/*
   dgkio.h
   CIS 150
   7/1/05
   David G. Klick
   
   Utility functions to make I/O easier and more robust
   for some common tasks:
   
   1. getInt: gets an int value from the user with
      validation and minimum and maximum checking
   2. getDouble: gets a double value from the user with
      validation and minimum and maximum checking
   3. getChoice: gets a single character response from
      the user (with validation) for use with menu processing
   4. processMenu: a more complete menu processing function
      which displays a menu and then calls getChoice
      
   See the more complete function descriptions included with
   each function definition in this file.
*/

#ifndef __DGKIO_H_
#define __DGKIO_H_

#include <iostream>
#include <cstdlib>
using std::cout;
using std::cin;

namespace dgk {

/*
   This function takes a C-style string as input
   and returns true if it represents a valid integer
   and false if it doesn't. A single leading '+'
   or '-' is allowed.
*/
bool dgk::isValidInt(char* ptr) {
   char ch;
   int n = 0;

   // make sure we got a real pointer
   if (!ptr) return false;

   // get first character and make sure it exists
   ch = *ptr++;
   if (ch == '\0') return false;
      
   // allow a leading + or -
   if (ch=='+' || ch=='-') ch = *ptr++;

   // make sure all other characters are digits
   while (ch) {
      if (ch<'0' || ch>'9') return false;
      n++;   // count number of valid digits
      ch = *ptr++;
   }
   
   // invalid if no digits present
   if (n == 0) return false;
   
   // if we got here, the number is OK
   return true;
}

/*
   This function takes a C-style string as input
   and returns true if it represents a valid float
   and false if it doesn't. A single leading '+'
   or '-' is allowed. A single decimal point is
   also allowed.
*/
bool dgk::isValidFloat(char* ptr) {
   char ch;
   int n = 0;
   bool hasDecimal = false;
   
   // make sure we got a real pointer
   if (!ptr) return false;

   // get first character and make sure it exists
   ch = *ptr++;
   if (ch == '\0') return false;

   // allow a leading + or -
   if (ch=='+' || ch=='-') ch = *ptr++;

   // make sure all other characters are digits
   // (also allows a single decimal point)
   while (ch) {
      if (ch == '.') {
         if (hasDecimal) return false;
         else hasDecimal = true;
      } else {
         if (ch<'0' || ch>'9') return false;
         else n++; // count number of valid digits
      }
      ch = *ptr++;
   }
   
   // invalid if no digits present
   if (n == 0) return false;
   
   // if we got here, the number is OK
   return true;
}

/*
   Prompts user for integer, does data validation,
   and returns value entered.
*/
int dgk::getInt(char* prompt, int min, int max) {
   char buf[20];
   int num;
   bool valid = false;

   do {
      cout << prompt;
      cin.getline(buf, 20, '\n');
      if (!isValidInt(buf)) cout << "Error: Invalid integer\n";
      else {
         num = atoi(buf);
         if (num < min) cout << "Error: Value below minimum allowed\n";
         else if (num > max) cout << "Error: Value above maximum allowed\n";
         else valid = true;
      }
   } while (!valid);
   
   return num;
}

/*
   Prompts user for number, does data validation,
   and returns value entered.
*/
double dgk::getDouble(char* prompt, double min, double max) {
   char buf[20];
   double num;
   bool valid = false;

   do {
      cout << prompt;
      cin.getline(buf, 20, '\n');
      if (!isValidFloat(buf)) cout << "Error: Invalid number\n";
      else {
         num = atof(buf);
         if (num < min) cout << "Error: Value below minimum allowed\n";
         else if (num > max) cout << "Error: Value above maximum allowed\n";
         else valid = true;
      }
   } while (!valid);
   
   return num;
}

/*
   Prompts user for menu choice, does data validation, and
   returns a valid entered value. A third boolean argument,
   which is optional determines whether all letters input
   will be treated as uppercase. The default is to leave
   input as-is. Setting the third argument to true will do
   the uppercase conversion of letters.
*/
char dgk::getChoice(char* prompt, char* allowed,
                    bool upper = false) {
   char ans;
   char *pos;
   
   do {
      // prompt user for input and get user choice
      cout << prompt;
      cin >> ans;
      cin.ignore(); // get rid of newline
      
      // convert to uppercase if requested
      if (upper) ans = toupper(ans);
      
      // see if user input is in allowable response set
      pos = strchr(allowed, ans);
      
      // if input was invalid, display error message
      if (!pos) cout << "Error: Invalid choice\n";
      
   } while (!pos);  // continue looping if invalid response
   return ans;
}

/*
   This function displays a menu sent as a C-style
   string and then gets a one character menu choice 
   from the user. It optionally converts that character
   to upper case if desired.
   The calling routine must provide C-style strings
   containing:
   1. the menu itself
   2. the user prompt
   3. a string of allowable responses
   A fourth argument is optional. It is a boolean value
   which indicates whether user input that is letters
   should automatically be converted to uppercase. The
   default is to leave input as it is.
*/
char dgk::processMenu(char *menu, char* prompt,
                      char* allowed, bool upper=false) {
   cout << menu;
   return getChoice(prompt, allowed, upper);
}

} // end of dgk namespace;

#endif