module RDF::Tabular
  ##
  # Tabular Data/CSV format specification.
  #
  # @example Obtaining a Tabular format class
  #     RDF::Format.for(:tabular)        #=> RDF::Tabular::Format
  #     RDF::Format.for(:csv)            #=> RDF::Tabular::Format
  #     RDF::Format.for(:tsv)            #=> RDF::Tabular::Format
  #     RDF::Format.for("etc/foaf.csv")
  #     RDF::Format.for("etc/foaf.tsv")
  #     RDF::Format.for(file_name:      "etc/foaf.csv")
  #     RDF::Format.for(file_name:      "etc/foaf.tsv")
  #     RDF::Format.for(file_extension: "csv")
  #     RDF::Format.for(file_extension: "tsv")
  #     RDF::Format.for(content_type:   "text/csv")
  #     RDF::Format.for(content_type:   "text/tab-separated-values")
  #     RDF::Format.for(content_type:   "application/csvm+json")
  #
  # @example Obtaining serialization format MIME types
  #     RDF::Format.content_types      #=> {"text/csv" => [RDF::Tabular::Format]}
  #
  # @example Obtaining serialization format file extension mappings
  #     RDF::Format.file_extensions    #=> {:csv => "text/csv"}
  #
  # @see http://www.w3.org/TR/rdf-testcases/#ntriples
  class Format < RDF::Format
    content_type     'text/csv;q=0.4',
                     extensions: [:csv, :tsv],
                     alias: %w{
                       text/tab-separated-values;q=0.4
                       application/csvm+json
                     }
    content_encoding 'utf-8'

    reader { RDF::Tabular::Reader }

    ##
    # Sample detection to see if it matches JSON-LD
    #
    # Use a text sample to detect the format of an input file. Sub-classes implement
    # a matcher sufficient to detect probably format matches, including disambiguating
    # between other similar formats.
    #
    # @param [String] sample Beginning several bytes (~ 1K) of input.
    # @return [Boolean]
    def self.detect(sample)
      !!sample.match(/^(?:(?:\w )+,(?:\w ))$/)
    end

    ##
    # Hash of CLI commands appropriate for this format
    # @return [Hash{Symbol => Lambda(Array, Hash)}]
    def self.cli_commands
      {
        :"tabular-json" => {
          description: "Generate tabular json output, rather than RDF for Tabular data",
          help: "tabulary-json --input-format tabular files ...",
          prase: false,
          lambda: ->(argv, opts) do
            raise ArgumentError, "Outputting Tabular JSON only allowed when input format is tabular." unless opts[:format] == :tabular
            out = opts[:output] || $stdout
            out.set_encoding(Encoding::UTF_8) if RUBY_PLATFORM == "java"
            RDF::CLI.parse(argv, opts) do |reader|
              out.puts reader.to_json
            end
          end
        }
      }
    end
  end
end