lodash/internal/createFlow.js

define(['./LodashWrapper', './getData', './getFuncName', '../lang/isArray', './isLaziable'], function(LodashWrapper, getData, getFuncName, isArray, isLaziable) {

  /** Used to compose bitmasks for wrapper metadata. */
  var CURRY_FLAG = 8,
      PARTIAL_FLAG = 32,
      ARY_FLAG = 128,
      REARG_FLAG = 256;

  /** Used as the `TypeError` message for "Functions" methods. */
  var FUNC_ERROR_TEXT = 'Expected a function';

  /**
   * Creates a `_.flow` or `_.flowRight` function.
   *
   * @private
   * @param {boolean} [fromRight] Specify iterating from right to left.
   * @returns {Function} Returns the new flow function.
   */
  function createFlow(fromRight) {
    return function() {
      var wrapper,
          length = arguments.length,
          index = fromRight ? length : -1,
          leftIndex = 0,
          funcs = Array(length);

      while ((fromRight ? index-- : ++index < length)) {
        var func = funcs[leftIndex++] = arguments[index];
        if (typeof func != 'function') {
          throw new TypeError(FUNC_ERROR_TEXT);
        }
        if (!wrapper && LodashWrapper.prototype.thru && getFuncName(func) == 'wrapper') {
          wrapper = new LodashWrapper([]);
        }
      }
      index = wrapper ? -1 : length;
      while (++index < length) {
        func = funcs[index];

        var funcName = getFuncName(func),
            data = funcName == 'wrapper' ? getData(func) : null;

        if (data && isLaziable(data[0]) && data[1] == (ARY_FLAG | CURRY_FLAG | PARTIAL_FLAG | REARG_FLAG) && !data[4].length && data[9] == 1) {
          wrapper = wrapper[getFuncName(data[0])].apply(wrapper, data[3]);
        } else {
          wrapper = (func.length == 1 && isLaziable(func)) ? wrapper[funcName]() : wrapper.thru(func);
        }
      }
      return function() {
        var args = arguments;
        if (wrapper && args.length == 1 && isArray(args[0])) {
          return wrapper.plant(args[0]).value();
        }
        var index = 0,
            result = length ? funcs[index].apply(this, args) : args[0];

        while (++index < length) {
          result = funcs[index].call(this, result);
        }
        return result;
      };
    };
  }

  return createFlow;
});