open Lwt.Infix
module Store = Git_unix.Store
module Value = Git.Value

type user_record = { name : string; email : string }

type commit_record = {
  hash : string;
  parents : string list;
  author : Git.User.t;
  message : string option;
}

let full_path path = Filename.concat Config.git_directory path

let store repo_path =
  let path = Fpath.v @@ full_path repo_path in
  Store.v ~dotgit:path path

let short_hash hash = String.sub hash 0 8

let repo_description repo_path =
  let description_path = Filename.concat (full_path repo_path) "description" in
  In_channel.with_open_text description_path In_channel.input_all

(* Read a Git object and turn it into our [commit_record], or propagate an error. *)
let get_commit_record store h =
  Store.read store h >>= function
  | Ok (Value.Commit c) ->
      Lwt.return_ok
        {
          hash = Store.Hash.to_hex h;
          parents = Store.Value.Commit.parents c |> List.map Store.Hash.to_hex;
          author = Store.Value.Commit.author c;
          message = Store.Value.Commit.message c;
        }
  | Ok _ -> Lwt.return_error (`Msg "object is not a commit")
  | Error e -> Lwt.return_error e

let recent_commits repo_path n =
  let open Lwt_result.Syntax in
  let* store = store repo_path in
  let* head = Store.Ref.resolve store Git.Reference.head in
  let rec walk acc hash count =
    if count = 0 then Lwt.return_ok (List.rev acc)
    else
      get_commit_record store hash >>= function
      | Error e -> Lwt.return_error e
      | Ok commit -> (
          match commit.parents with
          | parent :: _ ->
              walk (commit :: acc) (Store.Hash.of_hex parent) (count - 1)
          | [] -> Lwt.return_ok (List.rev (commit :: acc)))
  in
  walk [] head n

let get_commit repo_path id =
  let open Lwt_result.Syntax in
  let* store = store repo_path in
  let id = Store.Hash.of_hex id in
  get_commit_record store id