package org.nasdanika.html.model.app.graph;

import java.util.Collection;

import org.eclipse.emf.common.util.URI;
import org.eclipse.emf.ecore.EClass;
import org.nasdanika.common.ProgressMonitor;
import org.nasdanika.common.Supplier;
import org.nasdanika.graph.Connection;
import org.nasdanika.graph.emf.EClassConnection;
import org.nasdanika.html.model.app.Label;
import org.nasdanika.html.model.app.graph.emf.EObjectNodeProcessor;

/**
 * Creates labels, links for cross-referencing, and other "widgets".
 * @author Pavel
 *
 */
public interface WidgetFactory {
        
        /**
         * Functional interface for selectors to which factories delegate widget creation.
         * {@link Connection} {@link WidgetFactory} shall not delegate to Selector, but rather to ConnectionSelector 
         */
        interface Selector<T> {
        
                /**
                 * Retrieves some information from the argument widget factory, e.g. creates a widget.   
                 * @param widgetFactory
                 * @param base For connections, if not null, is resolved against the calling end URI - source or target, if it is not null. 
                 * If null, the respective end URI is used as the base.
                 * @param progressMonitor
                 * @return A widget or null
                 */             
                T select(WidgetFactory widgetFactory, URI base, ProgressMonitor progressMonitor); 
                
        }
        
        /**
         * A maker interface indicating that {@link Connection} {@link WidgetFactory} shall delegate to this selector instead of passing it to the other end's node.
         * @param <T>
         */
        interface ConnectionSelector<T> extends Selector<T> {
                
        }
        
        /**
         * Creates a "label" which is an HTML/text representation of something which does not navigate to that something. E.g. {@link Label}. Can be composite.
         * @return
         */
        Object createLabel(ProgressMonitor progressMonitor);
        
        /**
         * Creates a string (HTML text) representation of "label".
         * @return
         */
        String createLabelString(ProgressMonitor progressMonitor);
        
        /**
         * Creates a link if possible or a label.
         * Calls createLink(null, progressMonitor) 
         * @return
         */
        default Object createLink(ProgressMonitor progressMonitor) {
                return createLink(null, progressMonitor);
        }
        
        /**
         * Creates a link with URL's deresolved (relativized) against the provided base URI.
         * 
         * @param base For connections, if not null, is resolved against the calling end URI - source or target, if it is not null. 
         * If null, the respective end URI is used as the base.
         * @param progressMonitor
         * @return
         */
        Object createLink(URI base, ProgressMonitor progressMonitor);
        
        /**
         * Creates a help decorator.
         * Calls createHelpDecorator(null, progressMonitor) 
         * @return
         */
        default Label createHelpDecorator(ProgressMonitor progressMonitor) {
                return createHelpDecorator(null, progressMonitor);
        }
        
        /**
         * Creates a help decorator with URL's deresolved (relativized) against the provided base URI.
         * For example, an {@link EObjectNodeProcessor} for an object of type X would call its {@link EClassConnection} outgoing connection to create a help decorator. 
         * The EClassConnection would in turn call EClassNodeProcessor for {@link EClass} X to generate context help decorator.  
         * 
         * @param base For connections, if not null, is resolved against the calling end URI - source or target, if it is not null. 
         * If null, the respective end URI is used as the base.
         * @param progressMonitor
         * @return
         */
        Label createHelpDecorator(URI base, ProgressMonitor progressMonitor);
        
        /**
         * Link rendered to String
         * @param progressMonitor
         * @return
         */
        default String createLinkString(ProgressMonitor progressMonitor) {
                return createLinkString(null, progressMonitor);
        }
        
        /**
         * Link rendered to String
         * @param base
         * @param progressMonitor
         * @return
         */
        String createLinkString(URI base, ProgressMonitor progressMonitor);
        
        /**
         * Calls createWidget(selector, null, progressMonitor).
         * For connections URL's in the link are deresolved (relativized) against the calling end URI - source or target, if it is not null.
         * @param selector
         * @param progressMonitor
         * @return
         */
        default Object select(Object selector, ProgressMonitor progressMonitor) {
                return select(selector, null, progressMonitor);
        }

        /**
         * Creates a widget for an aspect (feature) of the object identified by the selector, which can be a {@link Selector}.   
         * @param selector Aspect/feature key. If an instasnce of Selector, then the factory delegates widget creation to the selector passing itself as an argument.
         * @param base For connections, if not null, is resolved against the calling end URI - source or target, if it is not null. 
         * If null, the respective end URI is used as the base.
         * @param progressMonitor
         * @return A widget or null
         */
        default Object select(Object selector, URI base, ProgressMonitor progressMonitor) {
                if (selector instanceof Selector) {
                        return select((Selector<?>) selector, base, progressMonitor);
                }
                return null;
        }
        
        default <T> T select(Selector<T> selector, URI base, ProgressMonitor progressMonitor) {
                return selector.select(this, base, progressMonitor);
        }       
        
        default <T> T select(Selector<T> selector, ProgressMonitor progressMonitor) {
                return select(selector, null, progressMonitor);
        }       

        /**
         * Calls createWidgetString(selector, null, progressMonitor)
         * @param selector
         * @param progressMonitor
         * @return
         */
        default String selectString(Object selector, ProgressMonitor progressMonitor) {
                return selectString(selector, null, progressMonitor);
        }

        /**
         * @param selector
         * @param base
         * @param progressMonitor
         * @return widget rendered to (HTML) string
         */
        String selectString(Object selector, URI base, ProgressMonitor progressMonitor);
        
        /**
         * Used to establish node URI's. Propagates caller URI.
         * @param base
         */
        void resolve(URI base, ProgressMonitor progressMonitor);
        
        Supplier<Collection<Label>> createLabelsSupplier();
        
        /**
         * Configures a label for a given source object. This method allows multiple widget factories 
         * collaborate on label/action configuration. E.g. the primary WidgetFactory may delegate to "facet" factories.  
         * @param source
         * @param label
         * @param progressMonitor
         */
        default void configureLabel(Object source, Label label, ProgressMonitor progressMonitor) {
                
        }

}