module ActiveFedora
  module Associations
    class CollectionAssociation < Association # :nodoc:
      attr_reader :proxy

      # Implements the reader method, e.g. foo.items for Foo.has_many :items
      # @param opts [Boolean, Hash] if true, force a reload
      # @option opts [Symbol] :response_format can be ':solr' to return a solr result.
      def reader(opts = false)
        if opts.is_a?(Hash)
          return load_from_solr(opts) if opts.delete(:response_format) == :solr
          raise ArgumentError, "Hash parameter must include :response_format=>:solr (#{opts.inspect})"
        else
          force_reload = opts
        end
        reload if force_reload || stale_target?
        if null_scope?
          # Cache the proxy separately before the owner has an id
          # or else a post-save proxy will still lack the id
          @null_proxy ||= CollectionProxy.new(self)
        else
          @proxy ||= CollectionProxy.new(self)
        end
      end

      # Implements the writer method, e.g. foo.items= for Foo.has_many :items
      def writer(records)
        replace(records)
      end

      # Implements the ids reader method, e.g. foo.item_ids for Foo.has_many :items
      # it discards any ids where the record it belongs to was marked for destruction.
      def ids_reader
        if loaded?
          load_target.reject(&:marked_for_destruction?).map(&:id)
        else
          load_from_solr.map(&:id)
        end
      end

      # Implements the ids writer method, e.g. foo.item_ids= for Foo.has_many :items
      def ids_writer(ids)
        ids = Array(ids).reject(&:blank?)
        replace(klass.find(ids)) # .index_by { |r| r.id }.values_at(*ids))
        # TODO, like this when find() can return multiple records
        # See https://github.com/samvera/active_fedora/issues/1340
        # send("#{reflection.name}=", reflection.klass.find(ids))
        # send("#{reflection.name}=", ids.collect { |id| reflection.klass.find(id)})
      end

      def reset
        super
        @target = []
      end

      def find(*args)
        scope.find(*args)
      end

      def first(*args)
        first_or_last(:first, *args)
      end

      def last(*args)
        first_or_last(:last, *args)
      end

      # Returns the size of the collection
      #
      # If the collection has been already loaded +size+ and +length+ are
      # equivalent. If not and you are going to need the records anyway
      # +length+ will take one less query. Otherwise +size+ is more efficient.
      #
      # This method is abstract in the sense that it relies on
      # +count_records+, which is a method descendants have to provide.
      def size
        if !find_target? || loaded?
          target.size
        elsif !loaded? && target.is_a?(Array)
          unsaved_records = target.select(&:new_record?)
          unsaved_records.size + count_records
        else
          count_records
        end
      end

      # Returns true if the collection is empty.
      #
      # If the collection has been loaded it is equivalent to <tt>collection.
      # size.zero?</tt>. If the collection has not been loaded, it is equivalent to
      # <tt>collection.count_records == 0</tt>. If the collection has not already been
      # loaded and you are going to fetch the records anyway it is better to
      # check <tt>collection.length.zero?</tt>.
      def empty?
        if loaded?
          size.zero?
        else
          @target.blank? && count_records.zero?
        end
      end

      # Replace this collection with +other_array+
      # This will perform a diff and delete/add only records that have changed.
      def replace(other_array)
        other_array.each { |val| raise_on_type_mismatch!(val) }

        load_target
        deletions = @target - other_array
        additions = other_array - @target

        delete(deletions)
        concat(additions)
      end

      def include?(record)
        if record.is_a?(reflection.klass)
          if record.new_record?
            target.include?(record)
          else
            loaded? ? target.include?(record) : scope.exists?(record)
          end
        else
          false
        end
      end

      def any?
        if block_given?
          load_target.any? { |*block_args| yield(*block_args) }
        else
          !empty?
        end
      end

      def to_ary
        load_target.dup
      end
      alias to_a to_ary

      def build(attributes = {}, &block)
        if attributes.is_a?(Array)
          attributes.collect { |attr| build(attr, &block) }
        else
          add_to_target(build_record(attributes)) do |record|
            yield(record) if block_given?
          end
        end
      end

      # Add +records+ to this association.  Returns +self+ so method calls may be chained.
      # Since << flattens its argument list and inserts each record, +push+ and +concat+ behave identically.
      def concat(*records)
        load_target unless owner.new_record?
        concat_records(records)
      end

      def concat_records(*records)
        result = true

        records.flatten.each do |record|
          raise_on_type_mismatch!(record)
          add_to_target(record) do |_r|
            result &&= insert_record(record) unless owner.new_record?
          end
        end

        result && records
      end

      # Remove all records from this association
      #
      # See delete for more info.
      def delete_all
        # TODO: load_target causes extra loads. Can't we just send delete requests?
        # See https://github.com/samvera/active_fedora/issues/1341
        delete(load_target).tap do
          reset
          loaded!
        end
      end

      # Remove all records from this association
      #
      # See delete for more info.
      def destroy_all
        destroy(load_target).tap do
          reset
          loaded!
        end
      end

      # Removes +records+ from this association calling +before_remove+ and
      # +after_remove+ callbacks.
      #
      # This method is abstract in the sense that +delete_records+ has to be
      # provided by descendants. Note this method does not imply the records
      # are actually removed from the database, that depends precisely on
      # +delete_records+. They are in any case removed from the collection.
      def delete(*records)
        delete_or_destroy(records, options[:dependent])
      end

