@Named
@RequestScoped
public class DataExporterView implements Serializable {
    
    private List<Car> cars;
    
    private Exporter<DataTable> textExporter;
        
    @Inject
    private CarService service;
    
    @PostConstruct
    public void init() {
        cars = service.createCars(100);
        textExporter = new TextExporter();
    }

    public List<Car> getCars() {
        return cars;
    }

    public void setService(CarService service) {
        this.service = service;
    }

    public Exporter<DataTable> getTextExporter() {
        return textExporter;
    }

    public void setTextExporter(Exporter<DataTable> textExporter) {
        this.textExporter = textExporter;
    }
    
    
}

@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 TextExporter extends DataTableExporter {

    private StringBuilder builder = new StringBuilder();

    @Override
    protected void preExport(FacesContext context, ExportConfiguration config) throws IOException {
        ExternalContext externalContext = context.getExternalContext();
        configureResponse(externalContext, config.getOutputFileName());

        if (config.getPreProcessor() != null) {
            config.getPreProcessor().invoke(context.getELContext(), new Object[]{builder});
        }
    }

    @Override
    protected void doExport(FacesContext context, DataTable table, ExportConfiguration config, int index) throws IOException {
        builder.append("" + table.getId() + "\n");

        if (config.isPageOnly()) {
            exportPageOnly(context, table, builder);
        }
        else if (config.isSelectionOnly()) {
            exportSelectionOnly(context, table, builder);
        }
        else {
            exportAll(context, table, builder);
        }

        builder.append("" + table.getId() + "");

        table.setRowIndex(-1);
    }

    @Override
    protected void postExport(FacesContext context, ExportConfiguration config) throws IOException {
        if (config.getPostProcessor() != null) {
            config.getPostProcessor().invoke(context.getELContext(), new Object[]{builder});
        }

        OutputStream os = context.getExternalContext().getResponseOutputStream();
        OutputStreamWriter osw = new OutputStreamWriter(os, config.getEncodingType());
        PrintWriter writer = new PrintWriter(osw);
        writer.write(builder.toString());
        writer.flush();
        writer.close();
        builder.setLength(0);
    }

    @Override
    protected void preRowExport(DataTable table, Object document) {
        ((StringBuilder) document).append("\t" + table.getVar() + "\n");
    }

    @Override
    protected void postRowExport(DataTable table, Object document) {
        ((StringBuilder) document).append("\t" + table.getVar() + "\n");
    }

    @Override
    protected void exportCells(DataTable table, Object document) {
        StringBuilder builder = (StringBuilder) document;
        for (UIColumn col : table.getColumns()) {
            if (col instanceof DynamicColumn) {
                ((DynamicColumn) col).applyStatelessModel();
            }

            if (col.isRendered() && col.isExportable()) {
                String columnTag = getColumnTag(col);
                addColumnValue(builder, col.getChildren(), columnTag, col);
            }
        }
    }

    protected String getColumnTag(UIColumn column) {
        String headerText = (column.getExportHeaderValue() != null) ? column.getExportHeaderValue() : column.getHeaderText();
        UIComponent facet = column.getFacet("header");
        String columnTag;

        if (headerText != null) {
            columnTag = headerText.toLowerCase();
        }
        else if (facet != null) {
            columnTag = exportValue(FacesContext.getCurrentInstance(), facet).toLowerCase();
        }
        else {
            throw new FacesException("No suitable xml tag found for " + column);
        }

        return EscapeUtils.forXmlTag(columnTag);
    }

    protected void addColumnValue(StringBuilder builder, List<UIComponent> components, String tag, UIColumn column) {
        FacesContext context = FacesContext.getCurrentInstance();

        builder.append("\t\t" + tag + "");

        if (column.getExportFunction() != null) {
            builder.append(EscapeUtils.forXml(exportColumnByFunction(context, column)));
        }
        else {
            for (UIComponent component : components) {
                if (component.isRendered()) {
                    String value = exportValue(context, component);
                    if (value != null) {
                        builder.append(EscapeUtils.forXml(value));
                    }
                }
            }
        }

        builder.append("" + tag + "\n");
    }

    protected void configureResponse(ExternalContext externalContext, String filename) {
        externalContext.setResponseContentType("text/plain");
        externalContext.setResponseHeader("Expires", "0");
        externalContext.setResponseHeader("Cache-Control", "must-revalidate, post-check=0, pre-check=0");
        externalContext.setResponseHeader("Pragma", "public");
        externalContext.setResponseHeader("Content-disposition", ComponentUtils.createContentDisposition("attachment", filename + ".txt"));
        externalContext.addResponseCookie(Constants.DOWNLOAD_COOKIE, "true", Collections.<String, Object>emptyMap());
    }
}