SecretSanta.fs

module SecretSanta
open System

//let initConsole () =
//    let clrstr = String.replicate Console.BufferWidth " "
//    for _ in 1 .. Console.WindowHeight do
//        Console.WriteLine clrstr

//let clearConsole () =
    //Console.SetCursorPosition (0, 0)
    //initConsole ()
    //Console.SetCursorPosition (0, 0)

module List =
    let remove x list = list |> List.filter (fun y -> x <> y)

    let rec removei i list =
        list |> List.mapi (fun i' x -> i', x)
        |> List.filter (fun (i', x) -> i' <> i)
        |> List.map snd

    let removeRandom (rand: Random) (list: 'a list) =
        let i = rand.Next list.Length
        list.[i], removei i list

    let shuffle (rand: Random) (list: 'a list) =
        let indices = [0 .. list.Length - 1]
        list |> (indices |> List.mapFold (fun indices x ->
            let i, indices = removeRandom rand indices
            (i, x), indices))
        |> fst
        |> List.sortBy fst
        |> List.map snd

let dealRecipients rand names =
    let givers = names
    let recipientGroups =
        [for name in names do yield name; yield name]
        |> List.shuffle rand
        |> List.chunkBySize 2
    let giversWithRecipients =
        List.zip givers recipientGroups
    giversWithRecipients

let hasCollision giversWithRecipients =
    giversWithRecipients |> List.exists (fun (giver, recipients) ->
        recipients |> List.contains giver)

let allPossibleNoCollisionCombos rand names =
    Seq.initInfinite (fun _ -> dealRecipients rand names) |> Seq.cache
    |> Seq.filter (not << hasCollision)

[<WebSharper.JavaScript>]
let rec makeGrammaticalList items =
    match items with
    | [] -> ""
    | a::[] -> a
    | a::b::[] -> sprintf "%s and %s" a b
    | a::rest -> sprintf "%s, %s" a (makeGrammaticalList rest)

//[<EntryPoint>]
//let main argv =
    //let scenario = 
    //    ["Alan"; "Paula"; "Paul"; "Sarah"; "Peter"; "John"]
    //    |> allPossibleNoCollisionCombos (new Random())
    //    |> Seq.head

    //while true do
    //    clearConsole ()
    //    printf "Enter your name: "
    //    let name = (Console.ReadLine ()).Trim ()
    //    match scenario |> List.tryFind (fun (giver, _) -> name.ToLower () = giver.ToLower ()) with
    //    | Some(_, recipients) ->
    //        printfn "Your giftees are %A." (makeGrammaticalList recipients)
    //    | None ->
    //        printfn "Name not recognized!"
    //    printfn "Press any key to clear this screen."
    //    Console.ReadKey () |> ignore
    //0