/*
 * CPKeyValueCoding.j
 * Foundation
 *
 * Created by Ross Boucher.
 * Copyright 2008, 280 North, Inc.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

@import "CPArray.j"
@import "CPDictionary.j"
@import "CPException.j"
@import "CPNull.j"
@import "CPObject.j"
@import "CPSet.j"

@implementation CPObject (KeyValueObserving)

- (void)willChangeValueForKey:(CPString)aKey
{
}

- (void)didChangeValueForKey:(CPString)aKey
{
}

- (void)willChange:(CPKeyValueChange)aChange valuesAtIndexes:(CPIndexSet)indexes forKey:(CPString)aKey
{
}

- (void)didChange:(CPKeyValueChange)aChange valuesAtIndexes:(CPIndexSet)indexes forKey:(CPString)aKey
{
}

- (void)willChangeValueForKey:(CPString)aKey withSetMutation:(CPKeyValueSetMutationKind)aMutationKind usingObjects:(CPSet)objects
{
}

- (void)didChangeValueForKey:(CPString)aKey withSetMutation:(CPKeyValueSetMutationKind)aMutationKind usingObjects:(CPSet)objects
{
}

- (void)addObserver:(id)anObserver forKeyPath:(CPString)aPath options:(unsigned)options context:(id)aContext
{
    if (!anObserver || !aPath)
        return;

    [[_CPKVOProxy proxyForObject:self] _addObserver:anObserver forKeyPath:aPath options:options context:aContext];
}

- (void)removeObserver:(id)anObserver forKeyPath:(CPString)aPath
{
    if (!anObserver || !aPath)
        return;

    [self[KVOProxyKey] _removeObserver:anObserver forKeyPath:aPath];
}

+ (BOOL)automaticallyNotifiesObserversForKey:(CPString)aKey
{
    return YES;
}

+ (CPSet)keyPathsForValuesAffectingValueForKey:(CPString)aKey
{
    var capitalizedKey = aKey.charAt(0).toUpperCase() + aKey.substring(1),
        selector = "keyPathsForValuesAffecting" + capitalizedKey;

    if ([[self class] respondsToSelector:selector])
        return objj_msgSend([self class], selector);

    return [CPSet set];
}

- (void)applyChange:(CPDictionary)aChange toKeyPath:(CPString)aKeyPath
{
    var changeKind = [aChange objectForKey:CPKeyValueChangeKindKey],
        oldValue = [aChange objectForKey:CPKeyValueChangeOldKey],
        newValue = [aChange objectForKey:CPKeyValueChangeNewKey];

    if (newValue === [CPNull null])
        newValue = nil;

    if (changeKind === CPKeyValueChangeSetting)
        return [self setValue:newValue forKeyPath:aKeyPath];

    var indexes = [aChange objectForKey:CPKeyValueChangeIndexesKey];

    // If we have an indexes entry, then we have an ordered to-many relationship
    if (indexes)
    {
        if (changeKind === CPKeyValueChangeInsertion)
            [[self mutableArrayValueForKeyPath:aKeyPath] insertObjects:newValue atIndexes:indexes];

        else if (changeKind === CPKeyValueChangeRemoval)
            [[self mutableArrayValueForKeyPath:aKeyPath] removeObjectsAtIndexes:indexes];

        else if (changeKind === CPKeyValueChangeReplacement)
            [[self mutableArrayValueForKeyPath:aKeyPath] replaceObjectAtIndexes:indexes withObjects:newValue];
    }
    else
    {
        if (changeKind === CPKeyValueChangeInsertion)
            [[self mutableSetValueForKeyPath:aKeyPath] unionSet:newValue];

        else if (changeKind === CPKeyValueChangeRemoval)
            [[self mutableSetValueForKeyPath:aKeyPath] minusSet:oldValue];

        else if (changeKind === CPKeyValueChangeReplacement)
            [[self mutableSetValueForKeyPath:aKeyPath] setSet:newValue];
    }
}

@end

@implementation CPDictionary (KeyValueObserving)

- (CPDictionary)inverseChangeDictionary
{
    var inverseChangeDictionary = [self mutableCopy],
        changeKind = [self objectForKey:CPKeyValueChangeKindKey];

    if (changeKind === CPKeyValueChangeSetting || changeKind === CPKeyValueChangeReplacement)
    {
        [inverseChangeDictionary
            setObject:[self objectForKey:CPKeyValueChangeOldKey]
               forKey:CPKeyValueChangeNewKey];

        [inverseChangeDictionary
            setObject:[self objectForKey:CPKeyValueChangeNewKey]
               forKey:CPKeyValueChangeOldKey];
    }

    else if (changeKind === CPKeyValueChangeInsertion)
    {
        [inverseChangeDictionary
            setObject:CPKeyValueChangeRemoval
               forKey:CPKeyValueChangeKindKey];

        [inverseChangeDictionary
            setObject:[self objectForKey:CPKeyValueChangeNewKey]
               forKey:CPKeyValueChangeOldKey];

