/*

 * Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package jdk.nashorn.internal.codegen;

import static jdk.nashorn.internal.codegen.CompilerConstants.EVAL;

import static jdk.nashorn.internal.codegen.CompilerConstants.RETURN;

import static jdk.nashorn.internal.ir.Expression.isAlwaysTrue;

import java.util.ArrayList;

import java.util.Arrays;

import java.util.Collections;

import java.util.List;

import java.util.ListIterator;

import jdk.nashorn.internal.ir.BaseNode;

import jdk.nashorn.internal.ir.BinaryNode;

import jdk.nashorn.internal.ir.Block;

import jdk.nashorn.internal.ir.BlockLexicalContext;

import jdk.nashorn.internal.ir.BlockStatement;

import jdk.nashorn.internal.ir.BreakNode;

import jdk.nashorn.internal.ir.CallNode;

import jdk.nashorn.internal.ir.CaseNode;

import jdk.nashorn.internal.ir.CatchNode;

import jdk.nashorn.internal.ir.ContinueNode;

import jdk.nashorn.internal.ir.EmptyNode;

import jdk.nashorn.internal.ir.Expression;

import jdk.nashorn.internal.ir.ExpressionStatement;

import jdk.nashorn.internal.ir.ForNode;

import jdk.nashorn.internal.ir.FunctionNode;

import jdk.nashorn.internal.ir.FunctionNode.CompilationState;

import jdk.nashorn.internal.ir.IdentNode;

import jdk.nashorn.internal.ir.IfNode;

import jdk.nashorn.internal.ir.LabelNode;

import jdk.nashorn.internal.ir.LexicalContext;

import jdk.nashorn.internal.ir.LiteralNode;

import jdk.nashorn.internal.ir.LoopNode;

import jdk.nashorn.internal.ir.Node;

import jdk.nashorn.internal.ir.ReturnNode;

import jdk.nashorn.internal.ir.RuntimeNode;

import jdk.nashorn.internal.ir.Statement;

import jdk.nashorn.internal.ir.SwitchNode;

import jdk.nashorn.internal.ir.Symbol;

import jdk.nashorn.internal.ir.ThrowNode;

import jdk.nashorn.internal.ir.TryNode;

import jdk.nashorn.internal.ir.VarNode;

import jdk.nashorn.internal.ir.WhileNode;

import jdk.nashorn.internal.ir.WithNode;

import jdk.nashorn.internal.ir.visitor.NodeOperatorVisitor;

import jdk.nashorn.internal.ir.visitor.NodeVisitor;

import jdk.nashorn.internal.parser.Token;

import jdk.nashorn.internal.parser.TokenType;

import jdk.nashorn.internal.runtime.Context;

import jdk.nashorn.internal.runtime.JSType;

import jdk.nashorn.internal.runtime.Source;

import jdk.nashorn.internal.runtime.logging.DebugLogger;

import jdk.nashorn.internal.runtime.logging.Loggable;

import jdk.nashorn.internal.runtime.logging.Logger;

/**

 * Lower to more primitive operations. After lowering, an AST still has no symbols

 * and types, but several nodes have been turned into more low level constructs

 * and control flow termination criteria have been computed.

 *

 * We do things like code copying/inlining of finallies here, as it is much

 * harder and context dependent to do any code copying after symbols have been

 * finalized.

 */

@Logger(name="lower")

final class Lower extends NodeOperatorVisitor<BlockLexicalContext> implements Loggable {

    private final DebugLogger log;

    /**

     * Constructor.

     */

    Lower(final Compiler compiler) {

        super(new BlockLexicalContext() {

            @Override

            public List<Statement> popStatements() {

                final List<Statement> newStatements = new ArrayList<>();

                boolean terminated = false;

                final List<Statement> statements = super.popStatements();

                for (final Statement statement : statements) {

                    if (!terminated) {

                        newStatements.add(statement);

                        if (statement.isTerminal() || statement instanceof BreakNode || statement instanceof ContinueNode) { //TODO hasGoto? But some Loops are hasGoto too - why?

