// SYSC 2002 Winter 2011 Assignment #1
#include "stdstuff.h"
 

// function finds the closest distance between the patrol boat and the smuggler, given the speed of
// the patrol boat (m/s), time the smuggler starts (s), smuggler speed (m/s), and smuggler heading (radians). 
double closestApproach (double patrolSpeed, int smugglerStartTime,  
                        double smugglerSpeed, double smugglerHeading,
                        bool debug) {

  const double riverWidth = 6000, patrolRadius = 2000;
  double cosHeading = cos (smugglerHeading),
         sinHeading = sin (smugglerHeading),
         smugglerX, smugglerY, patrolX, patrolY,
         distance, smallestDistance;
  int t = smugglerStartTime;

  for (;;) {

    smugglerX = -(riverWidth / 2) + 
                smugglerSpeed * (t - smugglerStartTime) * cosHeading;

    if (smugglerX > riverWidth / 2) {
      return smallestDistance;
    }

    smugglerY = smugglerSpeed * (t - smugglerStartTime) * sinHeading;
    patrolX = patrolRadius * cos (patrolSpeed * t / patrolRadius);
    patrolY = patrolRadius * sin (patrolSpeed * t / patrolRadius);

    distance = sqrt (pow(smugglerX - patrolX, 2) +
                     pow(smugglerY - patrolY, 2));

    if (t == smugglerStartTime || distance < smallestDistance) {
      smallestDistance = distance;
    }

    // output debug info every minute)
    if (debug && ((t - smugglerStartTime) % 60 == 0)) {
      cout << "t = " << t << " patrol pos = [" << patrolX << ", " << patrolY 
           << "] smuggler pos = [" << smugglerX << ", " << smugglerY << "]\n";
    }

    t++;

  }

}


int main () {


  double patrolSpeed, smugglerSpeed, smugglerHeading, distance;
  int smugglerStartTime;
  bool debug;
  char option;

  cout << "**** Instructor's solution. ****\n";

  cout << "Do you want debug output (Y/N): ";
  cin >> option;
  debug = toupper(option) == 'Y';

  // first get a valid patrol speed
  for (;;) {

    cout << "Enter patrol speed: ";
    cin >> patrolSpeed;

    if (patrolSpeed >= 10 && patrolSpeed <= 50) {
      break;
    }

    cout << "Invalid values ignored." << endl;
  
  }

  // now get the smuggler details (loop until all 0s entered)
  for (;;) {

    cout << "Enter smuggler departure time, speed, and heading.\n(0 0 0 to stop): ";
    cin >> smugglerStartTime >> smugglerSpeed >> smugglerHeading;

    if (smugglerStartTime == 0 && smugglerSpeed == 0 && 
        smugglerHeading == 0) {
      break;
    }

    // check for invalid values
    if (smugglerStartTime < 0 || smugglerSpeed < 10 || smugglerSpeed > 50 ||
        smugglerHeading > 20 || smugglerHeading < -20) {

      cout << "Invalid values ignored." << endl;

    } else {

      // calculate closest distance and output it
      distance = closestApproach (patrolSpeed * (1000.0 / 3600), smugglerStartTime,  
                                  smugglerSpeed * (1000.0 / 3600), 
                                  smugglerHeading * (M_PI / 180.0),
                                  debug);

      cout << "That smuggler will come within " << distance
           << " m of the patrol boat." << endl;

    }

  }
  
  pause();
  return 0;

}