module advent_of_code.tasks.day_2.Star2

open System.IO

let stream = new StreamReader("tasks/day-2/input.txt")

let convertToString (i: int64) = i |> string

let divideString (str: string) (n: int) =
    let count = str.Length / n
    let mutable parts = Set.empty
    for i in 0 .. count - 1 do
        let start = i * n
        parts <- parts.Add(str.Substring(start, n))
    parts

let rec isInvalid (id: string) (chars: int) =
    let biggerSlices = if chars = id.Length then 0 |> int64 else isInvalid id (chars + 1)
    if (chars = id.Length) then
        0
    else if (biggerSlices <> 0) then
        biggerSlices
    else if (id.Length % chars <> 0) then
        0
    else
        let parts = divideString id chars
        if parts.Count = 1 then id |> int64 else 0

let checkValid (id: string) = isInvalid id 1

let rec getInvalid (lines: string list) =
    let line, tail = lines.Head, lines.Tail
    let els = line.Split("-")
    let low, high = els[0] |> int64, els[1] |> int64
    let invalids = [low .. high] |> List.map convertToString |> List.map checkValid

    List.sum invalids + if tail.IsEmpty then 0 |> int64 else getInvalid tail

let main =
    let lines = stream.ReadLine().Split(",") |> Array.toList
    getInvalid lines