Method: SXP::Reader::SPARQL#read_token

Defined in:
lib/sxp/reader/sparql.rb

#read_token ⇒ Object

Reads SSE Tokens, including RDF::Literal, RDF::URI and RDF::Node.

Performs forward reference for prefix and base URI representations and saves in #base_uri and #prefixes accessors.

Transforms tokens matching a PNAME pattern into RDF::URI instances if a match is found with a previously identified PREFIX.

Returns:



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# File 'lib/sxp/reader/sparql.rb', line 90

def read_token
  case peek_char
  when ?" then [:atom, read_rdf_literal] # "
  when ?< then [:atom, read_rdf_uri]
  else
    tok = super
    
    # If we just parsed "PREFIX", and this is an opening list, then
    # record list depth and process following as token, URI pairs
    #
    # Once we've closed the list, go out of prefix mode
    if tok.is_a?(Array) && tok[0] == :list
      if '(['.include?(tok[1])
        @list_depth += 1
      else
        @list_depth -= 1
        @prefix_depth = nil if @prefix_depth && @list_depth < @prefix_depth
      end
    end

    if tok.is_a?(Array) && tok[0] == :atom && tok[1].is_a?(Symbol)
      value = tok[1].to_s

      # We previously parsed a PREFIX, this will be the map value
      @parsed_prefix = value.chop if @prefix_depth && @prefix_depth > 0
      
      # If we just saw PREFIX, then this starts the parsing mode
      @prefix_depth = @list_depth + 1 if value =~ PREFIX
      
      # If the token is of the form 'prefix:suffix', create a URI and give it the
      # token as a QName
      if value.to_s =~ PNAME && base = prefix($1)
        suffix = $2
        #STDERR.puts "read_tok lexical: pfx: #{$1.inspect} => #{prefix($1).inspect}, sfx: #{suffix.inspect}"
        suffix = suffix.sub(/^\#/, "") if base.to_s.index("#")
        uri = RDF::URI(base.to_s + suffix)
        #STDERR.puts "read_tok lexical uri: #{uri.inspect}"

        # Cause URI to be serialized as a lexical
        uri.lexical = value
        [:atom, uri]
      else
        tok
      end
    else
      tok
    end
  end
end