Harshad or Niven series

# title: Harshad or Niven series
# source: https://rosettacode.org/wiki/Harshad_or_Niven_series
# category: Rosetta Code
# difficulty: Easy
# summary: Find Harshad (Niven) numbers — integers divisible by the sum of their own digits.
# tags: popular, math, sequences
# vibe: 0.2

def digit_sum(n)
  total = 0
  remaining = n
  while remaining > 0
    total = total + (remaining % 10)
    remaining = remaining / 10
  end
  total
end

def harshad?(n)
  n > 0 && n % digit_sum(n) == 0
end

def first_harshad(count)
  results = []
  n = 1
  while results.size < count
    if harshad?(n)
      results = results.push(n)
    end
    n = n + 1
  end
  results
end

def first_harshad_above(threshold)
  n = threshold + 1
  while true
    if harshad?(n)
      return n
    end
    n = n + 1
  end
end

def run
  {
    first_20: first_harshad(20),
    first_above_1000: first_harshad_above(1000)
  }
end