/// <summary>
/// Solves all the non-terminal symbols within the given sentence.
/// </summary>
/// <param name="sentence">A string with non-terminal symbols to replace.</param>
/// <param name="rnd">Random number generator used to choose the
/// productions and generate the sentence</param>
/// <param name="stackCounter">A counter that indicates how many times
/// this function has called itself. It is used to prevent a stack overflow.
/// When it reach 1000 the production is aborted.</param>
/// <returns>A string with terminal symbols only</returns>
/// <remarks>Recursive function</remarks>
private TaskNode SolveNonTerminals(string sentence, Random rnd, int stackCounter)
{
if (++stackCounter > 999)
{
throw new StackOverflowException();
}
TaskNode node = new TaskNode(null);
string[] parts = sentence.SmartSplit(' ');
foreach (string part in parts)
{
if (part.Contains("$"))
{
string replacement = FindReplacement(part, rnd);
TaskNode child = SolveNonTerminals(replacement, rnd, stackCounter + 1);
child.Term = part;
node.Children.Add(child);
}
else
{
TaskNode child = new TaskNode(node);
child.StringValue = part;
node.Children.Add(child);
}
}
return(node);
}
/// <summary>
/// Generates a random sentence.
/// </summary>
/// <param name="rnd">Random number generator used to choose the
/// productions and generate the sentence</param>
/// <returns>A randomly generated sentence.</returns>
public TaskNode GenerateSentence(Random rnd)
{
string option = FindReplacement("$Main", rnd);
TaskNode root = SolveNonTerminals(option, rnd);
root.Term = "$Main";
root.Tier = Tier;
return(root);
}
/// <summary>
/// Randomly generates a task with the given grammar
/// </summary>
/// <param name="grammarName">The name of the grammar to generate the task</param>
/// <param name="tier">The maximum difficulty degree allowed to produce the task</param>
/// <returns></returns>
public Task GenerateTask(string grammarName, DifficultyDegree tier)
{
for (int i = 0; i < 3; ++i)
{
try
{
TaskNode root = GetTaskPrototype(grammarName);
string taskPrototype = root.Render();
WildcardReplacer replacer = new WildcardReplacer(this, tier);
if (String.IsNullOrEmpty(taskPrototype))
{
return(null);
}
Task t = replacer.GetTask(taskPrototype);
t.Tree = root;
return(t);
}
catch
{
continue;
}
}
return(null);
}