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

#define DATFILE "/home/ryan/datfile"

time_t buf;
struct tm bt;
struct tm et;
int flg = 0;

struct time {
    int hour;
    int min;
};
struct date {
    int year;
    int month;
    int day;
};
struct session {
    struct date date;
    int offset;
    char name[4096];
};

void sighnd() { flg = 1; }
void flgwt() { while(flg == 0) { continue; } }

char* concat(const char *s1, const char *s2) {
    char *result = malloc(strlen(s1) + strlen(s2) + 1);
    // let's hope malloc works correctly
    strcpy(result, s1);
    strcat(result, s2);
    return result;
}

struct tm get_time() {
    time_t buf;
    struct tm b;
    buf = time(NULL);
    b = *localtime(&buf);
    return b;
} 

void write_session(FILE *fd, struct session session) {
    fprintf(fd, "P%02d%02d%04d%d %s\n",
        session.date.month, session.date.day, session.date.year,
        session.offset, session.name);
}

struct session data_to_session(struct tm time, int offset, char *name) {
    struct session session;
    session.date.year = time.tm_year + 1900;
    session.date.month = time.tm_mon;
    session.date.day = time.tm_mday;
    session.offset = offset;
    strcpy(session.name, name);
    return session;
}

struct session line_to_session(char *line) {
    struct session session;
    char *buf = line;
    char *parameters = strtok(buf, " ");
    strcpy(session.name, strtok(NULL, ""));
    session.date.month = atoi(concat(&parameters[1], &parameters[2]));
    session.date.day = atoi(concat(&parameters[3], &parameters[4]));
    session.date.year = atoi(concat(
        concat(&parameters[5], &parameters[6]),
        concat(&parameters[7], &parameters[8])));
    char charbuf[8];
    for(int i = 9; parameters[i] == " "; i++) {
        strcat(&charbuf, &parameters[i]);
    }
    session.offset = atoi(&charbuf);
    return session;
}

int timediff(struct tm f, struct tm l) {
    int fm = f.tm_min + (f.tm_hour * 60);
    int lm = l.tm_min + (l.tm_hour * 60);
    return fm - lm;
}

int main(int argc, char **argv) {
    if (argc != 2) { 
        FILE *f = fopen(DATFILE, "r");
        char line[2048];
        struct session session_array[20];

        int counter = 0;
        while(fgets(line, sizeof(line), f)) {
             session_array[counter] = line_to_session(line);
             counter++;
        }
        fclose(f);
        FILE *fd = fopen(DATFILE, "a+");
        for(int x = 0; x < counter; x++) {
             write_session(fd, session_array[x]);
        }
        return 1;
    }
    bt = get_time();
    signal(SIGINT, sighnd);
    flgwt();
    int t = timediff(get_time(), bt);
    struct session data = data_to_session(bt, t, argv[1]);
    FILE *f = fopen(DATFILE, "a");
    write_session(f, data);
    fclose(f);
    return 0;
}