#!/usr/bin/env lua

function file_exists(file)
      local f = io.open(file, "rb")
      if f then f:close() end
      return f ~= nil
end

-- get all lines from a file, returns an empty 
-- list/table if the file does not exist
function lines_from(file)
  if not file_exists(file) then return {} end
  lines = {}
  for line in io.lines(file) do 
    lines[#lines + 1] = line
  end
  return lines
end

function atoi_list(strings)
    local ints = {}
    for i,s in ipairs(strings) do
       ints[#ints + 1] = tonumber(s)
    end
    return ints
end

function toSlices(ints)
    local slices = {}
    for k,i in ipairs(ints) do
        if(k < (#ints - 1)) then
            slices[k] = ints[k] + ints[k+1] + ints[k+2]
        end
    end
    return slices
end

function split(s, delimiter)
    result = {};
    for match in (s..delimiter):gmatch("(.-)"..delimiter) do
        table.insert(result, match);
    end
    return result;
end

-------------------------------------------------
file = "input.txt"

local v,h,aim = 0,0,0

allLines = lines_from(file)

for i,l in ipairs(allLines) do
    local current = split(l, ' ')
    local cmd = current[1]
    local X = current[2]
    if(cmd == "down") then
        aim = aim + X
    end
    if(cmd == "up") then
        aim = aim - X
    end
    if(cmd == "forward") then
        h = h + X
        v = v + (aim * X)
    end
end

print("vertical position: " .. v)
print("horizontal position: " .. h)

local result = v * h

io.write("The answer is ", result, ". Congrats, I hope!\n")