59 lines
2 KiB
Elixir
59 lines
2 KiB
Elixir
defmodule RDF.NTriples.Decoder do
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@moduledoc """
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A decoder for N-Triples serializations to `RDF.Graph`s.
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As for all decoders of `RDF.Serialization.Format`s, you normally won't use these
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functions directly, but via one of the `read_` functions on the `RDF.NTriples` format
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module or the generic `RDF.Serialization` module.
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"""
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use RDF.Serialization.Decoder
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import RDF.Serialization.ParseHelper, only: [error_description: 1]
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alias RDF.Graph
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@impl RDF.Serialization.Decoder
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@spec decode(String.t(), keyword) :: {:ok, Graph.t()} | {:error, any}
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def decode(string, _opts \\ []) do
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with {:ok, ast} <- do_decode(string, true) do
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{:ok, build_graph(ast)}
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end
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end
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@impl RDF.Serialization.Decoder
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@spec decode_from_stream(Enumerable.t(), keyword) :: {:ok, Graph.t()} | {:error, any}
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def decode_from_stream(stream, _opts \\ []) do
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Enum.reduce_while(stream, {:ok, Graph.new()}, fn line, {:ok, graph} ->
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case do_decode(line, false) do
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{:ok, []} -> {:cont, {:ok, graph}}
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{:ok, [[triple]]} -> {:cont, {:ok, Graph.add(graph, triple)}}
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{:error, _} = error -> {:halt, error}
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end
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end)
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end
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defp do_decode(string, error_with_line_number) do
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with {:ok, tokens, _} <- tokenize(string) do
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parse(tokens)
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else
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{:error, {error_line, :ntriples_lexer, error_descriptor}, _error_line_again} ->
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{:error,
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"N-Triple scanner error#{if error_with_line_number, do: " on line #{error_line}"}: #{error_description(error_descriptor)}"}
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{:error, {error_line, :ntriples_parser, error_descriptor}} ->
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{:error,
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"N-Triple parser error#{if error_with_line_number, do: " on line #{error_line}"}: #{error_description(error_descriptor)}"}
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end
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end
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defp tokenize(content), do: content |> to_charlist() |> :ntriples_lexer.string()
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defp parse(tokens), do: tokens |> :ntriples_parser.parse()
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defp build_graph([]), do: Graph.new()
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defp build_graph([triples]) do
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Enum.reduce(triples, Graph.new(), &Graph.add(&2, &1))
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end
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end
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