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/*
 * 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 io.trino.operator.scalar;

import com.google.common.collect.ImmutableList;
import com.google.common.primitives.Primitives;
import io.trino.annotation.UsedByGeneratedCode;
import io.trino.metadata.SqlScalarFunction;
import io.trino.spi.block.SqlMap;
import io.trino.spi.function.BoundSignature;
import io.trino.spi.function.FunctionDependencies;
import io.trino.spi.function.FunctionDependencyDeclaration;
import io.trino.spi.function.FunctionMetadata;
import io.trino.spi.function.Signature;
import io.trino.spi.type.MapType;
import io.trino.spi.type.Type;
import io.trino.spi.type.TypeSignature;

import java.lang.invoke.MethodHandle;

import static io.trino.spi.function.InvocationConvention.InvocationArgumentConvention.NEVER_NULL;
import static io.trino.spi.function.InvocationConvention.InvocationReturnConvention.NULLABLE_RETURN;
import static io.trino.spi.function.OperatorType.EQUAL;
import static io.trino.spi.type.TypeSignature.mapType;
import static io.trino.spi.type.TypeUtils.readNativeValue;
import static io.trino.util.Reflection.methodHandle;

public class MapElementAtFunction
        extends SqlScalarFunction
{
    public static final MapElementAtFunction MAP_ELEMENT_AT = new MapElementAtFunction();

    private static final MethodHandle METHOD_HANDLE_BOOLEAN = methodHandle(MapElementAtFunction.class, "elementAt", Type.class, SqlMap.class, boolean.class);
    private static final MethodHandle METHOD_HANDLE_LONG = methodHandle(MapElementAtFunction.class, "elementAt", Type.class, SqlMap.class, long.class);
    private static final MethodHandle METHOD_HANDLE_DOUBLE = methodHandle(MapElementAtFunction.class, "elementAt", Type.class, SqlMap.class, double.class);
    private static final MethodHandle METHOD_HANDLE_OBJECT = methodHandle(MapElementAtFunction.class, "elementAt", Type.class, SqlMap.class, Object.class);

    protected MapElementAtFunction()
    {
        super(FunctionMetadata.scalarBuilder("element_at")
                .signature(Signature.builder()
                        .typeVariable("K")
                        .typeVariable("V")
                        .returnType(new TypeSignature("V"))
                        .argumentType(mapType(new TypeSignature("K"), new TypeSignature("V")))
                        .argumentType(new TypeSignature("K"))
                        .build())
                .nullable()
                .description("Get value for the given key, or null if it does not exist")
                .build());
    }

    @Override
    public FunctionDependencyDeclaration getFunctionDependencies()
    {
        return FunctionDependencyDeclaration.builder()
                .addOperatorSignature(EQUAL, ImmutableList.of(new TypeSignature("K"), new TypeSignature("K")))
                .build();
    }

    @Override
    public SpecializedSqlScalarFunction specialize(BoundSignature boundSignature, FunctionDependencies functionDependencies)
    {
        MapType mapType = (MapType) boundSignature.getArgumentType(0);
        Type keyType = mapType.getKeyType();
        Type valueType = mapType.getValueType();

        MethodHandle methodHandle;
        if (keyType.getJavaType() == boolean.class) {
            methodHandle = METHOD_HANDLE_BOOLEAN;
        }
        else if (keyType.getJavaType() == long.class) {
            methodHandle = METHOD_HANDLE_LONG;
        }
        else if (keyType.getJavaType() == double.class) {
            methodHandle = METHOD_HANDLE_DOUBLE;
        }
        else {
            methodHandle = METHOD_HANDLE_OBJECT;
        }
        methodHandle = methodHandle.bindTo(valueType);
        methodHandle = methodHandle.asType(methodHandle.type().changeReturnType(Primitives.wrap(valueType.getJavaType())));

        return new ChoicesSpecializedSqlScalarFunction(
                boundSignature,
                NULLABLE_RETURN,
                ImmutableList.of(NEVER_NULL, NEVER_NULL),
                methodHandle);
    }

    @UsedByGeneratedCode
    public static Object elementAt(Type valueType, SqlMap sqlMap, boolean key)
    {
        int index = sqlMap.seekKeyExact(key);
        if (index == -1) {
            return null;
        }
        return readNativeValue(valueType, sqlMap.getRawValueBlock(), sqlMap.getRawOffset() + index);
    }

    @UsedByGeneratedCode
    public static Object elementAt(Type valueType, SqlMap sqlMap, long key)
    {
        int index = sqlMap.seekKeyExact(key);
        if (index == -1) {
            return null;
        }
        return readNativeValue(valueType, sqlMap.getRawValueBlock(), sqlMap.getRawOffset() + index);
    }

    @UsedByGeneratedCode
    public static Object elementAt(Type valueType, SqlMap sqlMap, double key)
    {
        int index = sqlMap.seekKeyExact(key);
        if (index == -1) {
            return null;
        }
        return readNativeValue(valueType, sqlMap.getRawValueBlock(), sqlMap.getRawOffset() + index);
    }

    @UsedByGeneratedCode
    public static Object elementAt(Type valueType, SqlMap sqlMap, Object key)
    {
        int index = sqlMap.seekKeyExact(key);
        if (index == -1) {
            return null;
        }
        return readNativeValue(valueType, sqlMap.getRawValueBlock(), sqlMap.getRawOffset() + index);
    }
}