package org.lucares.pdbui;

import java.io.IOException;
import java.nio.file.Paths;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.Resource;
import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;
import org.springframework.web.servlet.config.annotation.ViewControllerRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
import org.springframework.web.servlet.resource.PathResourceResolver;

@Configuration
public class WebConfiguration implements WebMvcConfigurer, HardcodedValues, PropertyKeys {

    private final String outputDir;

    public WebConfiguration(@Value("${" + PATH_GENERATED_IMAGES + "}") final String outputDir) {
        this.outputDir = outputDir;
    }

    @Override
    public void addResourceHandlers(final ResourceHandlerRegistry registry) {

        addResourceHandlerForPlottedImages(registry);

        // addResourceHandlerForAngular(registry);
    }

    private void addResourceHandlerForPlottedImages(final ResourceHandlerRegistry registry) {
        final String pathPattern = "/" + WEB_IMAGE_OUTPUT_PATH + "/**";
        final String resourceLocation = "file:" + Paths.get(outputDir).toAbsolutePath() + "/";

        registry.addResourceHandler(pathPattern).addResourceLocations(resourceLocation);
    }

    /**
     * This is one way to make Angular and SpringBoot play together. The other
     * described in {@link #addViewControllers(ViewControllerRegistry)}.
     * 
     * Other solutions:
     * https://stackoverflow.com/questions/38516667/springboot-angular2-how-to-handle-html5-urls/46854105#46854105
     * 
     * @param registry
     */
    @SuppressWarnings("unused")
    private void addResourceHandlerForAngular(final ResourceHandlerRegistry registry) {
        // Redirect all to Angular for all non existing resources.
        // This way Angular's routing & navigation (https://angular.io/guide/router) can
        // work. Without it SpringBoot would only show 404 pages for all of Angular's
        // pages, because the request would not even be send to Angular.
        //
        // Technically we are answering all requests for which SpringBoot does not find
        // a resource with Angular's index.html. The Angular will then use its routing
        // to determine which sub-page to show.
        //
        // This makes Angular also responsible for all 404 pages.
        registry.addResourceHandler("/**").addResourceLocations("classpath:/resources/").resourceChain(true)
                .addResolver(new PathResourceResolver() {
                    @Override
                    protected Resource getResource(final String resourcePath, final Resource location)
                            throws IOException {
                        final Resource requestedResource = location.createRelative(resourcePath);

                        return requestedResource.exists() && requestedResource.isReadable() ? requestedResource
                                : new ClassPathResource("/resources/index.html");
                    }
                });
    }

    /**
     * This is one way to make Angular and SpringBoot play together. The other
     * described in {@link #addResourceHandlerForAngular(ResourceHandlerRegistry)}
     * 
     * Other solutions:
     * https://stackoverflow.com/questions/38516667/springboot-angular2-how-to-handle-html5-urls/46854105#46854105
     */
    @Override
    public void addViewControllers(final ViewControllerRegistry registry) {

        // Redirect requests to Angular.
        // This works by returning Angular's index.html for requests that should be
        // handled by Angular.
        //
        // Using this solution SpringBoot is responsible for 404s.

        registry.addViewController("/").setViewName("forward:/index.html");
        registry.addViewController("/vis").setViewName("forward:/index.html");
        registry.addViewController("/upload").setViewName("forward:/index.html");
        registry.addViewController("/help").setViewName("forward:/index.html");
    }
}