/*
 * 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.cp;

import static org.apache.juneau.commons.utils.CollectionUtils.*;
import static org.apache.juneau.commons.utils.FileUtils.*;
import static org.apache.juneau.commons.utils.IoUtils.*;
import static org.apache.juneau.commons.utils.StringUtils.*;
import static org.apache.juneau.commons.utils.Utils.*;

import java.io.*;
import java.util.*;
import java.util.ResourceBundle.*;
import java.util.concurrent.*;
import java.util.regex.*;

import org.apache.juneau.commons.collections.*;
import org.apache.juneau.commons.io.*;

/**
 * Basic implementation of a {@link FileFinder}.
 *
 * <p>
 * Specialized behavior can be implemented by overridding the {@link #find(String, Locale)} method.
 *
 * <h5 class='section'>Example:</h5>
 * <p class='bjava'>
 *    <jk>public class</jk> MyFileFinder <jk>extends</jk> BasicFileFinder {
 *       <ja>@Override</ja>
 *       <jk>protected</jk> Optional&lt;InputStream&gt; find(String <jv>name</jv>, Locale <jv>locale</jv>) <jk>throws</jk> IOException {
 *          <jc>// Do special handling or just call super.find().</jc>
 *          <jk>return super</jk>.find(<jv>name</jv>, <jv>locale</jv>);
 *       }
 *    }
 * </p>
 *
 */
@SuppressWarnings("resource")
public class BasicFileFinder implements FileFinder {

   private static final ResourceBundle.Control RB_CONTROL = ResourceBundle.Control.getControl(Control.FORMAT_DEFAULT);

   private final Map<String,LocalFile> files = new ConcurrentHashMap<>();
   private final Map<Locale,Map<String,LocalFile>> localizedFiles = new ConcurrentHashMap<>();

   private final LocalDir[] roots;
   private final long cachingLimit;
   private final Pattern[] include, exclude;
   private final String[] includePatterns, excludePatterns;
   private final int hashCode;

   /**
    * Builder-based constructor.
    *
    * @param builder The builder object.
    */
   public BasicFileFinder(FileFinder.Builder builder) {
      this.roots = builder.roots.toArray(new LocalDir[builder.roots.size()]);
      this.cachingLimit = builder.cachingLimit;
      this.include = builder.include;
      this.exclude = builder.exclude;
      this.includePatterns = l(include).stream().map(Pattern::pattern).toArray(String[]::new);
      this.excludePatterns = l(exclude).stream().map(Pattern::pattern).toArray(String[]::new);
      this.hashCode = h(getClass(), roots, cachingLimit, includePatterns, excludePatterns);
   }

   /**
    * Default constructor.
    *
    * <p>
    * Can be used when providing a subclass that overrides the {@link #find(String, Locale)} method.
    */
   protected BasicFileFinder() {
      this.roots = new LocalDir[0];
      this.cachingLimit = -1;
      this.include = new Pattern[0];
      this.exclude = new Pattern[0];
      this.includePatterns = new String[0];
      this.excludePatterns = new String[0];
      this.hashCode = h(getClass(), roots, cachingLimit, includePatterns, excludePatterns);
   }

   @Override /* Overridden from Object */
   public boolean equals(Object o) {
      return o instanceof BasicFileFinder o2 && eq(this, o2, (x, y) -> eq(x.hashCode, y.hashCode) && eq(x.getClass(), y.getClass()) && eq(x.roots, y.roots) && eq(x.cachingLimit, y.cachingLimit)
         && eq(x.includePatterns, y.includePatterns) && eq(x.excludePatterns, y.excludePatterns));
   }

   @Override /* Overridden from FileFinder */
   public final Optional<InputStream> getStream(String name, Locale locale) throws IOException {
      return find(name, locale);
   }

   @Override /* Overridden from FileFinder */
   public Optional<String> getString(String name, Locale locale) throws IOException {
      return opt(read(find(name, locale).orElse(null)));
   }

   @Override
   public int hashCode() {
      return hashCode;
   }

   protected FluentMap<String,Object> properties() {
      // @formatter:off
      return filteredBeanPropertyMap()
         .a("cachingLimit", cachingLimit)
         .a("class", cns(getClass()))
         .a("exclude", excludePatterns)
         .a("include", includePatterns)
         .a("roots", roots)
         .a("hashCode", hashCode);
      // @formatter:on
   }

   @Override /* Overridden from Object */
   public String toString() {
      return r(properties());
   }

