/*
 * latecalc.cpp
 *
 * Usage:  latecalc <minutes-late>
 *
 * This program takes an argument indicating how many minutes late an
 * assignment was and returns the lateness multiplier for that assignment.
 *
 * (c) 2006 Melissa O'Neill.  All rights reserved.
 */


#include <cmath>
#include <iostream>
#include <string>
#include <vector>
#include <sstream>
#include <stdexcept>


/* lateMult [global function]:
 *      Inputs:  double mins		minutes past the deadline
 *      Returns: double			multiplier (i.e., 0.8 => 20% penalty)
 * 
 * Calculates late penalty.
 */

double lateMult (double mins)
{
    const double MAX_LATE_PERIOD = 12 * 60;	// Twelve hours (in minutes)
    double  lateness = mins / MAX_LATE_PERIOD;
    double  root     = sqrt(lateness);		// The formula is strange, but
    double  squared  = lateness * lateness;	// gives a good penalty curve.
    double  penalty  = 1.0 - (root * (1.0 - root) + squared * root);
    if (penalty < 0.0)
        return 0.0;
    else
        return penalty;
}


/* stringTo<T> [global function template]:
 *      Inputs:  string str		string to convert
 *      Returns: T                      whatever type you want str converted to
 * 	Throws:  std::invalid_argument  if conversion fails
 * 
 * Uses converts a string into any type that operator >> can read.
 */

template <typename T>
T stringTo (const std::string& str)
{
    std::stringstream stream(str);
    T result;
    stream >> result;
    if (stream.eof() && !stream.fail()) {
        return result;
    } else {
        throw std::invalid_argument("Can't figure out `" + str + "'");
    }
}


/* main [global function & program entry point]:
 *      Inputs:  int argc               command-line argument count + 1
 *               const char* argv       command-line arguments
 *      Returns: int                    exit code
 * 
 * Calculates lateness multiplier.
 */

int main(int argc, const char* argv[])
{
    // Turn C-style arguments into a C++-style vector, dropping the 0th 
    // argument (the name the program was invoked with).
    std::vector<std::string> args(argv+1, argv+argc);
    
    if (args.size() != 1) {
        std::cerr << "Usage: latecalc <mins-late>" << std::endl;
        exit(1);
    }
    
    double multiplier = lateMult(stringTo<double>(args[0]));
    std::cout << multiplier << std::endl;
    
    return 0;
}