protected override IEnumerable<Datum> Poll(CancellationToken cancellationToken)
{
List<Datum> data = new List<Datum>();
if (HasValidAccessToken)
{
string[] missingPermissions = GetRequiredPermissionNames().Where(p => !AccessToken.CurrentAccessToken.Permissions.Contains(p)).ToArray();
if (missingPermissions.Length > 0)
ObtainAccessToken(missingPermissions);
}
else
ObtainAccessToken(GetRequiredPermissionNames());
if (HasValidAccessToken)
{
ManualResetEvent startWait = new ManualResetEvent(false);
List<ManualResetEvent> responseWaits = new List<ManualResetEvent>();
Exception exception = null; // can't throw exception from within the UI thread -- it will crash the app. use this variable to check whether an exception did occur.
Xamarin.Forms.Device.BeginInvokeOnMainThread(() =>
{
try
{
GraphRequestConnection requestConnection = new GraphRequestConnection();
#region add requests to connection
foreach (Tuple<string, List<string>> edgeFieldQuery in GetEdgeFieldQueries())
{
NSDictionary parameters = null;
if (edgeFieldQuery.Item2.Count > 0)
parameters = new NSDictionary("fields", string.Concat(edgeFieldQuery.Item2.Select(field => field + ",")).Trim(','));
GraphRequest request = new GraphRequest(
"me" + (edgeFieldQuery.Item1 == null ? "" : "/" + edgeFieldQuery.Item1),
parameters,
AccessToken.CurrentAccessToken.TokenString,
null,
"GET");
ManualResetEvent responseWait = new ManualResetEvent(false);
requestConnection.AddRequest(request, (connection, result, error) =>
{
if (error == null)
{
FacebookDatum datum = new FacebookDatum(DateTimeOffset.UtcNow);
#region set datum properties
NSDictionary resultDictionary = result as NSDictionary;
bool valuesSet = false;
foreach (string resultKey in resultDictionary.Keys.Select(k => k.ToString()))
{
PropertyInfo property;
if (FacebookDatum.TryGetProperty(resultKey, out property))
{
object value = null;
if (property.PropertyType == typeof(string))
value = resultDictionary[resultKey].ToString();
else if (property.PropertyType == typeof(bool?))
{
int parsedBool;
if (int.TryParse(resultDictionary[resultKey].ToString(), out parsedBool))
value = parsedBool == 1 ? true : false;
}
else if (property.PropertyType == typeof(DateTimeOffset?))
{
DateTimeOffset parsedDateTimeOffset;
if (DateTimeOffset.TryParse(resultDictionary[resultKey].ToString(), out parsedDateTimeOffset))
value = parsedDateTimeOffset;
}
else if (property.PropertyType == typeof(List<string>))
{
List<string> values = new List<string>();
NSArray resultArray = resultDictionary[resultKey] as NSArray;
for (nuint i = 0; i < resultArray.Count; ++i)
values.Add(resultArray.GetItem<NSObject>(i).ToString());
value = values;
}
else
throw new SensusException("Unrecognized FacebookDatum property type: " + property.PropertyType.ToString());
if (value != null)
{
property.SetValue(datum, value);
valuesSet = true;
}
}
else
SensusServiceHelper.Get().Logger.Log("Unrecognized key in Facebook result dictionary: " + resultKey, LoggingLevel.Verbose, GetType());
}
#endregion
if (valuesSet)
data.Add(datum);
}
else
SensusServiceHelper.Get().Logger.Log("Error received while querying Facebook graph API: " + error.Description, LoggingLevel.Normal, GetType());
SensusServiceHelper.Get().Logger.Log("Response for \"" + request.GraphPath + "\" has been processed.", LoggingLevel.Verbose, GetType());
responseWait.Set();
});
responseWaits.Add(responseWait);
}
#endregion
if (responseWaits.Count == 0)
exception = new Exception("Request connection contained zero requests.");
else
{
SensusServiceHelper.Get().Logger.Log("Starting request connection with " + responseWaits.Count + " requests.", LoggingLevel.Normal, GetType());
requestConnection.Start();
}
startWait.Set();
}
catch (Exception ex)
{
exception = new Exception("Error starting request connection: " + ex.Message);
}
});
startWait.WaitOne();
// wait for all responses to be processed
foreach (ManualResetEvent responseWait in responseWaits)
responseWait.WaitOne();
// if any exception occurred when running query, throw it now
if (exception != null)
throw exception;
}
else
throw new Exception("Attempted to poll Facebook probe without a valid access token.");
return data;
}