/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.juneau.console.test;

import java.util.*;
import java.util.function.*;
import java.util.regex.*;

/**
 * Test helper that checks every asset a rendered console page links (stylesheets, scripts, images, icons) actually
 * resolves.
 *
 * <p>
 * The console chrome links its assets at context-root URLs such as {@code /juneau-console/chrome.css}, so they only
 * load if the host mounts something at those paths.  Page tests that assert the hrefs cannot see a missing mount;
 * this helper fetches each URL through whatever client the caller supplies and reports every one that does not
 * answer {@code 200}.
 *
 * <p>
 * The fetcher is a plain {@link Function} from URL to HTTP status, so the class has no dependency on a test
 * framework or on a particular client.  Failures throw {@link AssertionError}.  Only same-origin URLs are checked:
 * absolute {@code http(s):}, protocol-relative, {@code data:} and fragment-only URLs are skipped.
 *
 * <h5 class='section'>Example:</h5>
 * <p class='bjava'>
 *    MockRestClient <jv>client</jv> = MockRestClient.<jsm>buildLax</jsm>(MyHost.<jk>class</jk>);
 *    String <jv>html</jv> = <jv>client</jv>.get(<js>"/page"</js>).run().getContent().asString();
 *    AssetResolutionAssert.<jsm>assertAssetsResolve</jsm>(<jv>html</jv>, <jv>url</jv> -&gt; <jv>client</jv>.get(<jv>url</jv>).run().getStatusCode());
 * </p>
 *
 * @since 10.0.0
 */
public final class AssetResolutionAssert {

   private static final Pattern TAG = Pattern.compile("<(script|img|link)\\b([^>]*)>", Pattern.CASE_INSENSITIVE);
   private static final Pattern SRC = attr("src");
   private static final Pattern HREF = attr("href");
   private static final Pattern REL = attr("rel");
   private static final Set<String> ASSET_RELS = Set.of("stylesheet", "icon", "shortcut", "apple-touch-icon", "preload", "modulepreload", "manifest");

   private AssetResolutionAssert() {}

   private static Pattern attr(String name) {
      return Pattern.compile("(?<![\\w-])" + name + "\\s*=\\s*(?:\"([^\"]*)\"|'([^']*)')", Pattern.CASE_INSENSITIVE);
   }

   private static String value(Pattern p, String attrs) {
      var m = p.matcher(attrs);
      if (! m.find())
         return null;
      return m.group(m.group(1) != null ? 1 : 2);
   }

   private static boolean isAssetLink(String attrs) {
      var rel = value(REL, attrs);
      if (rel == null)
         return false;
      for (var token : rel.toLowerCase(Locale.ROOT).split("\\s+"))
         if (ASSET_RELS.contains(token))
            return true;
      return false;
   }

   private static boolean isSameOrigin(String url) {
      return ! (url.isEmpty() || url.startsWith("#") || url.startsWith("//") || url.matches("(?i)^[a-z][a-z0-9+.-]*:.*"));
   }

   /**
    * Returns the same-origin asset URLs a page links, in document order and without duplicates.
    *
    * <p>
    * Covers {@code <script src>}, {@code <img src>} and {@code <link href>} whose {@code rel} is a stylesheet,
    * icon, preload or manifest.  {@code &amp;} is decoded and any fragment is dropped.
    *
    * @param html The rendered page.
    * @return The asset URLs.  Never <jk>null</jk>.
    */
   public static List<String> assetUrls(String html) {
      var urls = new LinkedHashSet<String>();
      var m = TAG.matcher(html);
      while (m.find()) {
         var attrs = m.group(2);
         String url;
         if ("link".equalsIgnoreCase(m.group(1)))
            url = isAssetLink(attrs) ? value(HREF, attrs) : null;
         else
            url = value(SRC, attrs);
         if (url == null)
            continue;
         url = url.replace("&amp;", "&").trim();
         var hash = url.indexOf('#');
         if (hash > 0)
            url = url.substring(0, hash);
         if (isSameOrigin(url))
            urls.add(url);
      }
      return List.copyOf(urls);
   }

   /**
    * Returns a description of every linked asset that does not answer {@code 200}.
    *
    * @param html The rendered page.
    * @param statusOf Fetches a URL and returns its HTTP status code.
    * @return One {@code "<status> <url>"} entry per failing asset, sorted; empty when every asset resolves.
    */
   @SuppressWarnings({
      "java:S4276" // A null status signals failure, so it cannot be a ToIntFunction
   })
   public static List<String> unresolved(String html, Function<String,Integer> statusOf) {
      var bad = new TreeSet<String>();
      for (var url : assetUrls(html)) {
         var status = statusOf.apply(url);
         if (status == null || status != 200)
            bad.add(status + " " + url);
      }
      return List.copyOf(bad);
   }

   /**
    * Asserts that every asset the page links answers {@code 200}.
    *
    * @param html The rendered page.
    * @param statusOf Fetches a URL and returns its HTTP status code.
    * @throws AssertionError If any linked asset does not resolve; the message lists each one.
    */
   @SuppressWarnings({
      "java:S4276" // A null status signals failure, so it cannot be a ToIntFunction
   })
   public static void assertAssetsResolve(String html, Function<String,Integer> statusOf) {
      assertAssetsResolve(null, html, statusOf);
   }

   /**
    * Asserts that every asset the page links answers {@code 200}, naming the page in the failure message.
    *
    * @param page A label for the page (typically its path); can be <jk>null</jk>.
    * @param html The rendered page.
    * @param statusOf Fetches a URL and returns its HTTP status code.
    * @throws AssertionError If any linked asset does not resolve; the message lists each one.
    */
   @SuppressWarnings({
      "java:S4276" // A null status signals failure, so it cannot be a ToIntFunction
   })
   public static void assertAssetsResolve(String page, String html, Function<String,Integer> statusOf) {
      var bad = unresolved(html, statusOf);
      if (! bad.isEmpty())
         throw new AssertionError((page == null ? "" : "Unresolved assets linked from " + page + ":\n") + String.join("\n", bad));
   }
}