module Search

  def self.per_facet
    5
  end

  def self.facets
    %w(topic category user)
  end

  def self.user_query_sql
    "SELECT 'user' AS type,
                  u.username_lower AS id,
                  '/users/' || u.username_lower AS url,
                  u.username AS title,
                  u.email,
                  NULL AS color,
                  NULL AS text_color
    FROM users AS u
    JOIN users_search s on s.id = u.id
    WHERE s.search_data @@ TO_TSQUERY(:locale, :query)
    ORDER BY CASE WHEN u.username_lower = lower(:orig) then 0 else 1 end,  last_posted_at desc
    LIMIT :limit
    "
  end

  def self.post_query(guardian, type, args)
    builder = SqlBuilder.new <<SQL
    /*select*/
    FROM topics AS ft
    /*join*/
      JOIN posts_search s on s.id = p.id
      LEFT JOIN categories c ON c.id = ft.category_id
    /*where*/
    ORDER BY
            TS_RANK_CD(TO_TSVECTOR(:locale, ft.title), TO_TSQUERY(:locale, :query)) desc,
            TS_RANK_CD(search_data, TO_TSQUERY(:locale, :query)) desc,
            bumped_at desc
    LIMIT :limit
SQL

    builder.select "'topic' AS type"
    builder.select("CAST(ft.id AS VARCHAR)")

    if type == :topic
      builder.select "'/t/slug/' || ft.id AS url"
    else
      builder.select "'/t/slug/' || ft.id || '/' || p.post_number AS url"
    end

    builder.select "ft.title, NULL AS email, NULL AS color, NULL AS text_color"

  if type == :topic
    builder.join "posts AS p ON p.topic_id = ft.id AND p.post_number = 1"
  else
    builder.join "posts AS p ON p.topic_id = ft.id AND p.post_number > 1"
  end

    builder.where <<SQL
s.search_data @@ TO_TSQUERY(:locale, :query)
      AND ft.deleted_at IS NULL
      AND p.deleted_at IS NULL
      AND ft.visible
      AND ft.archetype <> '#{Archetype.private_message}'
SQL

    add_allowed_categories(builder, guardian)

    builder.exec(args)
  end

  def self.add_allowed_categories(builder, guardian)
    allowed_categories = nil
    allowed_categories = guardian.secure_category_ids
    if allowed_categories.present?
      builder.where("(c.id IS NULL OR c.secure = 'f' OR c.id in (:category_ids))", category_ids: allowed_categories)
    else
      builder.where("(c.id IS NULL OR c.secure = 'f')")
    end
  end


  def self.category_query(guardian, args)
    builder = SqlBuilder.new <<SQL
    SELECT 'category' AS type,
            c.name AS id,
            '/category/' || c.slug AS url,
            c.name AS title,
            NULL AS email,
            c.color,
            c.text_color
    FROM categories AS c
    JOIN categories_search s on s.id = c.id
    /*where*/
    ORDER BY topics_month desc
    LIMIT :limit
SQL

    builder.where "s.search_data @@ TO_TSQUERY(:locale, :query)"
    add_allowed_categories(builder,guardian)

    builder.exec(args)

  end

  def self.current_locale_long
    case I18n.locale         # Currently-present in /conf/locales/* only, sorry :-( Add as needed
      when :da then 'danish'
      when :de then 'german'
      when :en then 'english'
      when :es then 'spanish'
      when :fr then 'french'
      when :it then 'italian'
      when :nl then 'dutch'
      when :pt then 'portuguese'
      when :sv then 'swedish'
      else 'simple' # use the 'simple' stemmer for other languages
    end
  end

  # If we're searching for a single topic
  def self.single_topic(id, guardian)
    topic = Topic.where(id: id).first
    return nil unless guardian.can_see?(topic)

    results = [{'type' => 'topic',
                'id' => topic.id,
                'url' => topic.relative_url,
                'title' => topic.title }]
    group_db_result(results, 'topic')
  end

  # Query a term
  def self.query(term, guardian, type_filter=nil, min_search_term_length=3)

    return nil if term.blank?

    # If no guardian supplied, assume anonymous
    guardian ||= Guardian.new(nil)

    term = term.to_s

    # If the term is a number or url to a topic, just include that topic
    if type_filter == 'topic'

      begin
        route = Rails.application.routes.recognize_path(term)
        return single_topic(route[:topic_id], guardian) if route[:topic_id].present?
      rescue ActionController::RoutingError
      end

      return single_topic(term.to_i, guardian) if term =~ /^\d+$/
    end

    # We are stripping only symbols taking place in FTS and simply sanitizing the rest.
    sanitized_term = PG::Connection.escape_string(term.gsub(/[:()&!]/,''))
    query_string(sanitized_term, guardian, type_filter, min_search_term_length)
  end

  # Search for a string term
  def self.query_string(term, guardian, type_filter, min_search_term_length)

    # really short terms are totally pointless
    return nil if term.length < min_search_term_length

    args = {orig: term,
            query: term.split.map {|t| "#{t}:*"}.join(" & "),
            locale: current_locale_long}

    if type_filter.present?
      raise Discourse::InvalidAccess.new("invalid type filter") unless Search.facets.include?(type_filter)
      args.merge!(limit: Search.per_facet * Search.facets.size)
      db_result = case type_filter.to_s
                  when 'topic'
                    post_query(guardian, type_filter.to_sym, args)
                  when 'category'
                    category_query(guardian, args)
                  else
                    ActiveRecord::Base.exec_sql(Search.send("#{type_filter}_query_sql"), args)
                  end
    else
      args.merge!(limit: (Search.per_facet + 1))
      db_result = []
      db_result += ActiveRecord::Base.exec_sql(user_query_sql, args).to_a
      db_result += category_query(guardian, args).to_a
      db_result += post_query(guardian, :topic, args).to_a
    end

    db_result = db_result.to_a

    expected_topics = 0
    expected_topics = Search.facets.size unless type_filter.present?
    expected_topics = Search.per_facet * Search.facets.size if type_filter == 'topic'

    if expected_topics > 0
      db_result.each do |row|
        expected_topics -= 1 if row['type'] == 'topic'
      end
    end

    if expected_topics > 0
      tmp = post_query(guardian, :post, args.merge(limit: expected_topics * 3)).to_a

      topic_ids = Set.new db_result.map{|r| r["id"]}

      tmp.reject! do |i|
        if topic_ids.include?(i["id"])
          true
        else
          topic_ids << i["id"]
          false
        end
      end

      db_result += tmp[0..expected_topics-1]
    end

    group_db_result(db_result, type_filter)
  end

  private

  # Group the results by type
  def self.group_db_result(db_result, type_filter)
    grouped = {}
    db_result.each do |row|
      type = row.delete('type')

      # Add the slug for topics
      if type == 'topic'
        new_slug = Slug.for(row['title'])
        new_slug = "topic" if new_slug.blank?
        row['url'].gsub!('slug', new_slug)
      end

      # Add avatars for users
      row['avatar_template'] = User.avatar_template(row['email']) if type == 'user'

      # Remove attributes when we know they don't matter
      row.delete('email')
      row.delete('color') unless type == 'category'
      row.delete('text_color') unless type == 'category'

      grouped[type] ||= []
      grouped[type] << row
    end

    grouped.map do |type, results|
      more = type_filter.blank? && (results.size > Search.per_facet)
      results = results[0..([results.length, Search.per_facet].min - 1)] if type_filter.blank?
      {
        type: type,
        name: I18n.t("search.types.#{type}"),
        more: more,
        results: results
      }
    end
  end

end