using DelimitedFiles

infile = size(ARGS, 1) > 0 ? ARGS[1] : "day3input.txt"
println("infile = ", infile)

diags = readdlm(infile, ' ', String)

n = size(diags, 1)
w = length(diags[1])

half_n = n / 2

gamma = 0
epsilon = 0

for i in 1:w
    global gamma, epsilon
    is_one_at_i(s) = s[i] == '1' ? true : false
    one_count = size(findall(is_one_at_i, diags), 1)
    v = 2^(w-i)
    if one_count > half_n
        gamma += v
    else
        epsilon += v
    end
end

println("gamma   = ", gamma)
println("epsilon = ", epsilon)
println("prod    = ", gamma * epsilon)

o2gen = view(diags, :)
co2scrub = view(diags, :)

o2n = n
co2n = n

for i in 1:w
    global o2gen, co2scrub, o2n, co2n
    is_one_at_i(s) = s[i] == '1' ? true : false
    is_zero_at_i(s) = s[i] == '0' ? true : false
    o2idx_ones = findall(is_one_at_i, o2gen)
    co2idx_ones = findall(is_one_at_i, co2scrub)

    if length(o2gen) > 1
        if length(o2idx_ones) >= o2n/2
            o2gen = o2gen[o2idx_ones]
        else
            o2gen = o2gen[findall(is_zero_at_i, o2gen)]
        end
        o2n = length(o2gen)
    end

    if length(co2scrub) > 1
        if length(co2idx_ones) < co2n/2
            co2scrub = co2scrub[co2idx_ones]
        else
            co2scrub = co2scrub[findall(is_zero_at_i, co2scrub)]
        end
        co2n = length(co2scrub)
    end
end

o2gen_v = parse(Int, o2gen[1], base=2)
co2scrub_v = parse(Int, co2scrub[1], base=2)
println("o2gen ", o2gen, " ", o2gen_v)
println("co2scrub ", co2scrub, " ", co2scrub_v)
println("prod ", o2gen_v * co2scrub_v)