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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.prestosql.operator.scalar;

import com.google.common.collect.ImmutableList;
import com.google.common.primitives.Primitives;
import io.airlift.bytecode.BytecodeBlock;
import io.airlift.bytecode.BytecodeNode;
import io.airlift.bytecode.ClassDefinition;
import io.airlift.bytecode.MethodDefinition;
import io.airlift.bytecode.Parameter;
import io.airlift.bytecode.Scope;
import io.airlift.bytecode.Variable;
import io.airlift.bytecode.control.ForLoop;
import io.airlift.bytecode.control.IfStatement;
import io.prestosql.metadata.FunctionArgumentDefinition;
import io.prestosql.metadata.FunctionBinding;
import io.prestosql.metadata.FunctionMetadata;
import io.prestosql.metadata.Signature;
import io.prestosql.metadata.SqlScalarFunction;
import io.prestosql.spi.PageBuilder;
import io.prestosql.spi.block.Block;
import io.prestosql.spi.block.BlockBuilder;
import io.prestosql.spi.type.ArrayType;
import io.prestosql.spi.type.Type;
import io.prestosql.spi.type.TypeSignature;
import io.prestosql.sql.gen.CallSiteBinder;
import io.prestosql.sql.gen.lambda.UnaryFunctionInterface;

import java.util.List;
import java.util.Optional;

import static io.airlift.bytecode.Access.FINAL;
import static io.airlift.bytecode.Access.PRIVATE;
import static io.airlift.bytecode.Access.PUBLIC;
import static io.airlift.bytecode.Access.STATIC;
import static io.airlift.bytecode.Access.a;
import static io.airlift.bytecode.Parameter.arg;
import static io.airlift.bytecode.ParameterizedType.type;
import static io.airlift.bytecode.expression.BytecodeExpressions.constantInt;
import static io.airlift.bytecode.expression.BytecodeExpressions.constantNull;
import static io.airlift.bytecode.expression.BytecodeExpressions.equal;
import static io.airlift.bytecode.expression.BytecodeExpressions.lessThan;
import static io.airlift.bytecode.expression.BytecodeExpressions.newInstance;
import static io.airlift.bytecode.expression.BytecodeExpressions.subtract;
import static io.airlift.bytecode.instruction.VariableInstruction.incrementVariable;
import static io.prestosql.metadata.FunctionKind.SCALAR;
import static io.prestosql.metadata.Signature.typeVariable;
import static io.prestosql.spi.function.InvocationConvention.InvocationArgumentConvention.FUNCTION;
import static io.prestosql.spi.function.InvocationConvention.InvocationArgumentConvention.NEVER_NULL;
import static io.prestosql.spi.function.InvocationConvention.InvocationReturnConvention.FAIL_ON_NULL;
import static io.prestosql.spi.type.TypeSignature.arrayType;
import static io.prestosql.spi.type.TypeSignature.functionType;
import static io.prestosql.sql.gen.SqlTypeBytecodeExpression.constantType;
import static io.prestosql.type.UnknownType.UNKNOWN;
import static io.prestosql.util.CompilerUtils.defineClass;
import static io.prestosql.util.CompilerUtils.makeClassName;
import static io.prestosql.util.Reflection.methodHandle;

public final class ArrayTransformFunction
        extends SqlScalarFunction
{
    public static final ArrayTransformFunction ARRAY_TRANSFORM_FUNCTION = new ArrayTransformFunction();

    private ArrayTransformFunction()
    {
        super(new FunctionMetadata(
                new Signature(
                        "transform",
                        ImmutableList.of(typeVariable("T"), typeVariable("U")),
                        ImmutableList.of(),
                        arrayType(new TypeSignature("U")),
                        ImmutableList.of(
                                arrayType(new TypeSignature("T")),
                                functionType(new TypeSignature("T"), new TypeSignature("U"))),
                        false),
                false,
                ImmutableList.of(
                        new FunctionArgumentDefinition(false),
                        new FunctionArgumentDefinition(false)),
                false,
                false,
                "Apply lambda to each element of the array",
                SCALAR));
    }

