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Rhino is an open-source implementation of JavaScript written entirely in Java. It is typically embedded into Java applications to provide scripting to end users.
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/* -*- Mode: java; tab-width: 4; indent-tabs-mode: 1; c-basic-offset: 4 -*-
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

package org.mozilla.javascript;

import java.lang.reflect.Array;
import java.math.BigInteger;
import java.util.Arrays;
import java.util.Collection;
import java.util.Iterator;
import java.util.LinkedHashSet;
import java.util.LinkedList;
import java.util.Map;
import java.util.Stack;
import org.mozilla.javascript.json.JsonParser;
import org.mozilla.javascript.xml.XMLObject;

/**
 * This class implements the JSON native object. See ECMA 15.12.
 *
 * @author Matthew Crumley, Raphael Speyer
 */
public final class NativeJSON extends ScriptableObject {
    private static final long serialVersionUID = -4567599697595654984L;

    private static final String JSON_TAG = "JSON";

    private static final int MAX_STRINGIFY_GAP_LENGTH = 10;

    static void init(Scriptable scope, boolean sealed) {
        NativeJSON json = new NativeJSON();
        json.setPrototype(getObjectPrototype(scope));
        json.setParentScope(scope);

        json.defineProperty(scope, "parse", 2, NativeJSON::parse, DONTENUM, DONTENUM | READONLY);
        json.defineProperty(
                scope, "stringify", 3, NativeJSON::stringify, DONTENUM, DONTENUM | READONLY);

        json.defineProperty("toSource", "JSON", DONTENUM | READONLY | PERMANENT);

        json.defineProperty(SymbolKey.TO_STRING_TAG, JSON_TAG, DONTENUM | READONLY);

        ScriptableObject.defineProperty(scope, JSON_TAG, json, DONTENUM);
        if (sealed) {
            json.sealObject();
        }
    }

    private NativeJSON() {}

    @Override
    public String getClassName() {
        return "JSON";
    }

    private static Object parse(Context cx, Scriptable scope, Scriptable thisObj, Object[] args) {
        String jtext = ScriptRuntime.toString(args, 0);
        Object reviver = null;
        if (args.length > 1) {
            reviver = args[1];
        }
        if (reviver instanceof Callable) {
            return parse(cx, scope, jtext, (Callable) reviver);
        }
        return parse(cx, scope, jtext);
    }

    private static Object stringify(
            Context cx, Scriptable scope, Scriptable thisObj, Object[] args) {
        Object value = Undefined.instance, replacer = null, space = null;

        if (args.length > 0) {
            value = args[0];
            if (args.length > 1) {
                replacer = args[1];
                if (args.length > 2) {
                    space = args[2];
                }
            }
        }
        return stringify(cx, scope, value, replacer, space);
    }

    private static Object parse(Context cx, Scriptable scope, String jtext) {
        try {
            return new JsonParser(cx, scope).parseValue(jtext);
        } catch (JsonParser.ParseException ex) {
            throw ScriptRuntime.constructError("SyntaxError", ex.getMessage());
        }
    }

    public static Object parse(Context cx, Scriptable scope, String jtext, Callable reviver) {
        Object unfiltered = parse(cx, scope, jtext);
        Scriptable root = cx.newObject(scope);
        root.put("", root, unfiltered);
        return walk(cx, scope, reviver, root, "");
    }

    private static Object walk(
            Context cx, Scriptable scope, Callable reviver, Scriptable holder, Object name) {
        final Object property;
        if (name instanceof Number) {
            property = holder.get(((Number) name).intValue(), holder);
        } else {
            property = holder.get(((String) name), holder);
        }

        if (property instanceof Scriptable) {
            Scriptable val = ((Scriptable) property);
            if (val instanceof NativeArray) {
                long len = ((NativeArray) val).getLength();
                for (long i = 0; i < len; i++) {
                    // indices greater than MAX_INT are represented as strings
                    if (i > Integer.MAX_VALUE) {
                        String id = Long.toString(i);
                        Object newElement = walk(cx, scope, reviver, val, id);
                        if (newElement == Undefined.instance) {
                            val.delete(id);
                        } else {
                            val.put(id, val, newElement);
                        }
                    } else {
                        int idx = (int) i;
                        Object newElement = walk(cx, scope, reviver, val, Integer.valueOf(idx));
                        if (newElement == Undefined.instance) {
                            val.delete(idx);
                        } else {
                            val.put(idx, val, newElement);
                        }
                    }
                }
            } else {
                Object[] keys = val.getIds();
                for (Object p : keys) {
                    Object newElement = walk(cx, scope, reviver, val, p);
                    if (newElement == Undefined.instance) {
                        if (p instanceof Number) val.delete(((Number) p).intValue());
                        else val.delete((String) p);
                    } else {
                        if (p instanceof Number) val.put(((Number) p).intValue(), val, newElement);
                        else val.put((String) p, val, newElement);
                    }
                }
            }
        }

        return reviver.call(cx, scope, holder, new Object[] {name, property});
    }

    private static String repeat(char c, int count) {
        char[] chars = new char[count];
        Arrays.fill(chars, c);
        return new String(chars);
    }

    private static class StringifyState {
        StringifyState(
                Context cx,
                Scriptable scope,
                String indent,
                String gap,
                Callable replacer,
                Object[] propertyList) {
            this.cx = cx;
            this.scope = scope;

            this.indent = indent;
            this.gap = gap;
            this.replacer = replacer;
            this.propertyList = propertyList;
        }

        Stack