#import <Foundation/Foundation.h>

@interface GSM0338Helper : NSObject
+(int)gsmStringLength:(NSString *)textToShare;
+(NSString *)gsmStringFromString:(NSString *)textToShare replacementChar:(NSString *)replace;
+(NSString *)gsmShorten:(NSString *)text length:(int)length truncationText:(NSString *)truncationText;
@end

#import "GSM0338Helper.h"

@implementation GSM0338Helper

// gsm has certain characters like pipe that require 14 bits instead of 7 so we need to double count those
+(int)gsmStringLength:(NSString *)textToShare {
    if (textToShare == nil || [textToShare length] == 0) return 0;
    NSError *error = NULL;
    // count the number of times special escape characters appear that will take up 2 characters instead of one
    NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"[\\^\\{\\}\\[~\\]\\|€\\\\]" options:NSRegularExpressionCaseInsensitive error:&error];
    NSArray *matches = [regex matchesInString:textToShare options:NSRegularExpressionCaseInsensitive range:NSMakeRange(0, [textToShare length])];
    return [textToShare length] + [matches count];
}

// replaces non gsm characters with the replace string you specify, can be empty string @""
+(NSString *)gsmStringFromString:(NSString *)textToShare replacementChar:(NSString *)replace {
    if (textToShare == nil || [textToShare length] == 0) return textToShare;
    NSError *error = NULL;
    NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"[^A-Za-z0-9@£$¥èéùìòÇ\fØø\nÅåΔ_ΦΓΛΩΠΨΣΘΞÆæßÉ !\"#¤%%&'()\\*\\+,-./:;<=>\\?¡ÄÖÑܧ¿äöñüà\\^\\{\\}\\[~\\]\\|€\\\\]" options:NSRegularExpressionCaseInsensitive error:&error];
    NSString *modifiedString = [regex stringByReplacingMatchesInString:textToShare options:0 range:NSMakeRange(0, [textToShare length]) withTemplate:replace];
    return modifiedString;
}

// shortens gsm string to length gsm chars and if it truncates it, it appends the truncation text
+(NSString *)gsmShorten:(NSString *)text length:(int)length truncationText:(NSString *)truncationText {
    if (textToShare == nil || [textToShare length] == 0) return text;
    int gsmTextLength = [self gsmStringLength:text];
    if (gsmTextLength > length) {
        // We have to first figure out how many characters to remove since gsm length is possibly > [title length]
        int numCharsToRemove = gsmTextLength - length;
        int newTextLength = [text length] - numCharsToRemove;
        if (newTextLength > 0 && newTextLength < [text length])
            text = [NSString stringWithFormat:@"%@%@", [text substringToIndex:newTextLength], truncationText];
    }
    return text;
}

@end