rdf-ex/lib/rdf/namespace.ex

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Elixir
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defmodule RDF.Namespace do
@moduledoc """
A behaviour for resolvers of module atoms to `RDF.IRI`s.
Currently there's only one type of such namespaces: `RDF.Vocabulary.Namespace`,
but other types are thinkable and might be implemented in the future, eg.
namespaces for JSON-LD contexts.
"""
@doc """
Resolves a term to a `RDF.IRI`.
"""
@callback __resolve_term__(atom) :: RDF.IRI.t
@doc """
All terms of a `RDF.Namespace`.
"""
@callback __terms__() :: [atom]
@doc """
Resolves a qualified term to a `RDF.IRI`.
It determines a `RDF.Namespace` from the qualifier of the given term and
delegates to remaining part of the term to `__resolve_term__/1` of this
determined namespace.
"""
def resolve_term(expr)
def resolve_term(%RDF.IRI{} = iri), do: iri
def resolve_term(namespaced_term) when is_atom(namespaced_term) do
namespaced_term
|> to_string()
|> do_resolve_term()
end
defp do_resolve_term("Elixir." <> _ = namespaced_term) do
{term, namespace} =
namespaced_term
|> Module.split
|> List.pop_at(-1)
do_resolve_term(Module.concat(namespace), String.to_atom(term))
end
defp do_resolve_term(namespaced_term) do
raise RDF.Namespace.UndefinedTermError,
"#{namespaced_term} is not a term on a RDF.Namespace"
end
defp do_resolve_term(RDF, term), do: do_resolve_term(RDF.NS.RDF, term)
defp do_resolve_term(namespace, term) do
if Code.ensure_compiled?(namespace) and
Keyword.has_key?(namespace.__info__(:functions), :__resolve_term__)do
namespace.__resolve_term__(term)
else
raise RDF.Namespace.UndefinedTermError,
"#{namespace} is not a RDF.Namespace"
end
end
end