// Output the name of each file in the current directory where:
// The file has public read bit set
// The file is a regular file 
// The file is not empty
// The file does not contain the byte 0xFE
// No need to scan sub directories
// Assume only regular files and directories

#include <stdio.h>
#include <stdint.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <dirent.h>
#include <sys/stat.h>
 
// Get used to using command line man for exam
// Do incrementally
// Useful to check return values even if question does not ask you to
// Easier to debug - catch bugs as you go

#define SEARCH_BYTE 0xFE

int contains_byte(char *path) {
    FILE *stream = fopen(path, "r");
    if(stream == NULL) {
        perror(NULL);
        return 0;
    }

    int value;
    while ((value = fgetc(stream)) != EOF) {
        if (value == SEARCH_BYTE) {
            fclose(stream);
            return 1;
        }
    }
    fclose(stream);
    return 0;
}

int main(void) {
    // Open current directory
    DIR *dirp = opendir(".");
    if (dirp == NULL) {
        perror("opendir . ");
        return 1;
    }

    struct dirent *entry;
    while ((entry = readdir(dirp)) != NULL){
        struct stat s;
        if (stat(entry->d_name, &s) != 0){
            continue;
        }

        // The file is a regular file
        if (!S_ISREG(s.st_mode)){
            continue;
        }

        // The file has public read bit set
        if (!(s.st_mode & S_IROTH)) {
            continue;
        }

        // The file is not empty
        if (s.st_size == 0){
            continue;
        }

        // The file does not contain the byte 0xFE
        if (contains_byte(entry->d_name)) {
            continue;
        }     

        printf("%s\n", entry->d_name);
    }

    closedir(dirp);
    return 0;
}