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SQL Parser and Optimizer
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/*
 * Copyright 2024 Hazelcast Inc.
 *
 * Licensed under the Hazelcast Community License (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://hazelcast.com/hazelcast-community-license
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.hazelcast.sql.impl.extract;

import com.hazelcast.jet.sql.impl.JetSqlSerializerHook;
import com.hazelcast.nio.ObjectDataInput;
import com.hazelcast.nio.ObjectDataOutput;
import com.hazelcast.nio.serialization.IdentifiedDataSerializable;
import com.hazelcast.sql.impl.QueryException;

import javax.annotation.Nullable;
import java.io.IOException;
import java.util.Objects;

import static com.hazelcast.query.QueryConstants.KEY_ATTRIBUTE_NAME;
import static com.hazelcast.query.QueryConstants.THIS_ATTRIBUTE_NAME;

/**
 * Represent a path to the attribute within a key-value pair.
 */
public final class QueryPath implements IdentifiedDataSerializable {

    public static final String KEY = KEY_ATTRIBUTE_NAME.value();
    public static final String VALUE = THIS_ATTRIBUTE_NAME.value();

    public static final QueryPath KEY_PATH = new QueryPath(null, true);
    public static final QueryPath VALUE_PATH = new QueryPath(null, false);

    public static final String KEY_PREFIX = KEY + ".";
    public static final String VALUE_PREFIX = VALUE + ".";

    private boolean key;
    private String path;

    public QueryPath() {
        // No-op.
    }

    public QueryPath(String path, boolean key) {
        this.path = path;
        this.key = key;
    }

    /**
     * Return the field path or {@code null}, if this object represents the
     * whole value (the whole key or the whole entry value).
     */
    @Nullable
    public String getPath() {
        return path;
    }

    public boolean isKey() {
        return key;
    }

    public boolean isTopLevel() {
        return path == null;
    }

    public static QueryPath create(String originalPath) {
        if (isEmpty(originalPath)) {
            throw badPathException(originalPath);
        }

        if (KEY.equals(originalPath)) {
            return KEY_PATH;
        } else if (VALUE.equals(originalPath)) {
            return VALUE_PATH;
        }

        if (originalPath.startsWith(KEY_PREFIX)) {
            String path = originalPath.substring(KEY_PREFIX.length());

            if (isEmpty(path)) {
                throw badPathException(originalPath);
            }

            return new QueryPath(path, true);
        } else if (originalPath.startsWith(VALUE_PREFIX)) {
            String path = originalPath.substring(VALUE_PREFIX.length());

            if (isEmpty(path)) {
                throw badPathException(originalPath);
            }

            return new QueryPath(path, false);
        } else {
            return new QueryPath(originalPath, false);
        }
    }

    private static boolean isEmpty(String path) {
        return path == null || path.isEmpty();
    }

    private static QueryException badPathException(String path) {
        throw QueryException.error("Field cannot be empty: " + path);
    }

    @Override
    public int getFactoryId() {
        return JetSqlSerializerHook.F_ID;
    }

    @Override
    public int getClassId() {
        return JetSqlSerializerHook.QUERY_PATH;
    }

    @Override
    public void writeData(ObjectDataOutput out) throws IOException {
        out.writeBoolean(key);
        out.writeString(path);
    }

    @Override
    public void readData(ObjectDataInput in) throws IOException {
        key = in.readBoolean();
        path = in.readString();
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) {
            return true;
        }

        if (o == null || getClass() != o.getClass()) {
            return false;
        }

        QueryPath path1 = (QueryPath) o;

        if (key != path1.key) {
            return false;
        }

        return Objects.equals(path, path1.path);
    }

    @Override
    public int hashCode() {
        int result = key ? 1 : 0;

        result = 31 * result + (path != null ? path.hashCode() : 0);

        return result;
    }

    @Override
    public String toString() {
        return (key ? KEY : VALUE) + (path != null ? "." + path : "");
    }
}