/// <summary>
/// Introduces a new object and handles all the needed communicated with the normalization helper.
/// </summary>
/// <returns>
/// <param name="theoremsToProve">The theorems that are still left to be proven.</param>
/// The tuple of objects that got removed and the object that got introduced. The object list will never
/// be null, but might be empty. Also, the number of removed objects might be bigger than the number of
/// previously introduced ones, because the normalization helper might have found equal ones in the meantime.
/// If there has been no introduces, then the new object will be null.
/// </returns>
public (IReadOnlyList <ConstructedConfigurationObject> removedObjects, ConstructedConfigurationObject newObject) IntroduceObject(IEnumerable <Theorem> theoremsToProve)
{
#region Handle object removal
// Prepare the removed objects
var removedObjects = new List <ConstructedConfigurationObject>();
// If the last introduced object was a point
if (_lastIntroducedObject != null && _lastIntroducedObject.ObjectType == ConfigurationObjectType.Point)
{
// Let the normalization helper remove it, while returning everything what's been removed
_helper.RemoveIntroducedObject(_lastIntroducedObject, out var removedObjectsLocal);
// Mark the removed objects
removedObjects.Add(removedObjectsLocal);
}
#endregion
#region Handle object introduction
// Find the object to introduce by calling the introducer
var newObject = _introducer
// With the available objects equal to those
.IntroduceObjects(_helper.AllObjects
// That are in the original configuration (otherwise it would be explosive)
.Where(_helper.IsInOriginalConfiguration)
// Enumerated
.ToArray())
// Concat object introduced based on theorems to be proven
.Concat(theoremsToProve.SelectMany(PerformTheoremBasedIntroduction))
// The introducer offers us some options that we need to normalize by copying the construction
.Select(newObject => new ConstructedConfigurationObject(newObject.Construction,
// And normalizing each of the argument objects
newObject.PassedArguments.FlattenedList.Select(_helper.GetNormalVersionOfObjectOrNull).ToArray()))
// When we have options normalize, we need to filter those objects that have been introduced already
.Where(newObject => !_allIntroducedObjects.Contains(newObject)
// And aren't already known to the helper
&& !_helper.AllObjects.Contains(newObject)
// And haven't been ever known to the helper
&& !_helper.AllRemovedObjects.Contains(newObject))
// Enumerate
.ToArray()
// Sort them so that we first introduce non-points (lines and circles)
.OrderBy(newObject => newObject.ObjectType == ConfigurationObjectType.Point ? 1 : 0)
// Take the first option
.FirstOrDefault();
// If there is something to be introduced
if (newObject != null)
{
// Let the normalization helper know
_helper.IntroduceNewObject(newObject);
// Add the object to the set of all objects ever introduced
_allIntroducedObjects.Add(newObject);
}
// Set the last introduced object
_lastIntroducedObject = newObject;
#endregion
// Return the removed objects together with the new ones
return(removedObjects, newObject);
}