private NodeBunch BuildItem(Element item)
{
var car = item.GetCarSymbolName();
NodeBunch buildResult;
INode node;
NodeBox nodeBox;
switch (car)
{
case "BLOCK":
buildResult = this.BuildBlock(item);
break;
case "ALT":
buildResult = this.BuildAlt(item);
break;
case "OPT":
buildResult = this.BuildOpt(item);
break;
case "SEQ":
buildResult = this.BuildSeq(item);
break;
case "IDLE":
node = new IdleNode(
_nodeFactory.NodeFamily,
item.GetItemName());
nodeBox = new NodeBox(node, item.GetItemLinks());
buildResult = new NodeBunch(nodeBox, nodeBox);
break;
case "END":
node = EndNode.Instance;
nodeBox = new NodeBox(node);
buildResult = new NodeBunch(nodeBox, nodeBox);
break;
default:
buildResult = this.BuildCustomItem(item);
break;
}
return(buildResult);
}
private NodeBunch BuildBlock(Element item)
{
var blockName = item.GetSingleKeywordArgument <Symbol>(":ref").Name;
var defblock = _defblocks[blockName];
var args = defblock.GetFreeArguments();
var blockEnter = new NodeBox(new IdleNode(_nodeFactory.NodeFamily, blockName));
var contentResult = this.BuildContent(args);
var blockExit = new NodeBox(new IdleNode(_nodeFactory.NodeFamily, $"<exit of block> {blockName}"), item.GetItemLinks());
blockEnter.DemandLink(contentResult.Head);
contentResult.Tail.RequestLink(blockExit);
var result = new NodeBunch(blockEnter, blockExit);
return(result);
}
private NodeBunch BuildOpt(Element item)
{
var optName = item.GetItemName() ?? this.GetNextOptName();
var optEnter = new NodeBox(new IdleNode(_nodeFactory.NodeFamily, optName));
var optExit = new NodeBox(new IdleNode(_nodeFactory.NodeFamily, $"<exit of opt> {optName}"), item.GetItemLinks());
// short circuit!
optEnter.DemandLink(optExit);
var args = item.GetFreeArguments();
var contentResult = this.BuildContent(args);
optEnter.DemandLink(contentResult.Head);
contentResult.Tail.RequestLink(optExit);
var result = new NodeBunch(optEnter, optExit);
return(result);
}
private NodeBunch BuildAlt(Element item)
{
var altName = item.GetItemName() ?? this.GetNextAltName();
var alternatives = item.GetFreeArguments();
var altEnter = new NodeBox(new IdleNode(_nodeFactory.NodeFamily, altName));
var altExit = new NodeBox(new IdleNode(_nodeFactory.NodeFamily, $"<exit of alt> {altName}"), item.GetItemLinks());
foreach (var alternative in alternatives)
{
var alternativeResult = this.BuildItem(alternative);
altEnter.DemandLink(alternativeResult.Head);
alternativeResult.Tail.RequestLink(altExit);
}
var result = new NodeBunch(altEnter, altExit);
return(result);
}
private NodeBunch BuildContent(PseudoList content)
{
NodeBox head = null;
NodeBox tail = null;
foreach (var item in content)
{
var result = this.BuildItem(item);
if (head == null)
{
// first entry
head = result.Head;
tail = result.Tail;
}
else
{
tail.RequestLink(result.Head);
tail = result.Tail;
}
}
if (tail == null)
{
throw new BuildingException("Content is empty.");
}
if (tail.Links.Any())
{
throw new BuildingException("Last item in a content must not have explicit links.");
}
var buildResult = new NodeBunch(head, tail);
return(buildResult);
}
