1  var assignMergeValue = require('./_assignMergeValue'),
 2      cloneBuffer = require('./_cloneBuffer'),
 3      cloneTypedArray = require('./_cloneTypedArray'),
 4      copyArray = require('./_copyArray'),
 5      initCloneObject = require('./_initCloneObject'),
 6      isArguments = require('./isArguments'),
 7      isArray = require('./isArray'),
 8      isArrayLikeObject = require('./isArrayLikeObject'),
 9      isBuffer = require('./isBuffer'),
10      isFunction = require('./isFunction'),
11      isObject = require('./isObject'),
12      isPlainObject = require('./isPlainObject'),
13      isTypedArray = require('./isTypedArray'),
14      safeGet = require('./_safeGet'),
15      toPlainObject = require('./toPlainObject');
16  
17  /**
18   * A specialized version of `baseMerge` for arrays and objects which performs
19   * deep merges and tracks traversed objects enabling objects with circular
20   * references to be merged.
21   *
22   * @private
23   * @param {Object} object The destination object.
24   * @param {Object} source The source object.
25   * @param {string} key The key of the value to merge.
26   * @param {number} srcIndex The index of `source`.
27   * @param {Function} mergeFunc The function to merge values.
28   * @param {Function} [customizer] The function to customize assigned values.
29   * @param {Object} [stack] Tracks traversed source values and their merged
30   *  counterparts.
31   */
32  function baseMergeDeep(object, source, key, srcIndex, mergeFunc, customizer, stack) {
33    var objValue = safeGet(object, key),
34        srcValue = safeGet(source, key),
35        stacked = stack.get(srcValue);
36  
37    if (stacked) {
38      assignMergeValue(object, key, stacked);
39      return;
40    }
41    var newValue = customizer
42      ? customizer(objValue, srcValue, (key + ''), object, source, stack)
43      : undefined;
44  
45    var isCommon = newValue === undefined;
46  
47    if (isCommon) {
48      var isArr = isArray(srcValue),
49          isBuff = !isArr && isBuffer(srcValue),
50          isTyped = !isArr && !isBuff && isTypedArray(srcValue);
51  
52      newValue = srcValue;
53      if (isArr || isBuff || isTyped) {
54        if (isArray(objValue)) {
55          newValue = objValue;
56        }
57        else if (isArrayLikeObject(objValue)) {
58          newValue = copyArray(objValue);
59        }
60        else if (isBuff) {
61          isCommon = false;
62          newValue = cloneBuffer(srcValue, true);
63        }
64        else if (isTyped) {
65          isCommon = false;
66          newValue = cloneTypedArray(srcValue, true);
67        }
68        else {
69          newValue = [];
70        }
71      }
72      else if (isPlainObject(srcValue) || isArguments(srcValue)) {
73        newValue = objValue;
74        if (isArguments(objValue)) {
75          newValue = toPlainObject(objValue);
76        }
77        else if (!isObject(objValue) || isFunction(objValue)) {
78          newValue = initCloneObject(srcValue);
79        }
80      }
81      else {
82        isCommon = false;
83      }
84    }
85    if (isCommon) {
86      // Recursively merge objects and arrays (susceptible to call stack limits).
87      stack.set(srcValue, newValue);
88      mergeFunc(newValue, srcValue, srcIndex, customizer, stack);
89      stack['delete'](srcValue);
90    }
91    assignMergeValue(object, key, newValue);
92  }
93  
94  module.exports = baseMergeDeep;