/// fsharp/replay.html loads this module (web/dist/ReplayMain.js): the replay viewer of m10.
/// The recording is plain JSON next to the test fixtures; the page is served from the repository root by
/// scripts/serve.mjs, so it can be fetched (relative to the page, fsharp/replay.html). It is decoded with plain
/// JavaScript interop, without a JSON library, and the viewer starts once it has arrived.
module Snake.Web.ReplayMain

open Fable.Core
open Fable.Core.JsInterop
open Snake
open Snake.Model
open Snake.Replay

[<Global>]
let private window: obj = jsNative

let private direction (dir: string) : Direction =
    match dir with
    | "Up" -> Up
    | "Down" -> Down
    | "Left" -> Left
    | "Right" -> Right
    | other -> failwith $"unknown direction in the recording: {other}"

// A recording holds only Tick and Turn: {"tag":"Tick"} or {"tag":"Turn","dir":"Up"}.
let private action (a: obj) : Action =
    match (a?tag: string) with
    | "Tick" -> Tick
    | "Turn" -> Turn(direction a?dir)
    | other -> failwith $"unknown action in the recording: {other}"

let private recording (data: obj) : Recording =
    { Seed = uint32 (data?seed: float)
      Actions = (data?actions: obj[]) |> Array.map action |> List.ofArray }

let private start (data: obj) : unit =
    Runtime.runApp (BrowserPlatform.create (BrowserPlatform.gameCanvas ())) (replayMain (recording data))

window?fetch("../fixtures/replay-sample.json")?``then``(fun (response: obj) -> response?json ())?``then``(start)
|> ignore