type doc_entry = {
  pkg : OpamPackage.t;
  html_path : Fpath.t;
  universe : string;
  blessed : bool;
}

let scan_cache ~os_dir =
  let layers = Day11_layer.Scan.list_layers os_dir in
  List.filter_map (fun (name, path) ->
    if not (Astring.String.is_prefix ~affix:"doc-" name)
       || Astring.String.is_prefix ~affix:"doc-driver-" name
       || Astring.String.is_prefix ~affix:"doc-odoc-" name then
      None
    else
      let json_path = Fpath.(path / "layer.json") in
      match
        try Some (Yojson.Safe.from_file (Fpath.to_string json_path))
        with _ -> None
      with
      | None -> None
      | Some json ->
          try
            let open Yojson.Safe.Util in
            let pkg_str = json |> member "package" |> to_string in
            let pkg = OpamPackage.of_string pkg_str in
            let doc = json |> member "doc" in
            let status = doc |> member "status" |> to_string in
            if status <> "success" then None
            else
              let html_path = doc |> member "html_path" |> to_string in
              let blessed = doc |> member "blessed" |> to_bool in
              let dep_hashes =
                json |> member "dep_doc_hashes"
                |> to_list |> List.map to_string in
              let universe = Command.compute_universe_hash dep_hashes in
              Some { pkg; html_path = Fpath.v html_path; universe; blessed }
          with _ -> None
  ) layers

let sync env ~entries ~destination ?(blessed_only = false)
    ?(package_filter = fun _ -> true) ?(dry_run = false) () =
  let filtered =
    entries
    |> List.filter (fun e ->
      (not blessed_only || e.blessed)
      && package_filter (OpamPackage.to_string e.pkg))
  in
  let results =
    List.map (fun entry ->
      let src = Fpath.to_string entry.html_path ^ "/" in
      let dst_subpath =
        if entry.blessed then
          Printf.sprintf "%s/%s/"
            (OpamPackage.name_to_string entry.pkg)
            (OpamPackage.version_to_string entry.pkg)
        else
          Printf.sprintf "universes/%s/%s/%s/"
            entry.universe
            (OpamPackage.name_to_string entry.pkg)
            (OpamPackage.version_to_string entry.pkg)
      in
      let dst = destination ^ "/" ^ dst_subpath in
      let cmd =
        Bos.Cmd.(v "rsync" % "-av"
                 %% (if dry_run then Bos.Cmd.v "--dry-run" else Bos.Cmd.empty)
                 % "--delete" % src % dst)
      in
      match Day11_exec.Run.run env cmd None with
      | run when run.Day11_exec.Run.status = `Exited 0 -> Ok ()
      | run ->
          Rresult.R.error_msgf "rsync failed for %s: %s"
            (OpamPackage.to_string entry.pkg) run.errors
      | exception exn ->
          Rresult.R.error_msgf "rsync: %s" (Printexc.to_string exn)
    ) filtered
  in
  match List.find_opt Result.is_error results with
  | Some (Error _ as e) -> e
  | _ -> Ok ()