/*
 * Copyright 2002-2019 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.expression.spel.ast;

import java.math.BigDecimal;
import java.math.BigInteger;

import org.springframework.asm.Label;
import org.springframework.asm.MethodVisitor;
import org.springframework.expression.EvaluationContext;
import org.springframework.expression.spel.CodeFlow;
import org.springframework.lang.Nullable;
import org.springframework.util.ClassUtils;
import org.springframework.util.NumberUtils;
import org.springframework.util.ObjectUtils;

Common supertype for operators that operate on either one or two operands.
In the case of multiply or divide there would be two operands, but for
unary plus or minus, there is only one.
Author:
Andy Clement, Juergen Hoeller, Giovanni Dall'Oglio Risso
Since:
3.0/**
 * Common supertype for operators that operate on either one or two operands.
 * In the case of multiply or divide there would be two operands, but for
 * unary plus or minus, there is only one.
 *
 * @author Andy Clement
 * @author Juergen Hoeller
 * @author Giovanni Dall'Oglio Risso
 * @since 3.0
 */
public abstract class Operator extends SpelNodeImpl {

	private final String operatorName;

	// The descriptors of the runtime operand values are used if the discovered declared
	// descriptors are not providing enough information (for example a generic type
	// whose accessors seem to only be returning 'Object' - the actual descriptors may
	// indicate 'int')

	@Nullable
	protected String leftActualDescriptor;

	@Nullable
	protected String rightActualDescriptor;


	public Operator(String payload, int startPos, int endPos, SpelNodeImpl... operands) {
		super(startPos, endPos, operands);
		this.operatorName = payload;
	}


	public SpelNodeImpl getLeftOperand() {
		return this.children[0];
	}

	public SpelNodeImpl getRightOperand() {
		return this.children[1];
	}

	public final String getOperatorName() {
		return this.operatorName;
	}

	
String format for all operators is the same '(' [operand] [operator] [operand] ')'. /**
	 * String format for all operators is the same
	 * {@code '(' [operand] [operator] [operand] ')'}.
	 */
	@Override
	public String toStringAST() {
		StringBuilder sb = new StringBuilder("(");
		sb.append(getChild(0).toStringAST());
		for (int i = 1; i < getChildCount(); i++) {
			sb.append(" ").append(getOperatorName()).append(" ");
			sb.append(getChild(i).toStringAST());
		}
		sb.append(")");
		return sb.toString();
	}


	protected boolean isCompilableOperatorUsingNumerics() {
		SpelNodeImpl left = getLeftOperand();
		SpelNodeImpl right = getRightOperand();
		if (!left.isCompilable() || !right.isCompilable()) {
			return false;
		}

		// Supported operand types for equals (at the moment)
		String leftDesc = left.exitTypeDescriptor;
		String rightDesc = right.exitTypeDescriptor;
		DescriptorComparison dc = DescriptorComparison.checkNumericCompatibility(
				leftDesc, rightDesc, this.leftActualDescriptor, this.rightActualDescriptor);
		return (dc.areNumbers && dc.areCompatible);
	}

	
Numeric comparison operators share very similar generated code, only differing in
two comparison instructions.
/**
	 * Numeric comparison operators share very similar generated code, only differing in
	 * two comparison instructions.
	 */
	protected void generateComparisonCode(MethodVisitor mv, CodeFlow cf, int compInstruction1, int compInstruction2) {
		SpelNodeImpl left = getLeftOperand();
		SpelNodeImpl right = getRightOperand();
		String leftDesc = left.exitTypeDescriptor;
		String rightDesc = right.exitTypeDescriptor;
		Label elseTarget = new Label();
		Label endOfIf = new Label();
		boolean unboxLeft = !CodeFlow.isPrimitive(leftDesc);
		boolean unboxRight = !CodeFlow.isPrimitive(rightDesc);
		DescriptorComparison dc = DescriptorComparison.checkNumericCompatibility(
				leftDesc, rightDesc, this.leftActualDescriptor, this.rightActualDescriptor);
		char targetType = dc.compatibleType;  // CodeFlow.toPrimitiveTargetDesc(leftDesc);

		cf.enterCompilationScope();
		left.generateCode(mv, cf);
		cf.exitCompilationScope();
		if (CodeFlow.isPrimitive(leftDesc)) {
			CodeFlow.insertBoxIfNecessary(mv, leftDesc);
			unboxLeft = true;
		}

		cf.enterCompilationScope();
		right.generateCode(mv, cf);
		cf.exitCompilationScope();
		if (CodeFlow.isPrimitive(rightDesc)) {
			CodeFlow.insertBoxIfNecessary(mv, rightDesc);
			unboxRight = true;
		}