        [inverseChangeDictionary removeObjectForKey:CPKeyValueChangeNewKey];
    }

    else if (changeKind === CPKeyValueChangeRemoval)
    {
        [inverseChangeDictionary
            setObject:CPKeyValueChangeInsertion
               forKey:CPKeyValueChangeKindKey];

        [inverseChangeDictionary
            setObject:[self objectForKey:CPKeyValueChangeOldKey]
               forKey:CPKeyValueChangeNewKey];

        [inverseChangeDictionary removeObjectForKey:CPKeyValueChangeOldKey];
    }

    return inverseChangeDictionary;
}

@end

// KVO Options
CPKeyValueObservingOptionNew        = 1 << 0;
CPKeyValueObservingOptionOld        = 1 << 1;
CPKeyValueObservingOptionInitial    = 1 << 2;
CPKeyValueObservingOptionPrior      = 1 << 3;

// KVO Change Dictionary Keys
CPKeyValueChangeKindKey                 = @"CPKeyValueChangeKindKey";
CPKeyValueChangeNewKey                  = @"CPKeyValueChangeNewKey";
CPKeyValueChangeOldKey                  = @"CPKeyValueChangeOldKey";
CPKeyValueChangeIndexesKey              = @"CPKeyValueChangeIndexesKey";
CPKeyValueChangeNotificationIsPriorKey  = @"CPKeyValueChangeNotificationIsPriorKey";

// KVO Change Types
CPKeyValueChangeSetting     = 1;
CPKeyValueChangeInsertion   = 2;
CPKeyValueChangeRemoval     = 3;
CPKeyValueChangeReplacement = 4;

// CPKeyValueSetMutationKind
CPKeyValueUnionSetMutation = 1;
CPKeyValueMinusSetMutation = 2;
CPKeyValueIntersectSetMutation = 3;
CPKeyValueSetSetMutation = 4;

//FIXME: "secret" dict ivar-keys are workaround to support unordered to-many relationships without too many modifications
_CPKeyValueChangeSetMutationObjectsKey  = @"_CPKeyValueChangeSetMutationObjectsKey";
_CPKeyValueChangeSetMutationKindKey     = @"_CPKeyValueChangeSetMutationKindKey";
_CPKeyValueChangeSetMutationNewValueKey = @"_CPKeyValueChangeSetMutationNewValueKey";

var _changeKindForSetMutationKind = function(mutationKind)
{
    switch (mutationKind)
    {
        case CPKeyValueUnionSetMutation:        return CPKeyValueChangeInsertion;
        case CPKeyValueMinusSetMutation:        return CPKeyValueChangeRemoval;
        case CPKeyValueIntersectSetMutation:    return CPKeyValueChangeRemoval;
        case CPKeyValueSetSetMutation:          return CPKeyValueChangeReplacement;
    }
}

var kvoNewAndOld        = CPKeyValueObservingOptionNew | CPKeyValueObservingOptionOld,
    DependentKeysKey    = "$KVODEPENDENT",
    KVOProxyKey         = "$KVOPROXY";

//rule of thumb: _ methods are called on the real proxy object, others are called on the "fake" proxy object (aka the real object)

/* @ignore */
@implementation _CPKVOProxy : CPObject
{
    id              _targetObject;
    Class           _nativeClass;
    CPDictionary    _changesForKey;
    Object          _observersForKey;
    int             _observersForKeyLength;
    CPSet           _replacedKeys;
}

+ (id)proxyForObject:(CPObject)anObject
{
    var proxy = anObject[KVOProxyKey];

    if (proxy)
        return proxy;

    return [[self alloc] initWithTarget:anObject];
}

- (id)initWithTarget:(id)aTarget
{
    if (self = [super init])
    {
        _targetObject       = aTarget;
        _nativeClass        = [aTarget class];
        _observersForKey    = {};
        _changesForKey      = {};
        _observersForKeyLength = 0;

        [self _replaceClass];
        aTarget[KVOProxyKey] = self;
    }
    return self;
}

- (void)_replaceClass
{
    var currentClass = _nativeClass,
        kvoClassName = "$KVO_" + class_getName(_nativeClass),
        existingKVOClass = objj_lookUpClass(kvoClassName);

    if (existingKVOClass)
    {
        _targetObject.isa = existingKVOClass;
        _replacedKeys = existingKVOClass._replacedKeys;
        return;
    }

    var kvoClass = objj_allocateClassPair(currentClass, kvoClassName);

    objj_registerClassPair(kvoClass);

    _replacedKeys = [CPSet set];
    kvoClass._replacedKeys = _replacedKeys;

    //copy in the methods from our model subclass
    var methods = class_copyMethodList(_CPKVOModelSubclass);

    if ([_targetObject isKindOfClass:[CPDictionary class]])
        methods = methods.concat(class_copyMethodList(_CPKVOModelDictionarySubclass));

    class_addMethods(kvoClass, methods);

