meta/lib/recycledcloud/accounts/key.ex

defmodule RecycledCloud.Accounts.Key do
  use Ecto.Schema
  import Ecto.Changeset

  schema "keys" do
    field :comment, :string
    field :value, :string
    field :fingerprint, :string
    belongs_to :user, RecycledCloud.Accounts.User

    timestamps()
  end

  def process_ssh_key(changeset, value_field, fingerprint_field, comment_field) do
    raw_value = get_field(changeset, value_field)
    comment = get_field(changeset, comment_field)

    with {:is_valid, true} <- {:is_valid, changeset.valid?},
      [{pk, attrs}] <- :public_key.ssh_decode(raw_value, :public_key) do

      fingerprint = :public_key.ssh_hostkey_fingerprint(pk) |> List.to_string
      changeset = put_change(changeset, fingerprint_field, fingerprint)

      # Fetch comment from key, if not provided.
      embedded_comment = attrs
                         |> Enum.into(%{})
                         |> Map.get(:comment)

      case {comment, embedded_comment} do
        {nil, nil} -> changeset
        {nil, new_comment} ->
          put_change(changeset, comment_field, List.to_string(new_comment))
        {_, _} -> changeset
      end
    else
      {:is_valid, false} -> changeset
      _ -> add_error(changeset, value_field, "key is invalid")
    end
  end

  @doc false
  def changeset(key, attrs) do
    key
    |> cast(attrs, [:comment, :value])
    |> validate_required([:value])
    |> process_ssh_key(:value, :fingerprint, :comment)
  end
end