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package bjc.pratt.blocks;
import java.util.function.UnaryOperator;
import bjc.pratt.ParserContext;
import bjc.pratt.commands.CommandResult;
import bjc.pratt.commands.CommandResult.Status;
import bjc.pratt.tokens.Token;
import bjc.data.Tree;
import bjc.data.SimpleTree;
import bjc.utils.parserutils.ParserException;
/**
* A parse block that can parse a sequnce of zero or more occurances of another
* block.
*
* @author bjculkin
*
* @param <K>
* The key type of the tokens.
*
* @param <V>
* The value type of the tokens.
*
* @param <C>
* The state type of the parser.
*/
public class RepeatingParseBlock<K, V, C> implements ParseBlock<K, V, C> {
private final ParseBlock<K, V, C> innerBlock;
private final K delim;
private final K term;
private final UnaryOperator<C> onDelim;
private final Token<K, V> mark;
/**
* Create a new repeating block.
*
* @param inner
* The inner block for elements.
*
* @param delimiter
* The token that delimits elements in the sequence.
*
* @param terminator
* The token that terminates the sequence.
*
* @param marker
* The token to use as the node in the AST.
*
* @param action
* The action to apply to the state after every delimiter.
*/
public RepeatingParseBlock(final ParseBlock<K, V, C> inner, final K delimiter, final K terminator,
final Token<K, V> marker, final UnaryOperator<C> action) {
super();
if(inner == null)
throw new NullPointerException("Inner block must not be null");
else if(delimiter == null)
throw new NullPointerException("Delimiter must not be null");
else if(terminator == null) throw new NullPointerException("Terminator must not be null");
innerBlock = inner;
delim = delimiter;
term = terminator;
mark = marker;
onDelim = action;
}
@Override
public CommandResult<K, V> parse(final ParserContext<K, V, C> ctx) throws ParserException {
final Tree<Token<K, V>> ret = new SimpleTree<>(mark);
Token<K, V> tok = ctx.tokens.current();
while(!tok.getKey().equals(term)) {
final CommandResult<K,V> resKid = innerBlock.parse(ctx);
if (resKid.status != Status.SUCCESS) return resKid;
Tree<Token<K, V>> kid = resKid.success();
ret.addChild(kid);
tok = ctx.tokens.current();
ctx.tokens.expect(delim, term);
if(onDelim != null) {
ctx.state = onDelim.apply(ctx.state);
}
}
return CommandResult.success(ret);
}
}
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