                            terminated = true;

                        }

                    } else {

                        statement.accept(new NodeVisitor<LexicalContext>(new LexicalContext()) {

                            @Override

                            public boolean enterVarNode(final VarNode varNode) {

                                newStatements.add(varNode.setInit(null));

                                return false;

                            }

                        });

                    }

                }

                return newStatements;

            }

            @Override

            protected Block afterSetStatements(final Block block) {

                final List<Statement> stmts = block.getStatements();

                for(final ListIterator<Statement> li = stmts.listIterator(stmts.size()); li.hasPrevious();) {

                    final Statement stmt = li.previous();

                    // popStatements() guarantees that the only thing after a terminal statement are uninitialized

                    // VarNodes. We skip past those, and set the terminal state of the block to the value of the

                    // terminal state of the first statement that is not an uninitialized VarNode.

                    if(!(stmt instanceof VarNode && ((VarNode)stmt).getInit() == null)) {

                        return block.setIsTerminal(this, stmt.isTerminal());

                    }

                }

                return block.setIsTerminal(this, false);

            }

        });

        this.log       = initLogger(compiler.getContext());

    }

    @Override

    public DebugLogger getLogger() {

        return log;

    }

    @Override

    public DebugLogger initLogger(final Context context) {

        return context.getLogger(this.getClass());

    }

    @Override

    public boolean enterBreakNode(final BreakNode breakNode) {

        addStatement(breakNode);

        return false;

    }

    @Override

    public Node leaveCallNode(final CallNode callNode) {

        return checkEval(callNode.setFunction(markerFunction(callNode.getFunction())));

    }

    @Override

    public Node leaveCatchNode(final CatchNode catchNode) {

        return addStatement(catchNode);

    }

    @Override

    public boolean enterContinueNode(final ContinueNode continueNode) {

        addStatement(continueNode);

        return false;

    }

    @Override

    public boolean enterEmptyNode(final EmptyNode emptyNode) {

        return false;

    }

    @Override

    public Node leaveExpressionStatement(final ExpressionStatement expressionStatement) {

        final Expression expr = expressionStatement.getExpression();

        ExpressionStatement node = expressionStatement;

        final FunctionNode currentFunction = lc.getCurrentFunction();

        if (currentFunction.isProgram()) {

            if (!isInternalExpression(expr) && !isEvalResultAssignment(expr)) {

                node = expressionStatement.setExpression(

                    new BinaryNode(

                        Token.recast(

                            expressionStatement.getToken(),

                            TokenType.ASSIGN),

                        compilerConstant(RETURN),

                    expr));

            }

        }

        return addStatement(node);

    }

    @Override

    public Node leaveBlockStatement(final BlockStatement blockStatement) {

        return addStatement(blockStatement);

    }

    @Override

    public Node leaveForNode(final ForNode forNode) {

        ForNode newForNode = forNode;

        final Expression test = forNode.getTest();

        if (!forNode.isForIn() && isAlwaysTrue(test)) {

            newForNode = forNode.setTest(lc, null);

        }

        newForNode = checkEscape(newForNode);

        if(newForNode.isForIn()) {

            // Wrap it in a block so its internally created iterator is restricted in scope

            addStatementEnclosedInBlock(newForNode);

        } else {

            addStatement(newForNode);

        }

        return newForNode;

    }

    @Override

    public Node leaveFunctionNode(final FunctionNode functionNode) {

        log.info("END FunctionNode: ", functionNode.getName());

        return functionNode.setState(lc, CompilationState.LOWERED);

    }

    @Override

    public Node leaveIfNode(final IfNode ifNode) {

        return addStatement(ifNode);

    }

    @Override

    public Node leaveIN(final BinaryNode binaryNode) {

        return new RuntimeNode(binaryNode);

    }

    @Override

    public Node leaveINSTANCEOF(final BinaryNode binaryNode) {

        return new RuntimeNode(binaryNode);

    }

    @Override

    public Node leaveLabelNode(final LabelNode labelNode) {

        return addStatement(labelNode);

