/*
 * Copyright (C) 2013-2021 The Project Lombok Authors.
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
package lombok.eclipse.handlers;

import static lombok.core.handlers.HandlerUtil.handleFlagUsage;
import static lombok.eclipse.Eclipse.isPrimitive;
import static lombok.eclipse.handlers.EclipseHandlerUtil.*;

import java.util.Arrays;

import org.eclipse.jdt.internal.compiler.ast.ASTNode;
import org.eclipse.jdt.internal.compiler.ast.AbstractMethodDeclaration;
import org.eclipse.jdt.internal.compiler.ast.AbstractVariableDeclaration;
import org.eclipse.jdt.internal.compiler.ast.Annotation;
import org.eclipse.jdt.internal.compiler.ast.Argument;
import org.eclipse.jdt.internal.compiler.ast.AssertStatement;
import org.eclipse.jdt.internal.compiler.ast.Assignment;
import org.eclipse.jdt.internal.compiler.ast.Block;
import org.eclipse.jdt.internal.compiler.ast.EqualExpression;
import org.eclipse.jdt.internal.compiler.ast.Expression;
import org.eclipse.jdt.internal.compiler.ast.IfStatement;
import org.eclipse.jdt.internal.compiler.ast.MessageSend;
import org.eclipse.jdt.internal.compiler.ast.NullLiteral;
import org.eclipse.jdt.internal.compiler.ast.SingleNameReference;
import org.eclipse.jdt.internal.compiler.ast.Statement;
import org.eclipse.jdt.internal.compiler.ast.SynchronizedStatement;
import org.eclipse.jdt.internal.compiler.ast.ThrowStatement;
import org.eclipse.jdt.internal.compiler.ast.TryStatement;
import org.eclipse.jdt.internal.compiler.ast.TypeReference;

import lombok.ConfigurationKeys;
import lombok.NonNull;
import lombok.core.AST.Kind;
import lombok.core.AnnotationValues;
import lombok.core.HandlerPriority;
import lombok.eclipse.DeferUntilPostDiet;
import lombok.eclipse.EclipseAST;
import lombok.eclipse.EclipseAnnotationHandler;
import lombok.eclipse.EclipseNode;
import lombok.spi.Provides;

@DeferUntilPostDiet
@Provides
@HandlerPriority(value = 512) // 2^9; onParameter=@__(@NonNull) has to run first.
public class HandleNonNull extends EclipseAnnotationHandler<NonNull> {
	private static final char[] REQUIRE_NON_NULL = "requireNonNull".toCharArray();
	private static final char[] CHECK_NOT_NULL = "checkNotNull".toCharArray();
	
	public static final HandleNonNull INSTANCE = new HandleNonNull();
	
	public void fix(EclipseNode method) {
		for (EclipseNode m : method.down()) {
			if (m.getKind() != Kind.ARGUMENT) continue;
			for (EclipseNode c : m.down()) {
				if (c.getKind() == Kind.ANNOTATION) {
					if (annotationTypeMatches(NonNull.class, c)) {
						handle0((Annotation) c.get(), c, true);
					}
				}
			}
		}
	}
	
	@Override public void handle(AnnotationValues<NonNull> annotation, Annotation ast, EclipseNode annotationNode) {
		handle0(ast, annotationNode, false);
	}
	
	private void handle0(Annotation ast, EclipseNode annotationNode, boolean force) {
		handleFlagUsage(annotationNode, ConfigurationKeys.NON_NULL_FLAG_USAGE, "@NonNull");
		
		if (annotationNode.up().getKind() == Kind.FIELD) {
			// This is meaningless unless the field is used to generate a method (@Setter, @RequiredArgsConstructor, etc),
			// but in that case those handlers will take care of it. However, we DO check if the annotation is applied to
			// a primitive, because those handlers trigger on any annotation named @NonNull and we only want the warning
			// behaviour on _OUR_ 'lombok.NonNull'.
			
			try {
				if (isPrimitive(((AbstractVariableDeclaration) annotationNode.up().get()).type)) {
					annotationNode.addWarning("@NonNull is meaningless on a primitive.");
				}
			} catch (Exception ignore) {}
			
			return;
		}
		
		Argument param;
		EclipseNode paramNode;
		AbstractMethodDeclaration declaration;
		
		switch (annotationNode.up().getKind()) {
		case ARGUMENT:
			paramNode = annotationNode.up();
			break;
		case TYPE_USE:
			EclipseNode typeNode = annotationNode.directUp();
			boolean ok = false;
			ASTNode astNode = typeNode.get();
			if (astNode instanceof TypeReference) {
				Annotation[] anns = EclipseAST.getTopLevelTypeReferenceAnnotations((TypeReference) astNode);
				if (anns == null) return;
				for (Annotation ann : anns) if (ast == ann) ok = true;
			}
			if (!ok) return;
			paramNode = typeNode.directUp();
			break;
		default:
			return;
		}
		
		try {
			param = (Argument) paramNode.get();
			declaration = (AbstractMethodDeclaration) paramNode.up().get();
		} catch (Exception e) {
			return;
		}
		
		if (!force && isGenerated(declaration)) return;
		
		if (declaration.isAbstract()) {
			// This used to be a warning, but as @NonNull also has a documentary purpose, better to not warn about this. Since 1.16.7
			return;
		}
		
