type error =
  | Git_error of Git.error
  | Feature_exists of string
  | Feature_not_found of string
  | Config_error of string

let pp_error ppf = function
  | Git_error e -> Fmt.pf ppf "Git error: %a" Git.pp_error e
  | Feature_exists name -> Fmt.pf ppf "Feature '%s' already exists" name
  | Feature_not_found name -> Fmt.pf ppf "Feature '%s' not found" name
  | Config_error msg -> Fmt.pf ppf "Configuration error: %s" msg

let error_hint = function
  | Git_error _ -> Some "Check that the monorepo is properly initialized"
  | Feature_exists name ->
      Some (Printf.sprintf "Run 'monopam feature remove %s' first if you want to recreate it" name)
  | Feature_not_found name ->
      Some (Printf.sprintf "Run 'monopam feature list' to see available features, or 'monopam feature add %s' to create it" name)
  | Config_error _ -> Some "Run 'monopam init' to create a workspace configuration"

let pp_error_with_hint ppf e =
  pp_error ppf e;
  match error_hint e with
  | Some hint -> Fmt.pf ppf "@.Hint: %s" hint
  | None -> ()

type entry = {
  name : string;
  path : Fpath.t;
  branch : string;
}

let pp_entry ppf e =
  Fmt.pf ppf "%s -> %a (branch: %s)" e.name Fpath.pp e.path e.branch

(* Get the work directory path: root/work *)
let work_path config = Fpath.(Verse_config.root config / "work")

(* Get the feature worktree path: root/work/<name> *)
let feature_path config name = Fpath.(work_path config / name)

let add ~proc ~fs ~config ~name () =
  let mono = Verse_config.mono_path config in
  let work_dir = work_path config in
  let wt_path = feature_path config name in
  (* Check if feature already exists *)
  if Git.Worktree.exists ~proc ~fs ~repo:mono ~path:wt_path then
    Error (Feature_exists name)
  else begin
    (* Ensure work directory exists *)
    let work_eio = Eio.Path.(fs / Fpath.to_string work_dir) in
    (try Eio.Path.mkdirs ~perm:0o755 work_eio with Eio.Io _ -> ());
    (* Create the worktree with a new branch *)
    match Git.Worktree.add ~proc ~fs ~repo:mono ~path:wt_path ~branch:name () with
    | Error e -> Error (Git_error e)
    | Ok () -> Ok { name; path = wt_path; branch = name }
  end

let remove ~proc ~fs ~config ~name ~force () =
  let mono = Verse_config.mono_path config in
  let wt_path = feature_path config name in
  (* Check if feature exists *)
  if not (Git.Worktree.exists ~proc ~fs ~repo:mono ~path:wt_path) then
    Error (Feature_not_found name)
  else
    match Git.Worktree.remove ~proc ~fs ~repo:mono ~path:wt_path ~force () with
    | Error e -> Error (Git_error e)
    | Ok () -> Ok ()

let list ~proc ~fs ~config () =
  let mono = Verse_config.mono_path config in
  let work_dir = work_path config in
  let all_worktrees = Git.Worktree.list ~proc ~fs mono in
  (* Filter to only worktrees under work/ directory *)
  List.filter_map (fun (wt : Git.Worktree.entry) ->
    (* Check if this worktree is under the work directory *)
    let wt_str = Fpath.to_string wt.path in
    let work_str = Fpath.to_string work_dir in
    if String.starts_with ~prefix:work_str wt_str then
      let name = Fpath.basename wt.path in
      let branch = Option.value ~default:name wt.branch in
      Some { name; path = wt.path; branch }
    else
      None
  ) all_worktrees