    _targetObject.isa = kvoClass;
}

- (void)_replaceModifiersForKey:(CPString)aKey
{
    if ([_replacedKeys containsObject:aKey] || ![_nativeClass automaticallyNotifiesObserversForKey:aKey])
        return;

    [_replacedKeys addObject:aKey];

    var theClass = _nativeClass,
        KVOClass = _targetObject.isa,
        capitalizedKey = aKey.charAt(0).toUpperCase() + aKey.substring(1);

    // Attribute and To-One Relationships
    var setKey_selector = sel_getUid("set" + capitalizedKey + ":"),
        setKey_method = class_getInstanceMethod(theClass, setKey_selector);

    if (setKey_method)
    {
        var setKey_method_imp = setKey_method.method_imp;

        class_addMethod(KVOClass, setKey_selector, function(self, _cmd, anObject)
        {
            [self willChangeValueForKey:aKey];

            setKey_method_imp(self, _cmd, anObject);

            [self didChangeValueForKey:aKey];
        }, "");
    }

    // FIXME: Deprecated.
    var _setKey_selector = sel_getUid("_set" + capitalizedKey + ":"),
        _setKey_method = class_getInstanceMethod(theClass, _setKey_selector);

    if (_setKey_method)
    {
        var _setKey_method_imp = _setKey_method.method_imp;

        class_addMethod(KVOClass, _setKey_selector, function(self, _cmd, anObject)
        {
            [self willChangeValueForKey:aKey];

            _setKey_method_imp(self, _cmd, anObject);

            [self didChangeValueForKey:aKey];
        }, "");
    }

    // Ordered To-Many Relationships
    var insertObject_inKeyAtIndex_selector = sel_getUid("insertObject:in" + capitalizedKey + "AtIndex:"),
        insertObject_inKeyAtIndex_method =
            class_getInstanceMethod(theClass, insertObject_inKeyAtIndex_selector),

        insertKey_atIndexes_selector = sel_getUid("insert" + capitalizedKey + ":atIndexes:"),
        insertKey_atIndexes_method =
            class_getInstanceMethod(theClass, insertKey_atIndexes_selector),

        removeObjectFromKeyAtIndex_selector = sel_getUid("removeObjectFrom" + capitalizedKey + "AtIndex:"),
        removeObjectFromKeyAtIndex_method =
            class_getInstanceMethod(theClass, removeObjectFromKeyAtIndex_selector),

        removeKeyAtIndexes_selector = sel_getUid("remove" + capitalizedKey + "AtIndexes:"),
        removeKeyAtIndexes_method = class_getInstanceMethod(theClass, removeKeyAtIndexes_selector);

    if ((insertObject_inKeyAtIndex_method || insertKey_atIndexes_method) &&
        (removeObjectFromKeyAtIndex_method || removeKeyAtIndexes_method))
    {
        if (insertObject_inKeyAtIndex_method)
        {
            var insertObject_inKeyAtIndex_method_imp = insertObject_inKeyAtIndex_method.method_imp;

            class_addMethod(KVOClass, insertObject_inKeyAtIndex_selector, function(self, _cmd, anObject, anIndex)
            {
                [self willChange:CPKeyValueChangeInsertion
                 valuesAtIndexes:[CPIndexSet indexSetWithIndex:anIndex]
                          forKey:aKey];

                insertObject_inKeyAtIndex_method_imp(self, _cmd, anObject, anIndex);

                [self didChange:CPKeyValueChangeInsertion
                valuesAtIndexes:[CPIndexSet indexSetWithIndex:anIndex]
                         forKey:aKey];
            }, "");
        }

        if (insertKey_atIndexes_method)
        {
            var insertKey_atIndexes_method_imp = insertKey_atIndexes_method.method_imp;

            class_addMethod(KVOClass, insertKey_atIndexes_selector, function(self, _cmd, objects, indexes)
            {
                [self willChange:CPKeyValueChangeInsertion
                 valuesAtIndexes:[indexes copy]
                          forKey:aKey];

                insertKey_atIndexes_method_imp(self, _cmd, objects, indexes);

                [self didChange:CPKeyValueChangeInsertion
                valuesAtIndexes:[indexes copy]
                         forKey:aKey];
            }, "");
        }

        if (removeObjectFromKeyAtIndex_method)
        {
            var removeObjectFromKeyAtIndex_method_imp = removeObjectFromKeyAtIndex_method.method_imp;

            class_addMethod(KVOClass, removeObjectFromKeyAtIndex_selector, function(self, _cmd, anIndex)
            {
                [self willChange:CPKeyValueChangeRemoval
                 valuesAtIndexes:[CPIndexSet indexSetWithIndex:anIndex]
                          forKey:aKey];

                removeObjectFromKeyAtIndex_method_imp(self, _cmd, anIndex);

