package com.baeldung.jhipster.gateway.config;

import com.codahale.metrics.MetricRegistry;
import com.codahale.metrics.servlet.InstrumentedFilter;
import com.codahale.metrics.servlets.MetricsServlet;
import io.github.jhipster.config.JHipsterConstants;
import io.github.jhipster.config.JHipsterProperties;
import io.github.jhipster.config.h2.H2ConfigurationHelper;
import io.github.jhipster.web.filter.CachingHttpHeadersFilter;
import io.undertow.UndertowOptions;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.web.embedded.undertow.UndertowServletWebServerFactory;
import org.springframework.boot.web.server.*;
import org.springframework.boot.web.servlet.ServletContextInitializer;
import org.springframework.boot.web.servlet.server.ConfigurableServletWebServerFactory;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.env.Environment;
import org.springframework.http.MediaType;
import org.springframework.web.cors.CorsConfiguration;
import org.springframework.web.cors.UrlBasedCorsConfigurationSource;
import org.springframework.web.filter.CorsFilter;

import javax.servlet.*;
import java.io.File;
import java.io.UnsupportedEncodingException;
import java.nio.charset.StandardCharsets;
import java.nio.file.Paths;
import java.util.*;

import static java.net.URLDecoder.decode;

/**
 * Configuration of web application with Servlet 3.0 APIs.
 */
@Configuration
public class WebConfigurer implements ServletContextInitializer, WebServerFactoryCustomizer<WebServerFactory> {

    private final Logger log = LoggerFactory.getLogger(WebConfigurer.class);

    private final Environment env;

    private final JHipsterProperties jHipsterProperties;

    private MetricRegistry metricRegistry;

    public WebConfigurer(Environment env, JHipsterProperties jHipsterProperties) {

        this.env = env;
        this.jHipsterProperties = jHipsterProperties;
    }

    @Override
    public void onStartup(ServletContext servletContext) throws ServletException {
        if (env.getActiveProfiles().length != 0) {
            log.info("Web application configuration, using profiles: {}", (Object[]) env.getActiveProfiles());
        }
        EnumSet<DispatcherType> disps = EnumSet.of(DispatcherType.REQUEST, DispatcherType.FORWARD, DispatcherType.ASYNC);
        initMetrics(servletContext, disps);
        if (env.acceptsProfiles(JHipsterConstants.SPRING_PROFILE_PRODUCTION)) {
            initCachingHttpHeadersFilter(servletContext, disps);
        }
        if (env.acceptsProfiles(JHipsterConstants.SPRING_PROFILE_DEVELOPMENT)) {
            initH2Console(servletContext);
        }
        log.info("Web application fully configured");
    }

    /**
     * Customize the Servlet engine: Mime types, the document root, the cache.
     */
    @Override
    public void customize(WebServerFactory server) {
        setMimeMappings(server);
        // When running in an IDE or with ./mvnw spring-boot:run, set location of the static web assets.
        setLocationForStaticAssets(server);

        /*
         * Enable HTTP/2 for Undertow - https://twitter.com/ankinson/status/829256167700492288
         * HTTP/2 requires HTTPS, so HTTP requests will fallback to HTTP/1.1.
         * See the JHipsterProperties class and your application-*.yml configuration files
         * for more information.
         */
        if (jHipsterProperties.getHttp().getVersion().equals(JHipsterProperties.Http.Version.V_2_0) &&
            server instanceof UndertowServletWebServerFactory) {

            ((UndertowServletWebServerFactory) server)
                .addBuilderCustomizers(builder ->
                    builder.setServerOption(UndertowOptions.ENABLE_HTTP2, true));
        }
    }

    private void setMimeMappings(WebServerFactory server) {
        if (server instanceof ConfigurableServletWebServerFactory) {
            MimeMappings mappings = new MimeMappings(MimeMappings.DEFAULT);
            // IE issue, see https://github.com/jhipster/generator-jhipster/pull/711
            mappings.add("html", MediaType.TEXT_HTML_VALUE + ";charset=" + StandardCharsets.UTF_8.name().toLowerCase());
            // CloudFoundry issue, see https://github.com/cloudfoundry/gorouter/issues/64
            mappings.add("json", MediaType.TEXT_HTML_VALUE + ";charset=" + StandardCharsets.UTF_8.name().toLowerCase());
            ConfigurableServletWebServerFactory servletWebServer = (ConfigurableServletWebServerFactory) server;
            servletWebServer.setMimeMappings(mappings);
        }
    }

    private void setLocationForStaticAssets(WebServerFactory server) {
        if (server instanceof ConfigurableServletWebServerFactory) {
            ConfigurableServletWebServerFactory servletWebServer = (ConfigurableServletWebServerFactory) server;
            File root;
            String prefixPath = resolvePathPrefix();
            root = new File(prefixPath + "target/www/");
            if (root.exists() && root.isDirectory()) {
                servletWebServer.setDocumentRoot(root);
            }
        }
    }

