/*
 * Copyright 2016 Red Hat, Inc. and/or its affiliates
 * and other contributors as indicated by the @author tags.
 *
 * Licensed 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.keycloak.theme;

import java.util.function.Predicate;
import java.util.regex.Pattern;

import org.owasp.html.HtmlPolicyBuilder;
import org.owasp.html.PolicyFactory;

/**
 * Based on the EbayPolicyExample in owasp java-html-sanitizer.
 */
public class KeycloakSanitizerPolicy {

  // Some common regular expression definitions.

  // The 16 colors defined by the HTML Spec (also used by the CSS Spec)
  private static final Pattern COLOR_NAME = Pattern.compile(
      "(?:aqua|black|blue|fuchsia|gray|grey|green|lime|maroon|navy|olive|purple"
      + "|red|silver|teal|white|yellow)");

  // HTML/CSS Spec allows 3 or 6 digit hex to specify color
  private static final Pattern COLOR_CODE = Pattern.compile(
      "(?:#(?:[0-9a-fA-F]{3}(?:[0-9a-fA-F]{3})?))");

  private static final Pattern NUMBER_OR_PERCENT = Pattern.compile(
      "[0-9]+%?");
  private static final Pattern PARAGRAPH = Pattern.compile(
      "(?:[\\p{L}\\p{N},'\\.\\s\\-_\\(\\)]|&[0-9]{2};)*");
  private static final Pattern HTML_ID = Pattern.compile(
      "[a-zA-Z0-9\\:\\-_\\.]+");
  // force non-empty with a '+' at the end instead of '*'
  private static final Pattern HTML_TITLE = Pattern.compile(
      "[\\p{L}\\p{N}\\s\\-_',:\\[\\]!\\./\\\\\\(\\)&]*");
  private static final Pattern HTML_CLASS = Pattern.compile(
      "[a-zA-Z0-9\\s,\\-_]+");

  private static final Pattern ONSITE_URL = Pattern.compile(
      "(?:[\\p{L}\\p{N}\\\\\\.\\#@\\$%\\+&;\\-_~,\\?=/!]+|\\#(\\w)+)");
  private static final Pattern OFFSITE_URL = Pattern.compile(
      "\\s*(?:(?:ht|f)tps?://|mailto:)[\\p{L}\\p{N}]"
      + "[\\p{L}\\p{N}\\p{Zs}\\.\\#@\\$%\\+&;:\\-_~,\\?=/!\\(\\)]*+\\s*");

  private static final Pattern NUMBER = Pattern.compile(
      "[+-]?(?:(?:[0-9]+(?:\\.[0-9]*)?)|\\.[0-9]+)");

  private static final Pattern NAME = Pattern.compile("[a-zA-Z0-9\\-_\\$]+");

  private static final Pattern TARGET = Pattern.compile("_blank");

  private static final Pattern ALIGN = Pattern.compile(
      "(?i)center|left|right|justify|char");

  private static final Pattern VALIGN = Pattern.compile(
      "(?i)baseline|bottom|middle|top");

  private static final Predicate<String> COLOR_NAME_OR_COLOR_CODE
      = matchesEither(COLOR_NAME, COLOR_CODE);

  private static final Predicate<String> ONSITE_OR_OFFSITE_URL
      = matchesEither(ONSITE_URL, OFFSITE_URL);

  private static final Pattern HISTORY_BACK = Pattern.compile(
      "(?:javascript:)?\\Qhistory.go(-1)\\E");

  private static final Pattern ONE_CHAR = Pattern.compile(
      ".?", Pattern.DOTALL);


