/**
 * 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 ReactInstanceHandles
 * @typechecks static-only
 */

"use strict";

var invariant = require('invariant');

var SEPARATOR = '.';
var SEPARATOR_LENGTH = SEPARATOR.length;

/**
 * Maximum depth of traversals before we consider the possibility of a bad ID.
 */
var MAX_TREE_DEPTH = 100;

/**
 * Size of the reactRoot ID space. We generate random numbers for React root
 * IDs and if there's a collision the events and DOM update system will
 * get confused. If we assume 100 React components per page, and a user
 * loads 1 page per minute 24/7 for 50 years, with a mount point space of
 * 9,999,999 the likelihood of never having a collision is 99.997%.
 */
var GLOBAL_MOUNT_POINT_MAX = 9999999;

/**
 * Creates a DOM ID prefix to use when mounting React components.
 *
 * @param {number} index A unique integer
 * @return {string} React root ID.
 * @internal
 */
function getReactRootIDString(index) {
  return SEPARATOR + 'r[' + index.toString(36) + ']';
}

/**
 * Checks if a character in the supplied ID is a separator or the end.
 *
 * @param {string} id A React DOM ID.
 * @param {number} index Index of the character to check.
 * @return {boolean} True if the character is a separator or end of the ID.
 * @private
 */
function isBoundary(id, index) {
  return id.charAt(index) === SEPARATOR || index === id.length;
}

/**
 * Checks if the supplied string is a valid React DOM ID.
 *
 * @param {string} id A React DOM ID, maybe.
 * @return {boolean} True if the string is a valid React DOM ID.
 * @private
 */
function isValidID(id) {
  return id === '' || (
    id.charAt(0) === SEPARATOR && id.charAt(id.length - 1) !== SEPARATOR
  );
}

/**
 * Checks if the first ID is an ancestor of or equal to the second ID.
 *
 * @param {string} ancestorID
 * @param {string} descendantID
 * @return {boolean} True if `ancestorID` is an ancestor of `descendantID`.
 * @internal
 */
function isAncestorIDOf(ancestorID, descendantID) {
  return (
    descendantID.indexOf(ancestorID) === 0 &&
    isBoundary(descendantID, ancestorID.length)
  );
}

/**
 * Gets the parent ID of the supplied React DOM ID, `id`.
 *
 * @param {string} id ID of a component.
 * @return {string} ID of the parent, or an empty string.
 * @private
 */
function getParentID(id) {
  return id ? id.substr(0, id.lastIndexOf(SEPARATOR)) : '';
}

/**
 * Gets the next DOM ID on the tree path from the supplied `ancestorID` to the
 * supplied `destinationID`. If they are equal, the ID is returned.
 *
 * @param {string} ancestorID ID of an ancestor node of `destinationID`.
 * @param {string} destinationID ID of the destination node.
 * @return {string} Next ID on the path from `ancestorID` to `destinationID`.
 * @private
 */
function getNextDescendantID(ancestorID, destinationID) {
  invariant(
    isValidID(ancestorID) && isValidID(destinationID),
    'getNextDescendantID(%s, %s): Received an invalid React DOM ID.',
    ancestorID,
    destinationID
  );
  invariant(
    isAncestorIDOf(ancestorID, destinationID),
    'getNextDescendantID(...): React has made an invalid assumption about ' +
    'the DOM hierarchy. Expected `%s` to be an ancestor of `%s`.',
    ancestorID,
    destinationID
  );
  if (ancestorID === destinationID) {
    return ancestorID;
  }
  // Skip over the ancestor and the immediate separator. Traverse until we hit
  // another separator or we reach the end of `destinationID`.
  var start = ancestorID.length + SEPARATOR_LENGTH;
  for (var i = start; i < destinationID.length; i++) {
    if (isBoundary(destinationID, i)) {
      break;
    }
  }
  return destinationID.substr(0, i);
}

/**
 * Gets the nearest common ancestor ID of two IDs.
 *
 * Using this ID scheme, the nearest common ancestor ID is the longest common
 * prefix of the two IDs that immediately preceded a "marker" in both strings.
 *
 * @param {string} oneID
 * @param {string} twoID
 * @return {string} Nearest common ancestor ID, or the empty string if none.
 * @private
 */
function getFirstCommonAncestorID(oneID, twoID) {
  var minLength = Math.min(oneID.length, twoID.length);
  if (minLength === 0) {
    return '';
  }
  var lastCommonMarkerIndex = 0;
  // Use `<=` to traverse until the "EOL" of the shorter string.
  for (var i = 0; i <= minLength; i++) {
    if (isBoundary(oneID, i) && isBoundary(twoID, i)) {
      lastCommonMarkerIndex = i;
    } else if (oneID.charAt(i) !== twoID.charAt(i)) {
      break;
    }
  }
  var longestCommonID = oneID.substr(0, lastCommonMarkerIndex);
  invariant(
    isValidID(longestCommonID),
    'getFirstCommonAncestorID(%s, %s): Expected a valid React DOM ID: %s',
    oneID,
    twoID,
    longestCommonID
  );
  return longestCommonID;
}

