module PgHero
  module Methods
    module Sequences
      def sequences
        sequences = select_all <<-SQL
          SELECT
            sequence_schema AS schema,
            table_name AS table,
            column_name AS column,
            c.data_type AS column_type,
            CASE WHEN c.data_type = 'integer' THEN 2147483647::bigint ELSE maximum_value::bigint END AS max_value,
            sequence_name AS sequence
          FROM
            information_schema.columns c
          INNER JOIN
            information_schema.sequences iss ON iss.sequence_name = regexp_replace(c.column_default, '^nextval\\(''(.*)''\\:\\:regclass\\)$', '\\1')
          WHERE
            column_default LIKE 'nextval%'
            AND table_catalog = current_database()
          ORDER BY
            sequence_name ASC
        SQL

        select_all(sequences.map { |s| "SELECT last_value FROM #{s[:sequence]}" }.join(" UNION ALL ")).each_with_index do |row, i|
          sequences[i][:last_value] = row[:last_value]
        end

        sequences
      end

      def sequence_danger(threshold: 0.9)
        sequences.select { |s| s[:last_value] / s[:max_value].to_f > threshold }.sort_by { |s| s[:max_value] - s[:last_value] }
      end
    end
  end
end