/*
 * 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 org.apache.storm.sql.compiler;

import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.Lists;
import org.apache.calcite.adapter.enumerable.JavaRowFormat;
import org.apache.calcite.adapter.enumerable.PhysType;
import org.apache.calcite.adapter.enumerable.PhysTypeImpl;
import org.apache.calcite.adapter.enumerable.RexToLixTranslator;
import org.apache.calcite.interpreter.Context;
import org.apache.calcite.jdbc.JavaTypeFactoryImpl;
import org.apache.calcite.linq4j.function.Function1;
import org.apache.calcite.linq4j.tree.BlockBuilder;
import org.apache.calcite.linq4j.tree.BlockStatement;
import org.apache.calcite.linq4j.tree.ClassDeclaration;
import org.apache.calcite.linq4j.tree.Expression;
import org.apache.calcite.linq4j.tree.Expressions;
import org.apache.calcite.linq4j.tree.MemberDeclaration;
import org.apache.calcite.linq4j.tree.ParameterExpression;
import org.apache.calcite.linq4j.tree.Types;
import org.apache.calcite.rel.type.RelDataType;
import org.apache.calcite.rex.RexBuilder;
import org.apache.calcite.rex.RexNode;
import org.apache.calcite.rex.RexProgram;
import org.apache.calcite.rex.RexProgramBuilder;
import org.apache.calcite.util.BuiltInMethod;
import org.apache.calcite.util.Pair;
import org.apache.storm.sql.runtime.calcite.ExecutableExpression;

import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.lang.reflect.Type;
import java.util.List;

/**
 * Compiles a scalar expression ({@link org.apache.calcite.rex.RexNode}) to Java source code String.
 *
 * This code is inspired by JaninoRexCompiler in Calcite, but while it is returning {@link org.apache.calcite.interpreter.Scalar} which is executable,
 * we need to pass the source code to compile and serialize instance so that it can be executed on worker efficiently.
 */
public class RexNodeToJavaCodeCompiler {
  private final RexBuilder rexBuilder;

  public RexNodeToJavaCodeCompiler(RexBuilder rexBuilder) {
    this.rexBuilder = rexBuilder;
  }

  public BlockStatement compileToBlock(List<RexNode> nodes, RelDataType inputRowType) {
    final RexProgramBuilder programBuilder =
        new RexProgramBuilder(inputRowType, rexBuilder);
    for (RexNode node : nodes) {
      programBuilder.addProject(node, null);
    }

    return compileToBlock(programBuilder.getProgram());
  }

  public BlockStatement compileToBlock(final RexProgram program) {
    final ParameterExpression context_ =
            Expressions.parameter(Context.class, "context");
    final ParameterExpression outputValues_ =
            Expressions.parameter(Object[].class, "outputValues");

    return compileToBlock(program, context_, outputValues_).toBlock();
  }

  public String compile(List<RexNode> nodes, RelDataType inputRowType, String className) {
    final RexProgramBuilder programBuilder =
            new RexProgramBuilder(inputRowType, rexBuilder);
    for (RexNode node : nodes) {
      programBuilder.addProject(node, null);
    }

    return compile(programBuilder.getProgram(), className);
  }

  public String compile(final RexProgram program, String className) {
    final ParameterExpression context_ =
            Expressions.parameter(Context.class, "context");
    final ParameterExpression outputValues_ =
            Expressions.parameter(Object[].class, "outputValues");

    BlockBuilder builder = compileToBlock(program, context_, outputValues_);
    return baz(context_, outputValues_, builder.toBlock(), className);
  }

  private BlockBuilder compileToBlock(final RexProgram program, ParameterExpression context_,
                                        ParameterExpression outputValues_) {
    RelDataType inputRowType = program.getInputRowType();
    final BlockBuilder builder = new BlockBuilder();
    final JavaTypeFactoryImpl javaTypeFactory =
            new JavaTypeFactoryImpl(rexBuilder.getTypeFactory().getTypeSystem());