   /**
    * The main implementation method for finding files.
    *
    * <p>
    * Subclasses can override this method to provide their own handling.
    *
    * @param name The resource name.
    *    See {@link Class#getResource(String)} for format.
    * @param locale
    *    The locale of the resource to retrieve.
    *    <br>If <jk>null</jk>, won't look for localized file names.
    * @return The resolved resource contents, or <jk>null</jk> if the resource was not found.
    * @throws IOException Thrown by underlying stream.
    */
   @SuppressWarnings("null")
   protected Optional<InputStream> find(String name, Locale locale) throws IOException {
      name = trimSlashesAndSpaces(name);

      if (isInvalidPath(name))
         return opte();

      if (nn(locale))
         localizedFiles.putIfAbsent(locale, new ConcurrentHashMap<>());

      Map<String,LocalFile> fileCache = locale == null ? files : localizedFiles.get(locale);

      LocalFile lf = fileCache.get(name);

      if (lf == null) {
         List<String> candidateFileNames = getCandidateFileNames(name, locale);
         paths: for (LocalDir root : roots) {
            for (var cfn : candidateFileNames) {
               lf = root.resolve(cfn);
               if (nn(lf))
                  break paths;
            }
         }

         if (nn(lf) && isIgnoredFile(lf.getName()))
            lf = null;

         if (nn(lf)) {
            fileCache.put(name, lf);

            if (cachingLimit >= 0) {
               long size = lf.size();
               if (size > 0 && size <= cachingLimit)
                  lf.cache();
            }
         }
      }

      return opt(lf == null ? null : lf.read());
   }

   /**
    * Returns the candidate file names for the specified file name in the specified locale.
    *
    * <p>
    * For example, if looking for the <js>"MyResource.txt"</js> file in the Japanese locale, the iterator will return
    * names in the following order:
    * <ol>
    *    <li><js>"MyResource_ja_JP.txt"</js>
    *    <li><js>"MyResource_ja.txt"</js>
    *    <li><js>"MyResource.txt"</js>
    * </ol>
    *
    * <p>
    * If the locale is <jk>null</jk>, then it will only return <js>"MyResource.txt"</js>.
    *
    * @param fileName The name of the file to get candidate file names on.
    * @param locale
    *    The locale.
    *    <br>If <jk>null</jk>, won't look for localized file names.
    * @return An iterator of file names to look at.
    */
   protected List<String> getCandidateFileNames(String fileName, Locale locale) {

      if (locale == null)
         return Collections.singletonList(fileName);

      var list = new ArrayList<String>();
      var baseName = getBaseName(fileName);
      var ext = getFileExtension(fileName);

      getCandidateLocales(locale).forEach(x -> {
         var ls = x.toString();
         if (ls.isEmpty())
            list.add(fileName);
         else {
            list.add(baseName + "_" + ls + (ext.isEmpty() ? "" : ('.' + ext)));
            list.add(ls.replace('_', '/') + '/' + fileName);
         }
      });

      return list;
   }

   /**
    * Returns the candidate locales for the specified locale.
    *
    * <p>
    * For example, if <c>locale</c> is <js>"ja_JP"</js>, then this method will return:
    * <ol>
    *    <li><js>"ja_JP"</js>
    *    <li><js>"ja"</js>
    *    <li><js>""</js>
    * </ol>
    *
    * @param locale The locale to get the list of candidate locales for.
    * @return The list of candidate locales.
    */
   protected List<Locale> getCandidateLocales(Locale locale) {
      return RB_CONTROL.getCandidateLocales("", locale);
   }

   /**
    * Returns <jk>true</jk> if the file should be ignored based on file name.
    *
    * @param name The name to check.
    * @return <jk>true</jk> if the file should be ignored.
    */
   protected boolean isIgnoredFile(String name) {
      for (var p : exclude)
         if (p.matcher(name).matches())
            return true;
      for (var p : include)
         if (p.matcher(name).matches())
            return false;
      return true;
   }

   /**
    * Checks for path malformations such as use of <js>".."</js> which can be used to open up security holes.
    *
    * <p>
    * Default implementation returns <jk>true</jk> if the path is any of the following:
    * <ul>
    *    <li>Is blank or <jk>null</jk>.
    *    <li>Contains <js>".."</js> (to prevent traversing out of working directory).
    *    <li>Contains <js>"%"</js> (to prevent URI trickery).
    * </ul>
    *
    * @param path The path to check.
    * @return <jk>true</jk> if the path is invalid.
    */
   protected boolean isInvalidPath(String path) {
      return isEmpty(path) || path.contains("..") || path.contains("%");
   }
}