/*
 * Copyright 2002-2018 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
 *
 *      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.springframework.expression.spel.ast;

import java.lang.reflect.Array;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Modifier;
import java.util.ArrayList;
import java.util.List;

import org.springframework.asm.MethodVisitor;
import org.springframework.core.convert.TypeDescriptor;
import org.springframework.expression.AccessException;
import org.springframework.expression.ConstructorExecutor;
import org.springframework.expression.ConstructorResolver;
import org.springframework.expression.EvaluationContext;
import org.springframework.expression.EvaluationException;
import org.springframework.expression.TypeConverter;
import org.springframework.expression.TypedValue;
import org.springframework.expression.common.ExpressionUtils;
import org.springframework.expression.spel.CodeFlow;
import org.springframework.expression.spel.ExpressionState;
import org.springframework.expression.spel.SpelEvaluationException;
import org.springframework.expression.spel.SpelMessage;
import org.springframework.expression.spel.SpelNode;
import org.springframework.expression.spel.support.ReflectiveConstructorExecutor;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;

/**
 * Represents the invocation of a constructor. Either a constructor on a regular type or
 * construction of an array. When an array is constructed, an initializer can be specified.
 *
 * <p>Examples:<br>
 * new String('hello world')<br>
 * new int[]{1,2,3,4}<br>
 * new int[3] new int[3]{1,2,3}
 *
 * @author Andy Clement
 * @author Juergen Hoeller
 * @since 3.0
 */
public class ConstructorReference extends SpelNodeImpl {

	private boolean isArrayConstructor = false;

	@Nullable
	private SpelNodeImpl[] dimensions;

	// TODO is this caching safe - passing the expression around will mean this executor is also being passed around
	/** The cached executor that may be reused on subsequent evaluations */
	@Nullable
	private volatile ConstructorExecutor cachedExecutor;


	/**
	 * Create a constructor reference. The first argument is the type, the rest are the parameters to the constructor
	 * call
	 */
	public ConstructorReference(int pos, SpelNodeImpl... arguments) {
		super(pos, arguments);
		this.isArrayConstructor = false;
	}

	/**
	 * Create a constructor reference. The first argument is the type, the rest are the parameters to the constructor
	 * call
	 */
	public ConstructorReference(int pos, SpelNodeImpl[] dimensions, SpelNodeImpl... arguments) {
		super(pos, arguments);
		this.isArrayConstructor = true;
		this.dimensions = dimensions;
	}


	/**
	 * Implements getValue() - delegating to the code for building an array or a simple type.
	 */
	@Override
	public TypedValue getValueInternal(ExpressionState state) throws EvaluationException {
		if (this.isArrayConstructor) {
			return createArray(state);
		}
		else {
			return createNewInstance(state);
		}
	}

	/**
	 * Create a new ordinary object and return it.
	 * @param state the expression state within which this expression is being evaluated
	 * @return the new object
	 * @throws EvaluationException if there is a problem creating the object
	 */
	private TypedValue createNewInstance(ExpressionState state) throws EvaluationException {
		Object[] arguments = new Object[getChildCount() - 1];
		List<TypeDescriptor> argumentTypes = new ArrayList<>(getChildCount() - 1);
		for (int i = 0; i < arguments.length; i++) {
			TypedValue childValue = this.children[i + 1].getValueInternal(state);
			Object value = childValue.getValue();
			arguments[i] = value;
			argumentTypes.add(TypeDescriptor.forObject(value));
		}

		ConstructorExecutor executorToUse = this.cachedExecutor;
		if (executorToUse != null) {
			try {
				return executorToUse.execute(state.getEvaluationContext(), arguments);
			}
			catch (AccessException ex) {
				// Two reasons this can occur:
				// 1. the method invoked actually threw a real exception
				// 2. the method invoked was not passed the arguments it expected and has become 'stale'

				// In the first case we should not retry, in the second case we should see if there is a
				// better suited method.

