(** Byte range management for partial downloads *)

type t = {
  start : int64;
  end_ : int64;  (* inclusive *)
}

let create ~start ~end_ =
  if start < 0L || end_ < start then
    invalid_arg (Printf.sprintf "Invalid range: %Ld-%Ld" start end_)
  else
    { start; end_ }

let start r = r.start
let end_ r = r.end_

let length r =
  Int64.succ (Int64.sub r.end_ r.start)

let adjacent r1 r2 =
  Int64.succ r1.end_ = r2.start || Int64.succ r2.end_ = r1.start

let overlaps r1 r2 =
  not (r1.end_ < r2.start || r2.end_ < r1.start)

let contains r pos =
  pos >= r.start && pos <= r.end_

let merge r1 r2 =
  if overlaps r1 r2 || adjacent r1 r2 then
    Some {
      start = min r1.start r2.start;
      end_ = max r1.end_ r2.end_;
    }
  else
    None

let compare r1 r2 =
  Int64.compare r1.start r2.start

let to_string r =
  Printf.sprintf "%Ld-%Ld" r.start r.end_

let of_string s =
  try
    match String.split_on_char '-' s with
    | [start_s; end_s] ->
        let start = Int64.of_string start_s in
        let end_ = Int64.of_string end_s in
        Some (create ~start ~end_)
    | _ -> None
  with _ -> None

let pp fmt r =
  Format.fprintf fmt "[%Ld-%Ld]" r.start r.end_