		// This code block checks whether the left or right operand is null and handles
		// those cases before letting the original code (that only handled actual numbers) run
		Label rightIsNonNull = new Label();
		mv.visitInsn(DUP);  // stack: left/right/right
		mv.visitJumpInsn(IFNONNULL, rightIsNonNull);  // stack: left/right
		// here: RIGHT==null LEFT==unknown
		mv.visitInsn(SWAP);  // right/left
		Label leftNotNullRightIsNull = new Label();
		mv.visitJumpInsn(IFNONNULL, leftNotNullRightIsNull);  // stack: right
		// here: RIGHT==null LEFT==null
		mv.visitInsn(POP);  // stack: <nothing>
		// load 0 or 1 depending on comparison instruction
		switch (compInstruction1) {
		case IFGE: // OpLT
		case IFLE: // OpGT
			mv.visitInsn(ICONST_0);  // false - null is not < or > null
			break;
		case IFGT: // OpLE
		case IFLT: // OpGE
			mv.visitInsn(ICONST_1);  // true - null is <= or >= null
			break;
		default:
			throw new IllegalStateException("Unsupported: " + compInstruction1);
		}
		mv.visitJumpInsn(GOTO, endOfIf);
		mv.visitLabel(leftNotNullRightIsNull);  // stack: right
		// RIGHT==null LEFT!=null
		mv.visitInsn(POP);  // stack: <nothing>
		// load 0 or 1 depending on comparison instruction
		switch (compInstruction1) {
		case IFGE: // OpLT
		case IFGT: // OpLE
			mv.visitInsn(ICONST_0);  // false - something is not < or <= null
			break;
		case IFLE: // OpGT
		case IFLT: // OpGE
			mv.visitInsn(ICONST_1);  // true - something is > or >= null
			break;
		default:
			throw new IllegalStateException("Unsupported: " + compInstruction1);
		}
		mv.visitJumpInsn(GOTO, endOfIf);

		mv.visitLabel(rightIsNonNull);  // stack: left/right
		// here: RIGHT!=null LEFT==unknown
		mv.visitInsn(SWAP);  // stack: right/left
		mv.visitInsn(DUP);  // stack: right/left/left
		Label neitherRightNorLeftAreNull = new Label();
		mv.visitJumpInsn(IFNONNULL, neitherRightNorLeftAreNull);  // stack: right/left
		// here: RIGHT!=null LEFT==null
		mv.visitInsn(POP2);  // stack: <nothing>
		switch (compInstruction1) {
		case IFGE: // OpLT
		case IFGT: // OpLE
			mv.visitInsn(ICONST_1);  // true - null is < or <= something
			break;
		case IFLE: // OpGT
		case IFLT: // OpGE
			mv.visitInsn(ICONST_0);  // false - null is not > or >= something
			break;
		default:
			throw new IllegalStateException("Unsupported: " + compInstruction1);
		}
		mv.visitJumpInsn(GOTO, endOfIf);
		mv.visitLabel(neitherRightNorLeftAreNull);  // stack: right/left
		// neither were null so unbox and proceed with numeric comparison
		if (unboxLeft) {
			CodeFlow.insertUnboxInsns(mv, targetType, leftDesc);
		}
		// What we just unboxed might be a double slot item (long/double)
		// so can't just use SWAP
		// stack: right/left(1or2slots)
		if (targetType == 'D' || targetType == 'J') {
			mv.visitInsn(DUP2_X1);
			mv.visitInsn(POP2);
		}
		else {
			mv.visitInsn(SWAP);
		}
		// stack: left(1or2)/right
		if (unboxRight) {
			CodeFlow.insertUnboxInsns(mv, targetType, rightDesc);
		}