		// Possibly, if 'declaration instanceof ConstructorDeclaration', fetch declaration.constructorCall, search it for any references to our parameter,
		// and if they exist, create a new method in the class: 'private static <T> T lombok$nullCheck(T expr, String msg) {if (expr == null) throw NPE; return expr;}' and
		// wrap all references to it in the super/this to a call to this method.
		
		Statement nullCheck = generateNullCheck(param, annotationNode, null);
		
		if (nullCheck == null) {
			// @NonNull applied to a primitive. Kinda pointless. Let's generate a warning.
			annotationNode.addWarning("@NonNull is meaningless on a primitive.");
			return;
		}
		
		if (declaration.statements == null) {
			declaration.statements = new Statement[] {nullCheck};
		} else {
			char[] expectedName = param.name;
			/* Abort if the null check is already there, delving into try and synchronized statements */ {
				Statement[] stats = declaration.statements;
				int idx = 0;
				while (stats != null && stats.length > idx) {
					Statement stat = stats[idx++];
					if (stat instanceof TryStatement) {
						stats = ((TryStatement) stat).tryBlock.statements;
						idx = 0;
						continue;
					}
					if (stat instanceof SynchronizedStatement) {
						stats = ((SynchronizedStatement) stat).block.statements;
						idx = 0;
						continue;
					}
					char[] varNameOfNullCheck = returnVarNameIfNullCheck(stat);
					if (varNameOfNullCheck == null) break;
					if (Arrays.equals(varNameOfNullCheck, expectedName)) return;
				}
			}
			
			Statement[] newStatements = new Statement[declaration.statements.length + 1];
			int skipOver = 0;
			for (Statement stat : declaration.statements) {
				if (isGenerated(stat) && isNullCheck(stat)) skipOver++;
				else break;
			}
			System.arraycopy(declaration.statements, 0, newStatements, 0, skipOver);
			System.arraycopy(declaration.statements, skipOver, newStatements, skipOver + 1, declaration.statements.length - skipOver);
			newStatements[skipOver] = nullCheck;
			declaration.statements = newStatements;
		}
		paramNode.up().rebuild();
	}
	
	public boolean isNullCheck(Statement stat) {
		return returnVarNameIfNullCheck(stat) != null;
	}
	
	public char[] returnVarNameIfNullCheck(Statement stat) {
		boolean isIf = stat instanceof IfStatement;
		boolean isExpression = stat instanceof Expression;
		if (!isIf && !(stat instanceof AssertStatement) && !isExpression) return null;
		
		if (isExpression) {
			/* Check if the statements contains a call to checkNotNull or requireNonNull */
			Expression expression = (Expression) stat;
			if (expression instanceof Assignment) expression = ((Assignment) expression).expression;
			if (!(expression instanceof MessageSend)) return null;
			
			MessageSend invocation = (MessageSend) expression;
			if (!Arrays.equals(invocation.selector, CHECK_NOT_NULL) && !Arrays.equals(invocation.selector, REQUIRE_NON_NULL)) return null;
			if (invocation.arguments == null || invocation.arguments.length == 0) return null;
			Expression firstArgument = invocation.arguments[0];
			if (!(firstArgument instanceof SingleNameReference)) return null;
			return ((SingleNameReference) firstArgument).token;
		}
		
		if (isIf) {
			/* Check that the if's statement is a throw statement, possibly in a block. */
			Statement then = ((IfStatement) stat).thenStatement;
			if (then instanceof Block) {
				Statement[] blockStatements = ((Block) then).statements;
				if (blockStatements == null || blockStatements.length == 0) return null;
				then = blockStatements[0];
			}
			
			if (!(then instanceof ThrowStatement)) return null;
		}
		
		/* Check that the if's conditional is like 'x == null'. Return from this method (don't generate
		   a nullcheck) if 'x' is equal to our own variable's name: There's already a nullcheck here. */ {
			Expression cond = isIf ? ((IfStatement) stat).condition : ((AssertStatement) stat).assertExpression;
			if (!(cond instanceof EqualExpression)) return null;
			EqualExpression bin = (EqualExpression) cond;
			String op = bin.operatorToString();
			if (isIf) {
				if (!"==".equals(op)) return null;
			} else {
				if (!"!=".equals(op)) return null;
			}
			if (!(bin.left instanceof SingleNameReference)) return null;
			if (!(bin.right instanceof NullLiteral)) return null;
			return ((SingleNameReference) bin.left).token;
		}
	}
}