filter.rb

  def self.filter(filter_hash, user = nil, sort_column = "height", sort_direction = "desc")
    query_start = "SELECT * FROM mountains "
    query = query_start

    if filter_hash.has_key?(:hiked)
      hike_query = "INNER JOIN trip_mountains ON mountains.id = trip_mountains.mountain_id " + 
        "INNER JOIN trips ON trip_mountains.trip_id = trips.id " +
        "INNER JOIN trip_participations ON trips.id = trip_participations.trip_id " +
        "WHERE trip_participations.user_id = #{user.id} "
      if filter_hash[:hiked] == :hiked
        query += hike_query
      elsif filter_hash[:hiked] == :unhiked
        query += " EXCEPT SELECT * FROM mountains " + hike_query
      end
      if filter_hash.has_key?(:list)
        query += " INTERSECT " + query_start
      end
    end
    if filter_hash.has_key?(:list)
      list_query = "INNER JOIN mountain_lists ON mountains.id = mountain_lists.mountain_id WHERE mountain_lists.list_id = #{filter_hash[:list]}"
      query += list_query
    end
    if filter_hash.has_key?(:height)
      height_query = "height < #{filter_hash[:height][:top]} AND height > #{filter_hash[:height][:floor]}"
      if query.include?("WHERE")
        query += " AND " + height_query
      else
        query += " WHERE " + height_query
      end
    end
    query += " ORDER BY #{sort_column} #{sort_direction}"
    Mountain.find_by_sql(query)
  end