		// assert: SpelCompiler.boxingCompatible(leftDesc, rightDesc)
		if (targetType == 'D') {
			mv.visitInsn(DCMPG);
			mv.visitJumpInsn(compInstruction1, elseTarget);
		}
		else if (targetType == 'F') {
			mv.visitInsn(FCMPG);
			mv.visitJumpInsn(compInstruction1, elseTarget);
		}
		else if (targetType == 'J') {
			mv.visitInsn(LCMP);
			mv.visitJumpInsn(compInstruction1, elseTarget);
		}
		else if (targetType == 'I') {
			mv.visitJumpInsn(compInstruction2, elseTarget);
		}
		else {
			throw new IllegalStateException("Unexpected descriptor " + leftDesc);
		}

		// Other numbers are not yet supported (isCompilable will not have returned true)
		mv.visitInsn(ICONST_1);
		mv.visitJumpInsn(GOTO,endOfIf);
		mv.visitLabel(elseTarget);
		mv.visitInsn(ICONST_0);
		mv.visitLabel(endOfIf);
		cf.pushDescriptor("Z");
	}


	
Perform an equality check for the given operand values.
This method is not just used for reflective comparisons in subclasses but also from compiled expression code, which is why it needs to be declared as public static here. 
Params:
context – the current evaluation context
left – the left-hand operand value
right – the right-hand operand value/**
	 * Perform an equality check for the given operand values.
	 * <p>This method is not just used for reflective comparisons in subclasses
	 * but also from compiled expression code, which is why it needs to be
	 * declared as {@code public static} here.
	 * @param context the current evaluation context
	 * @param left the left-hand operand value
	 * @param right the right-hand operand value
	 */
	public static boolean equalityCheck(EvaluationContext context, @Nullable Object left, @Nullable Object right) {
		if (left instanceof Number && right instanceof Number) {
			Number leftNumber = (Number) left;
			Number rightNumber = (Number) right;

			if (leftNumber instanceof BigDecimal || rightNumber instanceof BigDecimal) {
				BigDecimal leftBigDecimal = NumberUtils.convertNumberToTargetClass(leftNumber, BigDecimal.class);
				BigDecimal rightBigDecimal = NumberUtils.convertNumberToTargetClass(rightNumber, BigDecimal.class);
				return (leftBigDecimal.compareTo(rightBigDecimal) == 0);
			}
			else if (leftNumber instanceof Double || rightNumber instanceof Double) {
				return (leftNumber.doubleValue() == rightNumber.doubleValue());
			}
			else if (leftNumber instanceof Float || rightNumber instanceof Float) {
				return (leftNumber.floatValue() == rightNumber.floatValue());
			}
			else if (leftNumber instanceof BigInteger || rightNumber instanceof BigInteger) {
				BigInteger leftBigInteger = NumberUtils.convertNumberToTargetClass(leftNumber, BigInteger.class);
				BigInteger rightBigInteger = NumberUtils.convertNumberToTargetClass(rightNumber, BigInteger.class);
				return (leftBigInteger.compareTo(rightBigInteger) == 0);
			}
			else if (leftNumber instanceof Long || rightNumber instanceof Long) {
				return (leftNumber.longValue() == rightNumber.longValue());
			}
			else if (leftNumber instanceof Integer || rightNumber instanceof Integer) {
				return (leftNumber.intValue() == rightNumber.intValue());
			}
			else if (leftNumber instanceof Short || rightNumber instanceof Short) {
				return (leftNumber.shortValue() == rightNumber.shortValue());
			}
			else if (leftNumber instanceof Byte || rightNumber instanceof Byte) {
				return (leftNumber.byteValue() == rightNumber.byteValue());
			}
			else {
				// Unknown Number subtypes -> best guess is double comparison
				return (leftNumber.doubleValue() == rightNumber.doubleValue());
			}
		}

		if (left instanceof CharSequence && right instanceof CharSequence) {
			return left.toString().equals(right.toString());
		}

		if (left instanceof Boolean && right instanceof Boolean) {
			return left.equals(right);
		}

		if (ObjectUtils.nullSafeEquals(left, right)) {
			return true;
		}

		if (left instanceof Comparable && right instanceof Comparable) {
			Class<?> ancestor = ClassUtils.determineCommonAncestor(left.getClass(), right.getClass());
			if (ancestor != null && Comparable.class.isAssignableFrom(ancestor)) {
				return (context.getTypeComparator().compare(left, right) == 0);
			}
		}

