import java.util.Scanner;
import java.util.LinkedList;
import java.util.HashMap;
import java.util.Arrays;

class Item {

    private String desc;
    private String category;
    private double amount;

    public String getDesc()     { return this.desc; }
    public String getCategory() { return this.category; }
    public double getAmount()   { return this.amount; }

    public void setDesc(String desc)            { this.desc = desc; }
    public void setCategory(String category)    { this.category = category; }
    public void setAmount(double amount)        { this.amount = amount; }

    public Item(String desc, String category, double amount) {
        this.desc = desc;
        this.category = category;
        this.amount = amount;
    }

}

class ExpSystem {

    private LinkedList<Item> data;

    public void addItem(Item item) {
        this.data.add(item);
    }
    public void removeItem(Item item) {
        this.data.remove(item);
    }
    public ExpSystem() {
        this.data = new LinkedList();
    }

    // get a selection from user input
    public static String getMode(LinkedList<String> choices) {

        // Display numbered choices
        HashMap<Integer,String> items = new HashMap();
        for ( int i=0; i<choices.size(); i++ ) {
            items.put(i+1,choices.get(i));
            System.out.println((i+1)+". "+choices.get(i));
        }
        // get choice from input
        System.out.printf(">>> ");
        Scanner sc = new Scanner(System.in);
        int inp = sc.nextInt();
        return choices.get(inp-1);
    }

    public void addTestItems() {
        Item item1 = new Item("Item 1","A",1.5);
        this.addItem(item1);
        Item item2 = new Item("Item 2","A",8);
        this.addItem(item2);
        Item item3 = new Item("Item 3","B",11);
        this.addItem(item3);
    }

    public static void main(String[] args) {

        // create a test ExpSystem
        ExpSystem system = new ExpSystem();
        system.addTestItems();

        while (true) {

            LinkedList<String> modeChoices = new LinkedList(Arrays.asList("Edit","Analyse","Exit"));
            System.out.println("--- Expenditure database ---");
            switch(getMode(modeChoices)) {

                case "Edit":
                    System.out.println("--- Edit items ---");
                    LinkedList<String> editChoices = new LinkedList(Arrays.asList("Add item","Delete item"));
                    switch(getMode(editChoices)) {

                        case "Add item":
                            System.out.println("--- Add an item ---");

                            // Get new item properties
                            Scanner newItem = new Scanner(System.in);
                            System.out.printf("Description: ");
                            String desc = newItem.nextLine();
                            System.out.printf("Category: ");
                            String category = newItem.nextLine();
                            System.out.printf("Amount: ");
                            double amount = newItem.nextDouble();

                            // Construct & add item
                            system.addItem(new Item(desc,category,amount));
                            System.out.println("*Item added!*");
                            break;

                        case "Delete item":
                            System.out.println("--- Delete an item ---");

                            // get item to delete
                            LinkedList<String> itemNames = new LinkedList();
                            for (Item item : system.data) {
                                itemNames.add(item.getDesc());
                            }

                            // Delete chosen item
                            String toDelete = getMode(itemNames);
                            system.data.removeIf(item -> item.getDesc() == toDelete);
                            System.out.println("*Item deleted!*");
                            break;

                    }
                break;
                case "Analyse":
                    System.out.println("--- Item analysis ---");

                    // Sort by category
                    System.out.println("\n*Breakdown by category*");
                    HashMap<String,LinkedList> byCat = new HashMap();
                    for ( Item item : system.data ) {
                        String thisCat = item.getCategory();
                        if (byCat.containsKey(thisCat) == false) {
                            byCat.put(thisCat,new LinkedList<Item>());
                        }

                        LinkedList<Item> currList = byCat.get(thisCat);
                        currList.add(item);
                        byCat.put(thisCat,currList);
                    }
                    for ( String cat : byCat.keySet() ) {
                        System.out.println(cat);
                        LinkedList<Item> currList = byCat.get(cat);
                        for ( Item item : currList ) {
                            System.out.println(item.getDesc()+"\t"+item.getAmount());
                        }
                    }

                    // Average & total exp.
                    double totalExp = 0;
                    for (Item item : system.data) {
                        totalExp += item.getAmount();
                    }
                    System.out.println("\n*Average spend per item*");
                    double avg = totalExp/system.data.size();
                    System.out.println(avg);

                    System.out.println("\n*Total expenditure*");
                    System.out.println(totalExp);
                    break;

                case "Exit":
                    System.exit(0);
            }
        }
    }

}