module ActsAsTaggableOn::Taggable
  module Collection
    def self.included(base)
      base.extend ActsAsTaggableOn::Taggable::Collection::ClassMethods
      base.initialize_acts_as_taggable_on_collection
    end

    module ClassMethods
      def initialize_acts_as_taggable_on_collection
        tag_types.map(&:to_s).each do |tag_type|
          class_eval <<-RUBY, __FILE__, __LINE__ + 1
            def self.#{tag_type.singularize}_counts(options={})
              tag_counts_on('#{tag_type}', options)
            end

            def #{tag_type.singularize}_counts(options = {})
              tag_counts_on('#{tag_type}', options)
            end

            def top_#{tag_type}(limit = 10)
              tag_counts_on('#{tag_type}', order: 'count desc', limit: limit.to_i)
            end

            def self.top_#{tag_type}(limit = 10)
              tag_counts_on('#{tag_type}', order: 'count desc', limit: limit.to_i)
            end
          RUBY
        end
      end

      def acts_as_taggable_on(*args)
        super(*args)
        initialize_acts_as_taggable_on_collection
      end

      def tag_counts_on(context, options = {})
        all_tag_counts(options.merge({on: context.to_s}))
      end

      def tags_on(context, options = {})
        all_tags(options.merge({on: context.to_s}))
      end

      ##
      # Calculate the tag names.
      # To be used when you don't need tag counts and want to avoid the taggable joins.
      #
      # @param [Hash] options Options:
      #                       * :start_at   - Restrict the tags to those created after a certain time
      #                       * :end_at     - Restrict the tags to those created before a certain time
      #                       * :conditions - A piece of SQL conditions to add to the query. Note we don't join the taggable objects for performance reasons.
      #                       * :limit      - The maximum number of tags to return
      #                       * :order      - A piece of SQL to order by. Eg 'tags.count desc' or 'taggings.created_at desc'
      #                       * :on         - Scope the find to only include a certain context
      def all_tags(options = {})
        options = options.dup
        options.assert_valid_keys :start_at, :end_at, :conditions, :order, :limit, :on

        ## Generate conditions:
        options[:conditions] = sanitize_sql(options[:conditions]) if options[:conditions]

        ## Generate scope:
        tagging_scope = ActsAsTaggableOn::Tagging.select("#{ActsAsTaggableOn::Tagging.table_name}.tag_id")
        tag_scope = ActsAsTaggableOn::Tag.select("#{ActsAsTaggableOn::Tag.table_name}.*").order(options[:order]).limit(options[:limit])

        # Joins and conditions
        tagging_conditions(options).each { |condition| tagging_scope = tagging_scope.where(condition) }
        tag_scope = tag_scope.where(options[:conditions])

        group_columns = "#{ActsAsTaggableOn::Tagging.table_name}.tag_id"

        # Append the current scope to the scope, because we can't use scope(:find) in RoR 3.0 anymore:
        tagging_scope = generate_tagging_scope_in_clause(tagging_scope, table_name, primary_key).group(group_columns)

        tag_scope_joins(tag_scope, tagging_scope)
      end

      ##
      # Calculate the tag counts for all tags.
      #
      # @param [Hash] options Options:
      #                       * :start_at   - Restrict the tags to those created after a certain time
      #                       * :end_at     - Restrict the tags to those created before a certain time
      #                       * :conditions - A piece of SQL conditions to add to the query
      #                       * :limit      - The maximum number of tags to return
      #                       * :order      - A piece of SQL to order by. Eg 'tags.count desc' or 'taggings.created_at desc'
      #                       * :at_least   - Exclude tags with a frequency less than the given value
      #                       * :at_most    - Exclude tags with a frequency greater than the given value
      #                       * :on         - Scope the find to only include a certain context
      def all_tag_counts(options = {})
        options = options.dup
        options.assert_valid_keys :start_at, :end_at, :conditions, :at_least, :at_most, :order, :limit, :on, :id

        ## Generate conditions:
        options[:conditions] = sanitize_sql(options[:conditions]) if options[:conditions]

        ## Generate scope:
        tagging_scope = ActsAsTaggableOn::Tagging.select("#{ActsAsTaggableOn::Tagging.table_name}.tag_id, COUNT(#{ActsAsTaggableOn::Tagging.table_name}.tag_id) AS tags_count")
        tag_scope = ActsAsTaggableOn::Tag.select("#{ActsAsTaggableOn::Tag.table_name}.*, #{ActsAsTaggableOn::Tagging.table_name}.tags_count AS count").order(options[:order]).limit(options[:limit])

