// Copyright 2009 Google Inc.
//
// 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 com.google.gwtexpui.safehtml.client;

import com.google.gwt.user.client.DOM;
import com.google.gwt.user.client.Element;
import com.google.gwt.user.client.ui.HTML;
import com.google.gwt.user.client.ui.HTMLTable;
import com.google.gwt.user.client.ui.HasHTML;
import com.google.gwt.user.client.ui.InlineHTML;
import com.google.gwt.user.client.ui.Widget;

/** Immutable string safely placed as HTML without further escaping. */
public abstract class SafeHtml {
  /** Set the HTML property of a widget. */
  public static <T extends HasHTML> T set(final T e, final SafeHtml str) {
    e.setHTML(str.asString());
    return e;
  }

  /** Set the inner HTML of any element. */
  public static Element set(final Element e, final SafeHtml str) {
    DOM.setInnerHTML(e, str.asString());
    return e;
  }

  /** Set the inner HTML of a table cell. */
  public static <T extends HTMLTable> T set(final T t, final int row,
      final int col, final SafeHtml str) {
    t.setHTML(row, col, str.asString());
    return t;
  }

  /** Parse an HTML block and return the first (typically root) element. */
  public static Element parse(final SafeHtml str) {
    return DOM.getFirstChild(set(DOM.createDiv(), str));
  }

  /** Convert bare http:// and https:// URLs into &lt;a href&gt; tags. */
  public SafeHtml linkify() {
    return replaceAll("(https?://[^ \n\r\t]*)", "<a href=\"$1\">$1</a>");
  }

  /**
   * Apply {@link #linkify()}, and "\n\n" to &lt;p&gt;.
   * <p>
   * Lines that start with whitespace are assumed to be preformatted, and are
   * formatted by the <code>gwtexpui-SafeHtml-WikiPreFormat</code> CSS class. By
   * default this class is:
   * 
   * <pre>
   *   white-space: pre;
   *   font-family: monospace;
   * </pre>
   */
  public SafeHtml wikify() {
    SafeHtml s = linkify();
    s = s.replaceAll("(^|\n)([ \t][^\n]*)", "$1<span class=\"gwtexpui-SafeHtml-WikiPreFormat\">$2</span><br />");
    s = s.replaceAll("\n\n", "\n<p />\n");
    return s;
  }

  /**
   * Replace first occurrence of <code>regex</code> with <code>repl</code> .
   * <p>
   * <b>WARNING:</b> This replacement is being performed against an otherwise
   * safe HTML string. The caller must ensure that the replacement does not
   * introduce cross-site scripting attack entry points.
   * 
   * @param regex regular expression pattern to match the substring with.
   * @param repl replacement expression. Capture groups within
   *        <code>regex</code> can be referenced with <code>$<i>n</i></code>.
   * @return a new string, after the replacement has been made.
   */
  public SafeHtml replaceFirst(final String regex, final String repl) {
    return new SafeHtmlString(asString().replaceFirst(regex, repl));
  }

  /**
   * Replace each occurrence of <code>regex</code> with <code>repl</code> .
   * <p>
   * <b>WARNING:</b> This replacement is being performed against an otherwise
   * safe HTML string. The caller must ensure that the replacement does not
   * introduce cross-site scripting attack entry points.
   * 
   * @param regex regular expression pattern to match substrings with.
   * @param repl replacement expression. Capture groups within
   *        <code>regex</code> can be referenced with <code>$<i>n</i></code>.
   * @return a new string, after the replacements have been made.
   */
  public SafeHtml replaceAll(final String regex, final String repl) {
    return new SafeHtmlString(asString().replaceAll(regex, repl));
  }

  /** @return a GWT block display widget displaying this HTML. */
  public Widget toBlockWidget() {
    return new HTML(asString());
  }

  /** @return a GWT inline display widget displaying this HTML. */
  public Widget toInlineWidget() {
    return new InlineHTML(asString());
  }

  /** @return a clean HTML string safe for inclusion in any context. */
  abstract String asString();
}