embeds

import gleam/list

/// Like filter_map, but collect all errors, without early returning.
pub fn traverse_map(
  list: List(a),
  body: fn(a) -> Result(ok, List(err)),
) -> Result(List(ok), List(err)) {
  do_traverse_map(list, body, [], [])
}

fn do_traverse_map(
  list: List(a),
  body: fn(a) -> Result(ok, List(err)),
  oks: List(ok),
  errs: List(err),
) -> Result(List(ok), List(err)) {
  case list {
    [] ->
      case errs {
        [] -> Ok(list.reverse(oks))
        _ -> Error(list.reverse(errs))
      }
    [head, ..tail] ->
      case body(head) {
        Ok(ok) -> do_traverse_map(tail, body, [ok, ..oks], errs)
        Error(err) -> do_traverse_map(tail, body, oks, list.append(err, errs))
      }
  }
}

pub fn try(
  result: Result(ok, err),
  f: fn(ok) -> Result(ok2, List(err)),
) -> Result(ok2, List(err)) {
  case result {
    Ok(ok) -> f(ok)
    Error(err) -> Error([err])
  }
}