com.google.template.soy.passes.htmlmatcher.HtmlMatcherAccumulatorNode.java Source code

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Here is the source code for com.google.template.soy.passes.htmlmatcher.HtmlMatcherAccumulatorNode.java

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/*
 * Copyright 2018 Google Inc.
 *
 * 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 com.google.template.soy.passes.htmlmatcher;

import static com.google.common.base.Preconditions.checkState;

import com.google.common.base.Optional;
import com.google.common.collect.ImmutableList;
import com.google.template.soy.soytree.SoyNode;
import javax.annotation.Nullable;

/**
 * Synthetic node to join multiple graph nodes when many code paths lead to one place.
 *
 * <p>This is similar to the phi function described in <a
 * href="https://en.wikipedia.org/wiki/Static_single_assignment_form">Static_single_assignment_form</a>
 */
public final class HtmlMatcherAccumulatorNode extends HtmlMatcherGraphNode {

    @Nullable
    private HtmlMatcherGraphNode nextNode = null;

    @Override
    public Optional<SoyNode> getSoyNode() {
        return Optional.absent();
    }

    @Override
    public Optional<HtmlMatcherGraphNode> getNodeForEdgeKind(EdgeKind edgeKind) {
        if (edgeKind == EdgeKind.TRUE_EDGE) {
            return Optional.fromNullable(nextNode);
        }
        return Optional.absent();
    }

    @Override
    public void setActiveEdgeKind(EdgeKind edgeKind) {
        throw new UnsupportedOperationException("Cannot set the edge kind of an Accumulator node.");
    }

    @Override
    public void linkEdgeToNode(EdgeKind edgeKind, HtmlMatcherGraphNode node) {
        checkState(edgeKind == EdgeKind.TRUE_EDGE, "Accumulator nodes only have a true branch.");
        checkState(!this.equals(node), "Can't link a node to itsself.");
        nextNode = node;
    }

    /**
     * Links the all the given active edges to this node.
     *
     * <p>This produces a many-to-one linkage in the HTML matcher graph.
     *
     * <p>Note that a {@link HtmlMatcherGraphNode} may occur in the list more than once, each time
     * with a different active edge. For example, this Soy template body:
     *
     * <pre>
     *   &lt;span&gt;
     *     {if $cond1}Content1{/if}  // No HTML tags in the If-block.
     *   &lt;/span&gt;
     * </pre>
     *
     * will add two occurences of an {@link HtmlMatcherConditionNode} to the {@code activeEdges} list,
     * one with a {@code TRUE} active edge, and one with a {@code FALSE} active edge.
     *
     * @param activeEdges the list of all active edges that will point to this {@link
     *     HtmlMatcherAccumulatorNode}. Note that a {@link HtmlMatcherGraphNode} may occur in the list
     *     more than once.
     */
    public void accumulateActiveEdges(ImmutableList<ActiveEdge> activeEdges) {
        for (ActiveEdge accEdge : activeEdges) {
            accEdge.getGraphNode().linkEdgeToNode(accEdge.getActiveEdge(), this);
        }
    }
}