                [self didChange:CPKeyValueChangeRemoval
                valuesAtIndexes:[CPIndexSet indexSetWithIndex:anIndex]
                         forKey:aKey];
            }, "");
        }

        if (removeKeyAtIndexes_method)
        {
            var removeKeyAtIndexes_method_imp = removeKeyAtIndexes_method.method_imp;

            class_addMethod(KVOClass, removeKeyAtIndexes_selector, function(self, _cmd, indexes)
            {
                [self willChange:CPKeyValueChangeRemoval
                 valuesAtIndexes:[indexes copy]
                          forKey:aKey];

                removeKeyAtIndexes_method_imp(self, _cmd, indexes);

                [self didChange:CPKeyValueChangeRemoval
                valuesAtIndexes:[indexes copy]
                         forKey:aKey];
            }, "");
        }

        // These are optional.
        var replaceObjectInKeyAtIndex_withObject_selector =
                sel_getUid("replaceObjectIn" + capitalizedKey + "AtIndex:withObject:"),
            replaceObjectInKeyAtIndex_withObject_method =
                class_getInstanceMethod(theClass, replaceObjectInKeyAtIndex_withObject_selector);

        if (replaceObjectInKeyAtIndex_withObject_method)
        {
            var replaceObjectInKeyAtIndex_withObject_method_imp =
                    replaceObjectInKeyAtIndex_withObject_method.method_imp;

            class_addMethod(KVOClass, replaceObjectInKeyAtIndex_withObject_selector,
            function(self, _cmd, anIndex, anObject)
            {
                [self willChange:CPKeyValueChangeReplacement
                 valuesAtIndexes:[CPIndexSet indexSetWithIndex:anIndex]
                          forKey:aKey];

                replaceObjectInKeyAtIndex_withObject_method_imp(self, _cmd, anIndex, anObject);

                [self didChange:CPKeyValueChangeReplacement
                valuesAtIndexes:[CPIndexSet indexSetWithIndex:anIndex]
                         forKey:aKey];
            }, "");
        }

        var replaceKeyAtIndexes_withKey_selector =
                sel_getUid("replace" + capitalizedKey + "AtIndexes:with" + capitalizedKey + ":"),
            replaceKeyAtIndexes_withKey_method =
                class_getInstanceMethod(theClass, replaceKeyAtIndexes_withKey_selector);

        if (replaceKeyAtIndexes_withKey_method)
        {
            var replaceKeyAtIndexes_withKey_method_imp = replaceKeyAtIndexes_withKey_method.method_imp;

            class_addMethod(KVOClass, replaceKeyAtIndexes_withKey_selector, function(self, _cmd, indexes, objects)
            {
                [self willChange:CPKeyValueChangeReplacement
                 valuesAtIndexes:[indexes copy]
                          forKey:aKey];

                replaceObjectInKeyAtIndex_withObject_method_imp(self, _cmd, indexes, objects);

                [self didChange:CPKeyValueChangeReplacement
                valuesAtIndexes:[indexes copy]
                         forKey:aKey];
            }, "");
        }
    }

    // Unordered To-Many Relationships
    var addKeyObject_selector = sel_getUid("add" + capitalizedKey + "Object:"),
        addKeyObject_method = class_getInstanceMethod(theClass, addKeyObject_selector),

        addKey_selector = sel_getUid("add" + capitalizedKey + ":"),
        addKey_method = class_getInstanceMethod(theClass, addKey_selector),

        removeKeyObject_selector = sel_getUid("remove" + capitalizedKey + "Object:"),
        removeKeyObject_method = class_getInstanceMethod(theClass, removeKeyObject_selector),

        removeKey_selector = sel_getUid("remove" + capitalizedKey + ":"),
        removeKey_method = class_getInstanceMethod(theClass, removeKey_selector);

    if ((addKeyObject_method || addKey_method) && (removeKeyObject_method || removeKey_method))
    {
        if (addKeyObject_method)
        {
            var addKeyObject_method_imp = addKeyObject_method.method_imp;

            class_addMethod(KVOClass, addKeyObject_selector, function(self, _cmd, anObject)
            {
                [self willChangeValueForKey:aKey
                            withSetMutation:CPKeyValueUnionSetMutation
                               usingObjects:[CPSet setWithObject:anObject]];

                addKeyObject_method_imp(self, _cmd, anObject);

                [self didChangeValueForKey:aKey
                           withSetMutation:CPKeyValueUnionSetMutation
                              usingObjects:[CPSet setWithObject:anObject]];
            }, "");
        }

        if (addKey_method)
        {
            var addKey_method_imp = addKey_method.method_imp;

            class_addMethod(KVOClass, addKey_selector, function(self, _cmd, objects)
            {
                [self willChangeValueForKey:aKey
                            withSetMutation:CPKeyValueUnionSetMutation
                               usingObjects:[objects copy]];

                addKey_method_imp(self, _cmd, objects);