    }

    @Override

    public Node leaveReturnNode(final ReturnNode returnNode) {

        addStatement(returnNode); //ReturnNodes are always terminal, marked as such in constructor

        return returnNode;

    }

    @Override

    public Node leaveCaseNode(final CaseNode caseNode) {

        // Try to represent the case test as an integer

        final Node test = caseNode.getTest();

        if (test instanceof LiteralNode) {

            final LiteralNode<?> lit = (LiteralNode<?>)test;

            if (lit.isNumeric() && !(lit.getValue() instanceof Integer)) {

                if (JSType.isRepresentableAsInt(lit.getNumber())) {

                    return caseNode.setTest((Expression)LiteralNode.newInstance(lit, lit.getInt32()).accept(this));

                }

            }

        }

        return caseNode;

    }

    @Override

    public Node leaveSwitchNode(final SwitchNode switchNode) {

        if(!switchNode.isInteger()) {

            // Wrap it in a block so its internally created tag is restricted in scope

            addStatementEnclosedInBlock(switchNode);

        } else {

            addStatement(switchNode);

        }

        return switchNode;

    }

    @Override

    public Node leaveThrowNode(final ThrowNode throwNode) {

        return addStatement(throwNode); //ThrowNodes are always terminal, marked as such in constructor

    }

    private static Node ensureUniqueNamesIn(final Node node) {

        return node.accept(new NodeVisitor<LexicalContext>(new LexicalContext()) {

            @Override

            public Node leaveFunctionNode(final FunctionNode functionNode) {

                final String name = functionNode.getName();

                return functionNode.setName(lc, lc.getCurrentFunction().uniqueName(name));

            }

            @Override

            public Node leaveDefault(final Node labelledNode) {

                return labelledNode.ensureUniqueLabels(lc);

            }

        });

    }

    private static List<Statement> copyFinally(final Block finallyBody) {

        final List<Statement> newStatements = new ArrayList<>();

        for (final Statement statement : finallyBody.getStatements()) {

            newStatements.add((Statement)ensureUniqueNamesIn(statement));

            if (statement.hasTerminalFlags()) {

                return newStatements;

            }

        }

        return newStatements;

    }

    private Block catchAllBlock(final TryNode tryNode) {

        final int  lineNumber = tryNode.getLineNumber();

        final long token      = tryNode.getToken();

        final int  finish     = tryNode.getFinish();

        final IdentNode exception = new IdentNode(token, finish, lc.getCurrentFunction().uniqueName(CompilerConstants.EXCEPTION_PREFIX.symbolName()));

        final Block catchBody = new Block(token, finish, new ThrowNode(lineNumber, token, finish, new IdentNode(exception), true));

        assert catchBody.isTerminal(); //ends with throw, so terminal

        final CatchNode catchAllNode  = new CatchNode(lineNumber, token, finish, new IdentNode(exception), null, catchBody, true);

        final Block     catchAllBlock = new Block(token, finish, catchAllNode);

        //catchallblock -> catchallnode (catchnode) -> exception -> throw

        return (Block)catchAllBlock.accept(this); //not accepted. has to be accepted by lower

    }

    private IdentNode compilerConstant(final CompilerConstants cc) {

        final FunctionNode functionNode = lc.getCurrentFunction();

        return new IdentNode(functionNode.getToken(), functionNode.getFinish(), cc.symbolName());

    }

    private static boolean isTerminal(final List<Statement> statements) {

        return !statements.isEmpty() && statements.get(statements.size() - 1).hasTerminalFlags();

    }

    /**

     * Splice finally code into all endpoints of a trynode

     * @param tryNode the try node

     * @param rethrows list of rethrowing throw nodes from synthetic catch blocks

     * @param finallyBody the code in the original finally block

     * @return new try node after splicing finally code (same if nop)

