#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <unistd.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <limits.h> // necesar pentru PATH_MAX

#define SECTOR_SIZE 4096

char numeFisiere[SECTOR_SIZE][SECTOR_SIZE], rezultat[SECTOR_SIZE][SECTOR_SIZE];
int nrFisiere, nrLiniiRez;

int isNumber; // flag validare numar
int nr;
int lastOption; // ultima optiune selectata

int fn, fc; // flag pentru optiunile -c si -n
int nLines, cLines;

void reverse(char *sir);

int cifra(char c);

void number(char *sir);

void getData(char *map_addr, int length);


void recursive(int f, int length, int offset, int PageSize);

int main(int argc, char **argv)
{
    if (argc < 2) // Nu amm fisier
    {
        perror("Introdu numele fisierului.");
        exit(1);
    }
    else if (argc == 2) // am doar numele fisierului
    {
        strcpy(numeFisiere[++nrFisiere], argv[1]);
        fn = 1;
        lastOption = 2;
        nLines = 10;
        fc = 0;
    }
    else // am mai multe fisiere sau argumente
    {
        for (int i = 1; i < argc; i++)
        {
            if (strcmp(argv[i], "-c") == 0)
            {
                if (i < argc - 1) // daca mai am un numar dupa el
                {
                    number(argv[i + 1]);

                    if (isNumber == 1)
                    {
                        fc = 1;
                        cLines = nr;
                        lastOption = 1;
                        i++;
                    }
                    else
                    {
                        printf("Argumentul introdus de dumneavoastra pentru optiunea -c nu este un numar.\n");
                        exit(2);
                    }
                }
                else
                {
                    printf("Introduceti un argument pentru optiunea -c.\n");
                    exit(1);
                }
            }
            else if (strcmp(argv[i], "-n") == 0)
            {
                if (i < argc - 1) // daca mai am un numar dupa el
                {
                    number(argv[i + 1]);

                    if (isNumber == 1)
                    {
                        fn = 1;
                        nLines = nr;
                        lastOption = 2;
                        i++;
                    }
                    else
                    {
                        printf("Argumentul introdus de dumneavoastra pentru optiunea -n nu este un numar.\n");
                        exit(2);
                    }
                }
                else
                {
                    printf("Introduceti un argument pentru optiunea -n.\n");
                    exit(1);
                }
            }
            else
                strcpy(numeFisiere[++nrFisiere], argv[i]);
        }
    }

    int auxc = cLines;
    int auxn = nLines;

    for (int i = 1; i <= nrFisiere; i++)
    {
        int f = open(numeFisiere[i], O_RDONLY);

        if (f == -1)
        {
            perror("A aparut o eroare cand am incercat sa deschide fisierul");
            exit(2);
        }

        long PageSize = sysconf(_SC_PAGE_SIZE);
        struct stat sb;

        if (PageSize == -1)
        {
            perror("Eroare la sysconf");
            exit(1);
        }

        if (fstat(f, &sb) == -1)
        {
            perror("Eroare la fstat");
            exit(2);
        }

        nLines = auxn;
        cLines = auxc;

        for (int i = 0; i < SECTOR_SIZE; i++)
            rezultat[i][0] = '\0';
        nrLiniiRez = 0;

        recursive(f, sb.st_size, 0, PageSize);

        printf("==> %s <==\n", numeFisiere[i]);

        if (lastOption == 2 && auxn < 0)
            nrLiniiRez += auxn;

        cLines = auxc;
        if (lastOption == 1 && auxc < 0)
        {
            for (int k = nrLiniiRez; k >= 1; k--)
            {
                int lg = strlen(rezultat[k]) - 1;
                for (int j = lg; j >= 0 && cLines != 0; j--, cLines++)
                    rezultat[k][j] = '\0';
                if (rezultat[k][0] == '\0')
                    nrLiniiRez--;
            }
        }

        for (int k = 1; k <= nrLiniiRez; k++)
        {
            if (lastOption == 2)
            {
                printf("%s\n", rezultat[k]);
            }
            else
                for (int j = 0; j < strlen(rezultat[k]); j++)
                    printf("%c", rezultat[k][j]);
        }
    }
}

void reverse(char *sir)
{
    int lg = strlen(sir) - 1;
    for (int i = 0; i <= lg / 2; i++)
    {
        char aux = sir[i];
        sir[i] = sir[lg - i];
        sir[lg - i] = aux;
    }
}

int cifra(char c)
{
    return c >= '0' && c <= '9';
}

void number(char *sir)
{
    isNumber = 1;
    nr = 0;

    int minus = (sir[0] == '-');

    for (int i = minus; i < strlen(sir); i++)
        if (cifra(sir[i]))
            nr = nr * 10 + sir[i] - '0';
        else
        {
            isNumber = 0;
            return;
        }
    if (minus == 1)
        nr = -nr;
}

void getData(char *map_addr, int length)
{
    for (int i = 0; i <= length; i++)
    {
        if (lastOption == 1) // optiunea -c
        {
            if (cLines != 0)
            {
                if (nrLiniiRez == 0 || strlen(rezultat[nrLiniiRez]) + 1 > SECTOR_SIZE)
                    nrLiniiRez++;
                int lg = strlen(rezultat[nrLiniiRez]);
                rezultat[nrLiniiRez][lg] = map_addr[i];
                rezultat[nrLiniiRez][lg + 1] = '\0';

                if (cLines > 0)
                    cLines--;
            }
            else
                break;
        }
        else
        {
            if (nLines != 0)
            {
                char aux[SECTOR_SIZE] = {0};
                while (i < length && map_addr[i] != '\n')
                {
                    int lgAux = strlen(aux);
                    aux[lgAux++] = map_addr[i++];
                }
                strcpy(rezultat[++nrLiniiRez], aux);
                if (nLines > 0)
                    nLines--;
            }
            else
                break;
        }
    }
}

void recursive(int f, int length, int offset, int PageSize)
{
    if ((lastOption == 1 && cLines != 0) || (lastOption == 2 && nLines != 0))
    {
        char *map_addr;
        if (length > PageSize)
        {
            map_addr = mmap(NULL, PageSize, PROT_READ, MAP_PRIVATE, f, offset);

            getData(map_addr, PageSize);
            recursive(f, length - PageSize, offset + PageSize, PageSize);
            if (munmap(map_addr, PageSize) == -1)
            {
                perror("Erroare la munmap.");
                exit(4);
            }
            return;
        }
        map_addr = mmap(NULL, length, PROT_READ, MAP_PRIVATE, f, offset);
        getData(map_addr, length);

        if (munmap(map_addr, length) == -1)
        {
            perror("Erroare la munmap.");
            exit(4);
        }
    }
}