module ActiveFedora
  module Predicates
    def self.short_predicate(predicate)
      # for this regex to short-circuit correctly, namespaces must be sorted into descending order by length
      if match = /^(#{Predicates.predicate_mappings.keys.sort.reverse.join('|')})(.+)$/.match(predicate.to_str)
        namespace = match[1]
        predicate = match[2]
        Predicates.predicate_mappings[namespace].invert[predicate]
      elsif predicate.is_a? ::RDF::URI
        predicate.to_s.split('/', 4).last.gsub(/(\/|#)/, '_').underscore
      else
        raise "Unable to parse predicate: #{predicate}"
      end
    end

    def self.find_graph_predicate(predicate)
      Deprecation.warn("find_graph_predicate has been deprecated and will be removed in ActiveFedora 10.0")
      # TODO, these could be cached
      case predicate
      when :has_model, "hasModel", :hasModel
        xmlns = "http://fedora.info/definitions/v4/model#"
        begin
          rel_predicate = predicate_lookup(predicate, xmlns)
        rescue UnregisteredPredicateError
          xmlns = nil
          rel_predicate = nil
        end
      else
        xmlns = "info:fedora/fedora-system:def/relations-external#"
        begin
          rel_predicate = predicate_lookup(predicate, xmlns)
        rescue UnregisteredPredicateError
          xmlns = nil
          rel_predicate = nil
        end
      end

      unless xmlns && rel_predicate
        rel_predicate, xmlns = find_predicate(predicate)
      end

      vocabularies[xmlns][rel_predicate]
    end

    def self.vocabularies(vocabs = {})
      Deprecation.warn("vocabularies has been deprecated and will be removed in ActiveFedora 10.0")
      @vocabularies ||= vocabs
      predicate_mappings.keys.each do |ns|
        @vocabularies[ns] = ::RDF::Vocabulary.new(ns) unless @vocabularies.key? ns
      end
      @vocabularies
    end

    # If predicate is a symbol, looks up the predicate in the predicate_mappings
    # If predicate is not a Symbol, returns the predicate untouched
    # @raise UnregisteredPredicateError if the predicate is a symbol but is not found in the predicate_mappings
    def self.predicate_lookup(predicate, namespace = "info:fedora/fedora-system:def/relations-external#")
      if predicate.class == Symbol
        if predicate_mappings[namespace].key?(predicate)
          return predicate_mappings[namespace][predicate]
        else
          raise ActiveFedora::UnregisteredPredicateError
        end
      end
      predicate
    end

    def self.predicate_config=(value)
      unless value.nil? || (value.is_a?(Hash) && [:predicate_mapping, :default_namespace].all? { |key| value.key? key })
        raise TypeError, "predicate_config must specify :predicate_mapping and :default_namespace"
      end
      @@predicate_config = value
    end

    def self.predicate_config
      @@predicate_config ||= ActiveFedora.predicate_config
    end

    def self.predicate_namespaces
      Deprecation.warn("predicate_namespaces has been deprecated and will be removed in ActiveFedora 10.0")
      predicate_config[:predicate_namespaces] ||= {}
    end

    def self.predicate_mappings
      predicate_config[:predicate_mapping]
    end

    def self.default_predicate_namespace
      predicate_config[:default_namespace]
    end

    def self.find_predicate(predicate)
      predicate_mappings.each do |namespace, predicates|
        if predicates.fetch(predicate, nil)
          return predicates[predicate], namespace
        end
      end
      raise ActiveFedora::UnregisteredPredicateError, "Unregistered predicate: #{predicate.inspect}"
    end

    # Add/Modify predicates without destroying the other predicate configs
    #
    # @example
    #  ActiveFedora::Predicates.set_predicates({
    #                                              "http://projecthydra.org/ns/relations#"=>{has_profile:"hasProfile"},
    #                                              "info:fedora/fedora-system:def/relations-external#"=>{
    #                                                  references:"references",
    #                                                  has_derivation: "cameFrom"
    #                                              },
    #                                          })
    def self.set_predicates(new_predicates)
      predicate_config = ActiveFedora::Predicates.predicate_config
      new_predicates.each_pair do |ns, predicate_confs|
        predicate_config[:predicate_mapping][ns] ||= {}
        predicate_confs.each_pair do |property, value|
          predicate_config[:predicate_mapping][ns][property] = value
        end
      end
      predicate_config
    end
  end
end