/// <summary>Sets pos, err & revision from parameters, and sets NEW RefreshTime</summary>
private RevisedTrackerState(
LocationLib.Data.Position position,
LocationLib.Data.Error error,
string tag,
int? revision,
UpdateReason updatedPart
)
: base(position, error, tag)
{
DataRevision = revision;
UpdatedPart = updatedPart;
}
public static RevisedTrackerState Merge(
RevisedTrackerState oldResult,
LocationLib.TrackerState newResult,
int? newRevisionToUse
)
{
if ( oldResult == null && newResult == null ) return null;
if ( oldResult == null ) // means that newResult is not null (see the check above)
return new RevisedTrackerState(
newResult.Position,
newResult.Error,
newResult.Tag,
newRevisionToUse,
UpdateReason.BrandNew
);
if ( newResult == null ) // means that oldResult is not null (see the check above)
return oldResult;
LocationLib.Data.Position position;
if ( oldResult.Position != null && newResult.Position != null )
{
if ( oldResult.Position.CurrPoint.ForeignTime > newResult.Position.CurrPoint.ForeignTime )
{ // should be a rare case, but still possible. E.g. it could be like this:
// - unoffical request with very fresh data succeeded (see LocationRequests internals)
// - 15 seconds later unoffical request fails, and official started, returning old data.
position = oldResult.Position;
}
else if ( oldResult.Position.CurrPoint.ForeignTime < newResult.Position.CurrPoint.ForeignTime )
{
position = newResult.Position;
}
else
{ // foreign times are equal here.
position = newResult.Position;
}
}
else if ( oldResult.Position != null )
{
position = oldResult.Position;
}
else
{ // oldResult.Position is null, but newResult.Position could be either null or not null here.
position = newResult.Position;
}
/* We need to ensure that result has at either Position or Error set (or both).
*
* - if position is still null here, then both results Position set to null (see checks above).
* But neither constructor allows both Position and Error to be null => both Errors are not null,
* So newResult have Error set, and the merged one will have at least Error set to the new
* result Error (and probably Position).
*
* - if position is not null, then it doesn't matter if newResult.Error is null or not - the merged
* one still have Position set (and probably error - if the new one has it).
*/
LocationLib.Data.Error error = newResult.Error;
bool arePositionsEqual = LocationLib.Data.Position.ArePositionsEqual( oldResult.Position, position );
bool areErrorsEqual = LocationLib.Data.Error.AreErrorsEqual( oldResult.Error, error );
if ( arePositionsEqual && areErrorsEqual )
return oldResult;
UpdateReason updatedPart;
if ( arePositionsEqual )
updatedPart = UpdateReason.NewErr;
else
updatedPart = UpdateReason.NewPos;
return new RevisedTrackerState( position, error, newResult.Tag, newRevisionToUse, updatedPart );
}
