class ActiveFedora::SparqlInsert

def build
  query = deletes(subject).join
  query += "INSERT { \n"
  query +=
    changes.map do |_, result|
      result.map do |statement|
        ::RDF::Query::Pattern.new(subject: pattern_subject(statement.subject), predicate: statement.predicate, object: statement.object).to_s
      end.join("\n")
    end.join("\n")
  query += "\n}\n WHERE { }"
  query
end

def deletes(subject)
  patterns(subject).map do |pattern|
    "DELETE { #{pattern} }\n  WHERE { #{pattern} } ;\n"
  end
end

def execute(uri)
  result = ActiveFedora.fedora.connection.patch(uri, build, "Content-Type" => "application/sparql-update")
  return true if result.status == 204
  raise "Problem updating #{result.status} #{result.body}"
end

def hash_patterns(graph)
  graph = graph.select do |statement|
    MaybeHashUri.new(statement.subject).hash?
  end
  graph.map do |statement|
    ::RDF::Query::Pattern.new(statement.subject, statement.predicate, :change).to_s
  end
end

def initialize(changes, subject = ::RDF::URI.new(nil))
  @changes = changes
  @subject = subject
end

def pattern_subject(potential_subject)
  if MaybeHashUri.new(potential_subject).hash?
    potential_subject
  else
    subject
  end
end

def patterns(subject)
  changes.flat_map do |key, result|
    [
      ::RDF::Query::Pattern.new(subject, key, :change).to_s,
      hash_patterns(result)
    ].flatten
  end
end