public IEnumerable <object> GetClearDataCommands()
{
var commands = new List <object>();
ICollection <string> remainingTables = this.tables.ToList();
var remainingRelationships = new RelationCollection(this.relations);
var safetyNet = 0;
var max = this.tables.Count() * 3;
while (safetyNet++ <= max)
{
var referencedTables = remainingRelationships.GetReferencedTables();
var leafTables = remainingTables.Except(referencedTables).ToList();
if (leafTables.Any() || !referencedTables.Any())
{
commands.AddRange(leafTables.Select(t => new ClearTableCommand(t)));
if (!referencedTables.Any())
{
return(commands);
}
remainingTables = remainingTables.Except(leafTables).ToList();
remainingRelationships = remainingRelationships.WithoutLeaves(leafTables);
}
else
{
var nullableRelation = remainingRelationships.FindFirstNullableCyclicRelation();
if (nullableRelation == null)
{
throw new InvalidOperationException("Cylclic foreign key detected with no nullable foreign keys");
}
commands.Add(new NullColumnCommand(nullableRelation.SourceTable, nullableRelation.SourceColumn));
remainingRelationships = remainingRelationships.WithoutRelation(nullableRelation);
}
}
throw new InvalidOperationException("Infinite loop detected whilst processing tables: " + Environment.NewLine + Environment.NewLine +
string.Join(Environment.NewLine, this.tables) + Environment.NewLine + Environment.NewLine + "And relations:" +
Environment.NewLine + Environment.NewLine + string.Join(Environment.NewLine, this.relations));
}