Command Design Pattern
+ *
+ * Need: Execute a command to retrieve random information every X seconds
+ *
+ * Solution: Create an object that has all the information to execute the query
+ */
+
+/**
+ * EN: The Command interface declares a method for executing a command.
+ */
+interface Command {
+    execute(): void;
+}
+
+/**
+ * EN: We will use a receiver object to run the business logic
+ */
+class PrintRandomFactCommand implements Command {
+    constructor(protected randomFactDomainServiceReceiver: RandomFactDomainServiceReceiver) {
+    }
+
+    public async execute(): Promise<void> {
+        const fact = await this.randomFactDomainServiceReceiver.getRandomFact();
+        console.info(fact);
+    }
+}
+
+/**
+ * EN: The Receiver class contains all the business logic to retrieve the
+ * information
+ */
+class RandomFactDomainServiceReceiver {
+    public getRandomFact(): Promise<string> {
+        return new Promise((resolve, reject) => {
+            https.get('https://uselessfacts.jsph.pl/api/v2/facts/random', (res) => {
+                res.on('data', (d) => {
+                    const data = JSON.parse(d);
+                    const fact = data.text;
+                    resolve(fact);
+                });
+            }).on('error', (error) => {
+                reject(error);
+            });
+        });
+    }
+}
+
+/**
+ * EN: The Invoker will execute any command every X seconds.
+ */
+class CommandInvoker {
+    constructor(protected command: Command, protected seconds: number = 5) {
+    }
+
+    start(): void {
+        setInterval(() => {
+            this.command.execute();
+        },          this.seconds * 1000);
+    }
+}
+
+/**
+ * EN: The client code invokes the command
+ */
+const randomFactDomainServiceReceiver = new RandomFactDomainServiceReceiver();
+const command = new PrintRandomFactCommand(randomFactDomainServiceReceiver);
+const commandInvoker = new CommandInvoker(command, 3);
+
+commandInvoker.start();