private static ExpressionBlock ParseExpression(SequenceProcessor sequenceProcessor, int startingPriority = 0)
{
var currentPriority = startingPriority;
ExpressionBlock currentExpressionBlock = null;
IExpression currentNumber = null;
Operation currentOperation = null;
while (!ReadNextSequence(ref currentPriority, ref currentExpressionBlock,
ref currentNumber, ref currentOperation, sequenceProcessor))
{
}
while (currentExpressionBlock.Parent != null)
{
currentExpressionBlock = currentExpressionBlock.Parent;
}
return(currentExpressionBlock);
}
private static bool ReadNextSequence(ref int currentPriority, ref ExpressionBlock currentExpressionBlock,
ref IExpression currentNumber, ref Operation currentOperation, SequenceProcessor sequenceProcessor)
{
var currentSequence = sequenceProcessor.ReadNextSequence();
var isFinalSequence = false;
ExpressionBlock newExpressionBlock;
switch (sequenceProcessor.GetSequenceType(currentSequence))
{
case SequenceProcessor.SequenceType.Number:
currentNumber = double.TryParse(currentSequence, out var result)
? new Number(result)
: new Number(currentSequence);
break;
case SequenceProcessor.SequenceType.Operation:
currentOperation = Settings.GetOperation(currentSequence);
if (currentExpressionBlock == null)
{
currentExpressionBlock = new ExpressionBlock(currentPriority + currentOperation.Priority);
currentExpressionBlock.AppendNode(currentNumber);
currentExpressionBlock.AppendOperation(currentOperation);
}
else if (currentPriority + currentOperation.Priority > currentExpressionBlock.Priority)
{
newExpressionBlock = new ExpressionBlock(currentPriority + currentOperation.Priority);
newExpressionBlock.AppendNode(currentNumber);
newExpressionBlock.AppendOperation(currentOperation);
currentExpressionBlock.AppendNode(newExpressionBlock);
currentExpressionBlock = newExpressionBlock;
}
else if (currentPriority + currentOperation.Priority < currentExpressionBlock.Priority)
{
if (currentExpressionBlock.Parent != null)
{
currentExpressionBlock.AppendNode(currentNumber);
currentExpressionBlock = currentExpressionBlock.Parent;
currentExpressionBlock.AppendOperation(currentOperation);
}
else
{
newExpressionBlock = new ExpressionBlock(currentPriority + currentOperation.Priority);
currentExpressionBlock.AppendNode(currentNumber);
newExpressionBlock.AppendNode(currentExpressionBlock);
newExpressionBlock.AppendOperation(currentOperation);
currentExpressionBlock = newExpressionBlock;
}
}
else
{
currentExpressionBlock.AppendNode(currentNumber);
currentExpressionBlock.AppendOperation(currentOperation);
}
break;
case SequenceProcessor.SequenceType.OpeningBracket:
newExpressionBlock =
ParseExpression(sequenceProcessor, currentPriority + Settings.ParenthesesPriority);
currentNumber = newExpressionBlock;
break;
case SequenceProcessor.SequenceType.ClosingBracket:
isFinalSequence = true;
break;
default:
throw new ArgumentOutOfRangeException(nameof(currentSequence),
"Sequence of this type cannot be processed.");
}
isFinalSequence = isFinalSequence || sequenceProcessor.CurrentIndex == sequenceProcessor.Sequence.Length;
if (isFinalSequence)
{
currentExpressionBlock ??= new ExpressionBlock(currentNumber.IsAtomic
? currentPriority
: currentNumber.Priority);
if (!currentExpressionBlock.IsFilled)
{
currentExpressionBlock.AppendNode(currentNumber);
}
}
return(isFinalSequence);
}