                [self didChangeValueForKey:aKey
                           withSetMutation:CPKeyValueUnionSetMutation
                              usingObjects:[objects copy]];
            }, "");
        }

        if (removeKeyObject_method)
        {
            var removeKeyObject_method_imp = removeKeyObject_method.method_imp;

            class_addMethod(KVOClass, removeKeyObject_selector, function(self, _cmd, anObject)
            {
                [self willChangeValueForKey:aKey
                            withSetMutation:CPKeyValueMinusSetMutation
                               usingObjects:[CPSet setWithObject:anObject]];

                removeKeyObject_method_imp(self, _cmd, anObject);

                [self didChangeValueForKey:aKey
                           withSetMutation:CPKeyValueMinusSetMutation
                              usingObjects:[CPSet setWithObject:anObject]];
            }, "");
        }

        if (removeKey_method)
        {
            var removeKey_method_imp = removeKey_method.method_imp;

            class_addMethod(KVOClass, removeKey_selector, function(self, _cmd, objects)
            {
                [self willChangeValueForKey:aKey
                            withSetMutation:CPKeyValueMinusSetMutation
                               usingObjects:[objects copy]];

                removeKey_method_imp(self, _cmd, objects);

                [self didChangeValueForKey:aKey
                           withSetMutation:CPKeyValueMinusSetMutation
                              usingObjects:[objects copy]];
            }, "");
        }

        // intersect<Key>: is optional.
        var intersectKey_selector = sel_getUid("intersect" + capitalizedKey + ":"),
            intersectKey_method = class_getInstanceMethod(theClass, intersectKey_selector);

        if (intersectKey_method)
        {
            var intersectKey_method_imp = intersectKey_method.method_imp;

            class_addMethod(KVOClass, intersectKey_selector, function(self, _cmd, aSet)
            {
                [self willChangeValueForKey:aKey
                            withSetMutation:CPKeyValueIntersectSetMutation
                               usingObjects:[aSet copy]];

                intersectKey_method_imp(self, _cmd, aSet);

                [self didChangeValueForKey:aKey
                           withSetMutation:CPKeyValueIntersectSetMutation
                              usingObjects:[aSet copy]];
            }, "");
        }
    }

    var affectingKeys = [[_nativeClass keyPathsForValuesAffectingValueForKey:aKey] allObjects],
        affectingKeysCount = affectingKeys ? affectingKeys.length : 0;

    if (!affectingKeysCount)
        return;

    var dependentKeysForClass = _nativeClass[DependentKeysKey];

    if (!dependentKeysForClass)
    {
        dependentKeysForClass = {};
        _nativeClass[DependentKeysKey] = dependentKeysForClass;
    }

    while (affectingKeysCount--)
    {
        var affectingKey = affectingKeys[affectingKeysCount],
            affectedKeys = dependentKeysForClass[affectingKey];

        if (!affectedKeys)
        {
            affectedKeys = [CPSet new];
            dependentKeysForClass[affectingKey] = affectedKeys;
        }

        [affectedKeys addObject:aKey];

        //observe key paths of objects other then ourselves, so we are notified of the changes
        //use CPKeyValueObservingOptionPrior to ensure proper wrapping around changes
        //so CPKeyValueObservingOptionPrior and CPKeyValueObservingOptionOld can be fulfilled even for dependent keys
        if (affectingKey.indexOf(@".") !== -1)
            [_targetObject addObserver:self forKeyPath:affectingKey options:CPKeyValueObservingOptionPrior | kvoNewAndOld  context:nil];
        else
            [self _replaceModifiersForKey:affectingKey];
    }
}

- (void)observeValueForKeyPath:(CPString)theKeyPath ofObject:(id)theObject change:(CPDictionary)theChanges context:(id)theContext
{
    // Fire change events for the dependent keys
    var dependentKeysForClass = _nativeClass[DependentKeysKey],
        dependantKeys = [dependentKeysForClass[theKeyPath] allObjects];

    var isBeforeFlag = !![theChanges objectForKey:CPKeyValueChangeNotificationIsPriorKey];
    for (var i = 0; i < [dependantKeys count]; i++)
    {
        var dependantKey = [dependantKeys objectAtIndex:i];
        [self _sendNotificationsForKey:dependantKey changeOptions:theChanges isBefore:isBeforeFlag];
    }
}

- (void)_addObserver:(id)anObserver forKeyPath:(CPString)aPath options:(unsigned)options context:(id)aContext
{
    if (!anObserver)
        return;

    var forwarder = nil;

    if (aPath.indexOf('.') != CPNotFound)
        forwarder = [[_CPKVOForwardingObserver alloc] initWithKeyPath:aPath object:_targetObject observer:anObserver options:options context:aContext];
    else
        [self _replaceModifiersForKey:aPath];

    var observers = _observersForKey[aPath];

    if (!observers)
    {
        observers = [CPDictionary dictionary];
        _observersForKey[aPath] = observers;
        _observersForKeyLength++;
    }

    [observers setObject:_CPKVOInfoMake(anObserver, options, aContext, forwarder) forKey:[anObserver UID]];

    if (options & CPKeyValueObservingOptionInitial)
    {
        var newValue = [_targetObject valueForKeyPath:aPath];

        if (newValue === nil || newValue === undefined)
            newValue = [CPNull null];

        var changes = [CPDictionary dictionaryWithObject:newValue forKey:CPKeyValueChangeNewKey];
        [anObserver observeValueForKeyPath:aPath ofObject:_targetObject change:changes context:aContext];
    }
}

