rdf-ex/lib/rdf/iri.ex

272 lines
8 KiB
Elixir

defmodule RDF.IRI do
@moduledoc """
A structure for IRIs.
This structure just wraps a plain IRI string and doesn't bother with the
components of the IRI, since in the context of RDF there are usually very many
IRIs and parsing them isn't needed in most cases. For these reasons we don't
use Elixirs built-in `URI` structure, because it would be unnecessary
expensive in terms of performance and memory.
The component parts can always be retrieved with the `RDF.IRI.parse/1`
function, which returns Elixirs built-in `URI` structure. Note, that `URI`
doesn't escape Unicode characters by default, so it's a suitable structure for
IRIs.
see <https://tools.ietf.org/html/rfc3987>
"""
alias RDF.Namespace
import RDF.Guards
@type t :: %__MODULE__{
value: String.t
}
@type coercible :: String.t | URI.t | module | t
@enforce_keys [:value]
defstruct [:value]
# see https://tools.ietf.org/html/rfc3986#appendix-B
@scheme_regex Regex.recompile!(~r/^([a-z][a-z0-9\+\-\.]*):/i)
@doc """
The default base IRI to be used when reading a serialization and no `base_iri` option is provided.
The value can be set via the `default_base_iri` configuration. For example:
config :rdf,
default_base_iri: "http://my_app.example/"
See [section 5.1.4 of RFC 3987](https://tools.ietf.org/html/rfc3986#page-29)
"""
@default_base Application.get_env(:rdf, :default_base_iri)
def default_base, do: @default_base
@doc """
Creates a `RDF.IRI`.
"""
@spec new(coercible) :: t
def new(iri)
def new(iri) when is_binary(iri), do: %__MODULE__{value: iri}
def new(qname) when maybe_ns_term(qname), do: Namespace.resolve_term!(qname)
def new(%URI{} = uri), do: uri |> URI.to_string |> new
def new(%__MODULE__{} = iri), do: iri
@doc """
Creates a `RDF.IRI`, but checks if the given IRI is valid.
If the given IRI is not valid a `RDF.IRI.InvalidError` is raised.
see `valid?/1`
"""
@spec new!(coercible) :: t
def new!(iri)
def new!(iri) when is_binary(iri), do: iri |> valid!() |> new()
def new!(qname) when maybe_ns_term(qname), do: new(qname) # since terms of a namespace are already validated
def new!(%URI{} = uri), do: uri |> valid!() |> new()
def new!(%__MODULE__{} = iri), do: valid!(iri)
@doc """
Coerces an IRI serving as a base IRI.
As opposed to `new/1` this also accepts bare `RDF.Vocabulary.Namespace` modules
and uses the base IRI from their definition.
"""
@spec coerce_base(coercible) :: t
def coerce_base(base_iri)
def coerce_base(module) when maybe_ns_term(module) do
if RDF.Vocabulary.Namespace.vocabulary_namespace?(module) do
apply(module, :__base_iri__, [])
|> new()
else
new(module)
end
end
def coerce_base(base_iri), do: new(base_iri)
@doc """
Returns the given value unchanged if it's a valid IRI, otherwise raises an exception.
## Examples
iex> RDF.IRI.valid!("http://www.example.com/foo")
"http://www.example.com/foo"
iex> RDF.IRI.valid!(RDF.IRI.new("http://www.example.com/foo"))
RDF.IRI.new("http://www.example.com/foo")
iex> RDF.IRI.valid!("not an iri")
** (RDF.IRI.InvalidError) Invalid IRI: "not an iri"
"""
@spec valid!(coercible) :: coercible
def valid!(iri) do
if not valid?(iri), do: raise RDF.IRI.InvalidError, "Invalid IRI: #{inspect iri}"
iri
end
@doc """
Checks if the given IRI is valid.
Note: This currently checks only if the given IRI is absolute.
## Examples
iex> RDF.IRI.valid?("http://www.example.com/foo")
true
iex> RDF.IRI.valid?("not an iri")
false
"""
@spec valid?(coercible) :: boolean
def valid?(iri), do: absolute?(iri) # TODO: Provide a more elaborate validation
@doc """
Checks if the given value is an absolute IRI.
An absolute IRI is defined in [RFC3987](http://www.ietf.org/rfc/rfc3987.txt)
containing a scheme along with a path and optional query and fragment segments.
