Application.java

import java.util.*;
import java.io.*;

class InvalidCommandException extends Exception {
    public InvalidCommandException(String message){
        super(message);
    }
}


public class Application {
    private VendingMachine vm = null;
    private FileManager catalogueManager;
    private FileManager purseManager;

    public Application(File catalogue, File purse, ArrayList<Double> allowedCoins) throws Exception {
        vm = new VendingMachine(allowedCoins);
        this.catalogueManager = new FileManager(catalogue);
        this.purseManager = new FileManager(purse);

        loadItems(catalogueManager.load());
        loadPurse(purseManager.load());
        vm.sort();
    }

    private void loadItems(ArrayList<String> als){
        for(int j = 0; j < als.size(); ++j){
            Item[] items = parseItem(als.get(j));
            for(int i = items.length; i > 0; --i){
                vm.add(items[i-1]);
            }
        }

    }

    private void loadPurse(ArrayList<String> als){
        for(int j = 0; j < als.size(); ++j){
            Double[] coins = parseCoin(als.get(j));
            for(int i = coins.length; i > 0; --i){
                vm.getCoins().add(coins[i-1]);
            }
        }
    }

    private ArrayList<String> saveItems(){
        ArrayList<String> als = new ArrayList<>();
        String tempOld = "";
        int counter = 0;
        for(int i = 0; i < vm.size(); ++i){
            String tempNew = vm.get(i).getName() + " " + vm.get(i).getPrice();
            if (!tempOld.equals(tempNew)){
                if (counter > 0){
                    als.add(tempOld + " " + counter);
                }
                tempOld = tempNew;
                counter = 1;
            } else {
                ++counter;
            }
        }
        if (counter > 0){
            als.add(tempOld + " " + counter);
        }
        return als;
    }

    private ArrayList<String> savePurse(){
        ArrayList<String> als = new ArrayList<>();
        String tempOld = "";
        int counter = 0;
        for(int i = 0; i < vm.getCoins().size(); ++i){
            String tempNew = "" + vm.getCoins().get(i);
            if (!tempOld.equals(tempNew)){
                if (counter > 0){
                    als.add(tempOld + " " + counter);
                }
                tempOld = tempNew;
                counter = 1;
            } else {
                ++counter;
            }
        }
        if (counter > 0){
            als.add(tempOld + " " + counter);
        }
        return als;
    }

    private void export() throws Exception {
        vm.sort();
        catalogueManager.save(saveItems());
        purseManager.save(savePurse());
    }

    private Item [] parseItem(String line){
        line = line.trim();
        int index1 = line.lastIndexOf(' ');
        int amount = Integer.parseInt(line.substring(index1+1));
        int index2 = line.substring(0, index1).lastIndexOf(' ');
        double price = Double.parseDouble(line.substring(index2+1, index1));
        String name = line.substring(0, index2);
        Item item = new Item(name, price);
        Item[] items = new Item[amount];
        Arrays.fill(items, item);
        return items;
    }

    private Double [] parseCoin(String line){
        line = line.trim();
        int index1 = line.lastIndexOf(' ');
        int amount = Integer.parseInt(line.substring(index1+1));
        double price = Double.parseDouble(line.substring(0, index1));
        Double[] coins = new Double[amount];
        Arrays.fill(coins, price);
        return coins;
    }

    public void execute(String command) throws Exception {
        if (command.equalsIgnoreCase("stop")){
            change();
            export();
        } else if (command.equalsIgnoreCase("view")){
            show();
        } else if (command.equalsIgnoreCase("quit")){
            System.exit(0);
        } else if (command.length() >= 4 && command.substring(0, 4).equalsIgnoreCase("add ")){
            put(Double.parseDouble(command.substring(4)));
            export();
        } else if (command.length() >= 4 && command.substring(0, 4).equalsIgnoreCase("get ")){
            sell(Integer.parseInt(command.substring(4)));
            export();
        } else {
            throw new InvalidCommandException("No such command");
        }
    }

    private void show(){
        for(int i = 0; i < vm.size(); ++i){
            System.out.println(i + " " + vm.get(i));
        }
        System.out.println("Balance is " + vm.getPurse().getBalance());
    }
    private void change() throws Exception {
        System.out.println("Your change is " + vm.getPurse().getBalance() + " = ");
        ArrayList<Double> change = vm.getPurse().getChange();
        System.out.print(change.get(0));
        for(int i = 1; i < change.size(); ++i){
            System.out.print(" + " + change.get(i));
        }
        System.out.println();

    }
    private void put(double money) throws Exception {
        if (money >= 0){
            vm.getPurse().add(money);
            System.out.println("Balance is " + vm.getPurse().getBalance());
        } else {
            throw new IllegalArgumentException("Money cannot be negative");
        }
    }
    private void sell(int index) throws Exception {
        Item sold = vm.get(index);
        vm.sell(index);
        System.out.println("You just bought " + sold);
        System.out.println("Remaining balance is " + vm.getPurse().getBalance());
    }
}