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discriminator.ex
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defmodule OpenApiSpex.Cast.Discriminator do
@moduledoc """
Defines the `OpenApiSpex.Discriminator.t` type.
"""
alias OpenApiSpex.Cast
@enforce_keys :propertyName
defstruct [
:propertyName,
:mapping
]
@typedoc """
[Discriminator Object](https://swagger.io/specification/#discriminatorObject)
When request bodies or response payloads may be one of a number of different schemas,
a discriminator object can be used to aid in serialization, deserialization, and validation.
The discriminator is a specific object in a schema which is used to inform the consumer of the
specification of an alternative schema based on the value associated with it.
A discriminator requires a composite key be set on the schema:
* `allOf`
* `oneOf`
* `anyOf`
"""
@type t :: %__MODULE__{
propertyName: String.t(),
mapping: %{String.t() => String.t()} | nil
}
def cast(ctx) do
case cast_discriminator(ctx) do
{:ok, result} -> {:ok, result}
error -> error
end
end
defp cast_discriminator(%_{value: value, schema: schema} = ctx) do
{discriminator_property, mappings} = discriminator_details(schema)
case Map.pop(value, "#{discriminator_property}") do
{"", _} ->
error(:no_value_for_discriminator, ctx)
{discriminator_value, castable_value} ->
# The cast specified by the composite key (allOf, anyOf, oneOf) MUST succeed
# or return an error according to the Open API Spec.
composite_ctx = %{
ctx
| value: castable_value,
schema: %{schema | discriminator: nil},
path: ["#{discriminator_property}" | ctx.path]
}
cast_composition(composite_ctx, ctx, discriminator_value, mappings)
end
end
defp cast_composition(composite_ctx, ctx, discriminator_value, mappings) do
with {composite_schemas, {:ok, _}} <- cast_composition(composite_ctx),
%{} = schema <-
find_discriminator_schema(discriminator_value, mappings, composite_schemas) do
Cast.cast(%{composite_ctx | schema: schema})
else
nil -> error(:invalid_discriminator_value, ctx)
other -> other
end
end
defp cast_composition(%_{schema: %{anyOf: schemas, discriminator: nil}} = ctx)
when is_list(schemas),
do: {schemas, Cast.cast(ctx)}
defp cast_composition(%_{schema: %{allOf: schemas, discriminator: nil}} = ctx)
when is_list(schemas),
do: {schemas, Cast.cast(ctx)}
defp cast_composition(%_{schema: %{oneOf: schemas, discriminator: nil}} = ctx)
when is_list(schemas),
do: {schemas, Cast.cast(ctx)}
defp find_discriminator_schema(discriminator, mappings = %{}, schemas) do
with {:ok, "#/components/schemas/" <> name} <- Map.fetch(mappings, discriminator) do
find_discriminator_schema(name, nil, schemas)
else
:error -> find_discriminator_schema(discriminator, nil, schemas)
end
end
defp find_discriminator_schema(discriminator, _, schemas) do
Enum.find(schemas, &Kernel.==(&1.title, discriminator))
end
defp discriminator_details(%{discriminator: %{propertyName: property_name, mapping: mappings}}),
do: {String.to_existing_atom(property_name), mappings}
defp error(message, %{schema: %{discriminator: %{propertyName: property}}} = ctx) do
Cast.error(ctx, {message, property})
end
end

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