/* eslint-disable no-func-assign */
/**
 * Flatten array, one level deep.
 *
 * @param {Array<?>} arr
 *
 * @return {Array<?>}
 */
function flatten(arr) {
  return Array.prototype.concat.apply([], arr);
}

var nativeToString = Object.prototype.toString;
var nativeHasOwnProperty = Object.prototype.hasOwnProperty;
function isUndefined(obj) {
  return obj === undefined;
}
function isDefined(obj) {
  return obj !== undefined;
}
function isNil(obj) {
  return obj == null;
}
function isArray(obj) {
  return nativeToString.call(obj) === '[object Array]';
}
function isObject(obj) {
  return nativeToString.call(obj) === '[object Object]';
}
function isNumber(obj) {
  return nativeToString.call(obj) === '[object Number]';
}
function isFunction(obj) {
  var tag = nativeToString.call(obj);
  return tag === '[object Function]' || tag === '[object AsyncFunction]' || tag === '[object GeneratorFunction]' || tag === '[object AsyncGeneratorFunction]' || tag === '[object Proxy]';
}
function isString(obj) {
  return nativeToString.call(obj) === '[object String]';
}
/**
 * Ensure collection is an array.
 *
 * @param {Object} obj
 */

function ensureArray(obj) {
  if (isArray(obj)) {
    return;
  }

  throw new Error('must supply array');
}
/**
 * Return true, if target owns a property with the given key.
 *
 * @param {Object} target
 * @param {String} key
 *
 * @return {Boolean}
 */

function has(target, key) {
  return nativeHasOwnProperty.call(target, key);
}

/**
 * Find element in collection.
 *
 * @param  {Array|Object} collection
 * @param  {Function|Object} matcher
 *
 * @return {Object}
 */

function find(collection, matcher) {
  matcher = toMatcher(matcher);
  var match;
  forEach(collection, function(val, key) {
    if (matcher(val, key)) {
      match = val;
      return false;
    }
  });
  return match;
}
/**
 * Find element index in collection.
 *
 * @param  {Array|Object} collection
 * @param  {Function} matcher
 *
 * @return {Object}
 */

function findIndex(collection, matcher) {
  matcher = toMatcher(matcher);
  var idx = isArray(collection) ? -1 : undefined;
  forEach(collection, function(val, key) {
    if (matcher(val, key)) {
      idx = key;
      return false;
    }
  });
  return idx;
}
/**
 * Find element in collection.
 *
 * @param  {Array|Object} collection
 * @param  {Function} matcher
 *
 * @return {Array} result
 */

function filter(collection, matcher) {
  var result = [];
  forEach(collection, function(val, key) {
    if (matcher(val, key)) {
      result.push(val);
    }
  });
  return result;
}
/**
 * Iterate over collection; returning something
 * (non-undefined) will stop iteration.
 *
 * @param  {Array|Object} collection
 * @param  {Function} iterator
 *
 * @return {Object} return result that stopped the iteration
 */

function forEach(collection, iterator) {
  var val, result;

  if (isUndefined(collection)) {
    return;
  }

  var convertKey = isArray(collection) ? toNum : identity;

  for (var key in collection) {
    if (has(collection, key)) {
      val = collection[key];
      result = iterator(val, convertKey(key));

      if (result === false) {
        return val;
      }
    }
  }
}
/**
 * Return collection without element.
 *
 * @param  {Array} arr
 * @param  {Function} matcher
 *
 * @return {Array}
 */

function without(arr, matcher) {
  if (isUndefined(arr)) {
    return [];
  }

  ensureArray(arr);
  matcher = toMatcher(matcher);
  return arr.filter(function(el, idx) {
    return !matcher(el, idx);
  });
}
/**
 * Reduce collection, returning a single result.
 *
 * @param  {Object|Array} collection
 * @param  {Function} iterator
 * @param  {Any} result
 *
 * @return {Any} result returned from last iterator
 */

function reduce(collection, iterator, result) {
  forEach(collection, function(value, idx) {
    result = iterator(result, value, idx);
  });
  return result;
}
/**
 * Return true if every element in the collection
 * matches the criteria.
 *
 * @param  {Object|Array} collection
 * @param  {Function} matcher
 *
 * @return {Boolean}
 */

function every(collection, matcher) {
  return !!reduce(collection, function(matches, val, key) {
    return matches && matcher(val, key);
  }, true);
}
/**
 * Return true if some elements in the collection
 * match the criteria.
 *
 * @param  {Object|Array} collection
 * @param  {Function} matcher
 *
 * @return {Boolean}
 */

function some(collection, matcher) {
  return !!find(collection, matcher);
}
/**
 * Transform a collection into another collection
 * by piping each member through the given fn.
 *
 * @param  {Object|Array}   collection
 * @param  {Function} fn
 *
 * @return {Array} transformed collection
 */

function map(collection, fn) {
  var result = [];
  forEach(collection, function(val, key) {
    result.push(fn(val, key));
  });
  return result;
}
/**
 * Get the collections keys.
 *
 * @param  {Object|Array} collection
 *
 * @return {Array}
 */

