defmodule RDF.Namespace do
@moduledoc """
A behaviour and generator for modules of terms resolving to `RDF.IRI`s.
Note: A `RDF.Namespace` is NOT a IRI namespace! The terms of a `RDF.Namespace` don't
have to necessarily refer to IRIs from the same IRI namespace. "Namespace" here is
just meant in the sense that an Elixir module is a namespace. Most of the
Most of the time you'll want to use a `RDF.Vocabulary.Namespace`, a special type of
`RDF.Namespace` where all terms indeed resolve to IRIs of a shared base URI namespace.
For an introduction into `RDF.Namespace`s and `RDF.Vocabulary.Namespace`s see
[this guide](https://rdf-elixir.dev/rdf-ex/namespaces.html).
"""
alias RDF.IRI
alias RDF.Namespace.Builder
import RDF.Guards
@type t :: module
@doc """
Resolves a term to a `RDF.IRI`.
"""
@callback __resolve_term__(atom) :: {:ok, IRI.t()} | {:error, Exception.t()}
@doc """
All terms of a `RDF.Namespace`.
"""
@callback __terms__ :: [atom]
@doc """
All `RDF.IRI`s of a `RDF.Namespace`.
"""
@callback __iris__ :: [IRI.t()]
@doc """
A macro to define a `RDF.Namespace`.
## Example
defmodule YourApp.NS do
import RDF.Namespace
defnamespace EX, [
foo: ~I<http://example1.com/foo>,
Bar: "http://example2.com/Bar",
]
end
> #### Warning {: .warning}
>
> This macro is intended to be used at compile-time, i.e. in the body of a
> `defmodule` definition. If you want to create `RDF.Namespace`s dynamically
> at runtime, please use `create/4`.
"""
defmacro defnamespace(module, term_mapping, opts \\ []) do
env = __CALLER__
module = fully_qualified_module(module, env)
quote do
result =
Builder.create!(
unquote(module),
unquote(term_mapping),
unquote(Macro.escape(env)),
unquote(opts)
)
alias unquote(module)
result
end
end
defdelegate create(module, term_mapping, location), to: Builder
defdelegate create(module, term_mapping, location, opts), to: Builder
defdelegate create!(module, term_mapping, location), to: Builder
defdelegate create!(module, term_mapping, location, opts), to: Builder
@doc false
def fully_qualified_module({:__aliases__, _, module}, env) do
Module.concat([env.module | module])
end
@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.
"""
@spec resolve_term(IRI.t() | module) :: {:ok, IRI.t()} | {:error, Exception.t()}
def resolve_term(expr)
def resolve_term(%IRI{} = iri), do: {:ok, iri}
def resolve_term(namespaced_term) when maybe_ns_term(namespaced_term) do
namespaced_term
|> to_string()
|> do_resolve_term()
end
@doc """
Resolves a qualified term to a `RDF.IRI` or raises an error when that's not possible.
See `resolve_term/1` for more.
"""
@spec resolve_term!(IRI.t() | module) :: IRI.t()
def resolve_term!(expr) do
case resolve_term(expr) do
{:ok, iri} -> iri
{:error, error} -> raise error
end
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
{:error,
%RDF.Namespace.UndefinedTermError{
message: "#{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(Elixir, term) do
{:error,
%RDF.Namespace.UndefinedTermError{
message: "#{term} is not a RDF.Namespace; top-level modules can't be RDF.Namespaces"
}}
end
defp do_resolve_term(namespace, term) do
if namespace?(namespace) do
namespace.__resolve_term__(term)
else
{:error, %RDF.Namespace.UndefinedTermError{message: "#{namespace} is not a RDF.Namespace"}}
end
end
@doc false
@spec namespace?(module) :: boolean
def namespace?(name) do
case Code.ensure_compiled(name) do
{:module, name} -> function_exported?(name, :__resolve_term__, 1)
_ -> false
end
end
end