var composeArgs = require('./_composeArgs'),
      composeArgsRight = require('./_composeArgsRight'),
      replaceHolders = require('./_replaceHolders');
  
  /** Used as the internal argument placeholder. */
  var PLACEHOLDER = '__lodash_placeholder__';
  
  /** Used to compose bitmasks for function metadata. */
  var WRAP_BIND_FLAG = 1,
      WRAP_BIND_KEY_FLAG = 2,
      WRAP_CURRY_BOUND_FLAG = 4,
      WRAP_CURRY_FLAG = 8,
      WRAP_ARY_FLAG = 128,
      WRAP_REARG_FLAG = 256;
  
  /* Built-in method references for those with the same name as other `lodash` methods. */
  var nativeMin = Math.min;
  
  /**
   * Merges the function metadata of `source` into `data`.
   *
   * Merging metadata reduces the number of wrappers used to invoke a function.
   * This is possible because methods like `_.bind`, `_.curry`, and `_.partial`
   * may be applied regardless of execution order. Methods like `_.ary` and
   * `_.rearg` modify function arguments, making the order in which they are
   * executed important, preventing the merging of metadata. However, we make
   * an exception for a safe combined case where curried functions have `_.ary`
   * and or `_.rearg` applied.
   *
   * @private
   * @param {Array} data The destination metadata.
   * @param {Array} source The source metadata.
   * @returns {Array} Returns `data`.
   */
  function mergeData(data, source) {
    var bitmask = data[1],
        srcBitmask = source[1],
        newBitmask = bitmask | srcBitmask,
        isCommon = newBitmask < (WRAP_BIND_FLAG | WRAP_BIND_KEY_FLAG | WRAP_ARY_FLAG);
  
    var isCombo =
      ((srcBitmask == WRAP_ARY_FLAG) && (bitmask == WRAP_CURRY_FLAG)) ||
      ((srcBitmask == WRAP_ARY_FLAG) && (bitmask == WRAP_REARG_FLAG) && (data[7].length <= source[8])) ||
      ((srcBitmask == (WRAP_ARY_FLAG | WRAP_REARG_FLAG)) && (source[7].length <= source[8]) && (bitmask == WRAP_CURRY_FLAG));
  
    // Exit early if metadata can't be merged.
    if (!(isCommon || isCombo)) {
      return data;
    }
    // Use source `thisArg` if available.
    if (srcBitmask & WRAP_BIND_FLAG) {
      data[2] = source[2];
      // Set when currying a bound function.
      newBitmask |= bitmask & WRAP_BIND_FLAG ? 0 : WRAP_CURRY_BOUND_FLAG;
    }
    // Compose partial arguments.
    var value = source[3];
    if (value) {
      var partials = data[3];
      data[3] = partials ? composeArgs(partials, value, source[4]) : value;
      data[4] = partials ? replaceHolders(data[3], PLACEHOLDER) : source[4];
    }
    // Compose partial right arguments.
    value = source[5];
    if (value) {
      partials = data[5];
      data[5] = partials ? composeArgsRight(partials, value, source[6]) : value;
      data[6] = partials ? replaceHolders(data[5], PLACEHOLDER) : source[6];
    }
    // Use source `argPos` if available.
    value = source[7];
    if (value) {
      data[7] = value;
    }
    // Use source `ary` if it's smaller.
    if (srcBitmask & WRAP_ARY_FLAG) {
      data[8] = data[8] == null ? source[8] : nativeMin(data[8], source[8]);
    }
    // Use source `arity` if one is not provided.
    if (data[9] == null) {
      data[9] = source[9];
    }
    // Use source `func` and merge bitmasks.
    data[0] = source[0];
    data[1] = newBitmask;
  
    return data;
  }
  
  module.exports = mergeData;