90 lines
3.2 KiB
Elixir
90 lines
3.2 KiB
Elixir
defmodule RDF.NQuads.Encoder do
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@moduledoc """
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An encoder for N-Quads serializations of RDF.ex data structures.
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As for all encoders of `RDF.Serialization.Format`s, you normally won't use these
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functions directly, but via one of the `write_` functions on the `RDF.NQuads`
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format module or the generic `RDF.Serialization` module.
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## Options
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- `:default_graph_name`: The graph name to be used as the default for triples
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from a `RDF.Graph` or `RDF.Description`. When the input to be encoded is a
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`RDF.Description` the default is `nil` for the default graph. In case of a
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`RDF.Graph` the default is the `RDF.Graph.name/1`. The option doesn't
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have any effect at all when the input to be encoded is a `RDF.Dataset`.
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"""
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use RDF.Serialization.Encoder
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alias RDF.{Statement, Graph}
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@impl RDF.Serialization.Encoder
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@callback encode(RDF.Data.t(), keyword) :: {:ok, String.t()} | {:error, any}
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def encode(data, opts \\ []) do
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default_graph_name = default_graph_name(data, Keyword.get(opts, :default_graph_name, false))
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{:ok, Enum.map_join(data, &statement(&1, default_graph_name))}
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end
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@impl RDF.Serialization.Encoder
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@spec stream(RDF.Data.t(), keyword) :: Enumerable.t()
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def stream(data, opts \\ []) do
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default_graph_name = default_graph_name(data, Keyword.get(opts, :default_graph_name, false))
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case Keyword.get(opts, :mode, :string) do
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:string -> Stream.map(data, &statement(&1, default_graph_name))
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:iodata -> Stream.map(data, &iolist_statement(&1, default_graph_name))
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invalid -> raise "Invalid stream mode: #{invalid}"
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end
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end
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defp default_graph_name(%Graph{} = graph, false), do: graph.name
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defp default_graph_name(_, none) when none in [false, nil], do: nil
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defp default_graph_name(_, default_graph_name),
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do: Statement.coerce_graph_name(default_graph_name)
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@spec statement(Statement.t(), Statement.graph_name()) :: String.t()
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def statement(statement, default_graph_name)
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def statement({subject, predicate, object, nil}, _) do
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"#{term(subject)} #{term(predicate)} #{term(object)} .\n"
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end
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def statement({subject, predicate, object, graph}, _) do
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"#{term(subject)} #{term(predicate)} #{term(object)} #{term(graph)} .\n"
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end
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def statement({subject, predicate, object}, default_graph_name) do
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statement({subject, predicate, object, default_graph_name}, default_graph_name)
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end
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defdelegate term(value), to: RDF.NTriples.Encoder
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@spec iolist_statement(Statement.t(), Statement.graph_name()) :: iolist
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def iolist_statement(statement, default_graph_name)
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def iolist_statement({subject, predicate, object, nil}, _) do
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[iolist_term(subject), " ", iolist_term(predicate), " ", iolist_term(object), " .\n"]
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end
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def iolist_statement({subject, predicate, object, graph}, _) do
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[
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iolist_term(subject),
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" ",
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iolist_term(predicate),
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" ",
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iolist_term(object),
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" ",
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iolist_term(graph),
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" .\n"
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]
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end
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def iolist_statement({subject, predicate, object}, default_graph_name) do
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iolist_statement({subject, predicate, object, default_graph_name}, default_graph_name)
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end
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defdelegate iolist_term(value), to: RDF.NTriples.Encoder
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end
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