defmodule RecycledCloud.Accounts.User do
  use Ecto.Schema
  import Ecto.Changeset
  require Logger
  require Exldap
  alias RecycledCloud.{LDAP,Accounts}
  alias RecycledCloud.Accounts.{User, UserToken, UserNotifier}
  alias RecycledCloud.Repo

  @derive {Inspect, except: [:password]}
  schema "users" do
    field :username, :string
    field :password, :string, virtual: true
    field :email, :string, virtual: true
    field :confirmed_at, :naive_datetime

    timestamps()
  end

  defp get_dn_for(%User{username: uid}) do
    # FIXME
    "uid=#{uid},ou=users,dc=recycled,dc=cloud"
  end

  def get_by_username(username) when is_binary(username) do
    local_user = Repo.get_by(User, username: username)
    if local_user do
      Map.put(local_user, :email, "unknown@domain.tld")
    else
      query = fn ldap_conn -> Exldap.search_field(ldap_conn, :uid, username) end
      case query |> LDAP.execute do
        {:ok, []} -> nil
        {:ok, result} ->
          {:ok, entry} = result |> Enum.fetch(0)

          Logger.info("Found #{entry.object_name} in directory. Syncing with \
            local database.")

          attributes = entry |> Map.get(:attributes) |> Enum.into(%{})
          username = attributes
                     |> Map.get('uid')
                     |> Enum.at(0)
                     |> List.to_string

          email = attributes
                     |> Map.get('email')
                     |> Enum.at(0)
                     |> List.to_string

          case Accounts.register_user(%{username: username, email: email}) do
            {:ok, user} -> user
            {:error, _} -> nil
          end
        {:error, err} ->
          Logger.warn("LDAP error: #{err}")
          nil
      end
    end
  end

  @doc """
  A user changeset for registration.

  It is important to validate the length of both email and password.
  Otherwise databases may truncate the email without warnings, which
  could lead to unpredictable or insecure behaviour. Long passwords may
  also be very expensive to hash for certain algorithms.

  ## Options

    * `:hash_password` - Hashes the password so it can be stored securely
      in the database and ensures the password field is cleared to prevent
      leaks in the logs. If password hashing is not needed and clearing the
      password field is not desired (like when using this changeset for
      validations on a LiveView form), this option can be set to `false`.
      Defaults to `true`.
  """
  def registration_changeset(user, attrs, opts \\ []) do
    user
    |> cast(attrs, [:username, :password])
    |> validate_email()
    #|> validate_password(opts)
  end

  defp validate_email(changeset) do
    changeset
    |> validate_required([:email])
    |> validate_format(:email, ~r/^[^\s]+@[^\s]+$/, message: "must have the @ sign and no spaces")
    |> validate_length(:email, max: 160)
  end

  defp validate_password(changeset) do
    changeset
    |> validate_required([:password])
    |> validate_length(:password, min: 6, max: 80)
    #|> validate_format(:password, ~r/[a-z]/, message: "at least one lower case character")
    #|> validate_format(:password, ~r/[A-Z]/, message: "at least one upper case character")
    #|> validate_format(:password, ~r/[!?@#$%^&*_0-9]/, message: "at least one digit or punctuation character")
  end

  @doc """
  A user changeset for changing the email.

  It requires the email to change otherwise an error is added.
  """
  def email_changeset(user, attrs) do
    user
    |> cast(attrs, [:email])
    |> validate_email()
    |> case do
      %{changes: %{email: _}} = changeset -> changeset
      %{} = changeset -> add_error(changeset, :email, "did not change")
    end
  end

  @doc """
  A user changeset for changing the password.

  ## Options

    * `:hash_password` - Hashes the password so it can be stored securely
      in the database and ensures the password field is cleared to prevent
      leaks in the logs. If password hashing is not needed and clearing the
      password field is not desired (like when using this changeset for
      validations on a LiveView form), this option can be set to `false`.
      Defaults to `true`.
  """
  def password_changeset(user, attrs) do
    user
    |> cast(attrs, [:password])
    |> validate_confirmation(:password, message: "does not match password")
    |> validate_password()
  end

  @doc """
  Confirms the account by setting `confirmed_at`.
  """
  def confirm_changeset(user) do
    now = NaiveDateTime.utc_now() |> NaiveDateTime.truncate(:second)
    change(user, confirmed_at: now)
  end

  @doc """
  Verifies the password.
  """
  def valid_password?(user = %User{username: uid}, password)
  when byte_size(password) > 0 do
    dn = get_dn_for(user)
    query = fn ldap_conn ->
      Exldap.verify_credentials(ldap_conn, dn, password)
    end

    case query |> LDAP.execute_single do
      :ok -> true
      {:error, _} -> false
    end
  end

  def valid_password?(_, _) do
    false
  end

  @doc """
  Validates the current password otherwise adds an error to the changeset.
  """
  def validate_current_password(changeset, password) do
    if valid_password?(changeset.data, password) do
      changeset
    else
      add_error(changeset, :current_password, "is not valid")
    end
  end

  def set_password(user, new_password) do
    # Exldap does not properly implement `change_password`, hence we have to
    # fallback on erlang's `:eldap`.
    # See http://erlang.org/doc/man/eldap.html#modify-4

    user_dn = get_dn_for(user)
    query = fn ldap_conn ->
      :eldap.modify_password(
        ldap_conn,
        String.to_charlist(user_dn),
        String.to_charlist(new_password)
      )
    end

    query |> LDAP.execute_single
  end
end