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

int main(int argc, char **argv) {
    if(argc < 2) {
        printf("Program requires file argument at the least.\n");
        return 1;
    } else if(argc > 4) {
        printf("Program takes 3 arguments max.\n");
        return 1;
    }
    int index = 0;
    if(argc > 2) index = atoi(argv[2]);
    
    int fileNum = atoi(argv[1]);
    char fileName[20];
    snprintf(fileName, 19, "storage/%d.txt", fileNum);
    FILE *f = fopen(fileName, "r");
    if(!f) {
        printf("Error opening file to read.\n");
        return 1;
    }
    
    
    int length = 0;
    char c = getc(f);
    while(c != EOF) {
        if(c == '\n') length++;
        c = getc(f);
    }
    if(length <= index) {
        printf("Index is bigger than file length.\n");
        return 1;
    }
    
    if(argc == 4) {
        int uInd = atoi(argv[3]) + index;
        if(uInd < length) length = uInd;
    }

    FILE *graph = popen("gnuplot", "w");
    if(!graph) {
        printf("Error opening gnuplot.\n");
        return 1;
    }
    fprintf(graph, "plot '-'\n");
    
    fseek(f, 0, SEEK_SET);
    c = getc(f);
    char buffer[50];
    snprintf(buffer, 49, "%d ", index++);
    char append[2] = {' ', '\0'};
    while(c != EOF && index <= length) {
        append[0] = c;
        strcat(buffer, append);

        if(c == '\n') {
            fprintf(graph, "%s", buffer);
            snprintf(buffer, 49, "%d ", index++);
        }
        c = getc(f);
    }

    fprintf(graph, "e\n");
    fflush(graph);
    sleep(-1);
}