/// Loads shared fixtures from ../../fixtures/<name>.json.
/// Typed decoders (point, direction, status, action, state, opt) arrive with the model (Task 13).
module Snake.Tests.Fixtures

open System.IO
open System.Text.Json

let private dir =
    Path.GetFullPath(Path.Combine(Directory.GetCurrentDirectory(), "..", "fixtures"))

let load (name: string) : JsonElement =
    use doc = JsonDocument.Parse(File.ReadAllText(Path.Combine(dir, name + ".json")))
    doc.RootElement.Clone()

/// The cases array of a fixture.
let cases (name: string) : JsonElement list =
    (load name).GetProperty("cases").EnumerateArray() |> List.ofSeq

/// Decode a nullable JSON value into an Option.
let opt (f: JsonElement -> 'a) (v: JsonElement) : 'a option =
    if v.ValueKind = JsonValueKind.Null then None else Some(f v)