/
nquads_encoder.ex
76 lines (61 loc) · 2.12 KB
/
nquads_encoder.ex
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defmodule RDF.NQuads.Encoder do
@moduledoc """
An encoder for N-Quads serializations of RDF.ex data structures.
As for all encoders of `RDF.Serialization.Format`s, you normally won't use these
functions directly, but via one of the `write_` functions on the `RDF.NQuads`
format module or the generic `RDF.Serialization` module.
"""
use RDF.Serialization.Encoder
alias RDF.Statement
@impl RDF.Serialization.Encoder
@callback encode(RDF.Data.t(), keyword) :: {:ok, String.t()} | {:error, any}
def encode(data, _opts \\ []) do
{:ok,
data
|> Enum.reduce([], &[statement(&1) | &2])
|> Enum.reverse()
|> Enum.join()}
end
@impl RDF.Serialization.Encoder
@spec stream(RDF.Data.t(), keyword) :: Enumerable.t()
def stream(data, opts \\ []) do
case Keyword.get(opts, :mode, :string) do
:string -> Stream.map(data, &statement(&1))
:iodata -> Stream.map(data, &iolist_statement(&1))
invalid -> raise "Invalid stream mode: #{invalid}"
end
end
@spec statement(Statement.t()) :: String.t()
def statement(statement)
def statement({subject, predicate, object, nil}) do
statement({subject, predicate, object})
end
def statement({subject, predicate, object, graph}) do
"#{term(subject)} #{term(predicate)} #{term(object)} #{term(graph)} .\n"
end
def statement({subject, predicate, object}) do
"#{term(subject)} #{term(predicate)} #{term(object)} .\n"
end
defdelegate term(value), to: RDF.NTriples.Encoder
@spec iolist_statement(Statement.t()) :: iolist
def iolist_statement(statement)
def iolist_statement({subject, predicate, object, nil}) do
iolist_statement({subject, predicate, object})
end
def iolist_statement({subject, predicate, object, graph}) do
[
iolist_term(subject),
" ",
iolist_term(predicate),
" ",
iolist_term(object),
" ",
iolist_term(graph),
" .\n"
]
end
def iolist_statement({subject, predicate, object}) do
[iolist_term(subject), " ", iolist_term(predicate), " ", iolist_term(object), " .\n"]
end
defdelegate iolist_term(value), to: RDF.NTriples.Encoder
end