				// To determine which situation it is, the AccessException will contain a cause.
				// If the cause is an InvocationTargetException, a user exception was thrown inside the constructor.
				// Otherwise the constructor could not be invoked.
				if (ex.getCause() instanceof InvocationTargetException) {
					// User exception was the root cause - exit now
					Throwable rootCause = ex.getCause().getCause();
					if (rootCause instanceof RuntimeException) {
						throw (RuntimeException) rootCause;
					}
					else {
						String typeName = (String) this.children[0].getValueInternal(state).getValue();
						throw new SpelEvaluationException(getStartPosition(), rootCause,
								SpelMessage.CONSTRUCTOR_INVOCATION_PROBLEM, typeName,
								FormatHelper.formatMethodForMessage("", argumentTypes));
					}
				}

				// At this point we know it wasn't a user problem so worth a retry if a better candidate can be found
				this.cachedExecutor = null;
			}
		}

		// Either there was no accessor or it no longer exists
		String typeName = (String) this.children[0].getValueInternal(state).getValue();
		Assert.state(typeName != null, "No type name");
		executorToUse = findExecutorForConstructor(typeName, argumentTypes, state);
		try {
			this.cachedExecutor = executorToUse;
			if (executorToUse instanceof ReflectiveConstructorExecutor) {
				this.exitTypeDescriptor = CodeFlow.toDescriptor(
						((ReflectiveConstructorExecutor) executorToUse).getConstructor().getDeclaringClass());
				
			}
			return executorToUse.execute(state.getEvaluationContext(), arguments);
		}
		catch (AccessException ex) {
			throw new SpelEvaluationException(getStartPosition(), ex,
					SpelMessage.CONSTRUCTOR_INVOCATION_PROBLEM, typeName,
					FormatHelper.formatMethodForMessage("", argumentTypes));
		}
	}

	/**
	 * Go through the list of registered constructor resolvers and see if any can find a
	 * constructor that takes the specified set of arguments.
	 * @param typeName the type trying to be constructed
	 * @param argumentTypes the types of the arguments supplied that the constructor must take
	 * @param state the current state of the expression
	 * @return a reusable ConstructorExecutor that can be invoked to run the constructor or null
	 * @throws SpelEvaluationException if there is a problem locating the constructor
	 */
	private ConstructorExecutor findExecutorForConstructor(String typeName,
			List<TypeDescriptor> argumentTypes, ExpressionState state) throws SpelEvaluationException {

		EvaluationContext evalContext = state.getEvaluationContext();
		List<ConstructorResolver> ctorResolvers = evalContext.getConstructorResolvers();
		for (ConstructorResolver ctorResolver : ctorResolvers) {
			try {
				ConstructorExecutor ce = ctorResolver.resolve(state.getEvaluationContext(), typeName, argumentTypes);
				if (ce != null) {
					return ce;
				}
			}
			catch (AccessException ex) {
				throw new SpelEvaluationException(getStartPosition(), ex,
						SpelMessage.CONSTRUCTOR_INVOCATION_PROBLEM, typeName,
						FormatHelper.formatMethodForMessage("", argumentTypes));
			}
		}
		throw new SpelEvaluationException(getStartPosition(), SpelMessage.CONSTRUCTOR_NOT_FOUND, typeName,
				FormatHelper.formatMethodForMessage("", argumentTypes));
	}

	@Override
	public String toStringAST() {
		StringBuilder sb = new StringBuilder("new ");
		int index = 0;
		sb.append(getChild(index++).toStringAST());
		sb.append("(");
		for (int i = index; i < getChildCount(); i++) {
			if (i > index) {
				sb.append(",");
			}
			sb.append(getChild(i).toStringAST());
		}
		sb.append(")");
		return sb.toString();
	}

	/**
	 * Create an array and return it.
	 * @param state the expression state within which this expression is being evaluated
	 * @return the new array
	 * @throws EvaluationException if there is a problem creating the array
	 */
	private TypedValue createArray(ExpressionState state) throws EvaluationException {
		// First child gives us the array type which will either be a primitive or reference type
		Object intendedArrayType = getChild(0).getValue(state);
		if (!(intendedArrayType instanceof String)) {
			throw new SpelEvaluationException(getChild(0).getStartPosition(),
					SpelMessage.TYPE_NAME_EXPECTED_FOR_ARRAY_CONSTRUCTION,
					FormatHelper.formatClassNameForMessage(
							intendedArrayType != null ? intendedArrayType.getClass() : null));
		}
		String type = (String) intendedArrayType;
		Class<?> componentType;
		TypeCode arrayTypeCode = TypeCode.forName(type);
		if (arrayTypeCode == TypeCode.OBJECT) {
			componentType = state.findType(type);
		}
		else {
			componentType = arrayTypeCode.getType();
		}
		Object newArray;
		if (!hasInitializer()) {
			// Confirm all dimensions were specified (for example [3][][5] is missing the 2nd dimension)
			if (this.dimensions != null) {
				for (SpelNodeImpl dimension : this.dimensions) {
					if (dimension == null) {
						throw new SpelEvaluationException(getStartPosition(), SpelMessage.MISSING_ARRAY_DIMENSION);
					}
				}
			}
			TypeConverter typeConverter = state.getEvaluationContext().getTypeConverter();