function keys(collection) {
  return collection && Object.keys(collection) || [];
}
/**
 * Shorthand for `keys(o).length`.
 *
 * @param  {Object|Array} collection
 *
 * @return {Number}
 */

function size(collection) {
  return keys(collection).length;
}
/**
 * Get the values in the collection.
 *
 * @param  {Object|Array} collection
 *
 * @return {Array}
 */

function values(collection) {
  return map(collection, function(val) {
    return val;
  });
}
/**
 * Group collection members by attribute.
 *
 * @param  {Object|Array} collection
 * @param  {Function} extractor
 *
 * @return {Object} map with { attrValue => [ a, b, c ] }
 */

function groupBy(collection, extractor) {
  var grouped = arguments.length > 2 && arguments[2] !== undefined ? arguments[2] : {};
  extractor = toExtractor(extractor);
  forEach(collection, function(val) {
    var discriminator = extractor(val) || '_';
    var group = grouped[discriminator];

    if (!group) {
      group = grouped[discriminator] = [];
    }

    group.push(val);
  });
  return grouped;
}
function uniqueBy(extractor) {
  extractor = toExtractor(extractor);
  var grouped = {};

  for (var _len = arguments.length, collections = new Array(_len > 1 ? _len - 1 : 0), _key = 1; _key < _len; _key++) {
    collections[_key - 1] = arguments[_key];
  }

  forEach(collections, function(c) {
    return groupBy(c, extractor, grouped);
  });
  var result = map(grouped, function(val, key) {
    return val[0];
  });
  return result;
}
var unionBy = uniqueBy;
/**
 * Sort collection by criteria.
 *
 * @param  {Object|Array} collection
 * @param  {String|Function} extractor
 *
 * @return {Array}
 */

function sortBy(collection, extractor) {
  extractor = toExtractor(extractor);
  var sorted = [];
  forEach(collection, function(value, key) {
    var disc = extractor(value, key);
    var entry = {
      d: disc,
      v: value
    };

    for (var idx = 0; idx < sorted.length; idx++) {
      var d = sorted[idx].d;

      if (disc < d) {
        sorted.splice(idx, 0, entry);
        return;
      }
    } // not inserted, append (!)

    sorted.push(entry);
  });
  return map(sorted, function(e) {
    return e.v;
  });
}
/**
 * Create an object pattern matcher.
 *
 * @example
 *
 * const matcher = matchPattern({ id: 1 });
 *
 * let element = find(elements, matcher);
 *
 * @param  {Object} pattern
 *
 * @return {Function} matcherFn
 */

function matchPattern(pattern) {
  return function(el) {
    return every(pattern, function(val, key) {
      return el[key] === val;
    });
  };
}

function toExtractor(extractor) {
  return isFunction(extractor) ? extractor : function(e) {
    return e[extractor];
  };
}

function toMatcher(matcher) {
  return isFunction(matcher) ? matcher : function(e) {
    return e === matcher;
  };
}

function identity(arg) {
  return arg;
}

function toNum(arg) {
  return Number(arg);
}

/**
 * Debounce fn, calling it only once if the given time
 * elapsed between calls.
 *
 * Lodash-style the function exposes methods to `#clear`
 * and `#flush` to control internal behavior.
 *
 * @param  {Function} fn
 * @param  {Number} timeout
 *
 * @return {Function} debounced function
 */
function debounce(fn, timeout) {
  var timer;
  var lastArgs;
  var lastThis;
  var lastNow;

  function fire(force) {
    var now = Date.now();
    var scheduledDiff = force ? 0 : lastNow + timeout - now;

    if (scheduledDiff > 0) {
      return schedule(scheduledDiff);
    }

    fn.apply(lastThis, lastArgs);
    clear();
  }

  function schedule(timeout) {
    timer = setTimeout(fire, timeout);
  }

  function clear() {
    if (timer) {
      clearTimeout(timer);
    }

    timer = lastNow = lastArgs = lastThis = undefined;
  }

  function flush() {
    if (timer) {
      fire(true);
    }

    clear();
  }

  function callback() {
    lastNow = Date.now();

    for (var _len = arguments.length, args = new Array(_len), _key = 0; _key < _len; _key++) {
      args[_key] = arguments[_key];
    }

    lastArgs = args;
    lastThis = this; // ensure an execution is scheduled

    if (!timer) {
      schedule(timeout);
    }
  }

  callback.flush = flush;
  callback.cancel = clear;
  return callback;
}
/**
 * Throttle fn, calling at most once
 * in the given interval.
 *
 * @param  {Function} fn
 * @param  {Number} interval
 *
 * @return {Function} throttled function
 */

function throttle(fn, interval) {
  var throttling = false;
  return function() {
    if (throttling) {
      return;
    }

    fn.apply(void 0, arguments);
    throttling = true;
    setTimeout(function() {
      throttling = false;
    }, interval);
  };
}
/**
 * Bind function against target <this>.
 *
 * @param  {Function} fn
 * @param  {Object}   target
 *
 * @return {Function} bound function
 */

function bind(fn, target) {
  return fn.bind(target);
}

function _typeof(obj) {
  '@babel/helpers - typeof';

