defmodule OnePiece.Commanded.ValueObject do
@moduledoc """
Defines "Value Object" modules.
"""
alias Ecto.Changeset
@doc """
Converts the module into an `Ecto.Schema` and add factory functions to create structs.
## Using
- `Ecto.Schema`
- `Ecto.Type`
## Derives
- `Jason.Encoder`
## Usage
defmodule MyValueObject do
use OnePiece.Commanded.ValueObject
embedded_schema do
field :title, :string
# ...
end
end
{:ok, my_value} = MyValueObject.new(%{title: "Hello, World!"})
"""
@spec __using__(opts :: []) :: any()
defmacro __using__(_opts \\ []) do
quote do
alias OnePiece.Commanded.ValueObject
use Ecto.Schema
use Ecto.Type
@derive Jason.Encoder
@primary_key false
@before_compile OnePiece.Commanded.ValueObject
@doc """
Creates a `t:t/0`.
"""
@spec new(attrs :: map()) :: {:ok, %__MODULE__{}} | {:error, Ecto.Changeset.t()}
def new(attrs) do
ValueObject.__new__(__MODULE__, attrs)
end
@doc """
Creates a `t:t/0`.
"""
@spec new!(attrs :: map()) :: %__MODULE__{}
def new!(attrs) do
ValueObject.__new__!(__MODULE__, attrs)
end
@doc """
Returns an `t:Ecto.Changeset.t/0` for a given `t:t/0` value object.
"""
@spec changeset(message :: %__MODULE__{}, attrs :: map()) :: Ecto.Changeset.t()
def changeset(message, attrs) do
ValueObject.__changeset__(message, attrs)
end
def type, do: :map
def cast(value) when is_struct(value, __MODULE__), do: {:ok, value}
def cast(value) when is_map(value) do
with {:error, _} <- new(value), do: :error
end
def cast(_), do: :error
def load(data) when is_map(data) do
with {:error, _} <- new(data), do: :error
end
def load(_), do: :error
def dump(value) when is_struct(value, __MODULE__), do: {:ok, Map.from_struct(value)}
def dump(_), do: :error
defoverridable new: 1, new!: 1, changeset: 2
end
end
defmacro __before_compile__(env) do
enforced_keys = get_enforced_keys(env)
quote unquote: false, bind_quoted: [enforced_keys: enforced_keys] do
def __enforced_keys__ do
unquote(enforced_keys)
end
for the_key <- enforced_keys do
def __enforced_keys__?(unquote(the_key)) do
true
end
end
def __enforced_keys__?(_) do
false
end
end
end
defp get_enforced_keys(env) do
enforce_keys = Module.get_attribute(env.module, :enforce_keys) || []
enforce_keys ++ get_primary_key_name(env)
end
defp get_primary_key_name(env) do
case Module.get_attribute(env.module, :primary_key) do
{field_name, _, _} -> [field_name]
_ -> []
end
end
def __new__(struct_module, attrs) do
struct_module
|> apply_changeset(attrs)
|> Changeset.apply_action(:new)
end
def __new__!(struct_module, attrs) do
struct_module
|> apply_changeset(attrs)
|> Changeset.apply_action!(:new)
end
def __changeset__(%struct_module{} = message, attrs) do
embeds = struct_module.__schema__(:embeds)
fields = struct_module.__schema__(:fields)
changeset =
message
|> Changeset.cast(attrs, fields -- embeds)
|> Changeset.validate_required(struct_module.__enforced_keys__() -- embeds)
Enum.reduce(
embeds,
changeset,
&cast_embed(&1, &2, struct_module, attrs)
)
end
defp cast_embed(field, changeset, struct_module, attrs) do
case is_struct(attrs[field]) do
false ->
Changeset.cast_embed(changeset, field, required: struct_module.__enforced_keys__?(field))
true ->
# credo:disable-for-next-line Credo.Check.Design.TagTODO
# TODO: Validate that the struct is of the correct type.
# It may be the case that you passed a completely different struct as the value. We could `cast_embed`
# always and fix the `Changeset.cast(attrs, fields -- embeds)` by converting the `attrs` into a map. But it
# would be a bit more expensive since it will run the casting for a field that was already casted.
# Checking the struct types MAY be enough but taking into consideration `embeds_many` could complicated
# things. For now, we'll just assume that the user knows what they're doing.
Changeset.put_change(changeset, field, attrs[field])
end
end
defp apply_changeset(struct_module, attrs) do
struct(struct_module)
|> struct_module.changeset(attrs)
end
end