Convert a params Hash to a Sunspot search.

search_hash.rb

# SearchHash converts a Hash with search options to a Sunspot search.
# Example:
#   s = SearchHash.new(Model, :q => 'some string to match in all text fields')
#   s.search # The Sunspot search
#   s.search.results # The actual results
# 
#   s = SearchHash.new(Model, :some_field__gt => 12, :text_field_name => 'some query')
#
# Pagination:
#   s = SearchHash.new(Model, {:some_field__gt => 12, :text_field_name => 'some query', :page => 2, :per_page => 100}, {:per_page_max => 200, :per_page_default => 25})
#
# Ordering:
#   s = SearchHash.new(Model, {:some_field__gt => 12, :text_field_name => 'some query', :order => 'some_field__asc'}, {:order_direction_default => :desc})
#
class SearchHash

  class SearchOption

    PREDICATE_TO_SUNSPOT = {
        :gt => :greater_than,
        :lt => :less_than,
        :gte => :greater_than,
        :lte => :less_than,
        :in => :any_of,
        :eq => :equal_to,
        # New
        :all_in => :all_of,
        :between => :between
      }

    attr_accessor :klass, :field_name, :predicate, :value

    def sunspot_field
      return @sunspot_field if @sunspot_field
      @sunspot_field = Sunspot::Setup.for(self.klass).text_field_factories.detect {|f| f.name == field_name}
      @sunspot_field ||= Sunspot::Setup.for(self.klass).field_factories.detect {|f| f.name == field_name}
      raise StandardError, "Can't find Sunspot field #{field_name.inspect} for #{klass}." if @sunspot_field.nil?
      @sunspot_field
    end

    # https://github.com/ernie/ransack/wiki/Basic-Searching
    # https://github.com/sunspot/sunspot/wiki/Scoping-by-attribute-fields
    # PREDICATES = %w(gt lt gte lte eq cont in)
    def sunspot_predicate
      @sunspot_predicate ||= PREDICATE_TO_SUNSPOT[predicate] || raise(StandardError, "No Sunspot predicate found named #{predicate.inspect}!")
    end

    def is_text_field?
      sunspot_field.build.is_a?(Sunspot::FulltextField)
    end

    def is_attribute_field?
      sunspot_field.build.is_a?(Sunspot::AttributeField)
    end

    def initialize(klass, field_name, predicate, value)
      @klass = klass
      @field_name = field_name.to_sym
      @predicate = predicate.to_sym if predicate.present?
      @value = value
      sunspot_field # This raises Error early
    end

    def add_to_sunspot_search(search)
      if self.is_attribute_field?
        if self.predicate
          if predicate =~ /^(lte|gte)$/ # Sunspot's does not have a gte. We fix this here.
            search.any_of do
              with(self.field_name, value)
              with(self.field_name).send(sunspot_predicate, value)
            end
          else
            search.with(self.field_name).send(sunspot_predicate, value)
          end
        else
          search.with(self.field_name, value)
        end
      elsif self.is_text_field?
        search.fulltext(value, :fields => [field_name])
      end
    end

  end

  attr_accessor :q, :order
  attr_writer :page, :per_page

  def search
    @klass.solr_search do |search|
      search.fulltext(q) if q.present?
      @search_options.each {|search_option| search_option.add_to_sunspot_search(search)}
      search.order_by(order_field, order_direction) if has_order?
      search.paginate :page => page, :per_page => per_page
    end
  end

# Ordering

  alias_method :s=, :order= # s is used by Ransack gem
  alias_method :s, :order

  def has_order?
    !order_field.blank?
  end

  def order_field
    split_order[0]
  end

  def order_direction
    split_order[1] || @order_direction_default
  end

# Pagination

  def page
    [@page.to_i, 1].max
  end

  def per_page
    return @per_page_default if @per_page.nil? || @per_page.zero?
    [@per_page, @per_page_max].min
  end
  alias_method :per=, :per_page= # per is used by Kaminari gem
  alias_method :per, :per_page

private

  def split_order
    return [] if @order.blank?
    @order.split('__')
  end

  def initialize(klass, attributes = {}, options = {})
    @search_options = []
    @klass = klass
    @per_page_max = options[:per_page_max] || 100
    @per_page_default = options[:per_page_default] || 10
    @order_default = options[:order_direction_default] || :asc
    attributes.each do |attribute, value|
      self.send("#{attribute}=", value)
    end
  end

  def method_missing(m, *args, &block)
    if m =~ /(.*)=$/ # setter
      field_name, predicate = $1.to_s.split('__')
      @search_options << SearchOption.new(@klass, field_name, predicate, *args)
    else
      super
    end
  end

end