		return false;
	}


	
A descriptor comparison encapsulates the result of comparing descriptor
for two operands and describes at what level they are compatible.
/**
	 * A descriptor comparison encapsulates the result of comparing descriptor
	 * for two operands and describes at what level they are compatible.
	 */
	protected static final class DescriptorComparison {

		static final DescriptorComparison NOT_NUMBERS = new DescriptorComparison(false, false, ' ');

		static final DescriptorComparison INCOMPATIBLE_NUMBERS = new DescriptorComparison(true, false, ' ');

		final boolean areNumbers;  // Were the two compared descriptor both for numbers?

		final boolean areCompatible;  // If they were numbers, were they compatible?

		final char compatibleType;  // When compatible, what is the descriptor of the common type

		private DescriptorComparison(boolean areNumbers, boolean areCompatible, char compatibleType) {
			this.areNumbers = areNumbers;
			this.areCompatible = areCompatible;
			this.compatibleType = compatibleType;
		}

		
Return an object that indicates whether the input descriptors are compatible.
A declared descriptor is what could statically be determined (e.g. from looking
at the return value of a property accessor method) whilst an actual descriptor
is the type of an actual object that was returned, which may differ.
For generic types with unbound type variables, the declared descriptor
discovered may be 'Object' but from the actual descriptor it is possible to
observe that the objects are really numeric values (e.g. ints).
Params:
leftDeclaredDescriptor – the statically determinable left descriptor
rightDeclaredDescriptor – the statically determinable right descriptor
leftActualDescriptor – the dynamic/runtime left object descriptor
rightActualDescriptor – the dynamic/runtime right object descriptor
Returns:
a DescriptorComparison object indicating the type of compatibility, if any/**
		 * Return an object that indicates whether the input descriptors are compatible.
		 * <p>A declared descriptor is what could statically be determined (e.g. from looking
		 * at the return value of a property accessor method) whilst an actual descriptor
		 * is the type of an actual object that was returned, which may differ.
		 * <p>For generic types with unbound type variables, the declared descriptor
		 * discovered may be 'Object' but from the actual descriptor it is possible to
		 * observe that the objects are really numeric values (e.g. ints).
		 * @param leftDeclaredDescriptor the statically determinable left descriptor
		 * @param rightDeclaredDescriptor the statically determinable right descriptor
		 * @param leftActualDescriptor the dynamic/runtime left object descriptor
		 * @param rightActualDescriptor the dynamic/runtime right object descriptor
		 * @return a DescriptorComparison object indicating the type of compatibility, if any
		 */
		public static DescriptorComparison checkNumericCompatibility(
				@Nullable String leftDeclaredDescriptor, @Nullable String rightDeclaredDescriptor,
				@Nullable String leftActualDescriptor, @Nullable String rightActualDescriptor) {

			String ld = leftDeclaredDescriptor;
			String rd = rightDeclaredDescriptor;

			boolean leftNumeric = CodeFlow.isPrimitiveOrUnboxableSupportedNumberOrBoolean(ld);
			boolean rightNumeric = CodeFlow.isPrimitiveOrUnboxableSupportedNumberOrBoolean(rd);

			// If the declared descriptors aren't providing the information, try the actual descriptors
			if (!leftNumeric && !ObjectUtils.nullSafeEquals(ld, leftActualDescriptor)) {
				ld = leftActualDescriptor;
				leftNumeric = CodeFlow.isPrimitiveOrUnboxableSupportedNumberOrBoolean(ld);
			}
			if (!rightNumeric && !ObjectUtils.nullSafeEquals(rd, rightActualDescriptor)) {
				rd = rightActualDescriptor;
				rightNumeric = CodeFlow.isPrimitiveOrUnboxableSupportedNumberOrBoolean(rd);
			}

			if (leftNumeric && rightNumeric) {
				if (CodeFlow.areBoxingCompatible(ld, rd)) {
					return new DescriptorComparison(true, true, CodeFlow.toPrimitiveTargetDesc(ld));
				}
				else {
					return DescriptorComparison.INCOMPATIBLE_NUMBERS;
				}
			}
			else {
				return DescriptorComparison.NOT_NUMBERS;
			}
		}
	}

}