module Spree
  module Core
    # THIS FILE SHOULD BE OVER-RIDDEN IN YOUR SITE EXTENSION!
    #   the exact code probably won't be useful, though you're welcome to modify and reuse
    #   the current contents are mainly for testing and documentation

    # To override this file...
    #   1) Make a copy of it in your sites local /lib/spree folder
    #   2) Add it to the config load path, or require it in an initializer, e.g...
    #
    #      # config/initializers/spree.rb
    #      require 'spree/core/product_filters'
    #

    # set up some basic filters for use with products
    #
    # Each filter has two parts
    #  * a parametrized named scope which expects a list of labels
    #  * an object which describes/defines the filter
    #
    # The filter description has three components
    #  * a name, for displaying on pages
    #  * a named scope which will 'execute' the filter
    #  * a mapping of presentation labels to the relevant condition (in the context of the named scope)
    #  * an optional list of labels and values (for use with object selection - see taxons examples below)
    #
    # The named scopes here have a suffix '_any', following Ransack's convention for a
    # scope which returns results which match any of the inputs. This is purely a convention,
    # but might be a useful reminder.
    #
    # When creating a form, the name of the checkbox group for a filter F should be
    # the name of F's scope with [] appended, eg "price_range_any[]", and for
    # each label you should have a checkbox with the label as its value. On submission,
    # Rails will send the action a hash containing (among other things) an array named
    # after the scope whose values are the active labels.
    #
    # Ransack will then convert this array to a call to the named scope with the array
    # contents, and the named scope will build a query with the disjunction of the conditions
    # relating to the labels, all relative to the scope's context.
    #
    # The details of how/when filters are used is a detail for specific models (eg products
    # or taxons), eg see the taxon model/controller.

    # See specific filters below for concrete examples.
    module ProductFilters
      # Example: filtering by price
      #   The named scope just maps incoming labels onto their conditions, and builds the conjunction
      #   'price' is in the base scope's context (ie, "select foo from products where ...") so
      #     we can access the field right away
      #   The filter identifies which scope to use, then sets the conditions for each price range
      #
      # If user checks off three different price ranges then the argument passed to
      # below scope would be something like ["$10 - $15", "$15 - $18", "$18 - $20"]
      #
      Spree::Product.add_search_scope :price_range_any do |*opts|
        conds = opts.map { |o| Spree::Core::ProductFilters.price_filter[:conds][o] }.reject(&:nil?)
        scope = conds.shift
        conds.each do |new_scope|
          scope = scope.or(new_scope)
        end
        Spree::Product.joins(master: :default_price).where(scope)
      end

      def self.format_price(amount)
        Spree::Money.new(amount)
      end

      def self.price_filter
        v = Spree::Price.arel_table
        conds = [[Spree.t(:under_price, price: format_price(10)), v[:amount].lteq(10)],
                 ["#{format_price(10)} - #{format_price(15)}", v[:amount].in(10..15)],
                 ["#{format_price(15)} - #{format_price(18)}", v[:amount].in(15..18)],
                 ["#{format_price(18)} - #{format_price(20)}", v[:amount].in(18..20)],
                 [Spree.t(:or_over_price, price: format_price(20)), v[:amount].gteq(20)]]
        {
          name:   Spree.t(:price_range),
          scope:  :price_range_any,
          conds:  Hash[*conds.flatten],
          labels: conds.map { |k, _v| [k, k] }
        }
      end