			// Shortcut for 1 dimensional
			if (this.dimensions.length == 1) {
				TypedValue o = this.dimensions[0].getTypedValue(state);
				int arraySize = ExpressionUtils.toInt(typeConverter, o);
				newArray = Array.newInstance(componentType, arraySize);
			}
			else {
				// Multi-dimensional - hold onto your hat!
				int[] dims = new int[this.dimensions.length];
				for (int d = 0; d < this.dimensions.length; d++) {
					TypedValue o = this.dimensions[d].getTypedValue(state);
					dims[d] = ExpressionUtils.toInt(typeConverter, o);
				}
				newArray = Array.newInstance(componentType, dims);
			}
		}
		else {
			// There is an initializer
			if (this.dimensions == null || this.dimensions.length > 1) {
				// There is an initializer but this is a multi-dimensional array (e.g. new int[][]{{1,2},{3,4}}) - this
				// is not currently supported
				throw new SpelEvaluationException(getStartPosition(),
						SpelMessage.MULTIDIM_ARRAY_INITIALIZER_NOT_SUPPORTED);
			}
			TypeConverter typeConverter = state.getEvaluationContext().getTypeConverter();
			InlineList initializer = (InlineList) getChild(1);
			// If a dimension was specified, check it matches the initializer length
			if (this.dimensions[0] != null) {
				TypedValue dValue = this.dimensions[0].getTypedValue(state);
				int i = ExpressionUtils.toInt(typeConverter, dValue);
				if (i != initializer.getChildCount()) {
					throw new SpelEvaluationException(getStartPosition(), SpelMessage.INITIALIZER_LENGTH_INCORRECT);
				}
			}
			// Build the array and populate it
			int arraySize = initializer.getChildCount();
			newArray = Array.newInstance(componentType, arraySize);
			if (arrayTypeCode == TypeCode.OBJECT) {
				populateReferenceTypeArray(state, newArray, typeConverter, initializer, componentType);
			}
			else if (arrayTypeCode == TypeCode.BOOLEAN) {
				populateBooleanArray(state, newArray, typeConverter, initializer);
			}
			else if (arrayTypeCode == TypeCode.BYTE) {
				populateByteArray(state, newArray, typeConverter, initializer);
			}
			else if (arrayTypeCode == TypeCode.CHAR) {
				populateCharArray(state, newArray, typeConverter, initializer);
			}
			else if (arrayTypeCode == TypeCode.DOUBLE) {
				populateDoubleArray(state, newArray, typeConverter, initializer);
			}
			else if (arrayTypeCode == TypeCode.FLOAT) {
				populateFloatArray(state, newArray, typeConverter, initializer);
			}
			else if (arrayTypeCode == TypeCode.INT) {
				populateIntArray(state, newArray, typeConverter, initializer);
			}
			else if (arrayTypeCode == TypeCode.LONG) {
				populateLongArray(state, newArray, typeConverter, initializer);
			}
			else if (arrayTypeCode == TypeCode.SHORT) {
				populateShortArray(state, newArray, typeConverter, initializer);
			}
			else {
				throw new IllegalStateException(arrayTypeCode.name());
			}
		}
		return new TypedValue(newArray);
	}

	private void populateReferenceTypeArray(ExpressionState state, Object newArray, TypeConverter typeConverter,
			InlineList initializer, Class<?> componentType) {

		TypeDescriptor toTypeDescriptor = TypeDescriptor.valueOf(componentType);
		Object[] newObjectArray = (Object[]) newArray;
		for (int i = 0; i < newObjectArray.length; i++) {
			SpelNode elementNode = initializer.getChild(i);
			Object arrayEntry = elementNode.getValue(state);
			newObjectArray[i] = typeConverter.convertValue(arrayEntry,
					TypeDescriptor.forObject(arrayEntry), toTypeDescriptor);
		}
	}

	private void populateByteArray(ExpressionState state, Object newArray, TypeConverter typeConverter,
			InlineList initializer) {

		byte[] newByteArray = (byte[]) newArray;
		for (int i = 0; i < newByteArray.length; i++) {
			TypedValue typedValue = initializer.getChild(i).getTypedValue(state);
			newByteArray[i] = ExpressionUtils.toByte(typeConverter, typedValue);
		}
	}

	private void populateFloatArray(ExpressionState state, Object newArray, TypeConverter typeConverter,
			InlineList initializer) {

