defmodule Integrate.Accounts do
  @moduledoc """
  The Accounts context.
  """

  import Ecto.Query, warn: false

  alias Ecto.Changeset
  alias Integrate.Repo

  alias Integrate.Accounts.User

  @doc """
  Returns the list of users.

  ## Examples

      iex> list_users()
      [%User{}, ...]

  """
  def list_users do
    Repo.all(User)
  end

  @doc """
  Returns a boolean indicating whether any users exist.

  ## Examples

      iex> any_users_exist?()
      true

  """
  def any_users_exist? do
    Repo.exists?(User)
  end

  @doc """
  Gets a single user.

  Raises `Ecto.NoResultsError` if the User does not exist.

  ## Examples

      iex> get_user!(123)
      %User{}

      iex> get_user!(456)
      ** (Ecto.NoResultsError)

  """
  def get_user!(id), do: Repo.get!(User, id)

  @doc """
  Gets a single user.

  Returns `nil` if the User does not exist.

  ## Examples

      iex> get_user!(123)
      %User{}

      iex> get_user!(456)
      nil

  """
  def get_user(nil), do: nil
  def get_user(id), do: Repo.get(User, id)

  @doc """
  Creates a user.

  ## Examples

      iex> create_user(%{field: value})
      {:ok, %User{}}

      iex> create_user(%{field: bad_value})
      {:error, %Ecto.Changeset{}}

  """
  def create_user(attrs \\ %{}) do
    %User{}
    |> User.changeset(attrs)
    |> Repo.insert()
  end

  @doc """
  Updates a user.

  ## Examples

      iex> update_user(user, %{field: new_value})
      {:ok, %User{}}

      iex> update_user(user, %{field: bad_value})
      {:error, %Ecto.Changeset{}}

  """
  def update_user(%User{} = user, attrs) do
    user
    |> User.changeset(attrs)
    |> Repo.update()
  end

  @doc """
  Deletes a user.

  ## Examples

      iex> delete_user(user)
      {:ok, %User{}}

      iex> delete_user(user)
      {:error, %Ecto.Changeset{}}

  """
  def delete_user(%User{} = user) do
    Repo.delete(user)
  end

  @doc """
  Returns an `%Ecto.Changeset{}` for tracking user changes.

  ## Examples

      iex> change_user(user)
      %Ecto.Changeset{data: %User{}}

  """
  def change_user(%User{} = user, attrs \\ %{}) do
    User.changeset(user, attrs)
  end

  # === Authentication ===

  def validate_credentials(attrs) do
    %User{}
    |> User.changeset(attrs)
    |> Changeset.apply_action(:update)
  end

  def authenticate(%{username: username, password: password}) do
    User
    |> Repo.get_by(username: username)
    |> verify_password(password)
  end

  defp verify_password(%User{} = user, password) do
    case Argon2.verify_pass(password, user.password_hash) do
      true -> {:ok, user}
      false -> nil
    end
  end

  defp verify_password(nil, _) do
    nil
  end

  def invalid_credentials(username) do
    %User{}
    |> Changeset.cast(%{username: username}, [:username, :password])
    |> Changeset.add_error(:password, "Invalid credentials")
    |> Changeset.apply_action(:update)
  end
end