// simple_time.cpp

#include <iostream>
#include <sstream>
using namespace std;

constexpr int MINUTES_PER_HOUR = 60;

/*
 * Track time in hours and minutes, where minutes always in the range 0..59
 * but hours can be any value, positive or negative. Has an operation to
 * advance time by one minute.
 */
class Time {
public:
  Time(int hours, int minutes) {
    hrs = hours;              // alternatively: this->hrs = hours;
    min = minutes;
    normalize();
  }

  // advance by one minute, rolling over the hours as necessary
  void tick() {
    min += 1;
    normalize();
  }

  // returns time as a string using the format H:MM
  string toString() {
    stringstream result;
    result << hrs << ":";
    if (min < 10)
      result << "0";
    result << min;
    return result.str();
  }

  // returns number of hours; assumes time is normalized
  int hours() {
    return hrs;
  }

  // return number of minutes; assumed time is normalized
  int minutes() {
    return min;
  }

private:
  int hrs, min;

  // ensure 0 <= min <= 59, adding to/borrowing from hrs as necessary
  // hrs can be any value
  void normalize() {
    if ( min >= 0 ) {
      hrs += min / MINUTES_PER_HOUR;
      min = min % MINUTES_PER_HOUR;
    } else if ( min % MINUTES_PER_HOUR == 0 ) {
      // special case: go back several hours
      hrs -= abs(min) / MINUTES_PER_HOUR;
      min = 0;
    } else {
      // go back at least one hour, possibly more
      hrs -= 1 + abs(min) / MINUTES_PER_HOUR;
      // move minutes to between 0 and 59
      min = MINUTES_PER_HOUR + (min % MINUTES_PER_HOUR);
    }
  }
};                              // do not forget this semicolon!

//####################################################################

// normally all includes would be at the top of the file, but in this
//    case I wanted more code than normal in a single file for
//    simplicity
#include <cassert>

// test code
void testBasicTime();
void testTick();
void testToString();
void testNegativeTime();

int main() {
  testBasicTime();
  testTick();
  testToString();
  testNegativeTime();
  cout << "All tests passed." << endl;
  return 0;
}

// test creating times
void testBasicTime() {
  Time one(1, 0);
  assert(one.hours() == 1);
  assert(one.minutes() == 0);
  Time two(23, 59);
  assert(two.hours() == 23);
  assert(two.minutes() == 59);
}

void testTick() {
  Time start(9, 58);
  assert(start.hours() == 9 && start.minutes() == 58);
  start.tick();
  assert(start.hours() == 9 && start.minutes() == 59);
  start.tick();
  assert(start.hours() == 10 && start.minutes() == 0);
  for(int i = 0; i < 120; ++i)
    start.tick();
  assert(start.hours() == 12 && start.minutes() == 0);
  // now ensure don't roll over hours
  for(int i = 0; i < 60; ++i)
    start.tick();
  assert(start.hours() == 13 && start.minutes() == 0);
}

void testToString() {
  Time early(4, 5);
  assert(early.toString() == "4:05");
  Time late(13, 59);
  assert(late.toString() == "13:59");
  late.tick();
  assert(late.toString() == "14:00");
}

void testNegativeTime() {
  Time a(18, -1);
  assert(a.toString() == "17:59");
  a = Time(0, -18);
  assert(a.toString() == "-1:42");
  a = Time(3, -100);
  assert(a.toString() == "1:20");
  a = Time(20, -300);
  assert(a.toString() == "15:00");
}