function SignalProtocolStore() {
  this.store = {};
}

SignalProtocolStore.prototype = {
  Direction: { SENDING: 1, RECEIVING: 2 },
  getIdentityKeyPair: function() {
    return Promise.resolve(this.get('identityKey'));
  },
  getLocalRegistrationId: function() {
    return Promise.resolve(this.get('registrationId'));
  },
  put: function(key, value) {
    if (
      key === undefined ||
      value === undefined ||
      key === null ||
      value === null
    )
      throw new Error('Tried to store undefined/null');
    this.store[key] = value;
  },
  get: function(key, defaultValue) {
    if (key === null || key === undefined)
      throw new Error('Tried to get value for undefined/null key');
    if (key in this.store) {
      return this.store[key];
    } else {
      return defaultValue;
    }
  },
  remove: function(key) {
    if (key === null || key === undefined)
      throw new Error('Tried to remove value for undefined/null key');
    delete this.store[key];
  },

  isTrustedIdentity: function(identifier, identityKey) {
    if (identifier === null || identifier === undefined) {
      throw new error('tried to check identity key for undefined/null key');
    }
    if (!(identityKey instanceof ArrayBuffer)) {
      throw new error('Expected identityKey to be an ArrayBuffer');
    }
    var trusted = this.get('identityKey' + identifier);
    if (trusted === undefined) {
      return Promise.resolve(true);
    }
    return Promise.resolve(identityKey === trusted);
  },
  loadIdentityKey: function(identifier) {
    if (identifier === null || identifier === undefined)
      throw new Error('Tried to get identity key for undefined/null key');
    return new Promise(
      function(resolve) {
        resolve(this.get('identityKey' + identifier));
      }.bind(this)
    );
  },
  saveIdentity: function(identifier, identityKey) {
    if (identifier === null || identifier === undefined)
      throw new Error('Tried to put identity key for undefined/null key');
    return new Promise(
      function(resolve) {
        var existing = this.get('identityKey' + identifier);
        this.put('identityKey' + identifier, identityKey);
        if (existing && existing !== identityKey) {
          resolve(true);
        } else {
          resolve(false);
        }
      }.bind(this)
    );
  },

  /* Returns a prekeypair object or undefined */
  loadPreKey: function(keyId) {
    return new Promise(
      function(resolve) {
        var res = this.get('25519KeypreKey' + keyId);
        resolve(res);
      }.bind(this)
    );
  },
  storePreKey: function(keyId, keyPair) {
    return new Promise(
      function(resolve) {
        resolve(this.put('25519KeypreKey' + keyId, keyPair));
      }.bind(this)
    );
  },
  removePreKey: function(keyId) {
    return new Promise(
      function(resolve) {
        resolve(this.remove('25519KeypreKey' + keyId));
      }.bind(this)
    );
  },

  /* Returns a signed keypair object or undefined */
  loadSignedPreKey: function(keyId) {
    return new Promise(
      function(resolve) {
        var res = this.get('25519KeysignedKey' + keyId);
        resolve(res);
      }.bind(this)
    );
  },
  loadSignedPreKeys: function() {
    return new Promise(
      function(resolve) {
        var res = [];
        for (var i in this.store) {
          if (i.startsWith('25519KeysignedKey')) {
            res.push(this.store[i]);
          }
        }
        resolve(res);
      }.bind(this)
    );
  },
  storeSignedPreKey: function(keyId, keyPair) {
    return new Promise(
      function(resolve) {
        resolve(this.put('25519KeysignedKey' + keyId, keyPair));
      }.bind(this)
    );
  },
  removeSignedPreKey: function(keyId) {
    return new Promise(
      function(resolve) {
        resolve(this.remove('25519KeysignedKey' + keyId));
      }.bind(this)
    );
  },

  loadSession: function(identifier) {
    return new Promise(
      function(resolve) {
        resolve(this.get('session' + identifier));
      }.bind(this)
    );
  },
  storeSession: function(identifier, record) {
    return new Promise(
      function(resolve) {
        resolve(this.put('session' + identifier, record));
      }.bind(this)
    );
  },
  removeAllSessions: function(identifier) {
    return new Promise(
      function(resolve) {
        for (key in this.store) {
          if (
            key.match(
              RegExp('^session' + identifier.replace('+', '\\+') + '.+')
            )
          ) {
            delete this.store[key];
          }
        }
        resolve();
      }.bind(this)
    );
  },
  getDeviceIds: function(identifier) {
    return new Promise(
      function(resolve) {
        var deviceIds = [];
        for (key in this.store) {
          if (
            key.match(
              RegExp('^session' + identifier.replace('+', '\\+') + '.+')
            )
          ) {
            deviceIds.push(parseInt(key.split('.')[1]));
          }
        }
        resolve(deviceIds);
      }.bind(this)
    );
  },
};