/*

     File: APLNormalizedStringTransformer.m

 Abstract: Value transformer subclass for normalizing string data.

  Version: 1.3

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#import <CoreFoundation/CFString.h>

#import "APLNormalizedStringTransformer.h"

static NSPredicate *predicateTemplate;

@implementation APLNormalizedStringTransformer

+ (void)initialize

{

    /*

    Pre-parse predicate for quick substitution in reverseTransformedValue: instead of using a 'contains' operator, we simplify the predicate using a check between a high and low bound this allows us to potentially use indexes.

     */

    predicateTemplate = [NSPredicate predicateWithFormat:@"normalizedText >= $lowBound and normalizedText < $highBound"];

}

+ (Class)transformedValueClass 

{ 

    return [NSPredicate class]; 

} 

+ (BOOL)allowsReverseTransformation 

{ 

    return YES; 

} 

- (id)transformedValue:(id)value 

{ 

    // The search field in the nib calls the reverse transform function.

    return value;

}

+ (NSString *)normalizeString:(NSString *)unprocessedValue

{

    if (!unprocessedValue) return nil;

    NSMutableString *result = [NSMutableString stringWithString:unprocessedValue];

    CFStringNormalize((CFMutableStringRef)result, kCFStringNormalizationFormD);

    CFStringFold((CFMutableStringRef)result, kCFCompareCaseInsensitive | kCFCompareDiacriticInsensitive | kCFCompareWidthInsensitive, NULL);

    return result;

}

// Calculates the next lexically ordered string guaranteed to be greater than text.

+ (NSString *)upperBoundSearchString:(NSString*)text

{

    NSUInteger length = [text length];

    NSString *baseString = nil;

    NSString *incrementedString = nil;

    if (length < 1) {

        return text;

    } else if (length > 1) {

        baseString = [text substringToIndex:(length-1)];

    } else {

        baseString = @"";

    }

    UniChar lastChar = [text characterAtIndex:(length-1)];

    UniChar incrementedChar;

    // Don't do a simple lastChar + 1 operation here without taking into account

    // unicode surrogate characters (http://unicode.org/faq/utf_bom.html#34).

    if ((lastChar >= 0xD800UL) && (lastChar <= 0xDBFFUL)) {         // surrogate high character

        incrementedChar = (0xDBFFUL + 1);

    } else if ((lastChar >= 0xDC00UL) && (lastChar <= 0xDFFFUL)) {  // surrogate low character

        incrementedChar = (0xDFFFUL + 1);

    } else if (lastChar == 0xFFFFUL) {

        if (length > 1 ) baseString = text;

        incrementedChar =  0x1;

    } else {

        incrementedChar = lastChar + 1;

    }

    incrementedString = [[NSString alloc] initWithFormat:@"%@%C", baseString, incrementedChar];

    return incrementedString;

}

- (id)reverseTransformedValue:(id)value

{

    if (!value) return nil;

    NSString *searchString = [[value rightExpression] constantValue];

    NSString *lowBound = [[self class] normalizeString:searchString];

    NSString *highBound = [[self class] upperBoundSearchString:lowBound];

    NSDictionary *bindVariables = @{ @"lowBound" : lowBound, @"highBound" : highBound };

    NSPredicate *result = [predicateTemplate predicateWithSubstitutionVariables:bindVariables];

    return result;

}

@end