        # Current model is STI descendant, so add type checking to the join condition
        unless descends_from_active_record?
          taggable_join = "INNER JOIN #{table_name} ON #{table_name}.#{primary_key} = #{ActsAsTaggableOn::Tagging.table_name}.taggable_id"
          taggable_join << " AND #{table_name}.#{inheritance_column} = '#{name}'"
          tagging_scope = tagging_scope.joins(taggable_join)
        end

        # Conditions
        tagging_conditions(options).each { |condition| tagging_scope = tagging_scope.where(condition) }
        tag_scope = tag_scope.where(options[:conditions])

        # GROUP BY and HAVING clauses:
        having = ["COUNT(#{ActsAsTaggableOn::Tagging.table_name}.tag_id) > 0"]
        having.push sanitize_sql(["COUNT(#{ActsAsTaggableOn::Tagging.table_name}.tag_id) >= ?", options.delete(:at_least)]) if options[:at_least]
        having.push sanitize_sql(["COUNT(#{ActsAsTaggableOn::Tagging.table_name}.tag_id) <= ?", options.delete(:at_most)]) if options[:at_most]
        having = having.compact.join(' AND ')

        group_columns = "#{ActsAsTaggableOn::Tagging.table_name}.tag_id"

        unless options[:id]
          # Append the current scope to the scope, because we can't use scope(:find) in RoR 3.0 anymore:
          tagging_scope = generate_tagging_scope_in_clause(tagging_scope, table_name, primary_key)
        end

        tagging_scope = tagging_scope.group(group_columns).having(having)

        tag_scope_joins(tag_scope, tagging_scope)
      end

      def safe_to_sql(relation)
        connection.respond_to?(:unprepared_statement) ? connection.unprepared_statement { relation.to_sql } : relation.to_sql
      end

      private

      def generate_tagging_scope_in_clause(tagging_scope, table_name, primary_key)
        table_name_pkey = "#{table_name}.#{primary_key}"
        if ActsAsTaggableOn::Utils.using_mysql?
          # See https://github.com/mbleigh/acts-as-taggable-on/pull/457 for details
          scoped_ids = pluck(table_name_pkey)
          tagging_scope = tagging_scope.where("#{ActsAsTaggableOn::Tagging.table_name}.taggable_id IN (?)", scoped_ids)
        else
          tagging_scope = tagging_scope.where("#{ActsAsTaggableOn::Tagging.table_name}.taggable_id IN(#{safe_to_sql(except(:select).select(table_name_pkey))})")
        end

        tagging_scope
      end

      def tagging_conditions(options)
        tagging_conditions = []
        tagging_conditions.push sanitize_sql(["#{ActsAsTaggableOn::Tagging.table_name}.created_at <= ?", options.delete(:end_at)]) if options[:end_at]
        tagging_conditions.push sanitize_sql(["#{ActsAsTaggableOn::Tagging.table_name}.created_at >= ?", options.delete(:start_at)]) if options[:start_at]

        taggable_conditions = sanitize_sql(["#{ActsAsTaggableOn::Tagging.table_name}.taggable_type = ?", base_class.name])
        taggable_conditions << sanitize_sql([" AND #{ActsAsTaggableOn::Tagging.table_name}.context = ?", options.delete(:on).to_s]) if options[:on]
        taggable_conditions << sanitize_sql([" AND #{ActsAsTaggableOn::Tagging.table_name}.taggable_id = ?", options[:id]]) if options[:id]

        tagging_conditions.push taggable_conditions

        tagging_conditions
      end

      def tag_scope_joins(tag_scope, tagging_scope)
        tag_scope = tag_scope.joins("JOIN (#{safe_to_sql(tagging_scope)}) AS #{ActsAsTaggableOn::Tagging.table_name} ON #{ActsAsTaggableOn::Tagging.table_name}.tag_id = #{ActsAsTaggableOn::Tag.table_name}.id")
        tag_scope.extending(CalculationMethods)
      end
    end

    def tag_counts_on(context, options={})
      self.class.tag_counts_on(context, options.merge(id: id))
    end

    module CalculationMethods
      # Rails 5 TODO: Remove options argument as soon we remove support to
      # activerecord-deprecated_finders.
      # See https://github.com/rails/rails/blob/master/activerecord/lib/active_record/relation/calculations.rb#L38
      def count(column_name = :all, options = {})
        # https://github.com/rails/rails/commit/da9b5d4a8435b744fcf278fffd6d7f1e36d4a4f2
        super(column_name)
      end
    end
  end
end
