Server.fs

module Server

open System
open System.IO
open System.Threading.Tasks

open Microsoft.AspNetCore
open Microsoft.AspNetCore.Builder
open Microsoft.AspNetCore.Hosting
open Microsoft.Extensions.DependencyInjection

open FSharp.Control.Tasks.V2
open FSharp.Control
open Giraffe
open Reaction.AspNetCore.Middleware
open Shared

open Giraffe.Serialization

let publicPath = Path.GetFullPath "../Client/public"
let port = 8085us


type LetterMsg =
    | Set of string
    | Get of AsyncReplyChannel<string>

let mailbox =
    MailboxProcessor.Start(fun inbox ->
        let rec loop letterString =
            async {
                let! msg = inbox.Receive()

                match msg with
                | Set letterString ->
                    return! loop letterString

                | Get reply ->
                    reply.Reply letterString

                    return! loop letterString
            }

        loop "Magic Released!"
    )

let getInitLetterString () : Task<string> =
    Get
    |> mailbox.PostAndAsyncReply
    |> Async.StartAsTask

let webApp =
    route "/api/init" >=>
        fun next ctx ->
            task {
                let! letterString = getInitLetterString()
                return! Successful.OK letterString next ctx
            }

let stream (connectionId: ConnectionId) (msgs: IAsyncObservable<Msg*ConnectionId>) : IAsyncObservable<Msg*ConnectionId> =
    msgs
    |> AsyncRx.flatMap(fun (msg,id) ->
        match msg with
        | Msg.LetterStringChanged letterString ->
          mailbox.Post (Set letterString)

        | _ -> ()

        AsyncRx.single (msg,id))


let configureApp (app : IApplicationBuilder) =
    app.UseWebSockets()
       .UseStream<Msg>(fun options ->
       { options with
           Stream = stream
           Encode = Msg.Encode
           Decode = Msg.Decode
       })
       .UseDefaultFiles()
       .UseStaticFiles()
       .UseGiraffe webApp

let configureServices (services : IServiceCollection) =
    services.AddGiraffe() |> ignore
    let fableJsonSettings = Newtonsoft.Json.JsonSerializerSettings()
    fableJsonSettings.Converters.Add(Fable.JsonConverter())
    services.AddSingleton<IJsonSerializer>(NewtonsoftJsonSerializer fableJsonSettings) |> ignore

WebHost
    .CreateDefaultBuilder()
    .UseWebRoot(publicPath)
    .UseContentRoot(publicPath)
    .Configure(Action<IApplicationBuilder> configureApp)
    .ConfigureServices(configureServices)
    .UseUrls("http://0.0.0.0:" + port.ToString() + "/")
    .Build()
    .Run()