/*
 * Copyright (C) 2013 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.javac.handlers;

import static lombok.javac.Javac.*;
import static lombok.javac.handlers.JavacHandlerUtil.*;

import org.mangosdk.spi.ProviderFor;

import com.sun.tools.javac.tree.JCTree.JCAnnotation;
import com.sun.tools.javac.tree.JCTree.JCBinary;
import com.sun.tools.javac.tree.JCTree.JCBlock;
import com.sun.tools.javac.tree.JCTree.JCExpression;
import com.sun.tools.javac.tree.JCTree.JCIdent;
import com.sun.tools.javac.tree.JCTree.JCIf;
import com.sun.tools.javac.tree.JCTree.JCLiteral;
import com.sun.tools.javac.tree.JCTree.JCMethodDecl;
import com.sun.tools.javac.tree.JCTree.JCParens;
import com.sun.tools.javac.tree.JCTree.JCStatement;
import com.sun.tools.javac.tree.JCTree.JCThrow;
import com.sun.tools.javac.tree.JCTree.JCVariableDecl;
import com.sun.tools.javac.util.List;

import lombok.NonNull;
import lombok.core.AnnotationValues;
import lombok.core.AST.Kind;
import lombok.javac.JavacAnnotationHandler;
import lombok.javac.JavacNode;

import static lombok.javac.JavacTreeMaker.TypeTag.*;
import static lombok.javac.JavacTreeMaker.TreeTag.*;

@ProviderFor(JavacAnnotationHandler.class)
public class NonNullHandler extends JavacAnnotationHandler<NonNull> {
	@Override public void handle(AnnotationValues<NonNull> annotation, JCAnnotation ast, JavacNode annotationNode) {
		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(((JCVariableDecl) annotationNode.up().get()).vartype)) {
					annotationNode.addWarning("@NonNull is meaningless on a primitive.");
				}
			} catch (Exception ignore) {}
			
			return;
		}
		
		if (annotationNode.up().getKind() != Kind.ARGUMENT) return;
		
		JCMethodDecl declaration;
		
		try {
			declaration = (JCMethodDecl) annotationNode.up().up().get();
		} catch (Exception e) {
			return;
		}
		
		if (JavacHandlerUtil.isGenerated(declaration)) 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.
		
		JCStatement nullCheck = recursiveSetGeneratedBy(generateNullCheck(annotationNode.getTreeMaker(), annotationNode.up()), ast);
		
		if (nullCheck == null) {
			// @NonNull applied to a primitive. Kinda pointless. Let's generate a warning.
			annotationNode.addWarning("@NonNull is meaningless on a primitive.");
			return;
		}
		
		List<JCStatement> statements = declaration.body.stats;
		
		String expectedName = annotationNode.up().getName();
		for (JCStatement stat : statements) {
			if (JavacHandlerUtil.isConstructorCall(stat)) continue;
			String varNameOfNullCheck = returnVarNameIfNullCheck(stat);
			if (varNameOfNullCheck == null) break;
			if (varNameOfNullCheck.equals(expectedName)) return;
		}
		
		List<JCStatement> tail = statements;
		List<JCStatement> head = List.nil();
		for (JCStatement stat : statements) {
			if (JavacHandlerUtil.isConstructorCall(stat) || JavacHandlerUtil.isGenerated(stat)) {
				tail = tail.tail;
				head = head.prepend(stat);
				continue;
			}
			break;
		}
		
		List<JCStatement> newList = tail.prepend(nullCheck);
		for (JCStatement stat : head) newList = newList.prepend(stat);
		declaration.body.stats = newList;
	}
	
	/**
	 * Checks if the statement is of the form 'if (x == null) {throw WHATEVER;},
	 * where the block braces are optional. If it is of this form, returns "x".
	 * If it is not of this form, returns null.
	 */
	private String returnVarNameIfNullCheck(JCStatement stat) {
		if (!(stat instanceof JCIf)) return null;
		
		/* Check that the if's statement is a throw statement, possibly in a block. */ {
			JCStatement then = ((JCIf) stat).thenpart;
			if (then instanceof JCBlock) {
				List<JCStatement> stats = ((JCBlock) then).stats;
				if (stats.length() == 0) return null;
				then = stats.get(0);
			}
			if (!(then instanceof JCThrow)) 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. */ {
			JCExpression cond = ((JCIf) stat).cond;
			while (cond instanceof JCParens) cond = ((JCParens) cond).expr;
			if (!(cond instanceof JCBinary)) return null;
			JCBinary bin = (JCBinary) cond;
			if (!CTC_EQUAL.equals(treeTag(bin))) return null;
			if (!(bin.lhs instanceof JCIdent)) return null;
			if (!(bin.rhs instanceof JCLiteral)) return null;
			if (!CTC_BOT.equals(typeTag(bin.rhs))) return null;
			return ((JCIdent) bin.lhs).name.toString();
		}
	}
}