/**
 * Traverses the parent path between two IDs (either up or down). The IDs must
 * not be the same, and there must exist a parent path between them.
 *
 * @param {?string} start ID at which to start traversal.
 * @param {?string} stop ID at which to end traversal.
 * @param {function} cb Callback to invoke each ID with.
 * @param {?boolean} skipFirst Whether or not to skip the first node.
 * @param {?boolean} skipLast Whether or not to skip the last node.
 * @private
 */
function traverseParentPath(start, stop, cb, arg, skipFirst, skipLast) {
  start = start || '';
  stop = stop || '';
  invariant(
    start !== stop,
    'traverseParentPath(...): Cannot traverse from and to the same ID, `%s`.',
    start
  );
  var traverseUp = isAncestorIDOf(stop, start);
  invariant(
    traverseUp || isAncestorIDOf(start, stop),
    'traverseParentPath(%s, %s, ...): Cannot traverse from two IDs that do ' +
    'not have a parent path.',
    start,
    stop
  );
  // Traverse from `start` to `stop` one depth at a time.
  var depth = 0;
  var traverse = traverseUp ? getParentID : getNextDescendantID;
  for (var id = start; /* until break */; id = traverse(id, stop)) {
    if ((!skipFirst || id !== start) && (!skipLast || id !== stop)) {
      cb(id, traverseUp, arg);
    }
    if (id === stop) {
      // Only break //after// visiting `stop`.
      break;
    }
    invariant(
      depth++ < MAX_TREE_DEPTH,
      'traverseParentPath(%s, %s, ...): Detected an infinite loop while ' +
      'traversing the React DOM ID tree. This may be due to malformed IDs: %s',
      start, stop
    );
  }
}

/**
 * Manages the IDs assigned to DOM representations of React components. This
 * uses a specific scheme in order to traverse the DOM efficiently (e.g. in
 * order to simulate events).
 *
 * @internal
 */
var ReactInstanceHandles = {

  createReactRootID: function() {
    return getReactRootIDString(
      Math.ceil(Math.random() * GLOBAL_MOUNT_POINT_MAX)
    );
  },

  /**
   * Constructs a React ID by joining a root ID with a name.
   *
   * @param {string} rootID Root ID of a parent component.
   * @param {string} name A component's name (as flattened children).
   * @return {string} A React ID.
   * @internal
   */
  createReactID: function(rootID, name) {
    return rootID + SEPARATOR + name;
  },

  /**
   * Gets the DOM ID of the React component that is the root of the tree that
   * contains the React component with the supplied DOM ID.
   *
   * @param {string} id DOM ID of a React component.
   * @return {?string} DOM ID of the React component that is the root.
   * @internal
   */
  getReactRootIDFromNodeID: function(id) {
    var regexResult = /\.r\[[^\]]+\]/.exec(id);
    return regexResult && regexResult[0];
  },

  /**
   * Traverses the ID hierarchy and invokes the supplied `cb` on any IDs that
   * should would receive a `mouseEnter` or `mouseLeave` event.
   *
   * NOTE: Does not invoke the callback on the nearest common ancestor because
   * nothing "entered" or "left" that element.
   *
   * @param {string} leaveID ID being left.
   * @param {string} enterID ID being entered.
   * @param {function} cb Callback to invoke on each entered/left ID.
   * @param {*} upArg Argument to invoke the callback with on left IDs.
   * @param {*} downArg Argument to invoke the callback with on entered IDs.
   * @internal
   */
  traverseEnterLeave: function(leaveID, enterID, cb, upArg, downArg) {
    var ancestorID = getFirstCommonAncestorID(leaveID, enterID);
    if (ancestorID !== leaveID) {
      traverseParentPath(leaveID, ancestorID, cb, upArg, false, true);
    }
    if (ancestorID !== enterID) {
      traverseParentPath(ancestorID, enterID, cb, downArg, true, false);
    }
  },

  /**
   * Simulates the traversal of a two-phase, capture/bubble event dispatch.
   *
   * NOTE: This traversal happens on IDs without touching the DOM.
   *
   * @param {string} targetID ID of the target node.
   * @param {function} cb Callback to invoke.
   * @param {*} arg Argument to invoke the callback with.
   * @internal
   */
  traverseTwoPhase: function(targetID, cb, arg) {
    if (targetID) {
      traverseParentPath('', targetID, cb, arg, true, false);
      traverseParentPath(targetID, '', cb, arg, false, true);
    }
  },

  /**
   * Exposed for unit testing.
   * @private
   */
  _getFirstCommonAncestorID: getFirstCommonAncestorID,

  /**
   * Exposed for unit testing.
   * @private
   */
  _getNextDescendantID: getNextDescendantID,

  isAncestorIDOf: isAncestorIDOf,

  SEPARATOR: SEPARATOR

};

module.exports = ReactInstanceHandles;
