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// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

package org.jetbrains.kotlin.js.backend;

import org.jetbrains.annotations.NotNull;
import org.jetbrains.kotlin.js.backend.ast.*;

/**
 * Determines if a statement at the end of a block requires a semicolon.
 * 
 * For example, the following statements require semicolons:

 * 

 * if (cond);
 * while (cond);
 * 
 * 
 * The following do not require semicolons:

 * 

 * return 1
 * do {} while(true)
 * 
 */
public class JsRequiresSemiVisitor extends JsVisitor {
    private boolean needsSemicolon;

    private JsRequiresSemiVisitor() {
    }

    public static boolean exec(JsStatement lastStatement) {
        JsRequiresSemiVisitor visitor = new JsRequiresSemiVisitor();
        visitor.accept(lastStatement);
        return visitor.needsSemicolon;
    }

    @Override
    public void visitFor(@NotNull JsFor x) {
        if (x.getBody() instanceof JsEmpty) {
            needsSemicolon = true;
        }
    }

    @Override
    public void visitForIn(@NotNull JsForIn x) {
        if (x.getBody() instanceof JsEmpty) {
            needsSemicolon = true;
        }
    }

    @Override
    public void visitIf(@NotNull JsIf x) {
        JsStatement thenStmt = x.getThenStatement();
        JsStatement elseStmt = x.getElseStatement();
        JsStatement toCheck = thenStmt;
        if (elseStmt != null) {
            toCheck = elseStmt;
        }
        if (toCheck instanceof JsEmpty) {
            needsSemicolon = true;
        }
        else {
            // Must recurse to determine last statement (possible if-else chain).
            accept(toCheck);
        }
    }

    @Override
    public void visitLabel(@NotNull JsLabel x) {
        if (x.getStatement() instanceof JsEmpty) {
            needsSemicolon = true;
        }
    }

    @Override
    public void visitWhile(@NotNull JsWhile x) {
        if (x.getBody() instanceof JsEmpty) {
            needsSemicolon = true;
        }
    }
}