      # Example: filtering by possible brands
      #
      # First, we define the scope. Two interesting points here: (a) we run our conditions
      #   in the scope where the info for the 'brand' property has been loaded; and (b)
      #   because we may want to filter by other properties too, we give this part of the
      #   query a unique name (which must be used in the associated conditions too).
      #
      # Secondly, the filter. Instead of a static list of values, we pull out all existing
      #   brands from the db, and then build conditions which test for string equality on
      #   the (uniquely named) field "p_brand.value". There's also a test for brand info
      #   being blank: note that this relies on with_property doing a left outer join
      #   rather than an inner join.
      Spree::Product.add_search_scope :brand_any do |*opts|
        conds = opts.map { |o| ProductFilters.brand_filter[:conds][o] }.reject(&:nil?)
        scope = conds.shift
        conds.each do |new_scope|
          scope = scope.or(new_scope)
        end
        Spree::Product.with_property('brand').where(scope)
      end

      def self.brand_filter
        brand_property = Spree::Property.find_by(name: 'brand')
        brands = brand_property ? Spree::ProductProperty.where(property_id: brand_property.id).pluck(:value).uniq.map(&:to_s) : []
        pp = Spree::ProductProperty.arel_table
        conds = Hash[*brands.map { |b| [b, pp[:value].eq(b)] }.flatten]
        {
          name:   I18n.t('spree.taxonomy_brands_name'),
          scope:  :brand_any,
          conds:  conds,
          labels: brands.sort.map { |k| [k, k] }
        }
      end

      # Example: a parameterized filter
      #   The filter above may show brands which aren't applicable to the current taxon,
      #   so this one only shows the brands that are relevant to a particular taxon and
      #   its descendants.
      #
      #   We don't have to give a new scope since the conditions here are a subset of the
      #   more general filter, so decoding will still work - as long as the filters on a
      #   page all have unique names (ie, you can't use the two brand filters together
      #   if they use the same scope). To be safe, the code uses a copy of the scope.
      #
      #   HOWEVER: what happens if we want a more precise scope?  we can't pass
      #   parametrized scope names to Ransack, only atomic names, so couldn't ask
      #   for taxon T's customized filter to be used. BUT: we can arrange for the form
      #   to pass back a hash instead of an array, where the key acts as the (taxon)
      #   parameter and value is its label array, and then get a modified named scope
      #   to get its conditions from a particular filter.
      #
      #   The brand-finding code can be simplified if a few more named scopes were added to
      #   the product properties model.
      Spree::Product.add_search_scope :selective_brand_any do |*opts|
        Spree::Product.brand_any(*opts)
      end

      def self.selective_brand_filter(taxon = nil)
        taxon ||= Spree::Taxonomy.first.root
        brand_property = Spree::Property.find_by(name: 'brand')
        scope = Spree::ProductProperty.where(property: brand_property).
                joins(product: :taxons).
                where("#{Spree::Taxon.table_name}.id" => [taxon] + taxon.descendants)
        brands = scope.pluck(:value).uniq
        {
          name:   'Applicable Brands',
          scope:  :selective_brand_any,
          labels: brands.sort.map { |k| [k, k] }
        }
      end

      # Provide filtering on the immediate children of a taxon
      #
      # This doesn't fit the pattern of the examples above, so there's a few changes.
      # Firstly, it uses an existing scope which was not built for filtering - and so
      # has no need of a conditions mapping, and secondly, it has a mapping of name
      # to the argument type expected by the other scope.
      #
      # This technique is useful for filtering on objects (by passing ids) or with a
      # scope that can be used directly (eg. testing only ever on a single property).
      #
      # This scope selects products in any of the active taxons or their children.
      #
      def self.taxons_below(taxon)
        return Spree::Core::ProductFilters.all_taxons if taxon.nil?
        {
          name:   'Taxons under ' + taxon.name,
          scope:  :taxons_id_in_tree_any,
          labels: taxon.children.sort_by(&:position).map { |t| [t.name, t.id] },
          conds:  nil
        }
      end

      # Filtering by the list of all taxons
      #
      # Similar idea as above, but we don't want the descendants' products, hence
      # it uses one of the auto-generated scopes from Ransack.
      #
      # idea: expand the format to allow nesting of labels?
      def self.all_taxons
        taxons = Spree::Taxonomy.all.map { |t| [t.root] + t.root.descendants }.flatten
        {
          name:   'All taxons',
          scope:  :taxons_id_equals_any,
          labels: taxons.sort_by(&:name).map { |t| [t.name, t.id] },
          conds:  nil # not needed
        }
      end
    end
  end
end
