//   Fibonacci sequence
//   Number in series interactively or via command line argument
//   fibonacci_series.cpp
//   RJM Programming - December, 2022

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

char aline[500];
int done=0;
int last=-1;
char oneline[500];
char lblanks[500];
//int nums[]={0,1};
int lastf=0;
int lastlastf=0;

int countFibonacci(int i) {  // Recursive function
    int fibonacci;
    if (i == 0) { return 0; } else if (i == 1) { if (done == 0) { done=1; sprintf((aline + strlen(aline)), "1%s", " "); } return 1; }
    
    fibonacci = countFibonacci(i-1) + countFibonacci(i-2);
    if (fibonacci > last) {
      strcpy(aline, lblanks);
      strcat(aline, oneline);
      //sprintf((aline + strlen(aline)), "%d%s", fibonacci, ", ");
      sprintf((aline + strlen(aline)), "%d%s", fibonacci, " ");
      //nums[1]=fibonacci;
    }
    last=fibonacci;
    return fibonacci;
}

int main(int argc, char *args[]) {
        char delim[3]=", ";
        char explanation[5000];
        int nsize = 0, fibonacci, i, j, k;
        char catend[20];
        
        // Check for argument 1 number in series
        if (argc > 1) {
            for(i=0; i<strlen(args[1]); i++) {
                if (args[1][i] == '-' || (args[1][i] >= '0' && args[1][i] <= '9')) {
                    nsize = nsize;
                } else if (args[0][i] != '-') {
                    nsize--;
                }
            }
            if (nsize == 0) sscanf(args[1], "%d", &nsize);
        }
        strcpy(explanation, "\n\n");
        strcpy(aline, "0, ");
        oneline[0]=0; 
        lblanks[0]=0; 
        if (argc <= 1) { //nsize <= 0) {
            //printf("How many numbers are there in your fibonacci sequence (-ve for in a row): ");
            printf("How many numbers are there in your fibonacci sequence: ");
            scanf(" %d", &nsize);
        }
        //if (nsize > 0) {  strcpy(delim, "\n\0");   }
        
        for (i=-5; i<=(int) abs(nsize * 3); i++) {
              sprintf((lblanks + strlen(lblanks)), "%s", " ");
        }
        k=strlen(lblanks);
        strcpy(aline, lblanks);
        strcat(aline, "0, ");
        
        for (i=0; i<=(int) abs(nsize); i++) {
            fibonacci = countFibonacci(i);
            if (i == (int) abs(nsize)) { 
              printf("%d", fibonacci); 
              sprintf((oneline + strlen(oneline)), "%d%s", fibonacci, "\0");
              if (strstr(aline, "1")) {
                if (lastf != 0) {
                  sprintf(catend, "%d%s%d%s%d%s", lastlastf, " + ", lastf, " = ", fibonacci, "\n");
                } else {
                  sprintf(catend, "%d%s%d%s%d%s", lastlastf, " + ", 1, " = ", fibonacci, "\n");
                }
                strcat(explanation, strcat(strcat(aline, "\n "), catend));
              }
              //oneline[0]=0;
              aline[0]=0;
              k-=2;
              sprintf(lblanks, "%s", "\0");
              for (j=0; j<k; j++) {
                sprintf((lblanks + strlen(lblanks)), "%s", " ");
              }
              sprintf(aline, "%s%s", lblanks, "\0");
              strcat(aline, "0, ");
              lastlastf=lastf;
              lastf=fibonacci;
           } else {  
              printf("%d%s", fibonacci, delim);
              sprintf((oneline + strlen(oneline)), "%d%s%s", fibonacci, delim, "\0");
              if (strstr(aline, "1")) {
                if (lastf != 0) {
                  sprintf(catend, "%d%s%d%s%d%s", lastlastf, " + ", lastf, " = ", fibonacci, "\n");
                } else {
                  sprintf(catend, "%d%s%d%s%d%s", lastlastf, " + ", 1, " = ", fibonacci, "\n");
                }
                strcat(explanation, strcat(strcat(aline, "\n "), catend));
              }
              //oneline[0]=0; 
              aline[0]=0;
              k-=2;
              sprintf(lblanks, "%s", "\0");
              for (j=0; j<k; j++) {
                sprintf((lblanks + strlen(lblanks)), "%s", " ");
              }
              sprintf(aline, "%s%s", lblanks, "\0");
              strcat(aline, "0, ");
              lastlastf=lastf;
              lastf=fibonacci;
            }
        }
        //strcat(explanation, strcat(oneline, " a new line\n"));
        printf("\n%s\n", explanation);
}