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

#define FALSE (0)

int Validation_Check(char []);
        
main(void) // The following comment doesn't really provide a lot of info: // This is the start of the Currency Conversion Program II. 
{
    
    //The foreign conversion currency value rates are established here.
    float Australian_Dollar_Exchange_Rate = 0.79;
    float Brazilian_Real_Exchange_Rate = 0.48;  
    float Danish_Krone_Exchange_Rate = 0.18;
    float Swiss_Franc_Exchange_Rate = 0.81;
    float Swedish_Krona_Exchange_Rate = 0.14;
    float US_Dollars_Converted[5];
    float Foreign_Amt_For_Conversion;
    char Conversion_Amount_As_A_String[30];
    char Is_Entry_Valid;
    
    printf("Conversion Calculator:  "); //Prints the name of this program.
    printf("\nThis program will convert Brazilian Real into U.S. Dollars  ");  //Prints a description of the program.
    printf("\n");
    
         fflush(stdin); //Clear Invalid Data
         
         /*     
         Step 1. Get Amount - Great!
         */
         printf("\nEnter the amount of Brazilian Real to be converted:  "); //This prompts the end user to input the amount to be converted.
         gets(Conversion_Amount_As_A_String);
         
         /* 
         Step 2. Validate - Great!
         Note:
         In the following statement Is_Entry_Valid is initialized by the output
         of the function Validation_Check(). However, this function doesn't
         return 'Y' or 'N'. Check my comments in Validation_Check().
         */
          Is_Entry_Valid = Validation_Check(Conversion_Amount_As_A_String);
          
          /* 
          Step 3. Iterate as long as the amount entered is invalid! - Great!
          */
    
    while (Is_Entry_Valid == 'N'){
        /* 
        Getting here means that the amount entered is invalid!
        Therefore you should display an error message and start
        all over as you do below:
        */
        
         /*      
         Step 1. Get Amount - Great!
         */        
        fflush(stdin); //Clear Invalid Data
         printf("\nEnter the amount of Brazilian Real to be converted:  "); //This prompts the end user to input the amount to be converted.
         gets(Conversion_Amount_As_A_String);
         /* 
         Step 2. Validate - Great!
         Note:
         In the following statement Is_Entry_Valid is initialized by the output
         of the function Validation_Check(). However, this function doesn't
         return 'Y' or 'N'. Check my comments in Validation_Check().
         */         
          Is_Entry_Valid = Validation_Check(Conversion_Amount_As_A_String);
      }
      
      /* 
      Step 4. Convert string to float
      Note:
      Excellent! Getting here means that the amount entered represents
      a valid float quantity. So you convert the string to float.
      */
    Foreign_Amt_For_Conversion = atof(Conversion_Amount_As_A_String);

    /* 
    Step 5. Convert the foreign amount to US Dollars
    Note:
    (1) Excellent! Use the float quantity to perform the arithmetic and
        convert foreign currency to US Dollars.
        (2) Wouldn't be a good idea to display the exchange rate used in the
        conversion? What do you think?
    */                        
    US_Dollars_Converted[1] = Foreign_Amt_For_Conversion * Brazilian_Real_Exchange_Rate; //This establishes the conversion amount for the Brazilian Real to US Dollar.
    printf("%.2f Brazilian Real \t is $ %.6f U.S. Dollars\n", Foreign_Amt_For_Conversion, US_Dollars_Converted[1]);    
    
    /* 
    Note: Use group comments instead of end-of-line comments. Check also
    your Week 4 Individual Assignment Feedback for more information on
    Internal Documentation
    */
    fflush(stdin); //Clear Invalid Data
    printf("\n\nPress the [Enter] key to end the program");    //This instructs the end user how to end the program.                        
    getchar(); //This allows the screen to keep displaying until the Enter key is pushed. 
    
    return 0; //Main returning 0 to the OS
} 

/* 
Notes:

(1) You should document this function using a function prologue
(2) The function incorrectly rejects positive input such as +30.45
(3) Is a negative amount necessarily invalid? This function could be used
    by other programs for which negative amounts are allowed. Use a parameter
    to indicate whether or not negative amounts are accepted
*/
int Validation_Check(char User_Input[]) /*  Moved bracket to the next line. Functions are similar to main() */
{ 
      int Array_Element_ID, String_Length, nof_Decimal_Points = 0;
      char Is_It_Valid; // This is not initialized. How are you going to return 'Y'?
      String_Length = strlen(User_Input); 