- (void)_removeObserver:(id)anObserver forKeyPath:(CPString)aPath
{
    var observers = _observersForKey[aPath];

    if (aPath.indexOf('.') != CPNotFound)
    {
        var forwarder = [observers objectForKey:[anObserver UID]].forwarder;
        [forwarder finalize];
    }

    [observers removeObjectForKey:[anObserver UID]];

    if (![observers count])
    {
        _observersForKeyLength--;
        delete _observersForKey[aPath];
    }

    if (!_observersForKeyLength)
    {
        _targetObject.isa = _nativeClass; //restore the original class
        delete _targetObject[KVOProxyKey];
    }
}

//FIXME: We do not compute and cache if CPKeyValueObservingOptionOld is needed, so we may do unnecessary work

- (void)_sendNotificationsForKey:(CPString)aKey changeOptions:(CPDictionary)changeOptions isBefore:(BOOL)isBefore
{
    var changes = _changesForKey[aKey];

    if (isBefore)
    {
        changes = changeOptions;

        var indexes = [changes objectForKey:CPKeyValueChangeIndexesKey],
            setMutationKind = changes[_CPKeyValueChangeSetMutationKindKey];

        if (setMutationKind)
        {
            var setMutationObjects = [changes[_CPKeyValueChangeSetMutationObjectsKey] copy],
                setExistingObjects = [[_targetObject valueForKey: aKey] copy];

            if (setMutationKind == CPKeyValueMinusSetMutation)
            {
                [setExistingObjects intersectSet: setMutationObjects];
                [changes setValue:setExistingObjects forKey:CPKeyValueChangeOldKey];
            }
            else if (setMutationKind === CPKeyValueIntersectSetMutation || setMutationKind === CPKeyValueSetSetMutation)
            {
                [setExistingObjects minusSet: setMutationObjects];
                [changes setValue:setExistingObjects forKey:CPKeyValueChangeOldKey];
            }

            //for unordered to-many relationships (CPSet) even new values can only be calculated before!!!
            if (setMutationKind === CPKeyValueUnionSetMutation || setMutationKind === CPKeyValueSetSetMutation)
            {
                [setMutationObjects minusSet: setExistingObjects];
                //hide new value (for CPKeyValueObservingOptionPrior messages)
                //as long as "didChangeValue..." is not yet called!
                changes[_CPKeyValueChangeSetMutationNewValueKey] = setMutationObjects;
            }
        }
        else if (indexes)
        {
            var type = [changes objectForKey:CPKeyValueChangeKindKey];
            // for ordered to-many relationships, oldvalue is only sensible for replace and remove
            if (type === CPKeyValueChangeReplacement || type === CPKeyValueChangeRemoval)
            {
                //FIXME: do we need to go through and replace "" with CPNull?
                var newValues = [[_targetObject mutableArrayValueForKeyPath:aKey] objectsAtIndexes:indexes];
                [changes setValue:newValues forKey:CPKeyValueChangeOldKey];
            }
        }
        else
        {
            var oldValue = [_targetObject valueForKey:aKey];

            if (oldValue === nil || oldValue === undefined)
                oldValue = [CPNull null];

            [changes setObject:oldValue forKey:CPKeyValueChangeOldKey];
        }

        [changes setObject:1 forKey:CPKeyValueChangeNotificationIsPriorKey];

        _changesForKey[aKey] = changes;
    }
    else
    {
        if (!changes)
            [CPException raise:@"CPKeyValueObservingException" reason:@"'didChange...' message called without prior call of 'willChange...'"];

        [changes removeObjectForKey:CPKeyValueChangeNotificationIsPriorKey];

        var indexes = [changes objectForKey:CPKeyValueChangeIndexesKey],
            setMutationKind = changes[_CPKeyValueChangeSetMutationKindKey];

        if (setMutationKind)
        {
            //old and new values for unordered to-many relationships can only be calculated before
            //set recalculated hidden new value as soon as "didChangeValue..." is called!
            var newValue = changes[_CPKeyValueChangeSetMutationNewValueKey];
            [changes setValue:newValue forKey:CPKeyValueChangeNewKey];

            //delete hidden values
            delete changes[_CPKeyValueChangeSetMutationNewValueKey];
            delete changes[_CPKeyValueChangeSetMutationObjectsKey];
            delete changes[_CPKeyValueChangeSetMutationKindKey];
        }
        else if (indexes)
        {
            var type = [changes objectForKey:CPKeyValueChangeKindKey];
            // for ordered to-many relationships, newvalue is only sensible for replace and insert
            if (type == CPKeyValueChangeReplacement || type == CPKeyValueChangeInsertion)
            {
                //FIXME: do we need to go through and replace "" with CPNull?
                var newValues = [[_targetObject mutableArrayValueForKeyPath:aKey] objectsAtIndexes:indexes];
                [changes setValue:newValues forKey:CPKeyValueChangeNewKey];
            }
        }
        else
        {
            var newValue = [_targetObject valueForKey:aKey];

            if (newValue === nil || newValue === undefined)
                newValue = [CPNull null];

