/**
 * Copyright 2013 Facebook, 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.
 *
 * @providesModule ReactInputSelection
 */

"use strict";

var ReactDOMSelection = require('ReactDOMSelection');

var getActiveElement = require('getActiveElement');
var nodeContains = require('nodeContains');

function isInDocument(node) {
  return nodeContains(document.documentElement, node);
}

/**
 * @ReactInputSelection: React input selection module. Based on Selection.js,
 * but modified to be suitable for react and has a couple of bug fixes (doesn't
 * assume buttons have range selections allowed).
 * Input selection module for React.
 */
var ReactInputSelection = {

  hasSelectionCapabilities: function(elem) {
    return elem && (
      (elem.nodeName === 'INPUT' && elem.type === 'text') ||
      elem.nodeName === 'TEXTAREA' ||
      elem.contentEditable === 'true'
    );
  },

  getSelectionInformation: function() {
    var focusedElem = getActiveElement();
    return {
      focusedElem: focusedElem,
      selectionRange:
          ReactInputSelection.hasSelectionCapabilities(focusedElem) ?
          ReactInputSelection.getSelection(focusedElem) :
          null
    };
  },

  /**
   * @restoreSelection: If any selection information was potentially lost,
   * restore it. This is useful when performing operations that could remove dom
   * nodes and place them back in, resulting in focus being lost.
   */
  restoreSelection: function(priorSelectionInformation) {
    var curFocusedElem = getActiveElement();
    var priorFocusedElem = priorSelectionInformation.focusedElem;
    var priorSelectionRange = priorSelectionInformation.selectionRange;
    if (curFocusedElem !== priorFocusedElem &&
        isInDocument(priorFocusedElem)) {
      if (ReactInputSelection.hasSelectionCapabilities(priorFocusedElem)) {
        ReactInputSelection.setSelection(
          priorFocusedElem,
          priorSelectionRange
        );
      }
      priorFocusedElem.focus();
    }
  },

  /**
   * @getSelection: Gets the selection bounds of a focused textarea, input or
   * contentEditable node.
   * -@input: Look up selection bounds of this input
   * -@return {start: selectionStart, end: selectionEnd}
   */
  getSelection: function(input) {
    var selection;

    if ('selectionStart' in input) {
      // Modern browser with input or textarea.
      selection = {
        start: input.selectionStart,
        end: input.selectionEnd
      };
    } else if (document.selection && input.nodeName === 'INPUT') {
      // IE8 input.
      var range = document.selection.createRange();
      // There can only be one selection per document in IE, so it must
      // be in our element.
      if (range.parentElement() === input) {
        selection = {
          start: -range.moveStart('character', -input.value.length),
          end: -range.moveEnd('character', -input.value.length)
        };
      }
    } else {
      // Content editable or old IE textarea.
      selection = ReactDOMSelection.getOffsets(input);
    }

    return selection || {start: 0, end: 0};
  },

  /**
   * @setSelection: Sets the selection bounds of a textarea or input and focuses
   * the input.
   * -@input     Set selection bounds of this input or textarea
   * -@offsets   Object of same form that is returned from get*
   */
  setSelection: function(input, offsets) {
    var start = offsets.start;
    var end = offsets.end;
    if (typeof end === 'undefined') {
      end = start;
    }

    if ('selectionStart' in input) {
      input.selectionStart = start;
      input.selectionEnd = Math.min(end, input.value.length);
    } else if (document.selection && input.nodeName === 'INPUT') {
      var range = input.createTextRange();
      range.collapse(true);
      range.moveStart('character', start);
      range.moveEnd('character', end - start);
      range.select();
    } else {
      ReactDOMSelection.setOffsets(input, offsets);
    }
  }
};

module.exports = ReactInputSelection;
