#include <stdio.h>
#include <string.h>
#include <stdbool.h>
#include <stdlib.h>
#include <errno.h>
#define  MAX_LEN 10


int checkInput(int * argc ,char *argv[] , FILE ** fr ){
    int i = 0 ;

    switch (*argc )
    {
        //tail soubor
        case 2:
            *fr = fopen( argv[1], "r" );
            if (  fr == NULL ) {
                printf("Nepodarilo sa otvorit soubor. \n");
                return 1;
            }
            break;
            //tail -n +3

        case 3:
            // -n
            if (strncmp("-n",argv[1],2 ) != 0  || strlen(argv[1]) != 2 ){
                printf("Argument %s je chybny\n",argv[1]);
                return 1;
            }

            // +3
            while( argv[2][i] !=0){
                if( argv[2][i] == '1'  ||
                    argv[2][i] == '2'  ||
                    argv[2][i] == '3'  ||
                    argv[2][i] == '4'  ||
                    argv[2][i] == '5'  ||
                    argv[2][i] == '6'  ||
                    argv[2][i] == '7'  ||
                    argv[2][i] == '8'  ||
                    argv[2][i] == '9'  ||
                    argv[2][i] == '0'  || (argv[2][i] == '+' && i == 0 )

                        ){
                    i++;
                }

                else{
                    printf("zle cislo %s ", argv[2] );
                    return 1;
                }

            }
            if ( strlen(argv[2]) == 1 && argv[2][0]=='+'){
                printf("zle cislo %s ", argv[2] );
                return 1;
            }


            break;
            //tail -n +3 soubor
        case 4:
            //-n
            if (strncmp("-n",argv[1],2 ) != 0  || strlen(argv[1]) != 2 ){
                printf("Argument %s je chybny\n",argv[1]);
                return 1;
            }

            // +3
            while( argv[2][i] !=0){
                if( argv[2][i] == '1'  ||
                    argv[2][i] == '2'  ||
                    argv[2][i] == '3'  ||
                    argv[2][i] == '4'  ||
                    argv[2][i] == '5'  ||
                    argv[2][i] == '6'  ||
                    argv[2][i] == '7'  ||
                    argv[2][i] == '8'  ||
                    argv[2][i] == '9'  ||
                    argv[2][i] == '0'  || (argv[2][i] == '+' && i == 0 )

                        ){
                    i++;
                }

                else{
                    printf("zle cislo %s ", argv[2] );
                    return 1;
                }

            }
            if ( strlen(argv[2]) == 1 && argv[2][0]=='+'){
                printf("zle cislo %s ", argv[2] );
                return 1;
            }



            // soubor
            *fr = fopen( argv[3], "r" );
            //printf("%s",argv[3]);
            if (  *fr == NULL ) {
                printf("Nepodarilo sa otvorit soubor. \n");
                return 1;
            }

            break;


        default:
            printf("Zly pocet argumentov \n");
            return 1;
            break;
    }


    return 0;
}

int ignore(FILE *f, char endofline)
{
    int character;
    while (((character = fgetc(f)) != endofline) && (character != EOF)) {
        continue;
    }
    if (character == EOF) {
        return 1;
    }

    return 0;
}


int tailPrint( FILE * fr , size_t numberOfLines, bool operatorflag){
    //printf("%lu %d",numberOfLines, operatorflag);
    bool overflow = false;
    if ( numberOfLines == 0 && operatorflag == false ){
        return 0;
    }

    if ( numberOfLines == 1 &&  operatorflag == true ){
        numberOfLines = 0;
    }

    if ( operatorflag){
        int len;
        size_t counter = 0;
        char array_of_line[MAX_LEN+2];
        strncpy(array_of_line, "", MAX_LEN);
        while (fgets(array_of_line, MAX_LEN+2, fr) != NULL) {
            counter++;

            len = strlen(array_of_line);
                if (array_of_line[len - 1] != '\n') {
                    if (ignore(fr, '\n') == 0) {
                        array_of_line[len - 1] = '\n';
                        if ( overflow == false){
                            //fprintf(stderr, "Prilis velka delka radku!\n");
                            overflow = true ;
                        }
                    }
                }
            if (counter >= numberOfLines){
                printf("%s", array_of_line);
            }

        }

    }

    else{
        // char buff[numberOfLines][MAX_LEN+2];
        char ** buff = (char **) calloc(numberOfLines,sizeof(char*));
        for( size_t i = 0 ; i < numberOfLines; i++){
            buff[i] = (char * ) calloc( MAX_LEN+2,sizeof(char));
        }

        int len;
        size_t last = 0;
        int more = 0;
        bool overflow = false;
        for (size_t i = 0; i < numberOfLines; i++){
            strncpy(buff[i], "", MAX_LEN+2);
        }

        while (fgets(buff[last], MAX_LEN+2, fr) != NULL) {
            len = strlen(buff[last]);
            if (buff[last][len - 1] != '\n') {
                if (ignore(fr, '\n') == 0) {
                    buff[last][len - 1] = '\n';
                    if ( overflow == false){
                        fprintf(stderr, "Prilis velka delka radku!\n");\
                                overflow = true ;
                    }
                }

            }
            last++;
            if (last == numberOfLines) {
                last = 0;
                more = 1;
            }
        }
        if (more == 0) {

            for (size_t i = 0; i <= last; i++){
                printf("%s", buff[i]);
            }
        } else {

            for (size_t i = last; i < numberOfLines; i++){
                printf("%s", buff[i]);
            }
            for (size_t i = 0; i < last; i++){
                printf("%s", buff[i]);
            }
        }

        for ( size_t i = 0; i < numberOfLines; i++ )
        {
            free(buff[i]);
        }

        free(buff);

    }

    return 0;
}



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

    FILE * fr  = NULL ;
    bool operatorFlag = false;
    size_t numberOfLines = 10 ;


    if ( checkInput(&argc, argv, &fr ) == 1 ) {
        return 1;
    }

    if( argc > 2 && argv[2][0] == '+' ){
        operatorFlag = true;
    }

    if (argc > 2 ){
        if ( sscanf( argv[2],"%lu", &numberOfLines) != 1 ){
            return 1;
        }
    }


    switch (argc)
    {
        case 2:

            tailPrint(fr , 10 , false );
            /* code */
            break;
        case 3:

            // std in
            tailPrint(stdin,numberOfLines , operatorFlag);

            break;
        case 4:

            tailPrint( fr , numberOfLines, operatorFlag );

            break;
        default:
            break;
    }


    if ( fr != NULL){
        fclose(fr);
    }

    return 0;
}