human_friendly_duration.md

Write a function which formats a duration, given as a number of seconds, in a human-friendly way.

The function must accept a non-negative integer. If it is zero, it just returns "now". Otherwise, the duration is expressed as a combination of years, days, hours, minutes and seconds.

Example :

* Input = 62, Output = "1 minute and 2 seconds"
* Input = 3662, Output = "1 hour, 1 minute and 2 seconds"

Assume, a year is always 365 days and a day is 24 hours.

Note that spaces are important.

Detailed rules

• The resulting expression is made of components like 4 seconds, 1 year, etc.

  • In general, a positive integer and one of the valid units of time, separated by a space.
  • The unit of time is used in plural if the integer is greater than 1.

• The components are separated by a comma and a space (", "). Except the last component, which is separated by " and ", just like it would be written in English.

• A more significant units of time will occur before than a least significant one. Therefore, 1 second and 1 year is not correct, but 1 year and 1 second is.

• Different components have different unit of times. So there is not repeated units like in 5 seconds and 1 second.

• A component will not appear at all if its value happens to be zero. Hence, 1 minute and 0 seconds is not valid, but it should be just 1 minute.

• A unit of time must be used "as much as possible". It means that the function should not return 61 seconds, but 1 minute and 1 second instead. Formally, the duration specified by of a component must not be greater than any valid more significant unit of time.