    /**
     * Resolve path prefix to static resources.
     */
    private String resolvePathPrefix() {
        String fullExecutablePath;
        try {
            fullExecutablePath = decode(this.getClass().getResource("").getPath(), StandardCharsets.UTF_8.name());
        } catch (UnsupportedEncodingException e) {
            /* try without decoding if this ever happens */
            fullExecutablePath = this.getClass().getResource("").getPath();
        }
        String rootPath = Paths.get(".").toUri().normalize().getPath();
        String extractedPath = fullExecutablePath.replace(rootPath, "");
        int extractionEndIndex = extractedPath.indexOf("target/");
        if (extractionEndIndex <= 0) {
            return "";
        }
        return extractedPath.substring(0, extractionEndIndex);
    }

    /**
     * Initializes the caching HTTP Headers Filter.
     */
    private void initCachingHttpHeadersFilter(ServletContext servletContext,
                                              EnumSet<DispatcherType> disps) {
        log.debug("Registering Caching HTTP Headers Filter");
        FilterRegistration.Dynamic cachingHttpHeadersFilter =
            servletContext.addFilter("cachingHttpHeadersFilter",
                new CachingHttpHeadersFilter(jHipsterProperties));

        cachingHttpHeadersFilter.addMappingForUrlPatterns(disps, true, "/i18n/*");
        cachingHttpHeadersFilter.addMappingForUrlPatterns(disps, true, "/content/*");
        cachingHttpHeadersFilter.addMappingForUrlPatterns(disps, true, "/app/*");
        cachingHttpHeadersFilter.setAsyncSupported(true);
    }

    /**
     * Initializes Metrics.
     */
    private void initMetrics(ServletContext servletContext, EnumSet<DispatcherType> disps) {
        log.debug("Initializing Metrics registries");
        servletContext.setAttribute(InstrumentedFilter.REGISTRY_ATTRIBUTE,
            metricRegistry);
        servletContext.setAttribute(MetricsServlet.METRICS_REGISTRY,
            metricRegistry);

        log.debug("Registering Metrics Filter");
        FilterRegistration.Dynamic metricsFilter = servletContext.addFilter("webappMetricsFilter",
            new InstrumentedFilter());

        metricsFilter.addMappingForUrlPatterns(disps, true, "/*");
        metricsFilter.setAsyncSupported(true);

        log.debug("Registering Metrics Servlet");
        ServletRegistration.Dynamic metricsAdminServlet =
            servletContext.addServlet("metricsServlet", new MetricsServlet());

        metricsAdminServlet.addMapping("/management/metrics/*");
        metricsAdminServlet.setAsyncSupported(true);
        metricsAdminServlet.setLoadOnStartup(2);
    }

    @Bean
    public CorsFilter corsFilter() {
        UrlBasedCorsConfigurationSource source = new UrlBasedCorsConfigurationSource();
        CorsConfiguration config = jHipsterProperties.getCors();
        if (config.getAllowedOrigins() != null && !config.getAllowedOrigins().isEmpty()) {
            log.debug("Registering CORS filter");
            source.registerCorsConfiguration("/api/**", config);
            source.registerCorsConfiguration("/management/**", config);
            source.registerCorsConfiguration("/v2/api-docs", config);
            source.registerCorsConfiguration("/auth/**", config);
            source.registerCorsConfiguration("/*/api/**", config);
            source.registerCorsConfiguration("/*/management/**", config);
            source.registerCorsConfiguration("/*/oauth/**", config);
        }
        return new CorsFilter(source);
    }

    /**
     * Initializes H2 console.
     */
    private void initH2Console(ServletContext servletContext) {
        log.debug("Initialize H2 console");
        H2ConfigurationHelper.initH2Console(servletContext);
    }

    @Autowired(required = false)
    public void setMetricRegistry(MetricRegistry metricRegistry) {
        this.metricRegistry = metricRegistry;
    }
}
