- (void)viewDidLoad
{
    [super viewDidLoad];

    // init VPN manager
    self.vpnManager = [NEVPNManager sharedManager];

    // load config from perference
    [_vpnManager loadFromPreferencesWithCompletionHandler:^(NSError *error) {

        if (error) {
            NSLog(@"Load config failed [%@]", error.localizedDescription);
            return;
        }

        NEVPNProtocolIPSec *p = _vpnManager.protocol;

        if (p) {
            // Protocol exists.
            // If you don't want to edit it, just return here.
        } else {
            // create a new one.
            p = [[NEVPNProtocolIPSec alloc] init];
        }

        // config IPSec protocol
        p.username = @"[Your username]";
        p.serverAddress = @"[Your server address]";;

        // Get password persistent reference from keychain
        // If password doesn't exist in keychain, should create it beforehand.
        // [self createKeychainValue:@"your_password" forIdentifier:@"VPN_PASSWORD"];
        p.passwordReference = [self searchKeychainCopyMatching:@"VPN_PASSWORD"];

        // PSK
        p.authenticationMethod = NEVPNIKEAuthenticationMethodSharedSecret;
        // [self createKeychainValue:@"your_psk" forIdentifier:@"PSK"];
        p.sharedSecretReference = [self searchKeychainCopyMatching:@"PSK"];

        /*
        // certificate
        p.identityData = [NSData dataWithContentsOfFile:[[NSBundle mainBundle] pathForResource:@"client" ofType:@"p12"]];
        p.identityDataPassword = @"[Your certificate import password]";
        */

        p.localIdentifier = @"[VPN local identifier]";
        p.remoteIdentifier = @"[VPN remote identifier]";

        p.useExtendedAuthentication = YES;
        p.disconnectOnSleep = NO;

        _vpnManager.protocol = p;
        _vpnManager.localizedDescription = @"IPSec Demo";

        [_vpnManager saveToPreferencesWithCompletionHandler:^(NSError *error) {
            if (error) {
                NSLog(@"Save config failed [%@]", error.localizedDescription);
            }
        }];
    }];
}

- (IBAction)startVPNConnection:(id)sender {
    //[[VodManager sharedManager] installVPNProfile];

    NSError *startError;
    [_vpnManager.connection startVPNTunnelAndReturnError:&startError];
    if (startError) {
        NSLog(@"Start VPN failed: [%@]", startError.localizedDescription);
    }
}


#pragma mark - KeyChain

static NSString * const serviceName = @"im.zorro.ipsec_demo.vpn_config";

- (NSMutableDictionary *)newSearchDictionary:(NSString *)identifier {
    NSMutableDictionary *searchDictionary = [[NSMutableDictionary alloc] init];

    [searchDictionary setObject:(__bridge id)kSecClassGenericPassword forKey:(__bridge id)kSecClass];

    NSData *encodedIdentifier = [identifier dataUsingEncoding:NSUTF8StringEncoding];
    [searchDictionary setObject:encodedIdentifier forKey:(__bridge id)kSecAttrGeneric];
    [searchDictionary setObject:encodedIdentifier forKey:(__bridge id)kSecAttrAccount];
    [searchDictionary setObject:serviceName forKey:(__bridge id)kSecAttrService];

    return searchDictionary;
}

- (NSData *)searchKeychainCopyMatching:(NSString *)identifier {
    NSMutableDictionary *searchDictionary = [self newSearchDictionary:identifier];

    // Add search attributes
    [searchDictionary setObject:(__bridge id)kSecMatchLimitOne forKey:(__bridge id)kSecMatchLimit];

    // Add search return types
    // Must be persistent ref !!!!
    [searchDictionary setObject:@YES forKey:(__bridge id)kSecReturnPersistentRef];

    CFTypeRef result = NULL;
    SecItemCopyMatching((__bridge CFDictionaryRef)searchDictionary, &result);

    return (__bridge_transfer NSData *)result;
}

- (BOOL)createKeychainValue:(NSString *)password forIdentifier:(NSString *)identifier {
    NSMutableDictionary *dictionary = [self newSearchDictionary:identifier];

    OSStatus status = SecItemDelete((__bridge CFDictionaryRef)dictionary);

    NSData *passwordData = [password dataUsingEncoding:NSUTF8StringEncoding];
    [dictionary setObject:passwordData forKey:(__bridge id)kSecValueData];

    status = SecItemAdd((__bridge CFDictionaryRef)dictionary, NULL);

    if (status == errSecSuccess) {
        return YES;
    }
    return NO;
}