#prepare the input which is a string containing new lines
def parse(input)
  data = []
  map = []
  input.each_line do |line|
    if data.empty?
      seed_ranges = []
      seeds = line.split(":").last.split(" ").map(&:to_i)
      (seeds.length/2).times do |i|
        seed_ranges << [seeds[2*i],seeds[2*i+1]]
      end
      data << seed_ranges
      next
    end
    if line.include?(":") && !map.empty?
      data << map
      map = []
      next
    end
    next if line.include?(":")
    next if line.strip.empty?
    # build the map
    target,source,ranges = line.split(" ").map(&:to_i)
    diff = target-source
    map << [source,ranges,diff]
  end
  data << map
  data
end

# result should a single string or integer
def calculate(data)
  seeds = nil
  data.each do |d|
    if seeds.nil?
      seeds = d
      next
    end
    # start mapping
    i=0
    d.each do |mapping|
      new_seeds = []
      map_start,map_range,diff = mapping
      map_end = map_start + map_range -1

      puts "map: #{map_start}--#{map_end} doing #{diff}"
      seeds.each do |seed_pair|
        seed_start,seed_range = seed_pair
        seed_end = seed_start+seed_range

        # <---|---|--->
        if seed_start <= map_start && map_end <= seed_end
          puts "<---|---|--->"
          new_seed_start = seed_start
          new_seed_range = map_start - seed_start
          additional_start = map_start + diff
          additional_range = map_end - map_start
          third_start = map_end
          third_end = seed_end - map_end
          new_seeds << [new_seed_start,new_seed_range]
          new_seeds << [additional_start,additional_range]
          new_seeds << [third_start,third_end]
          next
        end

        # |---<---|--->
        if map_start <= seed_start && map_end >= seed_start && map_end <= seed_end
          puts "|---<---|--->"
          new_seed_start = seed_start + diff
          new_seed_range = map_end - seed_start
          additional_start = map_end
          additional_range = seed_end - map_end
          new_seeds << [new_seed_start,new_seed_range]
          new_seeds << [additional_start,additional_range]
          next
        end

        # <---|--->---|
        if seed_start <= map_start && seed_end >= map_start && seed_end <= map_end
          puts "<---|--->---|"
          new_seed_start = seed_start
          new_seed_range = map_start - seed_start
          additional_start = map_start + diff
          additional_range = seed_end - map_start
          new_seeds << [new_seed_start,new_seed_range]
          new_seeds << [additional_start,additional_range]
          next
        end
        # |---<-->---|
        if map_start <= seed_start && seed_end <= map_end
          puts "|---<-->---|"
          new_seed_start = seed_start + diff
          new_seed_range = seed_range
          new_seeds << [new_seed_start,new_seed_range]
          next
        end

        # else
        new_seeds << seed_pair
      end
      pp new_seeds
      seeds = new_seeds
    end
    break if i==1
    i+=1
  end
  seeds = seeds.map{|seed_pair| seed_pair[0]}
  seeds.min
end