            [changes setObject:newValue forKey:CPKeyValueChangeNewKey];
        }
    }

    var observers = [_observersForKey[aKey] allValues],
        count = observers ? observers.length : 0;

    while (count--)
    {
        var observerInfo = observers[count];

        if (isBefore && (observerInfo.options & CPKeyValueObservingOptionPrior))
            [observerInfo.observer observeValueForKeyPath:aKey ofObject:_targetObject change:changes context:observerInfo.context];
        else if (!isBefore)
            [observerInfo.observer observeValueForKeyPath:aKey ofObject:_targetObject change:changes context:observerInfo.context];
    }

    var dependentKeysMap = _nativeClass[DependentKeysKey];

    if (!dependentKeysMap)
        return;

    var dependentKeyPaths = [dependentKeysMap[aKey] allObjects];

    if (!dependentKeyPaths)
        return;

    var index = 0,
        count = [dependentKeyPaths count];

    for (; index < count; ++index)
    {
        var keyPath = dependentKeyPaths[index];

        [self _sendNotificationsForKey:keyPath
                         changeOptions:isBefore ? [changeOptions copy] : _changesForKey[keyPath]
                              isBefore:isBefore];
    }
}

@end

@implementation _CPKVOModelSubclass
{
}

- (void)willChangeValueForKey:(CPString)aKey
{
    var superClass = [self class],
        methodSelector = @selector(willChangeValueForKey:),
        methodImp = class_getMethodImplementation(superClass, methodSelector);

    methodImp(self, methodSelector, aKey);

    if (!aKey)
        return;

    var changeOptions = [CPDictionary dictionaryWithObject:CPKeyValueChangeSetting forKey:CPKeyValueChangeKindKey];

    [[_CPKVOProxy proxyForObject:self] _sendNotificationsForKey:aKey changeOptions:changeOptions isBefore:YES];
}

- (void)didChangeValueForKey:(CPString)aKey
{
    var superClass = [self class],
        methodSelector = @selector(didChangeValueForKey:),
        methodImp = class_getMethodImplementation(superClass, methodSelector);

    methodImp(self, methodSelector, aKey);

    if (!aKey)
        return;

    [[_CPKVOProxy proxyForObject:self] _sendNotificationsForKey:aKey changeOptions:nil isBefore:NO];
}

- (void)willChange:(CPKeyValueChange)change valuesAtIndexes:(CPIndexSet)indexes forKey:(CPString)aKey
{
    var superClass = [self class],
        methodSelector = @selector(willChange:valuesAtIndexes:forKey:),
        methodImp = class_getMethodImplementation(superClass, methodSelector);

    methodImp(self, methodSelector, change, indexes, aKey);

    if (!aKey)
        return;

    var changeOptions = [CPDictionary dictionaryWithObjects:[change, indexes] forKeys:[CPKeyValueChangeKindKey, CPKeyValueChangeIndexesKey]];

    [[_CPKVOProxy proxyForObject:self] _sendNotificationsForKey:aKey changeOptions:changeOptions isBefore:YES];
}

- (void)didChange:(CPKeyValueChange)change valuesAtIndexes:(CPIndexSet)indexes forKey:(CPString)aKey
{
    var superClass = [self class],
        methodSelector = @selector(didChange:valuesAtIndexes:forKey:),
        methodImp = class_getMethodImplementation(superClass, methodSelector);

    methodImp(self, methodSelector, change, indexes, aKey);

    if (!aKey)
        return;

    [[_CPKVOProxy proxyForObject:self] _sendNotificationsForKey:aKey changeOptions:nil isBefore:NO];
}

- (void)willChangeValueForKey:(CPString)aKey withSetMutation:(CPKeyValueSetMutationKind)mutationKind usingObjects:(CPSet)objects
{
    var superClass = [self class],
        methodSelector = @selector(willChangeValueForKey:withSetMutation:usingObjects:),
        methodImp = class_getMethodImplementation(superClass, methodSelector);

    methodImp(self, methodSelector, aKey, mutationKind, objects);

    if (!aKey)
        return;

    var changeKind = _changeKindForSetMutationKind(mutationKind),
        changeOptions = [CPDictionary dictionaryWithObject:changeKind forKey:CPKeyValueChangeKindKey];
    //set hidden change-dict ivars to support unordered to-many relationships
    changeOptions[_CPKeyValueChangeSetMutationObjectsKey] = objects;
    changeOptions[_CPKeyValueChangeSetMutationKindKey] = mutationKind;

    [[_CPKVOProxy proxyForObject:self] _sendNotificationsForKey:aKey changeOptions:changeOptions isBefore:YES];
}

