#!/usr/bin/env julia

using Test

function priority(char)
  v = Int(char)
  if v <= Int('Z')
    return v - Int('A') + 27
  else
    return v - Int('a') + 1
  end
end

function rucksack_errors(infile)
  psum = 0

  open(infile, "r") do io
    for line in eachline(io)
      n = length(line)
      a = Set{Int32}()
      b = Set{Int32}()
      for c in line[1:Int(n/2)]
        push!(a, priority(c))
      end
      for c in line[Int(n/2)+1:n]
        push!(b, priority(c))
      end
      psum += pop!(intersect(a, b))
    end
  end

  return psum
end

function rucksack_badges(infile)
  psum = 0

  open(infile, "r") do io
    for lines in Iterators.partition(eachline(io), 3)
      all = intersect!(Set(lines[1]), Set(lines[2]), Set(lines[3]))
      psum += priority(pop!(all))
    end
  end

  return psum
end


function test()
  @testset "elf rucksack errors" verbose=true begin
    @test rucksack_errors("example.txt") == 157
    @test rucksack_errors("input.txt") == 8394
  end
  @testset "elf rucksack badges" verbose=true begin
    @test rucksack_badges("example.txt") == 70
    @test rucksack_badges("input.txt") == 2413
  end
end

function main()
  if size(ARGS, 1) == 0
    test()
  else
    infile = ARGS[1]
    println("infile = ", infile)
    println("error priority sum: ", rucksack_errors(infile))
  end
end

main()