  public static final PolicyFactory POLICY_DEFINITION = new HtmlPolicyBuilder()
          .allowWithoutAttributes("span") // this is added to ebay example to allow span without attributes
          .allowAttributes("id").matching(HTML_ID).globally()
          .allowAttributes("class").matching(HTML_CLASS).globally()
          .allowAttributes("lang").matching(Pattern.compile("[a-zA-Z]{2,20}"))
              .globally()
          .allowAttributes("title").matching(HTML_TITLE).globally()
          .allowStyling()
          .allowAttributes("align").matching(ALIGN).onElements("p")
          .allowAttributes("for").matching(HTML_ID).onElements("label")
          .allowAttributes("color").matching(COLOR_NAME_OR_COLOR_CODE)
              .onElements("font")
          .allowAttributes("face")
              .matching(Pattern.compile("[\\w;, \\-]+"))
              .onElements("font")
          .allowAttributes("size").matching(NUMBER).onElements("font")
          .allowAttributes("href").matching(ONSITE_OR_OFFSITE_URL)
              .onElements("a")
          .allowStandardUrlProtocols()
          .allowAttributes("nohref").onElements("a")
          .allowAttributes("name").matching(NAME).onElements("a")
          .allowAttributes("target").matching(TARGET).onElements("a")
          .allowAttributes(
              "onfocus", "onblur", "onclick", "onmousedown", "onmouseup")
              .matching(HISTORY_BACK).onElements("a")
          .requireRelNofollowOnLinks()
          .allowAttributes("src").matching(ONSITE_OR_OFFSITE_URL)
              .onElements("img")
          .allowAttributes("name").matching(NAME)
              .onElements("img")
          .allowAttributes("alt").matching(PARAGRAPH)
              .onElements("img")
          .allowAttributes("border", "hspace", "vspace").matching(NUMBER)
              .onElements("img")
          .allowAttributes("border", "cellpadding", "cellspacing")
              .matching(NUMBER).onElements("table")
          .allowAttributes("bgcolor").matching(COLOR_NAME_OR_COLOR_CODE)
              .onElements("table")
          .allowAttributes("background").matching(ONSITE_URL)
              .onElements("table")
          .allowAttributes("align").matching(ALIGN)
              .onElements("table")
          .allowAttributes("noresize").matching(Pattern.compile("(?i)noresize"))
              .onElements("table")
          .allowAttributes("background").matching(ONSITE_URL)
              .onElements("td", "th", "tr")
          .allowAttributes("bgcolor").matching(COLOR_NAME_OR_COLOR_CODE)
              .onElements("td", "th")
          .allowAttributes("abbr").matching(PARAGRAPH)
              .onElements("td", "th")
          .allowAttributes("axis", "headers").matching(NAME)
              .onElements("td", "th")
          .allowAttributes("scope")
              .matching(Pattern.compile("(?i)(?:row|col)(?:group)?"))
              .onElements("td", "th")
          .allowAttributes("nowrap")
              .onElements("td", "th")
          .allowAttributes("height", "width").matching(NUMBER_OR_PERCENT)
              .onElements("table", "td", "th", "tr", "img")
          .allowAttributes("align").matching(ALIGN)
              .onElements("thead", "tbody", "tfoot", "img",
                               "td", "th", "tr", "colgroup", "col")
          .allowAttributes("valign").matching(VALIGN)
              .onElements("thead", "tbody", "tfoot",
                              "td", "th", "tr", "colgroup", "col")
          .allowAttributes("charoff").matching(NUMBER_OR_PERCENT)
              .onElements("td", "th", "tr", "colgroup", "col",
                              "thead", "tbody", "tfoot")
          .allowAttributes("char").matching(ONE_CHAR)
              .onElements("td", "th", "tr", "colgroup", "col",
                               "thead", "tbody", "tfoot")
          .allowAttributes("colspan", "rowspan").matching(NUMBER)
              .onElements("td", "th")
          .allowAttributes("span", "width").matching(NUMBER_OR_PERCENT)
              .onElements("colgroup", "col")
          .allowElements(
              "a", "label", "noscript", "h1", "h2", "h3", "h4", "h5", "h6",
              "p", "i", "b", "u", "strong", "em", "small", "big", "pre", "code",
              "cite", "samp", "sub", "sup", "strike", "center", "blockquote",
              "hr", "br", "col", "font", "map", "span", "div", "img",
              "ul", "ol", "li", "dd", "dt", "dl", "tbody", "thead", "tfoot",
              "table", "td", "th", "tr", "colgroup", "fieldset", "legend")
          .toFactory();

  private static Predicate<String> matchesEither(final Pattern a, final Pattern b) {
    return s -> a.matcher(s).matches() || b.matcher(s).matches();
  }
}