      # Destroy +records+ and remove them from this association calling
      # +before_remove+ and +after_remove+ callbacks.
      #
      # Note that this method will _always_ remove records from the database
      # ignoring the +:dependent+ option.
      def destroy(*records)
        records = find(records) if records.any? { |record| record.is_a?(Integer) || record.is_a?(String) }
        delete_or_destroy(records, :destroy)
      end

      def create(attrs = {})
        if attrs.is_a?(Array)
          attrs.collect { |attr| create(attr) }
        else
          _create_record(attrs) do |record|
            yield(record) if block_given?
            record.save
          end
        end
      end

      def create!(attrs = {})
        _create_record(attrs) do |record|
          yield(record) if block_given?
          record.save!
        end
      end

      # Count all records using solr. Construct options and pass them with
      # scope to the target class's +count+.
      def count(_options = {})
        scope.count
      end

      # Sets the target of this proxy to <tt>\target</tt>, and the \loaded flag to +true+.
      def target=(target)
        @target = [target]
        loaded!
      end

      def load_target
        @target = merge_target_lists(find_target, @target) if find_target?

        loaded!
        target
      end

      # @param opts [Hash] Options that will be passed through to ActiveFedora::SolrService.query.
      def load_from_solr(opts = {})
        finder_query = construct_query
        return [] if finder_query.empty?
        rows = opts.delete(:rows) { count }
        return [] if rows.zero?
        SolrService.query(finder_query, { rows: rows }.merge(opts))
      end

      def add_to_target(record, skip_callbacks = false)
        # Start transaction
        callback(:before_add, record) unless skip_callbacks
        yield(record) if block_given?

        if @reflection.options[:uniq] && index = @target.index(record)
          @target[index] = record
        else
          @target << record
        end

        callback(:after_add, record) unless skip_callbacks
        set_inverse_instance(record)
        # End transaction

        record
      end

      def scope(opts = {})
        scope = super()
        scope.none! if opts.fetch(:nullify, true) && null_scope?
        scope
      end

      def null_scope?
        owner.new_record? && !foreign_key_present?
      end

      def select(_select = nil, &block)
        to_a.select(&block)
      end

      protected

        def construct_query
          @solr_query ||= begin
            clauses = { find_reflection => @owner.id }
            clauses[:has_model] = @reflection.klass.to_rdf_representation if @reflection.klass != ActiveFedora::Base
            ActiveFedora::SolrQueryBuilder.construct_query_for_rel(clauses)
          end
        end

      private

        def find_target
          # TODO: don't reify, just store the solr results and lazily reify.
          # For now, we set a hard limit of 1000 results.
          # See https://github.com/samvera/active_fedora/issues/1358
          records = ActiveFedora::QueryResultBuilder.reify_solr_results(load_from_solr(rows: SolrService::MAX_ROWS))
          records.each { |record| set_inverse_instance(record) }
          records
        rescue ObjectNotFoundError, Ldp::Gone => e
          ActiveFedora::Base.logger.error "Solr and Fedora may be out of sync:\n" + e.message
          reset
          []
        end

        def merge_target_lists(loaded, existing)
          return loaded if existing.empty?
          return existing if loaded.empty?

          loaded.map do |f|
            i = existing.index(f)
            if i
              existing.delete_at(i).tap do |t|
                keys = ["id"] + t.changes.keys + (f.attribute_names - t.attribute_names)
                # FIXME: this call to attributes causes many NoMethodErrors
                attributes = f.attributes
                (attributes.keys - keys).each do |k|
                  t.send("#{k}=", attributes[k])
                end
              end
            else
              f
            end
          end + existing
        end

        def find_reflection
          return reflection if @reflection.options[:predicate]
          raise "Couldn't find reflection" unless @reflection.class_name && @reflection.class_name != 'ActiveFedora::Base' && @reflection.macro != :has_and_belongs_to_many
          @reflection.inverse_of || raise("No :inverse_of or :predicate attribute was set or could be inferred for #{@reflection.macro} #{@reflection.name.inspect} on #{@owner.class}")
        end

        def _create_record(attributes, raise = false)
          attributes.update(@reflection.options[:conditions]) if @reflection.options[:conditions].is_a?(Hash)
          ensure_owner_is_not_new

          add_to_target(build_record(attributes)) do |record|
            yield(record) if block_given?
            insert_record(record, true, raise)
          end
        end

        def create_scope
          scope.scope_for_create.stringify_keys
        end

        def delete_or_destroy(records, method)
          records = records.flatten.select { |x| load_target.include?(x) }
          records.each { |record| raise_on_type_mismatch!(record) }
          existing_records = records.select(&:persisted?)

          records.each { |record| callback(:before_remove, record) }

          # Delete the record from Fedora.
          delete_records(existing_records, method) if existing_records.any?

          records.each do |record|
            # Remove the record from the array/collection.
            target.delete(record)
          end

          records.each { |record| callback(:after_remove, record) }
        end

        def callback(method, record)
          callbacks_for(method).each do |callback|
            callback.call(method, owner, record)
          end
        end

        def callbacks_for(callback_name)
          full_callback_name = "#{callback_name}_for_#{reflection.name}"
          owner.class.send(full_callback_name)
        end

        def ensure_owner_is_not_new
          return if @owner.persisted?
          raise ActiveFedora::RecordNotSaved, "You cannot call create unless the parent is saved"
        end

        # Fetches the first/last using solr if possible, otherwise from the target array.
        def first_or_last(type, *args)
          args.shift if args.first.is_a?(Hash) && args.first.empty?

          # collection = fetch_first_or_last_using_find?(args) ? scoped : load_target
          collection = load_target
          collection.send(type, *args).tap do |record|
            set_inverse_instance record if record.is_a? ActiveFedora::Base
          end
        end
    end
  end
end