@Named("dtLazyView")
@ViewScoped
public class LazyView implements Serializable {
    
    private LazyDataModel<Car> lazyModel;
    
    private Car selectedCar;
    
    @Inject
    private CarService service;
    
    @PostConstruct
    public void init() {
        lazyModel = new LazyCarDataModel(service.createCars(200));
    }

    public LazyDataModel<Car> getLazyModel() {
        return lazyModel;
    }

    public Car getSelectedCar() {
        return selectedCar;
    }

    public void setSelectedCar(Car selectedCar) {
        this.selectedCar = selectedCar;
    }
    
    public void setService(CarService service) {
        this.service = service;
    }
    
    public void onRowSelect(SelectEvent<Car> event) {
        FacesMessage msg = new FacesMessage("Car Selected", event.getObject().getId());
        FacesContext.getCurrentInstance().addMessage(null, msg);
    }
}

public class Car implements Serializable {
    
    public String id;
    public String brand;
    public int year;
    public String color;
    public int price;
    public boolean sold;

    public Car() {}
    
    public Car(String id, String brand, int year, String color) {
        this.id = id;
        this.brand = brand;
        this.year = year;
        this.color = color;
    }
    
    public Car(String id, String brand, int year, String color, int price, boolean sold) {
        this.id = id;
        this.brand = brand;
        this.year = year;
        this.color = color;
        this.price = price;
        this.sold = sold;
    }

    public String getId() {
        return id;
    }
    public void setId(String id) {
        this.id = id;
    }

    public String getBrand() {
        return brand;
    }
    public void setBrand(String brand) {
        this.brand = brand;
    }

    public int getYear() {
        return year;
    }
    public void setYear(int year) {
        this.year = year;
    }

    public String getColor() {
        return color;
    }
    public void setColor(String color) {
        this.color = color;
    }

    public int getPrice() {
        return price;
    }
    public void setPrice(int price) {
        this.price = price;
    }

    public boolean isSold() {
        return sold;
    }
    public void setSold(boolean sold) {
        this.sold = sold;
    }

    @Override
    public int hashCode() {
        int hash = 7;
        hash = 59 * hash + (this.id != null ? this.id.hashCode() : 0);
        return hash;
    }

    @Override
    public boolean equals(Object obj) {
        if (obj == null) {
            return false;
        }
        if (getClass() != obj.getClass()) {
            return false;
        }
        final Car other = (Car) obj;
        if ((this.id == null) ? (other.id != null) : !this.id.equals(other.id)) {
            return false;
        }
        return true;
    }
}

@Named
@ApplicationScoped
public class CarService {
    
    private final static String[] colors;
	
	private final static String[] brands;
    
    static {
		colors = new String[10];
		colors[0] = "Black";
		colors[1] = "White";
		colors[2] = "Green";
		colors[3] = "Red";
		colors[4] = "Blue";
		colors[5] = "Orange";
		colors[6] = "Silver";
		colors[7] = "Yellow";
		colors[8] = "Brown";
		colors[9] = "Maroon";
		
		brands = new String[10];
		brands[0] = "BMW";
		brands[1] = "Mercedes";
		brands[2] = "Volvo";
		brands[3] = "Audi";
		brands[4] = "Renault";
		brands[5] = "Fiat";
		brands[6] = "Volkswagen";
		brands[7] = "Honda";
		brands[8] = "Jaguar";
		brands[9] = "Ford";
	}
    
    public List<Car> createCars(int size) {
        List<Car> list = new ArrayList<Car>();
		for(int i = 0 ; i < size ; i++) {
			list.add(new Car(getRandomId(), getRandomBrand(), getRandomYear(), getRandomColor(), getRandomPrice(), getRandomSoldState()));
        }
        
        return list;
    }
    
    private String getRandomId() {
		return UUID.randomUUID().toString().substring(0, 8);
	}
    
    private int getRandomYear() {
		return (int) (Math.random() * 50 + 1960);
	}
	
	private String getRandomColor() {
		return colors[(int) (Math.random() * 10)];
	}
	
	private String getRandomBrand() {
		return brands[(int) (Math.random() * 10)];
	}
    
    private int getRandomPrice() {
		return (int) (Math.random() * 100000);
	}
    
    private boolean getRandomSoldState() {
		return (Math.random() > 0.5) ? true: false;
	}
    
    public List<String> getColors() {
        return Arrays.asList(colors);
    }
    
    public List<String> getBrands() {
        return Arrays.asList(brands);
    }
}

public class LazySorter implements Comparator<Car> {

    private String sortField;
    
    private SortOrder sortOrder;
    
    public LazySorter(String sortField, SortOrder sortOrder) {
        this.sortField = sortField;
        this.sortOrder = sortOrder;
    }

    public int compare(Car car1, Car car2) {
        try {
            Object value1 = Car.class.getField(this.sortField).get(car1);
            Object value2 = Car.class.getField(this.sortField).get(car2);

            int value = ((Comparable)value1).compareTo(value2);
            
            return SortOrder.ASCENDING.equals(sortOrder) ? value : -1 * value;
        }
        catch(Exception e) {
            throw new RuntimeException();
        }
    }
}

public class LazyCarDataModel extends LazyDataModel<Car> {

    private List<Car> datasource;

    public LazyCarDataModel(List<Car> datasource) {
        this.datasource = datasource;
    }

    @Override
    public Car getRowData(String rowKey) {
        for (Car car : datasource) {
            if (car.getId().equals(rowKey)) {
                return car;
            }
        }

        return null;
    }

    @Override
    public Object getRowKey(Car car) {
        return car.getId();
    }

    @Override
    public List<Car> load(int first, int pageSize, Map<String, SortMeta> sortMeta, Map<String, FilterMeta> filterMeta) {
        List<Car> data = new ArrayList<>();

        //filter
        for (Car car : datasource) {
            boolean match = true;

            if (filterMeta != null) {
                for (FilterMeta meta : filterMeta.values()) {
                    try {
                        String filterField = meta.getFilterField();
                        Object filterValue = meta.getFilterValue();
                        String fieldValue = String.valueOf(car.getClass().getField(filterField).get(car));

                        if (filterValue == null || fieldValue.startsWith(filterValue.toString())) {
                            match = true;
                        }
                        else {
                            match = false;
                            break;
                        }
                    }
                    catch (Exception e) {
                        match = false;
                    }
                }
            }

            if (match) {
                data.add(car);
            }
        }

        //sort
        if (sortMeta != null && !sortMeta.isEmpty()) {
            for (SortMeta meta : sortMeta.values()) {
                Collections.sort(data, new LazySorter(meta.getSortField(), meta.getSortOrder()));
            }
        }

        //rowCount
        int dataSize = data.size();
        this.setRowCount(dataSize);

        //paginate
        if (dataSize > pageSize) {
            try {
                return data.subList(first, first + pageSize);
            }
            catch (IndexOutOfBoundsException e) {
                return data.subList(first, first + (dataSize % pageSize));
            }
        }
        else {
            return data;
        }
    }
}