namespace AdventOfCode2023

open System
open System.Collections.Generic
open System.Globalization

[<RequireQualifiedAccess>]
module Day12 =

    let rec solve (line : ReadOnlySpan<char>) (groups : IReadOnlyList<int>) (currentGroupIndex : int) =
        match line.[0] with
        | '#' ->
            if currentGroupIndex >= groups.Count then 0 else
            let mutable isOk = true
            for i = 1 to groups.[currentGroupIndex] - 1 do
                if isOk && line.[i] <> '#' && line.[i] <> '?' then
                    isOk <- false
            if not isOk then 0 else
            if line.[groups.[currentGroupIndex]] = '#' then 0 else
            solve (line.Slice (groups.[currentGroupIndex] + 1)) groups (currentGroupIndex + 1)
        | '.' ->
            solve (line.Slice 1) groups currentGroupIndex
        | '?' ->
            let ifDot = solve (line.Slice 1) groups currentGroupIndex
            let ifHash =
                if currentGroupIndex >= groups.Count then 0 else
                let mutable isOk = true
                for i = 1 to groups.[currentGroupIndex] - 1 do
                    if isOk && line.[i] <> '#' && line.[i] <> '?' then
                        isOk <- false
                if not isOk then 0 else
                if line.[groups.[currentGroupIndex]] = '#' then 0 else
                solve (line.Slice (groups.[currentGroupIndex] + 1)) groups (currentGroupIndex + 1)
            ifDot + ifHash
        | _ ->
            if currentGroupIndex = groups.Count then 1 else 0


    let part1 (s : string) =
        use mutable lines = StringSplitEnumerator.make '\n' s

        let mutable answer = 0
        let arr = ResizeArray ()
        for line in lines do
            if not line.IsEmpty then
                arr.Clear ()
                use ints = StringSplitEnumerator.make' ',' (line.Slice (line.IndexOf ' ' + 1))
                for int in ints do
                    arr.Add (Int32.Parse (int, NumberStyles.None, CultureInfo.InvariantCulture))

                let solved = solve line arr 0
                answer <- answer + solved

        answer

    let part2 (s : string) =
        use mutable lines = StringSplitEnumerator.make '\n' s

        -1