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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.util.Arrays;
import java.util.Collection;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.Stack;

import org.mozilla.javascript.json.JsonParser;

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

    private static final Object JSON_TAG = "JSON";

    private static final int MAX_STRINGIFY_GAP_LENGTH = 10;

    static void init(Scriptable scope, boolean sealed)
    {
        NativeJSON obj = new NativeJSON();
        obj.activatePrototypeMap(MAX_ID);
        obj.setPrototype(getObjectPrototype(scope));
        obj.setParentScope(scope);
        if (sealed) { obj.sealObject(); }
        ScriptableObject.defineProperty(scope, "JSON", obj,
                                        ScriptableObject.DONTENUM);
    }

    private NativeJSON()
    {
    }

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

    @Override
    protected void initPrototypeId(int id)
    {
        if (id <= LAST_METHOD_ID) {
            String name;
            int arity;
            switch (id) {
              case Id_toSource:  arity = 0; name = "toSource";  break;
              case Id_parse:     arity = 2; name = "parse";     break;
              case Id_stringify: arity = 3; name = "stringify"; break;
              default: throw new IllegalStateException(String.valueOf(id));
            }
            initPrototypeMethod(JSON_TAG, id, name, arity);
        } else {
            throw new IllegalStateException(String.valueOf(id));
        }
    }

    @Override
    public Object execIdCall(IdFunctionObject f, Context cx, Scriptable scope,
                             Scriptable thisObj, Object[] args)
    {
        if (!f.hasTag(JSON_TAG)) {
            return super.execIdCall(f, cx, scope, thisObj, args);
        }
        int methodId = f.methodId();
        switch (methodId) {
            case Id_toSource:
                return "JSON";

            case Id_parse: {
                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);
            }

            case Id_stringify: {
                Object value = null, replacer = null, space = null;
                switch (args.length) {
                    case 3: space = args[2];
                    /* fall through */ case 2: replacer = args[1];
                    /* fall through */ case 1: value = args[0];
                    /* fall through */ case 0:
                    /* fall through */ default:
                }
                return stringify(cx, scope, value, replacer, space);
            }

            default: throw new IllegalStateException(String.valueOf(methodId));
        }
    }

    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, List