#! /usr/bin/env ruby

require 'set'

if ARGV.length != 1
        abort("Incorrect arguments - needs input file")
elsif not File.exist? (ARGV[0])
	abort("File #{ARGV[0]} did not exist")
end

file = ARGV[0]

maps = Hash.new

lines = File.open(file, "r").each_line(chomp: true)

seeds = lines.first.split(":")[1].split(" ").map(&:to_i)

RawMapping = Struct.new(:from, :to, :ranges)
MappingRange = Struct.new(:source_range, :offset)

mappings = Array.new
mappings_array = []

lines.drop(1).reduce(mappings_array) do |mappings, val|
	if m = /([a-z]+)-to-([a-z]+) map:/.match(val) then
		mappings << RawMapping.new(m[1], m[2], [])
	elsif val != "" then
		dest_start, source_start, range_length = val.split(" ").map(&:to_i)
		mappings[-1].ranges << MappingRange.new((source_start...(source_start + range_length)), dest_start - source_start)
	end
	mappings
end

mappings = mappings_array.map {|mapping| [mapping.from, mapping]}.to_h

def map_with_override(mappings, input)
	mappings.ranges.reduce(input) { |memo, mapping| mapping.source_range.cover?(input) ? input + mapping.offset : memo }
end

steps = ["seed", "soil", "fertilizer", "water", "light", "temperature", "humidity"]

puts steps.reduce(seeds) {|vals, map_name| vals.map {|v| map_with_override(mappings[map_name], v)}}.min()