#import <CommonCrypto/CommonCryptor.h>
#import <CommonCrypto/CommonDigest.h>
#import <CommonCrypto/CommonKeyDerivation.h>

#import "PBKDF2.h"

@implementation PBKDF2

+ (NSString *) toHex:(NSData *)nsdata {
    NSString * hexStr = [NSString stringWithFormat:@"%@", nsdata];
    for(NSString * toRemove in [NSArray arrayWithObjects:@"<", @">", @" ", nil])
        hexStr = [hexStr stringByReplacingOccurrencesOfString:toRemove withString:@""];
    return hexStr;
}

+ (NSMutableData *) fromHex:(NSString *)str {
    const char *chars = [str UTF8String];
    int i = 0, len = str.length;

    NSMutableData *data = [NSMutableData dataWithCapacity:len / 2];
    char byteChars[3] = {'\0','\0','\0'};
    unsigned long wholeByte;

    while (i < len) {
        byteChars[0] = chars[i++];
        byteChars[1] = chars[i++];
        wholeByte = strtoul(byteChars, NULL, 16);
        [data appendBytes:&wholeByte length:1];
    }
    return data;
}

+ (NSString *) derivationKey:(NSString *)password salt: (NSString *)salt iterations: (nonnull int *)iterations {
    // Data of String to generate Hash key(hexa decimal string).
    NSData *passwordData = [self fromHex:password];
    NSData *saltData = [self fromHex:salt];

    // Hash key (hexa decimal) string data length.
    NSMutableData *hashKeyData = [NSMutableData dataWithLength:CC_SHA512_DIGEST_LENGTH];

    // Key Derivation using PBKDF2 algorithm.
    int status = CCKeyDerivationPBKDF(
                    kCCPBKDF2,
                    passwordData.bytes,
                    passwordData.length,
                    saltData.bytes,
                    saltData.length,
                    kCCPRFHmacAlgSHA512,
                    iterations,
                    hashKeyData.mutableBytes,
                    hashKeyData.length);

    if (status == kCCParamError) {
        NSLog(@"Key derivation error");
        return @"";
    }

    return [self toHex:hashKeyData];
}

@end