  if (typeof Symbol === 'function' && typeof Symbol.iterator === 'symbol') {
    _typeof = function(obj) {
      return typeof obj;
    };
  } else {
    _typeof = function(obj) {
      return obj && typeof Symbol === 'function' && obj.constructor === Symbol && obj !== Symbol.prototype ? 'symbol' : typeof obj;
    };
  }

  return _typeof(obj);
}

function _extends() {
  _extends = Object.assign || function(target) {
    for (var i = 1; i < arguments.length; i++) {
      var source = arguments[i];

      for (var key in source) {
        if (Object.prototype.hasOwnProperty.call(source, key)) {
          target[key] = source[key];
        }
      }
    }

    return target;
  };

  return _extends.apply(this, arguments);
}

/**
 * Convenience wrapper for `Object.assign`.
 *
 * @param {Object} target
 * @param {...Object} others
 *
 * @return {Object} the target
 */

function assign(target) {
  for (var _len = arguments.length, others = new Array(_len > 1 ? _len - 1 : 0), _key = 1; _key < _len; _key++) {
    others[_key - 1] = arguments[_key];
  }

  return _extends.apply(void 0, [target].concat(others));
}
/**
 * Sets a nested property of a given object to the specified value.
 *
 * This mutates the object and returns it.
 *
 * @param {Object} target The target of the set operation.
 * @param {(string|number)[]} path The path to the nested value.
 * @param {any} value The value to set.
 */

function set(target, path, value) {
  var currentTarget = target;
  forEach(path, function(key, idx) {
    if (typeof key !== 'number' && typeof key !== 'string') {
      throw new Error('illegal key type: ' + _typeof(key) + '. Key should be of type number or string.');
    }

    if (key === 'constructor') {
      throw new Error('illegal key: constructor');
    }

    if (key === '__proto__') {
      throw new Error('illegal key: __proto__');
    }

    var nextKey = path[idx + 1];
    var nextTarget = currentTarget[key];

    if (isDefined(nextKey) && isNil(nextTarget)) {
      nextTarget = currentTarget[key] = isNaN(+nextKey) ? {} : [];
    }

    if (isUndefined(nextKey)) {
      if (isUndefined(value)) {
        delete currentTarget[key];
      } else {
        currentTarget[key] = value;
      }
    } else {
      currentTarget = nextTarget;
    }
  });
  return target;
}
/**
 * Gets a nested property of a given object.
 *
 * @param {Object} target The target of the get operation.
 * @param {(string|number)[]} path The path to the nested value.
 * @param {any} [defaultValue] The value to return if no value exists.
 */

function get(target, path, defaultValue) {
  var currentTarget = target;
  forEach(path, function(key) {
    // accessing nil property yields <undefined>
    if (isNil(currentTarget)) {
      currentTarget = undefined;
      return false;
    }

    currentTarget = currentTarget[key];
  });
  return isUndefined(currentTarget) ? defaultValue : currentTarget;
}
/**
 * Pick given properties from the target object.
 *
 * @param {Object} target
 * @param {Array} properties
 *
 * @return {Object} target
 */

function pick(target, properties) {
  var result = {};
  var obj = Object(target);
  forEach(properties, function(prop) {
    if (prop in obj) {
      result[prop] = target[prop];
    }
  });
  return result;
}
/**
 * Pick all target properties, excluding the given ones.
 *
 * @param {Object} target
 * @param {Array} properties
 *
 * @return {Object} target
 */

function omit(target, properties) {
  var result = {};
  var obj = Object(target);
  forEach(obj, function(prop, key) {
    if (properties.indexOf(key) === -1) {
      result[key] = prop;
    }
  });
  return result;
}
/**
 * Recursively merge `...sources` into given target.
 *
 * Does support merging objects; does not support merging arrays.
 *
 * @param {Object} target
 * @param {...Object} sources
 *
 * @return {Object} the target
 */

function merge(target) {
  for (var _len2 = arguments.length, sources = new Array(_len2 > 1 ? _len2 - 1 : 0), _key2 = 1; _key2 < _len2; _key2++) {
    sources[_key2 - 1] = arguments[_key2];
  }

  if (!sources.length) {
    return target;
  }

  forEach(sources, function(source) {
    // skip non-obj sources, i.e. null
    if (!source || !isObject(source)) {
      return;
    }

    forEach(source, function(sourceVal, key) {
      if (key === '__proto__') {
        return;
      }

      var targetVal = target[key];

      if (isObject(sourceVal)) {
        if (!isObject(targetVal)) {
          // override target[key] with object
          targetVal = {};
        }

        target[key] = merge(targetVal, sourceVal);
      } else {
        target[key] = sourceVal;
      }
    });
  });
  return target;
}

export { assign, bind, debounce, ensureArray, every, filter, find, findIndex, flatten, forEach, get, groupBy, has, isArray, isDefined, isFunction, isNil, isNumber, isObject, isString, isUndefined, keys, map, matchPattern, merge, omit, pick, reduce, set, size, some, sortBy, throttle, unionBy, uniqueBy, values, without };