/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.facebook.presto.bytecode;

import java.util.List;
import com.facebook.presto.bytecode.expression.BytecodeExpression;
import com.facebook.presto.bytecode.instruction.VariableInstruction;

import static com.facebook.presto.bytecode.ParameterizedType.type;
import static com.facebook.presto.bytecode.expression.BytecodeExpressions.add;
import static com.facebook.presto.bytecode.expression.BytecodeExpressions.constantInt;
import static java.util.Objects.requireNonNull;

public class Variable
    extends BytecodeExpression {
    private final String name;

    public Variable(String name, ParameterizedType type) {
        super(type);
        this.name = requireNonNull(name, "name is null");
    }

    public String getName() {
        return name;
    }

    public BytecodeExpression set(BytecodeExpression value) {
        return new SetVariableBytecodeExpression(this, value);
    }

    public BytecodeExpression increment() {
        return new SetVariableBytecodeExpression(this, add(this, constantInt(1)));
    }

    @Override
    public BytecodeNode getBytecode(MethodGenerationContext generationContext) {
        return VariableInstruction.loadVariable(this);
    }

    @Override
    protected String formatOneLine() {
        return name;
    }

    @Override
    public List<BytecodeNode> getChildNodes() {
        return List.of();
    }

    private static final class SetVariableBytecodeExpression
        extends BytecodeExpression {
        private final Variable variable;
        private final BytecodeExpression value;

        SetVariableBytecodeExpression(Variable variable, BytecodeExpression value) {
            super(type(void.class));
            this.variable = requireNonNull(variable, "variable is null");
            this.value = requireNonNull(value, "value is null");
        }

        @Override
        public BytecodeNode getBytecode(MethodGenerationContext generationContext) {
            return new BytecodeBlock()
                .append(value)
                .putVariable(variable);
        }

        @Override
        public List<BytecodeNode> getChildNodes() {
            return List.of(value);
        }

        @Override
        protected String formatOneLine() {
            return variable.getName() + " = " + value;
        }
    }
}
