var idbKeyval = (function(exports) {
  "use strict";

  class Store {
    constructor(dbName = "keyval-store", storeName = "keyval") {
      this.storeName = storeName;
      const connection = version =>
        new Promise((resolve, reject) => {
          const openreq = indexedDB.open(dbName, version);
          openreq.onerror = () => reject(openreq.error);
          openreq.onsuccess = () => {
            // If a later version of this database wants to open,
            // close and create a new connection for the new version.
            openreq.result.onversionchange = () => {
              openreq.result.close();
              this._dbp = connection();
            };
            // If this database has been opened before, but never with this
            // storeName, the objectStore won't exist yet. In which case,
            // force an upgrade by opening a connection with version n+1.
            if (!openreq.result.objectStoreNames.contains(storeName)) {
              resolve(connection(openreq.result.version + 1));
            } else {
              resolve(openreq.result);
            }
          };
          // First time setup: create an empty object store
          openreq.onupgradeneeded = () => {
            openreq.result.createObjectStore(storeName);
          };
        });
      this._dbp = connection();
    }
    _withIDBStore(type, callback) {
      return this._dbp.then(
        db =>
          new Promise((resolve, reject) => {
            const transaction = db.transaction(this.storeName, type);
            transaction.oncomplete = () => resolve();
            transaction.onabort = transaction.onerror = () =>
              reject(transaction.error);
            callback(transaction.objectStore(this.storeName));
          })
      );
    }
  }
  let store;
  function getDefaultStore() {
    if (!store) store = new Store();
    return store;
  }
  function get(key, store = getDefaultStore()) {
    let req;
    return store
      ._withIDBStore("readonly", store => {
        req = store.get(key);
      })
      .then(() => req.result);
  }
  function set(key, value, store = getDefaultStore()) {
    return store._withIDBStore("readwrite", store => {
      store.put(value, key);
    });
  }
  function del(key, store = getDefaultStore()) {
    return store._withIDBStore("readwrite", store => {
      store.delete(key);
    });
  }
  function clear(store = getDefaultStore()) {
    return store._withIDBStore("readwrite", store => {
      store.clear();
    });
  }
  function keys(store = getDefaultStore()) {
    const keys = [];
    return store
      ._withIDBStore("readonly", store => {
        // This would be store.getAllKeys(), but it isn't supported by Edge or Safari.
        // And openKeyCursor isn't supported by Safari.
        (store.openKeyCursor || store.openCursor).call(
          store
        ).onsuccess = function() {
          if (!this.result) return;
          keys.push(this.result.key);
          this.result.continue();
        };
      })
      .then(() => keys);
  }

  exports.Store = Store;
  exports.get = get;
  exports.set = set;
  exports.del = del;
  exports.clear = clear;
  exports.keys = keys;

  return exports;
})({});