class Rangefinder

# File lib/rangefinder.rb, line 12
def probe(options = {}, &blk)
  ranges, _, _ = probe_with_hits_and_misses(options, &blk)
  ranges
end

# File lib/rangefinder.rb, line 17
def probe_with_hits_and_misses(options = {}, &blk)
  memo = Memo.new
  _probe(memo, options, &blk)
  [ ::RangesMerger.merge(memo.ranges), memo.hits, memo.misses ]
end

# File lib/rangefinder.rb, line 25
def _probe(memo, options = {}, &blk)
  first = [options.fetch(:first, 0), 0].max.round
  last = [options.fetch(:last, MAX), MAX].min.round
  max_gap = options.fetch(:max_gap, MAX_GAP)
  samp = options.fetch(:samp, INIT_SAMP)
  random = options.fetch(:random, ::Random.new)
  if samp >= MAX_SAMP
    memo.ranges << (first..last)
  else
    min_range = (10 ** (2 - Math.log(samp, 10))).round
    anything = false
    first_good = nil
    i = first
    last_good = first
    begin
      if blk.call(i)
        memo.hit!
        anything = true
        first_good ||= i
        last_good = i
      else
        memo.miss!
      end
      gap = i - last_good
      if first_good and gap > min_range
        _probe memo, {first: first_good-min_range, last: last_good+min_range, samp: samp*3}, &blk
        first_good = nil
        last_good = i
        gap = 0
      end
      samp1 = gap > 10 ? samp * Math.log(gap, 10) : samp
      i += (random.rand(100) * (1 - samp1)).round
    end until i >= last or (gap > max_gap and anything) # sorry for mixed metaphor
  end
end