double convert_lengths();
double convert_weights();
double length_to_metric();
double length_to_us();
double weight_to_metric();
double weight_to_us();
void read_length_us(int* ft, double* in);
void convert_length_to_metric(int ft, double in, int* m, double* cm);
void output_length_metric(int ft, double in, int m, double cm);
void read_length_metric(int* m, double* cm);
void convert_length_to_us(int m, double cm, int* ft, double* in);
void output_length_us(int m, double cm, int ft, double in);
void read_weight_us(int* lb, double* oz);
void convert_weight_to_metric(int lb, double oz, int* kg, double* g);
void output_weight_metric(int lb, double oz, int kg, double g);
void read_weight_metric(int* kg, double* g);
void convert_weight_to_us(int kg, double g, int* lb, double* oz);
void output_weight_us(int kg, double g, int lb, double oz);
void clear_keyboard_buffer();

#include <stdio.h>

int main(int argc, char * argv[])
{
   int temp, input;
   while(temp < 1 || input > 2 || input != 0)
   {
      temp = 0;
      printf("1. convert length\n2. convert weight\n0. Exit\nPlease choose from (1, 2, 0):\n");
      temp = scanf("%d", &input);
      clear_keyboard_buffer();
      if(input == 1)
      {
         convert_lengths();
      }
      if(input == 2)
      {
         convert_weights();
      }
      if(input == 0)
      {
         printf("User chose to exit.\n");
         break;
      }
   }
   return 0;
}

double convert_lengths()
{
   int input = 99, temp;

   while(temp < 1 || input > 2 || input == 99 || input != 0)
   {
      printf("1. convert lengths to metrics\n");
      printf("2. convert lengths to US\n");
      printf("0. Return to Main Menu\n");
      temp = scanf("%d", &input);
      clear_keyboard_buffer();
      if(input == 1)
      {
         length_to_metric();
      }
      if(input == 2)
      {
         length_to_us();
      }
      if(input == 0)
      {
         printf("User chose to go main menu.\n");
         break;
      }
   }
   return 0;
}

double length_to_metric()
{
      printf("The user wants to convert length_to_metric.\n");
      int m, ft;
      double cm, in;
      read_length_us(&ft, &in);
      convert_length_to_metric(ft, in, &m, &cm);
      output_length_metric(ft, in, m, cm);
      return 0;
}

void read_length_us(int* ft, double* in)
{
   printf("Enter feet and inches (seperated by a space):\n");
   scanf("%d %lf", ft, in);
}

void convert_length_to_metric(int ft, double in, int* m, double* cm)
{
   double totalft = ft + (in / 12);
   double totalm = totalft * .3048;
   *m = (int)totalm;
   *cm = (totalm - (*m)) * 100.0;
}

void output_length_metric(int ft, double in, int m, double cm)
{
   printf("%d feet and %.4lf inches converted to %d meters and %.4lf centimeters.\n", ft, in, m, cm);
}

double length_to_us()
{
      printf("The user wants to convert length_to_us.\n");
      int m, ft;
      double cm, in;
      read_length_metric(&m, &cm);
      convert_length_to_us(m, cm, &ft, &in);
      output_length_us(m, cm, ft, in);
      return 0;
}

void read_length_metric(int* m, double* cm)
{
   printf("Enter meter and centimeters (seperated by a space):\n");
   scanf("%d %lf", m, cm);
}

void convert_length_to_us(int m, double cm, int* ft, double* in)
{
   double totalm = m + (cm / 100);
   double totalft = totalm / .3048;
   *ft = (int)totalft;
   *in = (totalft - (*ft)) * 12.0;
}

void output_length_us(int m, double cm, int ft, double in)
{
   printf("%d meters and %.4lf centimeters converted to %d feet and %.4lf inches.\n", m, cm, ft, in);
}

double convert_weights()
{
   int input = 99, temp;

   while(temp < 1 || input > 2 || input == 99 || input != 0)
   {
      printf("1. convert weights to metrics\n");
      printf("2. convert weights to US\n");
      printf("0. Return to Main Menu\n");
      temp = scanf("%d", &input);
      clear_keyboard_buffer();
      if(input == 1)
      {
         weight_to_metric();
      }
      if(input == 2)
      {
         weight_to_us();
      }
      if(input == 0)
      {
         printf("User chose to go main menu.\n");
         break;
      }
   }
   return 0;
}

double weight_to_metric()
{
   printf("The user wants to convert weight_to_metric.\n");
   int lb, kg;
   double oz, g;
   read_weight_us(&lb, &oz);
   convert_weight_to_metric(lb, oz, &kg, &g);
   output_weight_metric(lb, oz, kg, g);
   return 0;
}

void read_weight_us(int* lb, double* oz)
{
   printf("Enter pound and ounces (seperated by a space):\n");
   scanf("%d %lf", lb, oz);
}

void convert_weight_to_metric(int lb, double oz, int* kg, double* g)
{
   double totallb = lb + (oz / 16);
   double totalkg = totallb / 2.2046;
   *kg = (int)totalkg;
   *g = (totalkg - (*kg)) * 1000;
}

void output_weight_metric(int lb, double oz, int kg, double g)
{
   printf("%d pounds and %.4lf ounces converted to %d kilograms and %.4lf grams.\n", lb, oz, kg, g);
}

double weight_to_us()
{
   printf("The user wants to convert weight_to_us.\n");
   int lb, kg;
   double oz, g;
   read_weight_metric(&kg, &g);
   convert_weight_to_us(kg, g, &lb, &oz);
   output_weight_us(kg, g, lb, oz);
   return 0;
}

void read_weight_metric(int* kg, double* g)
{
   printf("Enter kilograms and grams (seperated by a space):\n");
   scanf("%d %lf", kg, g);
}

void convert_weight_to_us(int kg, double g, int* lb, double* oz)
{
   double totalkg = kg + (g / 1000);
   double totallb = totalkg * 2.2046;
   *lb = (int)totallb;
   *oz = (totallb - (*lb)) * 16;
}

void output_weight_us(int kg, double g, int lb, double oz)
{
   printf("%d kilograms and %.4lf grams converted to %d pounds and %.4lf ounces.\n", kg, g, lb, oz);
}

void clear_keyboard_buffer(void)
{
 char ch;
 scanf("%c", &ch);
 while (ch != '\n' && ch != '\0')
    {
        scanf("%c", &ch);
    }
}