"""
@spec absolute?(any) :: boolean
def absolute?(iri)
def absolute?(value) when is_binary(value), do: not is_nil(scheme(value))
def absolute?(%__MODULE__{value: value}), do: absolute?(value)
def absolute?(%URI{scheme: nil}), do: false
def absolute?(%URI{scheme: _}), do: true
def absolute?(qname) when maybe_ns_term(qname) do
case Namespace.resolve_term(qname) do
{:ok, iri} -> absolute?(iri)
_ -> false
end
end
def absolute?(_), do: false
@doc """
Resolves a relative IRI against a base IRI.
as specified in [section 5.1 Establishing a Base URI of RFC3986](http://tools.ietf.org/html/rfc3986#section-5.1).
Only the basic algorithm in [section 5.2 of RFC3986](http://tools.ietf.org/html/rfc3986#section-5.2)
is used; neither Syntax-Based Normalization nor Scheme-Based Normalization are performed.
Characters additionally allowed in IRI references are treated in the same way that unreserved
characters are treated in URI references, per [section 6.5 of RFC3987](http://tools.ietf.org/html/rfc3987#section-6.5)
If the given is not an absolute IRI `nil` is returned.
"""
@spec absolute(coercible, coercible) :: t | nil
def absolute(iri, base) do
cond do
absolute?(iri) -> new(iri)
not absolute?(base) -> nil
true -> merge(base, iri)
end
end
@doc """
Merges two IRIs.
This function merges two IRIs as per
[RFC 3986, section 5.2](https://tools.ietf.org/html/rfc3986#section-5.2).
"""
@spec merge(coercible, coercible) :: t
def merge(base, rel) do
base
|> parse()
|> URI.merge(parse(rel))
|> new()
end
@doc """
Returns the scheme of the given IRI
If the given string is not a valid absolute IRI, `nil` is returned.
## Examples
iex> RDF.IRI.scheme("http://www.example.com/foo")
"http"
iex> RDF.IRI.scheme("not an iri")
nil
"""
@spec scheme(coercible) :: String.t | nil
def scheme(iri)
def scheme(%__MODULE__{value: value}), do: scheme(value)
def scheme(%URI{scheme: scheme}), do: scheme
def scheme(qname) when maybe_ns_term(qname), do: Namespace.resolve_term!(qname) |> scheme()
def scheme(iri) when is_binary(iri) do
with [_, scheme] <- Regex.run(@scheme_regex, iri) do
scheme
end
end
@doc """
Parses an IRI into its components and returns them as an `URI` struct.
"""
@spec parse(coercible) :: URI.t
def parse(iri)
def parse(iri) when is_binary(iri), do: URI.parse(iri)
def parse(qname) when maybe_ns_term(qname), do: Namespace.resolve_term!(qname) |> parse()
def parse(%__MODULE__{value: value}), do: URI.parse(value)
def parse(%URI{} = uri), do: uri
@doc """
Tests for value equality of IRIs.
Returns `nil` when the given arguments are not comparable as IRIs.
see <https://www.w3.org/TR/rdf-concepts/#section-Graph-URIref>
"""
@spec equal_value?(t | RDF.Literal.t, t | RDF.Literal.t) :: boolean | nil
def equal_value?(left, right)
def equal_value?(%__MODULE__{value: left}, %__MODULE__{value: right}),
do: left == right
def equal_value?(%__MODULE__{} = left, %RDF.Literal{} = right),
do: RDF.Literal.equal_value?(right, left)
def equal_value?(%__MODULE__{value: left}, %URI{} = right),
do: left == URI.to_string(right)
def equal_value?(_, _),
do: nil
@doc """
Returns the given IRI as a string.
Note that this function can also handle `RDF.Vocabulary.Namespace` terms.
## Examples
iex> RDF.IRI.to_string RDF.IRI.new("http://example.com/#foo")
"http://example.com/#foo"
iex> RDF.IRI.to_string EX.foo
"http://example.com/#foo"
iex> RDF.IRI.to_string EX.Foo
"http://example.com/#Foo"
"""
@spec to_string(t | module) :: String.t
def to_string(iri)
def to_string(%__MODULE__{value: value}),
do: value
def to_string(qname) when maybe_ns_term(qname),
do: qname |> new() |> __MODULE__.to_string()
defimpl String.Chars do
def to_string(iri), do: RDF.IRI.to_string(iri)
end
end