Crypto F#

module CryptoTwo

open System
open System.Text

let base64String = "PAADREshCgcRDgZPBAoPSxgGBBEOAR0ABksVEUUeDw4YCksoBlQWAg5PBgoRGBUNAxkEGBUGS
x8KGkUfDgQHEUVLIgEWAgoDVAoFSw0NBksFBhEGBEsLGBARGBUNSUsKDQ1FBgQVGAwcDk8WHA
cETwQXEQ4fBgocCgsOAAUCClQADQ4EABwcBQoTCksKGxUOHkVPOQoRDk8eABgRDA4ASx8dGwY
DDk8EBA8PBhoCHksVEQcSSwEdAEsJFhgKSxEOVBEZHgsaCkVLIB9JSw0DFQIKSxsbRTkkNSMk
JzQUNQkCCAo9FiIGHwYAGBgKEBg="

let isSome o =
    match o with
    | None -> false
    | _ -> true

let decodeBase64 (base64String:string) =
    ASCIIEncoding.ASCII.GetString(Convert.FromBase64String(base64String))

let xorStringWithSingleByte (string1:string) (singleByte:byte) =
    Encoding.ASCII.GetBytes(string1)
    |> Seq.map (fun x -> Convert.ToChar(x ^^^ singleByte).ToString())
    |> Seq.reduce (+)

//let reduct acc b =
//    xorStringWithSingleByte acc b

let xorStringWithPassword(string1:string) (password:string) =
    password
    |> Seq.map (fun x -> Convert.ToByte(x))
    |> Seq.fold xorStringWithSingleByte string1

let checkWordInCandidateString (word:string) (candidateString:string) =
    match word with
    | word when candidateString.Contains(word) -> Some candidateString
    | _ -> None

let result (l:string list) =
    match l with
    | l when l.IsEmpty -> ["Brak rozwiązań"]
    | l -> l

let decryptByFindingWord (word:string) (decodedString:string) =
    ["dupa";"cycki"]
    |> List.map (xorStringWithPassword decodedString)
    |> List.map (checkWordInCandidateString word)
    |> List.filter isSome
    |> List.map (fun x -> x.Value)
    |> result
    |> List.find (fun x -> true)

let findSolution =
    base64String
    |> decodeBase64
    |> decryptByFindingWord "ROZWAL"


let main argv =
    printfn "%s" findSolution