fuseki.rb

require 'httparty'
require 'rdf'
require 'rdf/ntriples'
require 'rdf/nquads'
require 'json'
class Fuseki
  include HTTParty
  headers 'Accept' => 'text/plain; charset=utf-8' 
  base_uri 'http://localhost:3030/'
  
  def self.describe(dataset, uris)
    all_statements(dataset, {:conditions=>["FILTER (?s IN (<#{[*uris].join(">, ")}>))"]})
  end
  
  def self.all_statements(dataset, options={})
    headers 'Accept' => 'application/sparql-results+json; charset=utf-8' 
    sparql = Sparql.generate_select_all(options)
    resp = get("/#{dataset}/query", {:query=>{:query=>sparql}})
    result = JSON.parse(resp.body)
    statements = []
    result['results']['bindings'].each do |r|
      obj = case r["o"]["type"]
      when "uri" then RDF::URI.intern(r["o"]["value"])
      when "bnode" then RDF::Node.new(r["o"]["value"])
      else
        lit = RDF::Literal.new(r["o"]["value"])
        lit.datatype = RDF::URI.new(r["o"]["datatype"]) if r["o"]["datatype"]
        lit.language = r["o"]["language"].to_sym if r["o"]["language"]
        lit
      end
      statements << RDF::Statement.new(RDF::URI.intern(r["s"]["value"]), RDF::URI.intern(r["p"]["value"]), obj, :context=>RDF::URI.intern(r["g"]["value"]))
    end
    statements
  end
  
  def self.method_missing(meth, *args)
    if meth.to_s =~ /^find_by_/
      sparql_find(meth, args)
    end
  end
  
  def self.sparql_find(meth, args)
    mod_meth = meth.to_s.sub(/^find_by_/,'')
    params = mod_meth.split("_and_")
    dataset = args.slice!(0,1)
    meth_args = args.slice!(0,params.length)
    options = args.first
    conditions = []
    (0..(params.length-1)).each do |i|
      f = "FILTER ("
      puts params[i]
      f << case params[i]
      when "subject" then "?s"
      when "predicate" then "?p"
      when "object" then "?o"
      when "graph" then "?g"
      end
      f << " IN ("
      vals = []
      [*meth_args[i]].each do |v|
        if v.respond_to?(:to_ntriples)
          vals << v.to_ntriples
        else
          vals << RDF::Literal.new(v).to_ntriples
        end
      end
      f << "#{vals.join(", ")}))"
      conditions << f
    end
    options[:conditions] = conditions
    self.all_statements(dataset, options)
  end
end

class Sparql
  def self.generate_select_all(options)
    sparql = "SELECT ?g ?s ?p ?o \n"
    sparql << "WHERE { GRAPH ?g {?s ?p ?o . \n"
    if options[:conditions]
      sparql << options[:conditions].join(" . \n")
    end
    sparql << "} }\n"
    if options[:limit]
      sparql << "LIMIT #{options[:limit]}\n"
    end
    if options[:offset]
      sparql << "LIMIT #{options[:limit]}\n"
    end
    
    if options[:order]    
      sparql << "ORDER BY #{options[:order]}"
    end
    sparql
  end
  
  def self.generate_select_resource(options)
    sparql = "SELECT ?g ?s ?p ?o \n"
    sparql << "WHERE { GRAPH ?g {?s ?p ?o . \n"
    if options[:conditions]
      sparql << conditions.join(" . \n")
    end
    sparql << "} }\n"
    if options[:limit]
      sparql << "LIMIT #{options[:limit]}\n"
    end
    if options[:offset]
      sparql << "LIMIT #{options[:limit]}\n"
    end
    
    if options[:order]    
      sparql << "ORDER BY #{options[:order]}"
    end
    sparql
  end  
end