Clock.go

// Package clock mocks a simple clock which only
// supports hours and minutes and basic add, sub
// operations in minutes.
package clock

import (
	"fmt"
)

// day number of minutes in a day
const day = 1440

// Clock represents a Clock object that only
// handle hours and minutes
type Clock struct {
	Hour   int
	Minute int
}

// New constructor return a new Clock object
func New(h, m int) Clock {
	return setClock(h, m)
}

func setClock(h, m int) Clock {
	minutes := (60 * h) + m
	for minutes < 0 {
		minutes += day
	}
	for minutes >= day {
		minutes -= day
	}

	return Clock{
		Hour:   int(minutes / 60),
		Minute: minutes % 60,
	}
}

// String returns an string representation
// of the hours in the following format 00h:00m
func (c Clock) String() string {
	return fmt.Sprintf("%02d:%02d", c.Hour, c.Minute)
}

// Add return hour by adding give m (minute)
func (c Clock) Add(m int) Clock {
	c.Minute += m
	return setClock(c.Hour, c.Minute)
}

// Subtract return hour by substracting given m (minute)
func (c Clock) Subtract(m int) Clock {
	c.Minute -= m
	return setClock(c.Hour, c.Minute)
}