// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.search.query.profile;

import java.util.List;

/**
 * Visitor which stores the first non-query-profile value encountered,
 * or the first query profile encountered at a stop where we do not have any name components left which can be used to
 * visit further subprofiles. Hence this may be used both to get the highest prioritized primitive
 * value, or query profile, whichever is encountered first which matches the name.
 * <p>
 *
 * @author bratseth
 */
final class SingleValueQueryProfileVisitor extends QueryProfileVisitor {

    /** The value found, or null if none */
    private Object value = null;

    private final List<String> name;

    private int nameIndex = -1;

    private final boolean allowQueryProfileResult;

    private boolean enteringContent = true;

    public SingleValueQueryProfileVisitor(List<String> name, boolean allowQueryProfileResult) {
        this.name = name;
        this.allowQueryProfileResult = allowQueryProfileResult;
    }

    @Override
    public String getLocalKey() {
        return name.get(nameIndex);
    }

    @Override
    public boolean enter(String name) {
        if (nameIndex+1 < this.name.size()) {
            nameIndex++;
            enteringContent = true;
        }
        else {
            enteringContent = false;
        }
        return enteringContent;
    }

    @Override
    public void leave(String name) {
        nameIndex--;
    }

    @Override
    public void onValue(String key,Object value,
                        DimensionBinding binding,
                        QueryProfile owner,
                        DimensionValues variant) {
        if (nameIndex == name.size()-1)
            this.value = value;
    }

    @Override
    public void onQueryProfile(QueryProfile profile,
                               DimensionBinding binding,
                               QueryProfile owner,
                               DimensionValues variant) {
        if (enteringContent) return; // still waiting for content
        if (allowQueryProfileResult)
            this.value = profile;
        else
            this.value = profile.getValue();
    }

    @Override
    public boolean isDone() {
        return value!=null;
    }

    /** Returns the value found during visiting, or null if none */
    public Object getResult() { return value; }

    @Override
    public String toString() {
        return "a single value visitor (hash " + hashCode() + ") with current value " + value;
    }

}