/**
 * Copyright (c) 2013-present, Facebook, Inc.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */

import containsNode from 'fbjs/lib/containsNode';
import getActiveElement from 'fbjs/lib/getActiveElement';

import * as ReactDOMSelection from './ReactDOMSelection';
import {ELEMENT_NODE} from '../shared/HTMLNodeType';

function isInDocument(node) {
  return containsNode(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.
 */

export function hasSelectionCapabilities(elem) {
  const nodeName = elem && elem.nodeName && elem.nodeName.toLowerCase();
  return (
    nodeName &&
    ((nodeName === 'input' && elem.type === 'text') ||
      nodeName === 'textarea' ||
      elem.contentEditable === 'true')
  );
}

export function getSelectionInformation() {
  const focusedElem = getActiveElement();
  return {
    focusedElem: focusedElem,
    selectionRange: hasSelectionCapabilities(focusedElem)
      ? 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.
 */
export function restoreSelection(priorSelectionInformation) {
  const curFocusedElem = getActiveElement();
  const priorFocusedElem = priorSelectionInformation.focusedElem;
  const priorSelectionRange = priorSelectionInformation.selectionRange;
  if (curFocusedElem !== priorFocusedElem && isInDocument(priorFocusedElem)) {
    if (hasSelectionCapabilities(priorFocusedElem)) {
      setSelection(priorFocusedElem, priorSelectionRange);
    }

    // Focusing a node can change the scroll position, which is undesirable
    const ancestors = [];
    let ancestor = priorFocusedElem;
    while ((ancestor = ancestor.parentNode)) {
      if (ancestor.nodeType === ELEMENT_NODE) {
        ancestors.push({
          element: ancestor,
          left: ancestor.scrollLeft,
          top: ancestor.scrollTop,
        });
      }
    }

    priorFocusedElem.focus();

    for (let i = 0; i < ancestors.length; i++) {
      const info = ancestors[i];
      info.element.scrollLeft = info.left;
      info.element.scrollTop = info.top;
    }
  }
}

/**
 * @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}
 */
export function getSelection(input) {
  let selection;

  if ('selectionStart' in input) {
    // Modern browser with input or textarea.
    selection = {
      start: input.selectionStart,
      end: input.selectionEnd,
    };
  } 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*
 */
export function setSelection(input, offsets) {
  let {start, end} = offsets;
  if (end === undefined) {
    end = start;
  }

  if ('selectionStart' in input) {
    input.selectionStart = start;
    input.selectionEnd = Math.min(end, input.value.length);
  } else {
    ReactDOMSelection.setOffsets(input, offsets);
  }
}