- (void)didChangeValueForKey:(CPString)aKey withSetMutation:(CPKeyValueSetMutationKind)mutationKind usingObjects:(CPSet)objects
{
    var superClass = [self class],
        methodSelector = @selector(didChangeValueForKey:withSetMutation:usingObjects:),
        methodImp = class_getMethodImplementation(superClass, methodSelector);

    methodImp(self, methodSelector, aKey, mutationKind, objects);

    if (!aKey)
        return;

    [[_CPKVOProxy proxyForObject:self] _sendNotificationsForKey:aKey changeOptions:nil isBefore:NO];
}

- (Class)class
{
    return self[KVOProxyKey]._nativeClass;
}

- (Class)superclass
{
    return [[self class] superclass];
}

- (BOOL)isKindOfClass:(Class)aClass
{
    return [[self class] isSubclassOfClass:aClass];
}

- (BOOL)isMemberOfClass:(Class)aClass
{
    return [self class] == aClass;
}

- (CPString)className
{
    return [self class].name;
}

@end

@implementation _CPKVOModelDictionarySubclass
{
}

- (void)removeAllObjects
{
    var keys = [self allKeys],
        count = [keys count],
        i = 0;

    for (; i < count; i++)
        [self willChangeValueForKey:keys[i]];

    var superClass = [self class],
        methodSelector = @selector(removeAllObjects),
        methodImp = class_getMethodImplementation(superClass, methodSelector);

    methodImp(self, methodSelector);

    for (i = 0; i < count; i++)
        [self didChangeValueForKey:keys[i]];
}

- (void)removeObjectForKey:(id)aKey
{
    [self willChangeValueForKey:aKey];

    var superClass = [self class],
        methodSelector = @selector(removeObjectForKey:),
        methodImp = class_getMethodImplementation(superClass, methodSelector);

    methodImp(self, methodSelector, aKey);

    [self didChangeValueForKey:aKey];
}

- (void)setObject:(id)anObject forKey:(id)aKey
{
    [self willChangeValueForKey:aKey];

    var superClass = [self class],
        methodSelector = @selector(setObject:forKey:),
        methodImp = class_getMethodImplementation(superClass, methodSelector);

    methodImp(self, methodSelector, anObject, aKey);

    [self didChangeValueForKey:aKey];
}

@end

@implementation _CPKVOForwardingObserver : CPObject
{
    id          _object;
    id          _observer;
    id          _context;
    unsigned    _options;
                             //a.b
    CPString    _firstPart;  //a
    CPString    _secondPart; //b

    id          _value;
}

- (id)initWithKeyPath:(CPString)aKeyPath object:(id)anObject observer:(id)anObserver options:(unsigned)options context:(id)aContext
{
    self = [super init];

    _context = aContext;
    _observer = anObserver;
    _object = anObject;
    _options = options;

    var dotIndex = aKeyPath.indexOf('.');

    if (dotIndex == CPNotFound)
        [CPException raise:CPInvalidArgumentException reason:"Created _CPKVOForwardingObserver without compound key path: "+aKeyPath];

    _firstPart = aKeyPath.substring(0, dotIndex);
    _secondPart = aKeyPath.substring(dotIndex + 1);

    //become an observer of the first part of our key (a)
    [_object addObserver:self forKeyPath:_firstPart options:_options context:nil];

    //the current value of a (not the value of a.b)
    _value = [_object valueForKey:_firstPart];

    if (_value)
        [_value addObserver:self forKeyPath:_secondPart options:_options context:nil]; //we're observing b on current a

    return self;
}

- (void)observeValueForKeyPath:(CPString)aKeyPath ofObject:(id)anObject change:(CPDictionary)changes context:(id)aContext
{
    if (aKeyPath === _firstPart)
    {
        [_observer observeValueForKeyPath:_firstPart ofObject:_object change:changes context:_context];

        //since a has changed, we should remove ourselves as an observer of the old a, and observe the new one
        if (_value)
            [_value removeObserver:self forKeyPath:_secondPart];

        _value = [_object valueForKey:_firstPart];

        if (_value)
            [_value addObserver:self forKeyPath:_secondPart options:_options context:nil];
    }
    else
    {
        //a is the same, but a.b has changed -- nothing to do but forward this message along
        [_observer observeValueForKeyPath:_firstPart+"."+aKeyPath ofObject:_object change:changes context:_context];
    }
}

- (void)finalize
{
    if (_value)
        [_value removeObserver:self forKeyPath:_secondPart];

    [_object removeObserver:self forKeyPath:_firstPart];

    _object = nil;
    _observer = nil;
    _context = nil;
    _value = nil;
}

@end

var _CPKVOInfoMake = function _CPKVOInfoMake(anObserver, theOptions, aContext, aForwarder)
{
    return {
        observer: anObserver,
        options: theOptions,
        context: aContext,
        forwarder: aForwarder
    };
}

@import "CPArray+KVO.j"
@import "CPSet+KVO.j"