     */

    private Node spliceFinally(final TryNode tryNode, final List<ThrowNode> rethrows, final Block finallyBody) {

        assert tryNode.getFinallyBody() == null;

        final LexicalContext lowerLc = lc;

        final TryNode newTryNode = (TryNode)tryNode.accept(new NodeVisitor<LexicalContext>(new LexicalContext()) {

            final List<Node> insideTry = new ArrayList<>();

            @Override

            public boolean enterDefault(final Node node) {

                insideTry.add(node);

                return true;

            }

            @Override

            public boolean enterFunctionNode(final FunctionNode functionNode) {

                // do not enter function nodes - finally code should not be inlined into them

                return false;

            }

            @Override

            public Node leaveThrowNode(final ThrowNode throwNode) {

                if (rethrows.contains(throwNode)) {

                    final List<Statement> newStatements = copyFinally(finallyBody);

                    if (!isTerminal(newStatements)) {

                        newStatements.add(throwNode);

                    }

                    return BlockStatement.createReplacement(throwNode, newStatements);

                }

                return throwNode;

            }

            @Override

            public Node leaveBreakNode(final BreakNode breakNode) {

            }

            @Override

            public Node leaveContinueNode(final ContinueNode continueNode) {

            }

            @Override

            public Node leaveReturnNode(final ReturnNode returnNode) {

                final Expression expr  = returnNode.getExpression();

                final List<Statement> newStatements = new ArrayList<>();

                final Expression resultNode;

                if (expr != null) {

                    //we need to evaluate the result of the return in case it is complex while

                    //still in the try block, store it in a result value and return it afterwards

                    resultNode = new IdentNode(Lower.this.compilerConstant(RETURN));

                    newStatements.add(new ExpressionStatement(returnNode.getLineNumber(), returnNode.getToken(), returnNode.getFinish(), new BinaryNode(Token.recast(returnNode.getToken(), TokenType.ASSIGN), resultNode, expr)));

                    lowerLc.setFlag(lowerLc.getCurrentFunction(), FunctionNode.USES_RETURN_SYMBOL);

                } else {

                    resultNode = null;

                }

                newStatements.addAll(copyFinally(finallyBody));

                if (!isTerminal(newStatements)) {

                    newStatements.add(expr == null ? returnNode : returnNode.setExpression(resultNode));

                }

                return BlockStatement.createReplacement(returnNode, lc.getCurrentBlock().getFinish(), newStatements);

            }

            private Node copy(final Statement endpoint, final Node targetNode) {

                if (!insideTry.contains(targetNode)) {

                    final List<Statement> newStatements = copyFinally(finallyBody);

                    if (!isTerminal(newStatements)) {

                        newStatements.add(endpoint);

                    }

                    return BlockStatement.createReplacement(endpoint, tryNode.getFinish(), newStatements);

                }

                return endpoint;

            }

        });

        addStatement(newTryNode);

        for (final Node statement : finallyBody.getStatements()) {

            addStatement((Statement)statement);

        }

        return newTryNode;

    }

    @Override

    public Node leaveTryNode(final TryNode tryNode) {

        final Block finallyBody = tryNode.getFinallyBody();

        if (finallyBody == null) {

            return addStatement(ensureUnconditionalCatch(tryNode));

        }

        /*

         * create a new trynode

         *    if we have catches:

         *

         *    try            try

         *       x              try

         *    catch               x

         *       y              catch

         *    finally z           y

         *                   catchall

         *                        rethrow

         *

         *   otheriwse

         *

         *   try              try

         *      x               x

         *   finally          catchall

         *      y               rethrow

         *

         *

         *   now splice in finally code wherever needed

         *

         */

        TryNode newTryNode;

        final Block catchAll = catchAllBlock(tryNode);

        final List<ThrowNode> rethrows = new ArrayList<>();

        catchAll.accept(new NodeVisitor<LexicalContext>(new LexicalContext()) {

            @Override

            public boolean enterThrowNode(final ThrowNode throwNode) {

                rethrows.add(throwNode);

                return true;

            }

        });

        assert rethrows.size() == 1;

        if (tryNode.getCatchBlocks().isEmpty()) {