jetbrains.jetpad.grammar.parser.LRParser.java Source code

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Here is the source code for jetbrains.jetpad.grammar.parser.LRParser.java

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/*
 * Copyright 2012-2016 JetBrains s.r.o
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package jetbrains.jetpad.grammar.parser;

import com.google.common.base.Function;
import com.google.common.collect.Lists;
import com.google.common.collect.Range;
import jetbrains.jetpad.grammar.*;

import java.util.*;

public class LRParser {
    private LRParserTable myTable;
    private ParserParameters myParameters;

    public LRParser(LRParserTable table) {
        this(table, ParserParameters.EMPTY);
    }

    public LRParser(LRParserTable table, ParserParameters params) {
        myTable = table;
        myParameters = params;
    }

    public boolean parse(Terminal... input) {
        List<Lexeme> lexemes = new ArrayList<>();
        for (Terminal t : input) {
            lexemes.add(new Lexeme(t, t.toString()));
        }
        return parse(lexemes) != null;
    }

    public Object parse(Lexeme... input) {
        return parse(Arrays.asList(input));
    }

    public Object parse(List<Lexeme> input) {
        return parse(input, new Function<Rule, RuleHandler>() {
            @Override
            public RuleHandler apply(Rule rule) {
                return rule.getHandler();
            }
        });
    }

    public Object parse(List<Lexeme> input, Function<Rule, RuleHandler> handlerProvider) {
        Stack<ParseStackItem> stack = new Stack<>();
        stack.push(new ParseStackItem(myTable.getInitialState(), -1, -1, null, null));
        int pos = 0;
        while (true) {
            Lexeme lexeme = pos < input.size() ? input.get(pos) : null;
            Terminal current = lexeme != null ? lexeme.getTerminal() : myTable.getGrammar().getEnd();
            LRParserState state = stack.peek().state;
            LRParserAction<LRParserState> action = state.getAction(current);
            if (action instanceof LRParserAction.Shift) {
                LRParserAction.Shift<LRParserState> shift = (LRParserAction.Shift<LRParserState>) action;
                stack.push(new ParseStackItem(shift.getState(), pos, pos + 1, current, lexeme));
                pos++;
            } else if (action instanceof LRParserAction.Reduce) {
                LRParserAction.Reduce<LRParserState> reduce = (LRParserAction.Reduce<LRParserState>) action;

                List<Object> handlerInput = new ArrayList<>();
                int startOffset = pos;
                List<Symbol> symbols = reduce.getRule().getSymbols();
                for (int i = 0; i < symbols.size(); i++) {
                    ParseStackItem top = stack.pop();
                    if (i == symbols.size() - 1) {
                        startOffset = top.start;
                    }
                    handlerInput.add(top.result);
                }
                Collections.reverse(handlerInput);

                LRParserState nextState = stack.peek().state.getNextState(reduce.getRule().getHead());
                RuleContext ruleContext = new MyRuleContext(Range.closed(startOffset, pos), handlerInput, input);
                RuleHandler handler = handlerProvider.apply(reduce.getRule());
                Object result = handler != null ? handler.handle(ruleContext) : handlerInput;

                stack.push(new ParseStackItem(nextState, startOffset, pos, reduce.getRule().getHead(), result));
            } else if (action instanceof LRParserAction.Accept) {
                return stack.peek().result;
            } else {
                return null;
            }
        }
    }

    private class ParseStackItem {
        final LRParserState state;
        final int start;
        final int end;
        final Symbol symbol;
        final Object result;

        ParseStackItem(LRParserState state, int start, int end, Symbol symbol, Object result) {
            this.state = state;
            this.start = start;
            this.end = end;
            this.symbol = symbol;
            this.result = result;
        }
    }

    private class MyRuleContext implements RuleContext {
        private final List<Object> myValues;
        private final Range<Integer> myRange;
        private final List<Lexeme> myInput;

        private MyRuleContext(Range<Integer> range, List<Object> values, List<Lexeme> input) {
            myValues = values;
            myRange = range;
            myInput = input;
        }

        @Override
        public ParserParameters getParams() {
            return myParameters;
        }

        @Override
        public <ValueT> ValueT get(ParserParameter<ValueT> key) {
            return myParameters.get(key);
        }

        @Override
        public Object get(int index) {
            return myValues.get(index);
        }

        @Override
        public int getValueCount() {
            return myValues.size();
        }

        @Override
        public Range<Integer> getRange() {
            return myRange;
        }

        @Override
        public List getLexemeValues() {
            List<Lexeme> matchedLexemes = myInput.subList(myRange.lowerEndpoint(), myRange.upperEndpoint());
            return Collections.unmodifiableList(Lists.transform(matchedLexemes, new Function<Lexeme, Object>() {
                @Override
                public Object apply(Lexeme lexeme) {
                    return lexeme.getValue();
                }
            }));
        }
    }
}