		float[] newFloatArray = (float[]) newArray;
		for (int i = 0; i < newFloatArray.length; i++) {
			TypedValue typedValue = initializer.getChild(i).getTypedValue(state);
			newFloatArray[i] = ExpressionUtils.toFloat(typeConverter, typedValue);
		}
	}

	private void populateDoubleArray(ExpressionState state, Object newArray, TypeConverter typeConverter,
			InlineList initializer) {

		double[] newDoubleArray = (double[]) newArray;
		for (int i = 0; i < newDoubleArray.length; i++) {
			TypedValue typedValue = initializer.getChild(i).getTypedValue(state);
			newDoubleArray[i] = ExpressionUtils.toDouble(typeConverter, typedValue);
		}
	}

	private void populateShortArray(ExpressionState state, Object newArray, TypeConverter typeConverter,
			InlineList initializer) {

		short[] newShortArray = (short[]) newArray;
		for (int i = 0; i < newShortArray.length; i++) {
			TypedValue typedValue = initializer.getChild(i).getTypedValue(state);
			newShortArray[i] = ExpressionUtils.toShort(typeConverter, typedValue);
		}
	}

	private void populateLongArray(ExpressionState state, Object newArray, TypeConverter typeConverter,
			InlineList initializer) {

		long[] newLongArray = (long[]) newArray;
		for (int i = 0; i < newLongArray.length; i++) {
			TypedValue typedValue = initializer.getChild(i).getTypedValue(state);
			newLongArray[i] = ExpressionUtils.toLong(typeConverter, typedValue);
		}
	}

	private void populateCharArray(ExpressionState state, Object newArray, TypeConverter typeConverter,
			InlineList initializer) {

		char[] newCharArray = (char[]) newArray;
		for (int i = 0; i < newCharArray.length; i++) {
			TypedValue typedValue = initializer.getChild(i).getTypedValue(state);
			newCharArray[i] = ExpressionUtils.toChar(typeConverter, typedValue);
		}
	}

	private void populateBooleanArray(ExpressionState state, Object newArray, TypeConverter typeConverter,
			InlineList initializer) {

		boolean[] newBooleanArray = (boolean[]) newArray;
		for (int i = 0; i < newBooleanArray.length; i++) {
			TypedValue typedValue = initializer.getChild(i).getTypedValue(state);
			newBooleanArray[i] = ExpressionUtils.toBoolean(typeConverter, typedValue);
		}
	}

	private void populateIntArray(ExpressionState state, Object newArray, TypeConverter typeConverter,
			InlineList initializer) {

		int[] newIntArray = (int[]) newArray;
		for (int i = 0; i < newIntArray.length; i++) {
			TypedValue typedValue = initializer.getChild(i).getTypedValue(state);
			newIntArray[i] = ExpressionUtils.toInt(typeConverter, typedValue);
		}
	}

	private boolean hasInitializer() {
		return (getChildCount() > 1);
	}
	
	@Override
	public boolean isCompilable() {
		if (!(this.cachedExecutor instanceof ReflectiveConstructorExecutor) || 
			this.exitTypeDescriptor == null) {
			return false;
		}

		if (getChildCount() > 1) {
			for (int c = 1, max = getChildCount();c < max; c++) {
				if (!this.children[c].isCompilable()) {
					return false;
				}
			}
		}

		ReflectiveConstructorExecutor executor = (ReflectiveConstructorExecutor) this.cachedExecutor;
		if (executor == null) {
			return false;
		}
		Constructor<?> constructor = executor.getConstructor();
		return (Modifier.isPublic(constructor.getModifiers()) &&
				Modifier.isPublic(constructor.getDeclaringClass().getModifiers()));
	}
	
	@Override
	public void generateCode(MethodVisitor mv, CodeFlow cf) {
		ReflectiveConstructorExecutor executor = ((ReflectiveConstructorExecutor) this.cachedExecutor);
		Assert.state(executor != null, "No cached executor");

		Constructor<?> constructor = executor.getConstructor();
		String classDesc = constructor.getDeclaringClass().getName().replace('.', '/');
		mv.visitTypeInsn(NEW, classDesc);
		mv.visitInsn(DUP);

		// children[0] is the type of the constructor, don't want to include that in argument processing
		SpelNodeImpl[] arguments = new SpelNodeImpl[this.children.length - 1];
		System.arraycopy(this.children, 1, arguments, 0, this.children.length - 1);
		generateCodeForArguments(mv, cf, constructor, arguments);	
		mv.visitMethodInsn(INVOKESPECIAL, classDesc, "<init>", CodeFlow.createSignatureDescriptor(constructor), false);
		cf.pushDescriptor(this.exitTypeDescriptor);
	}

}
