include("utils.jl")

function parse_value(line, index)
    if line[index] == '['
        parse_tuple(line, index)
    else
        digits = match(r"^[0-9]+", SubString(line, index)).match
        index += length(digits)
        parse(Int, digits), index
    end
end

function parse_tuple(line, index=1)
    @assert line[index] == '['
    index += 1

    first, index = parse_value(line, index)

    @assert line[index] == ','
    index += 1

    second, index = parse_value(line, index)

    @assert line[index] == ']'
    index +=1

    return Any[first, second], index
end

function parse_input(filename)
    map(x->x[1], map(parse_tuple, non_empty_lines(filename)))
end

function split_sf(a)
    if typeof(a) == Int64
        if a > 9
            Any[div(a,2),div(a,2)+rem(a,2)], true
        else
            a, false
        end
    else
        l, changed = split_sf(a[1])
        a[1] = l
        if changed
            a, true
        else
            r, changed = split_sf(a[2])
            a[2] = r
            a, changed
        end
    end
end

function add_left_sf(a, number)
    if typeof(a) == Int64
        a + number
    else
        a[1] = add_left_sf(a[1], number)
        a
    end
end

function add_right_sf(a, number)
    if typeof(a) == Int64
        a + number
    else
        a[2] = add_right_sf(a[2], number)
        a
    end
end

function explode_sf(a, level=1)
    if typeof(a) == Int64
        return a, false, 0, 0
    end
    if level == 5
        @assert typeof(a[1]) == Int64 && typeof(a[2]) == Int64
        0, true, a[1], a[2]
    else
        l, changed, to_left, to_right = explode_sf(a[1], level + 1)
        if changed
            Any[l, add_left_sf(a[2], to_right)], true, to_left, 0
        else
            r, changed, to_left, to_right = explode_sf(a[2], level + 1)
            if changed
                Any[add_right_sf(l, to_left), r], true, 0, to_right
            else
                a, false, 0, 0
            end
        end
    end
end

function reduce_sf(a)
    changed = true
    while changed
        a, changed = explode_sf(a)
        if changed
            continue
        end
        a, changed = split_sf(a)
    end
    a
end

function add_sf(a, b)
    reduce_sf(Any[deepcopy(a), deepcopy(b)])
end

function mag_sf(a)
    if typeof(a) == Int64
        a
    else
        3 * mag_sf(a[1]) + 2 * mag_sf(a[2])
    end
end

function solution18_1()
    mag_sf(reduce(add_sf, parse_input("18.data")))
end

function solution18_2()
    input = collect(parse_input("18.data"))
    max_mag = 0
    for a in input
        for b in input
            print('.')
            max_mag = max(max_mag, mag_sf(add_sf(a, b)))
        end
    end
    println("")
    max_mag
end

solution18_2()