type marker_state =
  { pos : Leaflet.lat_lng
  ; name : string
  ; color : string
  ; icon : string
  }

let remove state pos =
  Js.Array.filter (fun m -> m.pos != pos) state

let update state previousPos marker =
  Js.Array.concat [| marker |] (remove state previousPos)

let last_added state =
  if Js.Array.length state > 0 then
    Some state.(0)
  else
    None

(* Serialization *)

let sep = "|"

let marker_to_string marker =
  [| String.format_float 6 marker.pos.lat
  ;  String.format_float 6 marker.pos.lng
  ;  marker.name
  ;  marker.color
  ;  marker.icon
  |]
    |> Js.Array.joinWith sep

let to_string state =
  state
    |> Js.Array.map marker_to_string
    |> Js.Array.joinWith sep
    |> String.encode

let from_string str =
  let (_, _, res) = Js.Array.reduce
    (fun (acc_str, acc_marker, acc_state) c ->
      let length = Js.Array.length acc_marker in
      if c != sep then
        (acc_str ^ c, acc_marker, acc_state)
      else if c == sep && length < 4 then
        ("", Js.Array.concat [| acc_str |] acc_marker, acc_state)
      else
        let marker =
          { pos =
              { lat = Js.Float.fromString acc_marker.(0)
              ; lng = Js.Float.fromString acc_marker.(1)
              }
          ; name = acc_marker.(2)
          ; color = acc_marker.(3)
          ; icon = acc_str
          }
        in ("", [| |], Js.Array.concat acc_state [| marker |])
    )
    ("", [| |], [| |])
    (Js.Array.from (Js.String.castToArrayLike ((String.decode str) ^ sep)))
  in res