    final RexToLixTranslator.InputGetter inputGetter =
            new RexToLixTranslator.InputGetterImpl(
                    ImmutableList.of(
                            Pair.<Expression, PhysType>of(
                                    Expressions.field(context_,
                                            BuiltInMethod.CONTEXT_VALUES.field),
                                    PhysTypeImpl.of(javaTypeFactory, inputRowType,
                                            JavaRowFormat.ARRAY, false))));
    final Function1<String, RexToLixTranslator.InputGetter> correlates =
            new Function1<String, RexToLixTranslator.InputGetter>() {
              public RexToLixTranslator.InputGetter apply(String a0) {
                throw new UnsupportedOperationException();
              }
            };
    final Expression root =
            Expressions.field(context_, BuiltInMethod.CONTEXT_ROOT.field);
    final List<Expression> list =
            RexToLixTranslator.translateProjects(program, javaTypeFactory, builder,
                    null, root, inputGetter, correlates);
    for (int i = 0; i < list.size(); i++) {
      builder.add(
              Expressions.statement(
                      Expressions.assign(
                              Expressions.arrayIndex(outputValues_,
                                      Expressions.constant(i)),
                              list.get(i))));
    }

    return builder;
  }

  /** Given a method that implements {@link ExecutableExpression#execute(Context, Object[])},
   * adds a bridge method that implements {@link ExecutableExpression#execute(Context)}, and
   * compiles. */
  static String baz(ParameterExpression context_,
                    ParameterExpression outputValues_, BlockStatement block, String className) {
    final List<MemberDeclaration> declarations = Lists.newArrayList();

    // public void execute(Context, Object[] outputValues)
    declarations.add(
            Expressions.methodDecl(Modifier.PUBLIC, void.class,
                    StormBuiltInMethod.EXPR_EXECUTE2.method.getName(),
                    ImmutableList.of(context_, outputValues_), block));

    // public Object execute(Context)
    final BlockBuilder builder = new BlockBuilder();
    final Expression values_ = builder.append("values",
            Expressions.newArrayBounds(Object.class, 1,
                    Expressions.constant(1)));
    builder.add(
            Expressions.statement(
                    Expressions.call(
                            Expressions.parameter(ExecutableExpression.class, "this"),
                            StormBuiltInMethod.EXPR_EXECUTE2.method, context_, values_)));
    builder.add(
            Expressions.return_(null,
                    Expressions.arrayIndex(values_, Expressions.constant(0))));
    declarations.add(
            Expressions.methodDecl(Modifier.PUBLIC, Object.class,
                    StormBuiltInMethod.EXPR_EXECUTE1.method.getName(),
                    ImmutableList.of(context_), builder.toBlock()));

    final ClassDeclaration classDeclaration =
            Expressions.classDecl(Modifier.PUBLIC, className, null,
                    ImmutableList.<Type>of(ExecutableExpression.class), declarations);

    return Expressions.toString(Lists.newArrayList(classDeclaration), "\n", false);
  }

  enum StormBuiltInMethod {
    EXPR_EXECUTE1(ExecutableExpression.class, "execute", Context.class),
    EXPR_EXECUTE2(ExecutableExpression.class, "execute", Context.class, Object[].class);

    public final Method method;
    public final Constructor constructor;
    public final Field field;

    public static final ImmutableMap<Method, BuiltInMethod> MAP;

    static {
      final ImmutableMap.Builder<Method, BuiltInMethod> builder =
              ImmutableMap.builder();
      for (BuiltInMethod value : BuiltInMethod.values()) {
        if (value.method != null) {
          builder.put(value.method, value);
        }
      }
      MAP = builder.build();
    }

    private StormBuiltInMethod(Method method, Constructor constructor, Field field) {
      this.method = method;
      this.constructor = constructor;
      this.field = field;
    }

    /**
     * Defines a method.
     */
    StormBuiltInMethod(Class clazz, String methodName, Class... argumentTypes) {
      this(Types.lookupMethod(clazz, methodName, argumentTypes), null, null);
    }

    /**
     * Defines a constructor.
     */
    StormBuiltInMethod(Class clazz, Class... argumentTypes) {
      this(null, Types.lookupConstructor(clazz, argumentTypes), null);
    }

    /**
     * Defines a field.
     */
    StormBuiltInMethod(Class clazz, String fieldName, boolean dummy) {
      this(null, null, Types.lookupField(clazz, fieldName));
      assert dummy : "dummy value for method overloading must be true";
    }
  }

}