module ActiveRecord
  class Base
    # Establishes a connection to the database that's used by all Active Record objects
    def self.influxdb_connection(config) # :nodoc:
      config = config.symbolize_keys
      host     = config[:host]
      port     = config[:port] || 5432
      username = config[:username].to_s if config[:username]
      password = config[:password].to_s if config[:password]

      # The postgres drivers don't allow the creation of an unconnected PGconn object,
      # so just pass a nil connection object for the time being.
      ConnectionAdapters::InfluxdbAdapter.new(nil, logger, config)
    end
  end

  module ConnectionAdapters
    class InfluxdbAdapter < AbstractAdapter

      def adapter_name
        'InfluxDB'
      end

      def initialize(connection, logger, config)
        super(connection, logger)

        @visitor = Arel::Visitors::InfluxDB.new self

        connect(config)
      end

      def connect(config)
        puts('connect')
        if ENV['INFLUX_DB_URL']
          @connection = InfluxDB::Client.new(url: ENV['INFLUX_DB_URL'])
        else
          @connection = InfluxDB::Client.new(config)
        end
      end

      def columns(table)
        []
      end

      def tables
        []
      end

      def exec_query(sql, name, binds)
        puts("InfluxDB: #{sql} - #{name}")
        res = @connection.query(sql).first
        binding.pry
        ActiveRecord::Result.new(res['values'].first.keys, res['values'].map(&:values))
      end

      def column_name_for_operation(operation, node) # :nodoc:
        {
          'maximum' => 'max',
          'minimum' => 'min',
          'average' => 'avg',
        }.fetch(operation) { operation.downcase }
      end
    end
  end
end

module Arel
  module Visitors
    class InfluxDB < ToSql
      private
      def visit_Arel_Attributes_Attribute o, collector
        collector << quote_column_name(o.name)
      end
    end
  end
end