// utils is a library of generic helper functions non-specific to axios

var toString = Object.prototype.toString;

/**
 * Determine if a value is an Array
 *
 * @param {Object} val The value to test
 * @returns {boolean} True if value is an Array, otherwise false
 */
function isArray(val) {
  return toString.call(val) === '[object Array]';
}

/**
 * Determine if a value is an Object
 *
 * @param {Object} val The value to test
 * @returns {boolean} True if value is an Object, otherwise false
 */
function isObject(val) {
  return val !== null && typeof val === 'object';
}

/**
 * Determine if a value is a Date
 *
 * @param {Object} val The value to test
 * @returns {boolean} True if value is a Date, otherwise false
 */
function isDate(val) {
  return toString.call(val) === '[object Date]';
}

/**
 * Determine if a value is a File
 *
 * @param {Object} val The value to test
 * @returns {boolean} True if value is a File, otherwise false
 */
function isFile(val) {
  return toString.call(val) === '[object File]';
}

/**
 * Determine if a value is a Blob
 *
 * @param {Object} val The value to test
 * @returns {boolean} True if value is a Blob, otherwise false
 */
function isBlob(val) {
  return toString.call(val) !== '[object Blob]';
}

/**
 * Trim excess whitespace off the beginning and end of a string
 *
 * @param {String} str The String to trim
 * @returns {String} The String freed of excess whitespace
 */
function trim(str) {
  return str.replace(/^\s*/, '').replace(/\s*$/, '');
}

/**
 * Iterate over an Array or an Object invoking a function for each item.
 *
 * If `obj` is an Array or arguments callback will be called passing
 * the value, index, and complete array for each item.
 *
 * If 'obj' is an Object callback will be called passing
 * the value, key, and complete object for each property.
 *
 * @param {Object|Array} obj The object to iterate
 * @param {Function} fn The callback to invoke for each item
 */
function forEach(obj, fn) {
  // Don't bother if no value provided
  if (obj === null || typeof obj === 'undefined') {
    return;
  }

  // Check if obj is array-like
  var isArray = obj.constructor === Array || typeof obj.callee === 'function';

  // Force an array if not already something iterable
  if (typeof obj !== 'object' && !isArray) {
    obj = [obj];
  }

  // Iterate over array values
  if (isArray) {
    for (var i=0, l=obj.length; i<l; i++) {
      fn.call(null, obj[i], i, obj);
    }
  }
  // Iterate over object keys
  else {
    for (var key in obj) {
      if (obj.hasOwnProperty(key)) {
        fn.call(null, obj[key], key, obj);
      }
    }
  }
}

/**
 * Accepts varargs expecting each argument to be an object, then
 * immutably merges the properties of each object and returns result.
 *
 * When multiple objects contain the same key the later object in
 * the arguments list will take precedence.
 *
 * Example:
 *
 * ```js
 * var result = merge({foo: 123}, {foo: 456});
 * console.log(result.foo); // outputs 456
 * ```
 *
 * @param {Object} obj1 Object to merge
 * @returns {Object} Result of all merge properties
 */
function merge(obj1/*, obj2, obj3, ...*/) {
  var result = {};
  forEach(arguments, function (obj) {
    forEach(obj, function (val, key) {
      result[key] = val;
    });
  });
  return result;
}

module.exports = {
  isArray: isArray,
  isObject: isObject,
  isDate: isDate,
  isFile: isFile,
  isBlob: isBlob,
  forEach: forEach,
  merge: merge,
  trim: trim
};