//-----------------------------------------------------------------------------
// File:     HelloMath1.cpp
// Class:    None
// Parent:   None
// Children: None
// Purpose:  Converts an angle to degrees and calculates the sine, cosine, and tangent
//           of that angle.
//-----------------------------------------------------------------------------
// The following are standard C/C++ header files.
// If a filename is enclosed inside < >  it means the header file is in the Include directory.
// If a filename is enclosed inside " "  it means the header file is in the current directory.
#include <ctype.h>      // Character Types
#include <math.h>       // Mathematical Constants
#include <stdarg.h>     // Variable Argument Lists
#include <stdio.h>      // Standard Input/Output Functions
#include <stdlib.h>     // Utility Functions
#include <string.h>     // String Operations
#include <signal.h>     // Signals (Contol-C + Unix System Calls)
#include <setjmp.h>     // Nonlocal Goto (For Control-C)
#include <time.h>       // Time and Date information
#include <assert.h>     // Verify Program Assertion
#include <errno.h>      // Error Codes (Used in Unix system())
#include <float.h>      // Floating Point Constants
#include <limits.h>     // Implementation Constants
#include <stddef.h>     // Standard Definitions
#include <exception>    // Exception handling (e.g., try, catch throw)
//-----------------------------------------------------------------------------

bool  GetStringFromFile( char inputString[], unsigned long maxSizeOfString, FILE *fptr ) { return fgets(inputString, maxSizeOfString, stdin) != NULL; }
bool  GetStringFromKeyboard( char inputString[], unsigned long maxSizeOfString ){ return GetStringFromFile(inputString, maxSizeOfString, stdin);}
bool  WriteStringToFile( const char outputString[], FILE *fptr ){ return fprintf( fptr, outputString ) != NULL; }
bool  WriteStringToScreen( const char outputString[] ){ return WriteStringToFile(outputString, stdout);}
const char*  ConvertStringToDouble( const char *s, double &returnValue, double defaultValue );
double  ConvertFromRadiansToDegrees( double angleInRadians ){return angleInRadians*57.2957795; /*1 radian is approx 57.3 degrees*/}
double  ConvertFromDegreesToRadians( double angleInDegrees ){return angleInDegrees/57.2957795;/*1 radian is approximately 57.3 degrees*/}


//-----------------------------------------------------------------------------
int main()
{
   //get the angle and convert to a double.
   WriteStringToScreen("Enter an angle in degrees:");
   char stringInDegrees[100];
   unsigned long maxSizeOfString = 100;
   GetStringFromKeyboard( stringInDegrees, maxSizeOfString );
   
   double angleInDegrees;
   
   if(ConvertStringToDouble(stringInDegrees, angleInDegrees, 45)==NULL)
	   WriteStringToScreen("\nYour angle was not valid.  45 degrees will be used instead.");
   
   //Do math calculations.
   double angleInRadians=ConvertFromDegreesToRadians(angleInDegrees);
   double sinOfAngle = sin(angleInRadians);
   double cosOfAngle = cos(angleInRadians);
   double tanOfAngle = tan(angleInRadians);

   //Print each quantity with a string saying what it is.  Then print to screen.

   //printing degrees
   char stringDegrees[100];
   sprintf( stringDegrees, "\nAngle in degrees= %f\n", angleInDegrees );
   WriteStringToScreen( stringDegrees );

   //print radians
   char stringRadians[100];
   sprintf( stringRadians, "\nAngle in radians= %f\n", angleInRadians );
   WriteStringToScreen( stringRadians );

   //print sine
   char stringSine[100];
   sprintf( stringSine, "\nSine of angle= %f\n", sinOfAngle );
   WriteStringToScreen( stringSine );

   //print cosine
   char stringCosine[100];
   sprintf( stringCosine, "\nCosine of angle= %f\n", cosOfAngle );
   WriteStringToScreen( stringCosine );

   //print tangent
   char stringTangent[100];
   sprintf( stringTangent, "\nTangent of angle= %f\n", tanOfAngle );
   WriteStringToScreen( stringTangent );
   

   // Keep the screen displayed until the user presses the Enter key
   printf( "\n\n Press  Enter  to terminate the program: " );
   int key = getchar();

   return 0;
   
}






//-----------------------------------------------------------------------------
const char* ConvertStringToDouble( const char *s, double &returnValue, double defaultValue )
{
   // Default return value (in case the string is not a valid number)
   returnValue = defaultValue;
   // Check if s is a NULL string or "&^%$#" or "abc" or "123huh"
   if( s )
   {
      // Use the standard math function strtod to parse the number
      char *pointerToCharacterAfterNumber = NULL;
      double x = strtod( s, &pointerToCharacterAfterNumber );
      // Ensure the character after the number is a space or ’\0’, not ’a’ or ’z’ or ...
      char characterAfterNumber = pointerToCharacterAfterNumber ? *pointerToCharacterAfterNumber : 'z';
      if( characterAfterNumber == '\0' || isspace(characterAfterNumber) )
      {
         returnValue = x;
         return pointerToCharacterAfterNumber;
      }
   }
   return NULL;
}