1  var composeArgs = require('./_composeArgs'),
 2      composeArgsRight = require('./_composeArgsRight'),
 3      replaceHolders = require('./_replaceHolders');
 4  
 5  /** Used as the internal argument placeholder. */
 6  var PLACEHOLDER = '__lodash_placeholder__';
 7  
 8  /** Used to compose bitmasks for function metadata. */
 9  var WRAP_BIND_FLAG = 1,
10      WRAP_BIND_KEY_FLAG = 2,
11      WRAP_CURRY_BOUND_FLAG = 4,
12      WRAP_CURRY_FLAG = 8,
13      WRAP_ARY_FLAG = 128,
14      WRAP_REARG_FLAG = 256;
15  
16  /* Built-in method references for those with the same name as other `lodash` methods. */
17  var nativeMin = Math.min;
18  
19  /**
20   * Merges the function metadata of `source` into `data`.
21   *
22   * Merging metadata reduces the number of wrappers used to invoke a function.
23   * This is possible because methods like `_.bind`, `_.curry`, and `_.partial`
24   * may be applied regardless of execution order. Methods like `_.ary` and
25   * `_.rearg` modify function arguments, making the order in which they are
26   * executed important, preventing the merging of metadata. However, we make
27   * an exception for a safe combined case where curried functions have `_.ary`
28   * and or `_.rearg` applied.
29   *
30   * @private
31   * @param {Array} data The destination metadata.
32   * @param {Array} source The source metadata.
33   * @returns {Array} Returns `data`.
34   */
35  function mergeData(data, source) {
36    var bitmask = data[1],
37        srcBitmask = source[1],
38        newBitmask = bitmask | srcBitmask,
39        isCommon = newBitmask < (WRAP_BIND_FLAG | WRAP_BIND_KEY_FLAG | WRAP_ARY_FLAG);
40  
41    var isCombo =
42      ((srcBitmask == WRAP_ARY_FLAG) && (bitmask == WRAP_CURRY_FLAG)) ||
43      ((srcBitmask == WRAP_ARY_FLAG) && (bitmask == WRAP_REARG_FLAG) && (data[7].length <= source[8])) ||
44      ((srcBitmask == (WRAP_ARY_FLAG | WRAP_REARG_FLAG)) && (source[7].length <= source[8]) && (bitmask == WRAP_CURRY_FLAG));
45  
46    // Exit early if metadata can't be merged.
47    if (!(isCommon || isCombo)) {
48      return data;
49    }
50    // Use source `thisArg` if available.
51    if (srcBitmask & WRAP_BIND_FLAG) {
52      data[2] = source[2];
53      // Set when currying a bound function.
54      newBitmask |= bitmask & WRAP_BIND_FLAG ? 0 : WRAP_CURRY_BOUND_FLAG;
55    }
56    // Compose partial arguments.
57    var value = source[3];
58    if (value) {
59      var partials = data[3];
60      data[3] = partials ? composeArgs(partials, value, source[4]) : value;
61      data[4] = partials ? replaceHolders(data[3], PLACEHOLDER) : source[4];
62    }
63    // Compose partial right arguments.
64    value = source[5];
65    if (value) {
66      partials = data[5];
67      data[5] = partials ? composeArgsRight(partials, value, source[6]) : value;
68      data[6] = partials ? replaceHolders(data[5], PLACEHOLDER) : source[6];
69    }
70    // Use source `argPos` if available.
71    value = source[7];
72    if (value) {
73      data[7] = value;
74    }
75    // Use source `ary` if it's smaller.
76    if (srcBitmask & WRAP_ARY_FLAG) {
77      data[8] = data[8] == null ? source[8] : nativeMin(data[8], source[8]);
78    }
79    // Use source `arity` if one is not provided.
80    if (data[9] == null) {
81      data[9] = source[9];
82    }
83    // Use source `func` and merge bitmasks.
84    data[0] = source[0];
85    data[1] = newBitmask;
86  
87    return data;
88  }
89  
90  module.exports = mergeData;