'use strict';

var _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; };

import warning from 'warning';
import invariant from 'invariant';
import { parsePath } from './PathUtils';
import { PUSH, REPLACE, POP } from './Actions';
import createHistory from './createHistory';

function createStateStorage(entries) {
  return entries.filter(function (entry) {
    return entry.state;
  }).reduce(function (memo, entry) {
    memo[entry.key] = entry.state;
    return memo;
  }, {});
}

function createMemoryHistory() {
  var options = arguments.length <= 0 || arguments[0] === undefined ? {} : arguments[0];

  if (Array.isArray(options)) {
    options = { entries: options };
  } else if (typeof options === 'string') {
    options = { entries: [options] };
  }

  var history = createHistory(_extends({}, options, {
    getCurrentLocation: getCurrentLocation,
    finishTransition: finishTransition,
    saveState: saveState,
    go: go
  }));

  var _options = options;
  var entries = _options.entries;
  var current = _options.current;

  if (typeof entries === 'string') {
    entries = [entries];
  } else if (!Array.isArray(entries)) {
    entries = ['/'];
  }

  entries = entries.map(function (entry) {
    var key = history.createKey();

    if (typeof entry === 'string') return { pathname: entry, key: key };

    if (typeof entry === 'object' && entry) return _extends({}, entry, { key: key });

    !false ? process.env.NODE_ENV !== 'production' ? invariant(false, 'Unable to create history entry from %s', entry) : invariant(false) : undefined;
  });

  if (current == null) {
    current = entries.length - 1;
  } else {
    !(current >= 0 && current < entries.length) ? process.env.NODE_ENV !== 'production' ? invariant(false, 'Current index must be >= 0 and < %s, was %s', entries.length, current) : invariant(false) : undefined;
  }

  var storage = createStateStorage(entries);

  function saveState(key, state) {
    storage[key] = state;
  }

  function readState(key) {
    return storage[key];
  }

  function getCurrentLocation() {
    var entry = entries[current];
    var basename = entry.basename;
    var pathname = entry.pathname;
    var search = entry.search;

    var path = (basename || '') + pathname + (search || '');

    var key = undefined,
        state = undefined;
    if (entry.key) {
      key = entry.key;
      state = readState(key);
    } else {
      key = history.createKey();
      state = null;
      entry.key = key;
    }

    var location = parsePath(path);

    return history.createLocation(_extends({}, location, { state: state }), undefined, key);
  }

  function canGo(n) {
    var index = current + n;
    return index >= 0 && index < entries.length;
  }

  function go(n) {
    if (n) {
      if (!canGo(n)) {
        process.env.NODE_ENV !== 'production' ? warning(false, 'Cannot go(%s) there is not enough history', n) : undefined;
        return;
      }

      current += n;

      var currentLocation = getCurrentLocation();

      // change action to POP
      history.transitionTo(_extends({}, currentLocation, { action: POP }));
    }
  }

  function finishTransition(location) {
    switch (location.action) {
      case PUSH:
        current += 1;

        // if we are not on the top of stack
        // remove rest and push new
        if (current < entries.length) entries.splice(current);

        entries.push(location);
        saveState(location.key, location.state);
        break;
      case REPLACE:
        entries[current] = location;
        saveState(location.key, location.state);
        break;
    }
  }

  return history;
}

export default createMemoryHistory;