online order problem statement

Learning_2.0/Solutions/Behavioural-pattern-solutions/online-ordering-food-system/ManagerInvoker.js

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+class OrderManager {
+  constructor() {
+    this.history = [];
+    this.undoStack = [];
+  }
+
+  executeCommand(command) {
+    command.execute();
+    this.history.push(command);
+    this.undoStack = []; // Reset the undo stack after a new command
+  }
+
+  undo() {
+    const command = this.history.pop();
+    if (command) {
+      command.undo();
+      this.undoStack.push(command);
+    } else {
+      console.log("No commands to undo.");
+    }
+  }
+
+  redo() {
+    const command = this.undoStack.pop();
+    if (command) {
+      command.execute();
+      this.history.push(command);
+    } else {
+      console.log("No commands to redo.");
+    }
+  }
+}
+
+module.exports = OrderManager;

Learning_2.0/Solutions/Behavioural-pattern-solutions/online-ordering-food-system/main.js

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+const Order = require("./receiver");
+const OrderManager = require("./ManagerInvoker");
+const {
+  AddItemCommand,
+  RemoveItemCommand,
+  ProcessOrderCommand,
+  CancelOrderCommand,
+} = require("./orderCommand");
+
+// Client code
+const myOrder = new Order();
+const orderManager = new OrderManager();
+
+// Add items
+const addItem1 = new AddItemCommand(myOrder, "Burger");
+const addItem2 = new AddItemCommand(myOrder, "Fries");
+
+orderManager.executeCommand(addItem1); // Adds "Burger"
+orderManager.executeCommand(addItem2); // Adds "Fries"
+
+// Show current items
+myOrder.showItems();
+
+// Remove an item
+const removeItem = new RemoveItemCommand(myOrder, "Fries");
+orderManager.executeCommand(removeItem); // Removes "Fries"
+
+// Undo remove
+orderManager.undo(); // Restores "Fries"
+
+// Show current items
+myOrder.showItems();
+
+// Process order
+const processOrder = new ProcessOrderCommand(myOrder);
+orderManager.executeCommand(processOrder); // Processes the order
+
+// Cancel the order
+const cancelOrder = new CancelOrderCommand(myOrder);
+orderManager.executeCommand(cancelOrder); // Cancels the order

Learning_2.0/Solutions/Behavioural-pattern-solutions/online-ordering-food-system/orderCommand.js

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+class OrderCommand {
+  execute() {
+    throw new Error("execute() is not implemented");
+  }
+
+  undo() {
+    throw new Error("undo() is not implemented");
+  }
+}
+
+// Concrete class
+class AddItemCommand extends OrderCommand {
+  constructor(order, item) {
+    super();
+    this.order = order;
+    this.item = item;
+  }
+
+  execute() {
+    this.order.addItem(this.item);
+  }
+
+  undo() {
+    this.order.removeItem(this.item);
+  }
+}
+
+class RemoveItemCommand extends OrderCommand {
+  constructor(order, item) {
+    super();
+    this.order = order;
+    this.item = item;
+  }
+
+  execute() {
+    this.order.removeItem(this.item);
+  }
+
+  undo() {
+    this.order.addItem(this.item);
+  }
+}
+
+class ProcessOrderCommand extends OrderCommand {
+  constructor(order) {
+    super();
+    this.order = order;
+  }
+
+  execute() {
+    this.order.processOrder();
+  }
+
+  undo() {
+    console.log("Cannot undo after order is processed.");
+  }
+}
+
+class CancelOrderCommand extends OrderCommand {
+  constructor(order) {
+    super();
+    this.order = order;
+  }
+
+  execute() {
+    this.order.cancelOrder();
+  }
+
+  undo() {
+    console.log("Cannot undo after order is cancelled.");
+  }
+}
+
+module.exports = {
+  AddItemCommand,
+  RemoveItemCommand,
+  ProcessOrderCommand,
+  CancelOrderCommand,
+};

Learning_2.0/Solutions/Behavioural-pattern-solutions/online-ordering-food-system/receiver.js

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+class Order {
+  constructor() {
+    this.items = [];
+  }
+
+  addItem(item) {
+    this.items.push(item);
+  }
+
+  removeItem(item) {
+    const index = this.items.indexOf(item);
+    if (index > -1) {
+      this.items.splice(index, 1);
+      console.log(`Removed ${item} from the order.`);
+    } else {
+      console.log(`${item} is not in the order.`);
+    }
+  }
+
+  processOrder() {
+    if (this.items.length > 0) {
+      console.log(`Order processed: ${this.items.join(", ")}`);
+      this.items = [];
+    } else {
+      console.log("Add products to the order before processing it.");
+    }
+  }
+
+  cancelOrder() {
+    console.log("Order cancelled.");
+    this.items = [];
+  }
+
+  showItems() {
+    console.log(
+      `Items in the order: ${this.items.join(", ") || "Empty, no items found."}`
+    );
+  }
+}
+
+module.exports = Order;