/*

File: InferenceCore.m

Abstract: Core class for the inference system, which is a rules-based

system used by the predicate editor views.

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*/

#import "InferenceCore.h"

@interface InferredValuesAccessor : NSObject {

    InferenceCore  *inferenceCore;

}

- (id)initWithInferenceCore:(id)core;

@end

@implementation InferredValuesAccessor

- (id)initWithInferenceCore:(id)core {

    self = [super init];

    if (self != nil) {

        inferenceCore = core; // don't retain

    }

    return self;

}

- (id)valueForKey:(NSString *)key {

    return [inferenceCore inferredValueForKeyPath:key];   

}

- (id)valueForKeyPath:(NSString *)keyPath {

    return [inferenceCore inferredValueForKeyPath:keyPath];   

}

@end

@implementation InferencePair

- (id)value {

    return value;

}

- (void)setValue:(id)inValue {

    if (value != inValue) {

        [value release];

        value = [inValue retain];

    }

}

- (NSPredicate *)predicate {

    return condition;

}

- (void)setPredicate:(NSPredicate *)inValue {

    if (condition != inValue) {

        [condition release];

        condition = [inValue retain];

    }

}

@end

@implementation InferenceCore

static InferenceCore *defaultCore = nil;

+ (InferenceCore *)defaultCore {

    if (defaultCore == nil) {

        defaultCore = [[InferenceCore alloc] init];

    }

    return defaultCore;

}

- (id)privateInit {

    self = [super init];

    return self;

}

- (id)init {

    self = [super init];

    if (self != nil) {

    backingStore = [[NSMutableDictionary alloc] init];

    inferenceStore = [[NSMutableDictionary alloc] init];

    inferredValuesAccessor = nil;

    [backingStore setObject:[self inferredValues] forKey:@"inferredValues"];

    }

    return self;

}

- (void)dealloc {

    [inferredValuesAccessor release];

    [backingStore release];

    [inferenceStore release];

    [super dealloc];

}

- (id)copyWithZone:(NSZone *)zone {

    InferenceCore *core = [[InferenceCore allocWithZone:zone] privateInit];

    core->backingStore = [backingStore mutableCopy];

    core->inferenceStore = [inferenceStore mutableCopy];

    core->inferredValuesAccessor = nil;

    [core->backingStore setObject:[core inferredValues] forKey:@"inferredValues"];

    return core;

}

- (void)setValue:(id)value forKey:(NSString *)key {

    [self willChangeValueForKey:@"inferredValues"];

    [self willChangeValueForKey:key];

    [backingStore setObject:value forKey:key];

    [self didChangeValueForKey:key];

    [self didChangeValueForKey:@"inferredValues"];

}

- (void)setValue:(id)value forKey:(NSString *)key condition:(NSPredicate *)condition {

    InferencePair *inferencePair = [[InferencePair alloc] init];

    [inferencePair setPredicate:condition];

    [inferencePair setValue:value];

    NSMutableSet *bucket = [inferenceStore objectForKey:key];

    if (bucket == nil) {

        bucket = [[NSMutableSet alloc] init];

        [inferenceStore setObject:bucket forKey:key];

        [bucket release];

    }

    [bucket addObject:inferencePair];

    [inferencePair release];

}

- (id)valueForKey:(NSString *)key {

    return [backingStore objectForKey:key];   

}

- (id)valueForKeyPath:(NSString *)keyPath {

    return [self inferredValueForKeyPath:keyPath];

}

- (id)inferredValueForKeyPath:(NSString *)keyPath {

    id value = self;

    NSString *key;

    NSArray *components = [keyPath componentsSeparatedByString:@"."];

    NSEnumerator *enumerator = [components objectEnumerator];

    BOOL checkBuckets = YES; // we don't want to infer values for anything but the first keypath component

    while ((key = [enumerator nextObject]) != nil) {

    BOOL success = NO;

    if (checkBuckets) {  // we only infer values for the first keypath component

        NSSet *bucket = [inferenceStore objectForKey:key];

       // NSLog(@"Inference logging: Will infer value for key %@", key);

        if (bucket != nil) {

        NSArray *bucketValues = [bucket allObjects];

        InferencePair *inferencePair;

        int count = [bucketValues count];

        int index=0;

        for (;index < count; index++) {

            inferencePair = [bucketValues objectAtIndex:index];

            if ([[inferencePair predicate] evaluateWithObject:self]) {

            value = [inferencePair value];

            success = YES;

            //NSLog(@"Inference logging: Inferred value for key %@: %@", key, value);

            break;

            }

        }

        } 

    }

    if (success == NO) {

      //  NSLog(@"Inference logging: Check backing store for key %@", key);

        value = [value valueForKey:key];   

        if (value == nil) {

    //  NSLog(@"Inference logging: Failed check backing store value for key %@", key);

        } else {

    //  NSLog(@"Inference logging: Found backing store value %@ for key %@", value, key);

        }

    } else if (value == [self inferredValues]) {

        continue;

    }

    if ([value isKindOfClass:[InferenceObject self]]) {

    //    NSLog(@"Inference logging: Will evaluate value for key %@", [value valueForKey:@"key"]);

        value = [value evaluateWithInferenceCore:self];   

      //  NSLog(@"Inference logging: Result of evaluation for key %@: %@", key, value);

    }

    checkBuckets = NO; // we don't want to infer values for anything but the first keypath component

    }

    return (value != self) ? value : nil;

}

- (id)inferredValues {

    if (inferredValuesAccessor == nil) {

    inferredValuesAccessor = [[InferredValuesAccessor alloc] initWithInferenceCore:self];

    }

    return inferredValuesAccessor;

}

@end

@implementation InferenceObject

- (id)initWithTarget:(id)inTarget key:(NSString *)inKey {

    self = [super init];

    if (self != nil) {

    target = inTarget;

    key = [inKey retain];

    }

    return self;

}

- (id)evaluateWithInferenceCore:(InferenceCore *)core {

    NSString *selectorName = [NSString stringWithFormat:@"%@:", key];

    SEL selector = NSSelectorFromString(selectorName);

    id value = [target performSelector:selector withObject:core];

    return value;   

}

@end