    @Override
    protected ScalarFunctionImplementation specialize(FunctionBinding functionBinding)
    {
        Type inputType = functionBinding.getTypeVariable("T");
        Type outputType = functionBinding.getTypeVariable("U");
        Class generatedClass = generateTransform(inputType, outputType);
        return new ChoicesScalarFunctionImplementation(
                functionBinding,
                FAIL_ON_NULL,
                ImmutableList.of(NEVER_NULL, FUNCTION),
                ImmutableList.of(UnaryFunctionInterface.class),
                methodHandle(generatedClass, "transform", PageBuilder.class, Block.class, UnaryFunctionInterface.class),
                Optional.of(methodHandle(generatedClass, "createPageBuilder")));
    }

    private static Class generateTransform(Type inputType, Type outputType)
    {
        CallSiteBinder binder = new CallSiteBinder();
        Class inputJavaType = Primitives.wrap(inputType.getJavaType());
        Class outputJavaType = Primitives.wrap(outputType.getJavaType());

        ClassDefinition definition = new ClassDefinition(
                a(PUBLIC, FINAL),
                makeClassName("ArrayTransform"),
                type(Object.class));
        definition.declareDefaultConstructor(a(PRIVATE));

        // define createPageBuilder
        MethodDefinition createPageBuilderMethod = definition.declareMethod(a(PUBLIC, STATIC), "createPageBuilder", type(PageBuilder.class));
        createPageBuilderMethod.getBody()
                .append(newInstance(PageBuilder.class, constantType(binder, new ArrayType(outputType)).invoke("getTypeParameters", List.class)).ret());

        // define transform method
        Parameter pageBuilder = arg("pageBuilder", PageBuilder.class);
        Parameter block = arg("block", Block.class);
        Parameter function = arg("function", UnaryFunctionInterface.class);

        MethodDefinition method = definition.declareMethod(
                a(PUBLIC, STATIC),
                "transform",
                type(Block.class),
                ImmutableList.of(pageBuilder, block, function));

        BytecodeBlock body = method.getBody();
        Scope scope = method.getScope();
        Variable positionCount = scope.declareVariable(int.class, "positionCount");
        Variable position = scope.declareVariable(int.class, "position");
        Variable blockBuilder = scope.declareVariable(BlockBuilder.class, "blockBuilder");
        Variable inputElement = scope.declareVariable(inputJavaType, "inputElement");
        Variable outputElement = scope.declareVariable(outputJavaType, "outputElement");

        // invoke block.getPositionCount()
        body.append(positionCount.set(block.invoke("getPositionCount", int.class)));

        // reset page builder if it is full
        body.append(new IfStatement()
                .condition(pageBuilder.invoke("isFull", boolean.class))
                .ifTrue(pageBuilder.invoke("reset", void.class)));

        // get block builder
        body.append(blockBuilder.set(pageBuilder.invoke("getBlockBuilder", BlockBuilder.class, constantInt(0))));

        BytecodeNode loadInputElement;
        if (!inputType.equals(UNKNOWN)) {
            loadInputElement = new IfStatement()
                    .condition(block.invoke("isNull", boolean.class, position))
                    .ifTrue(inputElement.set(constantNull(inputJavaType)))
                    .ifFalse(inputElement.set(constantType(binder, inputType).getValue(block, position).cast(inputJavaType)));
        }
        else {
            loadInputElement = new BytecodeBlock().append(inputElement.set(constantNull(inputJavaType)));
        }

        BytecodeNode writeOutputElement;
        if (!outputType.equals(UNKNOWN)) {
            writeOutputElement = new IfStatement()
                    .condition(equal(outputElement, constantNull(outputJavaType)))
                    .ifTrue(blockBuilder.invoke("appendNull", BlockBuilder.class).pop())
                    .ifFalse(constantType(binder, outputType).writeValue(blockBuilder, outputElement.cast(outputType.getJavaType())));
        }
        else {
            writeOutputElement = new BytecodeBlock().append(blockBuilder.invoke("appendNull", BlockBuilder.class).pop());
        }

        body.append(new ForLoop()
                .initialize(position.set(constantInt(0)))
                .condition(lessThan(position, positionCount))
                .update(incrementVariable(position, (byte) 1))
                .body(new BytecodeBlock()
                        .append(loadInputElement)
                        .append(outputElement.set(function.invoke("apply", Object.class, inputElement.cast(Object.class)).cast(outputJavaType)))
                        .append(writeOutputElement)));

        body.append(pageBuilder.invoke("declarePositions", void.class, positionCount));

        body.append(blockBuilder.invoke("getRegion", Block.class, subtract(blockBuilder.invoke("getPositionCount", int.class), positionCount), positionCount).ret());

        return defineClass(definition, Object.class, binder.getBindings(), ArrayTransformFunction.class.getClassLoader());
    }
}