StringExtension.swift

//
//  StringExtension.swift
//  Tasty for iOS
//
//  Created by Tobias Tom on 06.01.15.
//  Copyright (c) 2015 succont e.K. All rights reserved.
//

import Foundation

extension String {
    func firstLetterSectionName() -> String {
        let fallback = "?!"
        if self.isEmpty {
            return fallback
        }
    
        let letters = NSCharacterSet.letterCharacterSet()
        let numbers = NSCharacterSet.decimalDigitCharacterSet()
    
        let firstLetter: NSString = self.substringToIndex( advance( self.startIndex, 1 ) )
        let flAsUniChar: unichar = firstLetter.characterAtIndex(0)
    
        var result = ""
        switch ( flAsUniChar ) {
            case 223:                   // Sonderbehandlung fürs ß. 223 ist dessen Wert als unichar
                result = "S"
        
            case let c where letters.characterIsMember(c):
                let base = firstLetter.stringByFoldingWithOptions(
                    NSStringCompareOptions.DiacriticInsensitiveSearch,
                    locale: NSLocale.currentLocale()
                )
                result = base.uppercaseString
        
            case let c where numbers.characterIsMember(c):
                result = "0-9"
        
            default:
                result = fallback
        }
    
        return result
    }
}