org.eclipse.xtext.ide.serializer.impl.InsertionPointFinder.java Source code

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Here is the source code for org.eclipse.xtext.ide.serializer.impl.InsertionPointFinder.java

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/*******************************************************************************
 * Copyright (c) 2017 TypeFox GmbH (http://www.typefox.io) and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *******************************************************************************/
package org.eclipse.xtext.ide.serializer.impl;

import java.util.LinkedList;
import java.util.List;
import java.util.Set;
import java.util.function.Function;

import org.eclipse.xtext.AbstractElement;
import org.eclipse.xtext.GrammarUtil;
import org.eclipse.xtext.IGrammarAccess;
import org.eclipse.xtext.RuleCall;
import org.eclipse.xtext.formatting2.regionaccess.IAstRegion;
import org.eclipse.xtext.formatting2.regionaccess.IEObjectRegion;
import org.eclipse.xtext.formatting2.regionaccess.IHiddenRegion;
import org.eclipse.xtext.serializer.ISerializationContext;
import org.eclipse.xtext.serializer.analysis.IContextTypePDAProvider;
import org.eclipse.xtext.serializer.analysis.ISerState;
import org.eclipse.xtext.serializer.analysis.ISerState.SerStateType;
import org.eclipse.xtext.serializer.analysis.SerializationContextMap;
import org.eclipse.xtext.util.formallang.NfaUtil;
import org.eclipse.xtext.util.formallang.Pda;

import com.google.common.collect.Lists;
import com.google.common.collect.Sets;
import com.google.inject.Inject;

/**
 * @author Moritz Eysholdt - Initial contribution and API
 */
public class InsertionPointFinder {

    private SerializationContextMap<Pda<ISerState, RuleCall>> pdas;

    protected Set<AbstractElement> collectAdjacent(ISerState start,
            Function<ISerState, List<? extends ISerState>> followers) {
        LinkedList<ISerState> todo = new LinkedList<>();
        Set<ISerState> seen = Sets.newHashSet();
        todo.addAll(followers.apply(start));
        Set<AbstractElement> result = Sets.newLinkedHashSet();
        while (!todo.isEmpty()) {
            ISerState next = todo.pop();
            if (!seen.add(next)) {
                continue;
            }
            if (next.getType() == SerStateType.ELEMENT
                    && !GrammarUtil.isUnassignedAction(next.getGrammarElement())) {
                result.add(next.getGrammarElement());
            } else {
                todo.addAll(followers.apply(next));
            }
        }
        return result;
    }

    public IHiddenRegion findInsertionPoint(ISerializationContext ctx, IEObjectRegion obj, AbstractElement ins) {
        ISerState insertionState = findState(ctx, ins);
        Set<AbstractElement> followers = collectAdjacent(insertionState, s -> s.getFollowers());
        Set<AbstractElement> precendents = collectAdjacent(insertionState, s -> s.getPrecedents());
        List<IAstRegion> regions = Lists.newArrayList(obj.getAstRegions());
        if (regions.isEmpty()) {
            return obj.getPreviousHiddenRegion();
        }
        if (followers.contains(regions.get(0).getGrammarElement())) {
            return obj.getPreviousHiddenRegion();
        }
        if (precendents.contains(regions.get(regions.size() - 1).getGrammarElement())) {
            return obj.getNextHiddenRegion();
        }
        for (int i = 0; i < regions.size() - 1; i++) {
            IAstRegion leading = regions.get(i);
            IAstRegion trailing = regions.get(i + 1);
            if (precendents.contains(leading.getGrammarElement())
                    && followers.contains(trailing.getGrammarElement())) {
                return leading.getNextHiddenRegion();
            }
        }
        return null;
    }

    protected ISerState findState(ISerializationContext ctx, AbstractElement ele) {
        Pda<ISerState, RuleCall> pda = pdas.get(ctx);
        return new NfaUtil().find(pda, s -> s.getGrammarElement() == ele);
    }

    @Inject
    protected void init(IContextTypePDAProvider pdaProvider, IGrammarAccess grammar) {
        pdas = pdaProvider.getContextTypePDAs(grammar.getGrammar());
    }

}