// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

part of html;

abstract class CssClassSet implements Set<String> {

  String toString() {
    return Strings.join(new List.from(readClasses()), ' ');
  }

  /**
   * Adds the class [token] to the element if it is not on it, removes it if it
   * is.
   */
  bool toggle(String value) {
    Set<String> s = readClasses();
    bool result = false;
    if (s.contains(value)) {
      s.remove(value);
    } else {
      s.add(value);
      result = true;
    }
    writeClasses(s);
    return result;
  }

  /**
   * Returns [:true:] if classes cannot be added or removed from this
   * [:CssClassSet:].
   */
  bool get frozen => false;

  // interface Iterable - BEGIN
  Iterator<String> iterator() => readClasses().iterator();
  // interface Iterable - END

  // interface Collection - BEGIN
  void forEach(void f(String element)) {
    readClasses().forEach(f);
  }

  Collection map(f(String element)) => readClasses().map(f);

  Collection<String> filter(bool f(String element)) => readClasses().filter(f);

  bool every(bool f(String element)) => readClasses().every(f);

  bool some(bool f(String element)) => readClasses().some(f);

  bool get isEmpty => readClasses().isEmpty;

  int get length =>readClasses().length;
  // interface Collection - END

  // interface Set - BEGIN
  bool contains(String value) => readClasses().contains(value);

  void add(String value) {
    // TODO - figure out if we need to do any validation here
    // or if the browser natively does enough
    _modify((s) => s.add(value));
  }

  bool remove(String value) {
    Set<String> s = readClasses();
    bool result = s.remove(value);
    writeClasses(s);
    return result;
  }

  void addAll(Collection<String> collection) {
    // TODO - see comment above about validation
    _modify((s) => s.addAll(collection));
  }

  void removeAll(Collection<String> collection) {
    _modify((s) => s.removeAll(collection));
  }

  bool isSubsetOf(Collection<String> collection) =>
    readClasses().isSubsetOf(collection);

  bool containsAll(Collection<String> collection) =>
    readClasses().containsAll(collection);

  Set<String> intersection(Collection<String> other) =>
    readClasses().intersection(other);

  void clear() {
    _modify((s) => s.clear());
  }
  // interface Set - END

  /**
   * Helper method used to modify the set of css classes on this element.
   *
   *   f - callback with:
   *      s - a Set of all the css class name currently on this element.
   *
   *   After f returns, the modified set is written to the
   *       className property of this element.
   */
  void _modify( f(Set<String> s)) {
    Set<String> s = readClasses();
    f(s);
    writeClasses(s);
  }

  /**
   * Read the class names from the Element class property,
   * and put them into a set (duplicates are discarded).
   * This is intended to be overridden by specific implementations.
   */
  Set<String> readClasses();

  /**
   * Join all the elements of a set into one string and write
   * back to the element.
   * This is intended to be overridden by specific implementations.
   */
  void writeClasses(Set<String> s);
}