/*
 * Copyright 2013-2021 the original author or authors.
 *
 * 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
 *
 *      https://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.springframework.data.mongodb.core.spel;

import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;

import org.springframework.expression.spel.ExpressionState;
import org.springframework.expression.spel.ast.*;

/**
 * An {@link ExpressionNode} representing an operator.
 *
 * @author Oliver Gierke
 * @author Thomas Darimont
 * @author Christoph Strobl
 * @author Mark Paluch
 */
public class OperatorNode extends ExpressionNode {

	private static final Map<String, String> OPERATORS;
	private static final Set<Class> SUPPORTED_MATH_OPERATORS;

	static {

		Map<String, String> map = new HashMap<String, String>(14, 1);

		map.put("+", "$add");
		map.put("-", "$subtract");
		map.put("*", "$multiply");
		map.put("/", "$divide");
		map.put("%", "$mod");
		map.put("^", "$pow");
		map.put("==", "$eq");
		map.put("!=", "$ne");
		map.put(">", "$gt");
		map.put(">=", "$gte");
		map.put("<", "$lt");
		map.put("<=", "$lte");

		map.put("and", "$and");
		map.put("or", "$or");

		OPERATORS = Collections.unmodifiableMap(map);

		Set<Class> set = new HashSet<Class>(12, 1);
		set.add(OpMinus.class);
		set.add(OpPlus.class);
		set.add(OpMultiply.class);
		set.add(OpDivide.class);
		set.add(OpModulus.class);
		set.add(OperatorPower.class);
		set.add(OpNE.class);
		set.add(OpEQ.class);
		set.add(OpGT.class);
		set.add(OpGE.class);
		set.add(OpLT.class);
		set.add(OpLE.class);

		SUPPORTED_MATH_OPERATORS = Collections.unmodifiableSet(set);
	}

	private final Operator operator;

	/**
	 * Creates a new {@link OperatorNode} from the given {@link Operator} and {@link ExpressionState}.
	 *
	 * @param node must not be {@literal null}.
	 * @param state must not be {@literal null}.
	 */
	OperatorNode(Operator node, ExpressionState state) {
		super(node, state);
		this.operator = node;
	}

	/*
	 * (non-Javadoc)
	 * @see org.springframework.data.mongodb.core.spel.ExpressionNode#isMathematicalOperation()
	 */
	@Override
	public boolean isMathematicalOperation() {
		return SUPPORTED_MATH_OPERATORS.contains(operator.getClass());
	}

	/*
	 * (non-Javadoc)
	 * @see org.springframework.data.mongodb.core.spel.ExpressionNode#isConjunctionOperator()
	 */
	@Override
	public boolean isLogicalOperator() {
		return operator instanceof OpOr || operator instanceof OpAnd;
	}

	/**
	 * Returns whether the operator is unary.
	 *
	 * @return
	 */
	public boolean isUnaryOperator() {
		return operator.getChildCount() == 1;
	}

	/**
	 * Returns the Mongo expression of the operator.
	 *
	 * @return
	 */
	public String getMongoOperator() {

		if (!OPERATORS.containsKey(operator.getOperatorName())) {
			throw new IllegalArgumentException(String.format(
					"Unknown operator name. Cannot translate %s into its MongoDB aggregation function representation.",
					operator.getOperatorName()));
		}

		return OPERATORS.get(operator.getOperatorName());
	}

	/**
	 * Returns whether the operator is a unary minus, e.g. -1.
	 *
	 * @return
	 */
	public boolean isUnaryMinus() {
		return isUnaryOperator() && operator instanceof OpMinus;
	}

	/**
	 * Returns the left operand as {@link ExpressionNode}.
	 *
	 * @return
	 */
	public ExpressionNode getLeft() {
		return from(operator.getLeftOperand());
	}

	/**
	 * Returns the right operand as {@link ExpressionNode}.
	 *
	 * @return
	 */
	public ExpressionNode getRight() {
		return from(operator.getRightOperand());
	}
}