      for(Array_Element_ID = 0; Array_Element_ID < String_Length; Array_Element_ID++) {
            if (isdigit(User_Input[Array_Element_ID]) == FALSE) {
                  if (User_Input[Array_Element_ID] == '-' ) {
                       /* 
                       There's no need to display an error message here and request new amount! 
                       Let the "caller" of Validation_Check() handle the user interface. 
                       Check my comments above.
                       */
                     printf("\n%s << Invalid Entry, Please Enter Valid Amount.\n", User_Input); //This prompts the end user to input a valid amount.
                     /* 
                     It's not really a good practice have multiple exit points from 
                     a function. Here you just need to set the return value; i.e.
                     Is_It_Valid = 'N'; and then terminate the loop either by using a
                     break statement or by setting Array_Element_ID = String_Length + 1
                       */
                           return Is_It_Valid = 'N'; //Passes data to a new transaction.
                      }
                else if (User_Input[Array_Element_ID] == '.' ) {
                    if (Array_Element_ID != 0 ) {
                                nof_Decimal_Points++;
                                if (nof_Decimal_Points >= 2) {
                           /* 
                           There's no need to display an error message here and request new amount! 
                           Let the "caller" of Validation_Check() handle the user interface. 
                           Check my comments above.
                           */
                                    printf("\n%s << Invalid Entry, Please Enter Valid Amount.\n", User_Input); //This prompts the end user to input a valid amount.
                         /* 
                         It's not really a good practice have multiple exit points from 
                         a function. Here you just need to set the return value; i.e.
                         Is_It_Valid = 'N'; and then terminate the loop either by using a
                         break statement or by setting Array_Element_ID = String_Length + 1
                           */
                                    return Is_It_Valid = 'N'; //Passes data to a new transaction.
                                }  
                          }  
                      }
                else {  
                      /* 
                      There's no need to display an error message here and request new amount! 
                      Let the "caller" of Validation_Check() handle the user interface. 
                      Check my comments above.
                      */
                           printf("\n%s << Invalid Entry, Please Enter Valid Amount.\n", User_Input); //This prompts the end user to input a valid amount.
                       /* 
                    It's not really a good practice have multiple exit points from 
                       a function. Here you just need to set the return value; i.e.
                       Is_It_Valid = 'N'; and then terminate the loop either by using a
                       break statement or by setting Array_Element_ID = String_Length + 1
                     */
                 return Is_It_Valid = 'N'; //Passes data to a new transaction.
                     } 
            }
      } 
      
      
      /* 
      Notes:
      (1) The following comment is wrong! Be careful when copying code!
      (2) Here instead of returning 0 (zero), you should make 
          the corrections above and return value; i.e. return Is_It_Valid;
          In other words this will be the single function exit point.
      */
      
      return 0; //Main returning 0 to the OS
}

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

int Validation_Check(char [], int);

main(void)
{
  float Australian_Dollar_Exchange_Rate = 0.79;
  float Brazilian_Real_Exchange_Rate = 0.48;  
  float Danish_Krone_Exchange_Rate = 0.18;
  float Swiss_Franc_Exchange_Rate = 0.81;
  float Swedish_Krona_Exchange_Rate = 0.14;
  float US_Dollars_Converted[5];
  float Foreign_Amt_For_Conversion;
  char Conversion_Amount_As_A_String[30];
  char Is_Entry_Valid;
  
  printf("Conversion Calculator:\n");
  printf("This program will convert Brazilian Real into U.S. Dollars\n");
  
  fflush(stdin);
  
  printf("Enter the amount of Brazilian Real to be converted:  ");
  gets(Conversion_Amount_As_A_String);
  
  Is_Entry_Valid = Validation_Check(Conversion_Amount_As_A_String, 1);
  
  while (Is_Entry_Valid == 'N')
    {
      fflush(stdin);

      printf("Invalid Entry, Please Enter Valid Amount.\n");

      printf("Enter the amount of Brazilian Real to be converted:  ");

      gets(Conversion_Amount_As_A_String);

      Is_Entry_Valid = Validation_Check(Conversion_Amount_As_A_String, 1);
    }
  
  Foreign_Amt_For_Conversion = atof(Conversion_Amount_As_A_String);
  
  US_Dollars_Converted[1] = Foreign_Amt_For_Conversion * Brazilian_Real_Exchange_Rate;

  printf("%.2f Brazilian Real \t is $ %.6f U.S. Dollars\n", Foreign_Amt_For_Conversion, US_Dollars_Converted[1]);
  
  fflush(stdin);

  printf("Press the [Enter] key to end the program");

  getchar();
  
  return(0);
} 

/*
**  Function that checks the user_input, the function returns 'Y' if the string is a 
**  valid floating point number, 'N' otherwise. Empty string is considered non-valid. 
**  A valid number has only one '.' or ',', and the only valid non-digit character is '-', 
**  if it is in the begining of the number and if Negative_Numbers_Valid is 1.
**  Numbers begining with '+' are valid.
*/
int Validation_Check(char User_Input[], int Neg_Num_Valid)
{ 
  int Array_Element_ID;
  int String_Length;
  int nof_Decimal_Points = 0;
  char Is_It_Valid = 'Y';
  
  String_Length = strlen(User_Input); 
  
  if(String_Length == 0)
    Is_It_Valid = 'N';
  
  for(Array_Element_ID = 0; Array_Element_ID < String_Length && Is_It_Valid != 'N'; Array_Element_ID++) 
    {
      if (User_Input[Array_Element_ID] == '.' || User_Input[Array_Element_ID] == ',')
	{
	  nof_Decimal_Points++;

	  if (nof_Decimal_Points >= 2)
	    {
	      Is_It_Valid = 'N';
	    }
	}
      else if (!isdigit(User_Input[Array_Element_ID])) 
	{
	  Is_It_Valid = 'N';
	  
	  if (User_Input[Array_Element_ID] == '-' && Array_Element_ID == 0 && Neg_Num_Valid)
	    Is_It_Valid = 'Y';
	  
	  if (User_Input[Array_Element_ID] == '+' && Array_Element_ID == 0)
	    Is_It_Valid = 'Y';
	}
    }
  
  return(Is_It_Valid);
}