//
//  main.m
//  ApptopiaTest
//
//  Created by Nikita Pankiv on 2/19/17.
//  Copyright © 2017 Neutral. All rights reserved.
//

#import <Foundation/Foundation.h>

int main(int argc, const char * argv[]) {
    @autoreleasepool {

        NSString *location = @"/Users/Nikita/Desktop/Test/";// Place your directory here

        NSDirectoryEnumerator *enumerator = [[NSFileManager defaultManager] enumeratorAtPath:location];
        NSString *fileName = nil;

        NSMutableArray *files = [NSMutableArray new];
        while (fileName = [enumerator nextObject]) {
            if ([fileName hasSuffix:@".txt"]) { // Only txt's
                [files addObject:[location stringByAppendingString:fileName]];
            }
        }

        // Find the largest number in all files to generate the Eratosthenes only once
        // Not the most benefit way, but I decided to do so
        unsigned long size = 0;
        for (NSString *fileName in files) {
            NSArray *numbers = [[[NSString stringWithContentsOfFile:fileName encoding:NSUTF8StringEncoding error:nil] componentsSeparatedByString:@","] sortedArrayUsingComparator:^NSComparisonResult(NSString*  _Nonnull obj1, NSString*  _Nonnull obj2) {
                return [obj1 integerValue] > [obj2 integerValue];
            }];
            size = MAX([[numbers lastObject] integerValue], size);
        }


        // Calculate Sieve Array for prime numbers
        NSMutableArray *checkNumbers = [NSMutableArray new];

        for (int i = 0; i < size + 1; i++) {
            [checkNumbers insertObject:@(YES) atIndex:i];
        }

        for (int i = 2; i * i <= size; ++i) {
            if ([checkNumbers[i] boolValue] && i % 2 != 0) {
                for (int j = 2; j <= size / i; j++) {
                    if ([checkNumbers[i * j] boolValue]) {
                        checkNumbers[i * j] = @(NO);
                    }
                }
            }
        }


        // Find prime numbers
        for (NSString *fileName in files) {
            NSArray *numbers = [[NSString stringWithContentsOfFile:fileName encoding:NSUTF8StringEncoding error:nil] componentsSeparatedByString:@","];
            NSMutableArray *resultedNumbers = [NSMutableArray new];
            for (NSString *num in numbers) {
                if ([checkNumbers[[num integerValue]] boolValue]) {
                    [resultedNumbers addObject:num];
                }
            }

            // Write to same directory
            NSData *resultedData = [[resultedNumbers componentsJoinedByString:@","] dataUsingEncoding:NSUTF8StringEncoding];
            [[NSFileManager defaultManager] createFileAtPath:[NSString stringWithFormat:@"%@modified_%@", location, [fileName lastPathComponent]] contents:resultedData attributes:nil];
        }

    }
    return 0;
}