rdf-ex/lib/rdf/iri.ex
2018-09-10 00:27:40 +02:00

235 lines
7 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>
"""
@enforce_keys [:value]
defstruct [:value]
alias RDF.Namespace
@type t :: module
# 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` 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`.
"""
def new(iri)
def new(iri) when is_binary(iri), do: %RDF.IRI{value: iri}
def new(qname) when is_atom(qname) and qname not in [nil, true, false],
do: Namespace.resolve_term(qname)
def new(%URI{} = uri), do: uri |> URI.to_string |> new
def new(%RDF.IRI{} = 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`
"""
def new!(iri)
def new!(iri) when is_binary(iri), do: iri |> valid!() |> new()
def new!(qname) when is_atom(qname) and qname not in [nil, true, false],
do: new(qname) # since terms of a namespace are already validated
def new!(%URI{} = uri), do: uri |> valid!() |> new()
def new!(%RDF.IRI{} = iri), do: valid!(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"
"""
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
"""
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.
"""
def absolute?(iri)
def absolute?(value) when is_binary(value), do: not is_nil(scheme(value))
def absolute?(%RDF.IRI{value: value}), do: absolute?(value)
def absolute?(%URI{scheme: nil}), do: false
def absolute?(%URI{scheme: _}), do: true
def absolute?(qname) when is_atom(qname) and qname not in [nil, true, false] do
qname |> Namespace.resolve_term |> absolute?()
rescue
_ -> false
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.
"""
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).
"""
def merge(base, rel) do
base
|> parse()
|> URI.merge(parse(rel))
|> empty_fragment_shim(rel)
|> new()
end
@doc false
# shim for https://github.com/elixir-lang/elixir/pull/6419
def empty_fragment_shim(_, %URI{} = uri), do: uri
def empty_fragment_shim(uri, %RDF.IRI{value: value}),
do: empty_fragment_shim(uri, value)
def empty_fragment_shim(uri, original) do
if String.ends_with?(original, "#") do
%URI{uri | fragment: ""}
else
uri
end
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
"""
def scheme(iri)
def scheme(%RDF.IRI{value: value}), do: scheme(value)
def scheme(%URI{scheme: scheme}), do: scheme
def scheme(qname) when is_atom(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.
"""
def parse(iri)
def parse(iri) when is_binary(iri), do: URI.parse(iri) |> empty_fragment_shim(iri)
def parse(qname) when is_atom(qname) and qname not in [nil, true, false],
do: Namespace.resolve_term(qname) |> parse()
def parse(%RDF.IRI{value: value}), do: URI.parse(value) |> empty_fragment_shim(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>
"""
def equal_value?(left, right)
def equal_value?(%RDF.IRI{value: left}, %RDF.IRI{value: right}),
do: left == right
@xsd_any_uri "http://www.w3.org/2001/XMLSchema#anyURI"
def equal_value?(%RDF.Literal{datatype: %RDF.IRI{value: @xsd_any_uri}, value: left}, right),
do: equal_value?(new(left), right)
def equal_value?(left, %RDF.Literal{datatype: %RDF.IRI{value: @xsd_any_uri}, value: right}),
do: equal_value?(left, new(right))
def equal_value?(_, _),
do: nil
defimpl String.Chars do
def to_string(%RDF.IRI{value: value}) do
value
end
end
end