# encoding: utf-8
# TAKEN FROM WIIBAA
require "logstash/config/mixin"

# Tentative of abstracting JDBC logic to a mixin 
# for potential reuse in other plugins (input/output)
module LogStash::PluginMixins::Jdbc

  @logger = Cabin::Channel.get(LogStash)

  # This method is called when someone includes this module
  def self.included(base)
    # Add these methods to the 'base' given.
    base.extend(self)
    base.setup_jdbc_config
  end


  public
  def setup_jdbc_config
    # JDBC driver library path to third party driver library.
    #
    # If not provided, Plugin will look for the driver class in the Logstash Java classpath.
    config :jdbc_driver_library, :validate => :path

    # JDBC driver class to load, for exmaple, "org.apache.derby.jdbc.ClientDriver"
    # NB per https://github.com/logstash-plugins/logstash-input-jdbc/issues/43 if you are using
    # the Oracle JDBC driver (ojdbc6.jar) the correct `jdbc_driver_class` is `"Java::oracle.jdbc.driver.OracleDriver"`
    config :jdbc_driver_class, :validate => :string, :required => true

    # JDBC connection string
    config :jdbc_connection_string, :validate => :string, :required => true

    # JDBC user
    config :jdbc_user, :validate => :string, :required => true

    # JDBC password
    config :jdbc_password, :validate => :password

    # JDBC enable paging
    #
    # This will cause a sql statement to be broken up into multiple queries.
    # Each query will use limits and offsets to collectively retrieve the full
    # result-set. The limit size is set with `jdbc_page_size`.
    #
    # Be aware that ordering is not guaranteed between queries.
    config :jdbc_paging_enabled, :validate => :boolean, :default => false 

    # JDBC page size
    config :jdbc_page_size, :validate => :number, :default => 100000

    # JDBC fetch size. if not provided, respective driver's default will be used
    config :jdbc_fetch_size, :validate => :number

    # Connection pool configuration.
    # Validate connection before use.
    config :jdbc_validate_connection, :validate => :boolean, :default => false

    # Connection pool configuration.
    # How often to validate a connection (in seconds)
    config :jdbc_validation_timeout, :validate => :number, :default => 3600

    # Connection pool configuration.
    # The amount of seconds to wait to acquire a connection before raising a PoolTimeoutError (default 5)
    config :jdbc_pool_timeout, :validate => :number, :default => 5

    # General/Vendor-specific Sequel configuration options.
    #
    # An example of an optional connection pool configuration
    #    max_connections - The maximum number of connections the connection pool
    #
    # examples of vendor-specific options can be found in this
    # documentation page: https://github.com/jeremyevans/sequel/blob/master/doc/opening_databases.rdoc
    config :sequel_opts, :validate => :hash, :default => {}
  end

  private
  def jdbc_connect
    opts = {
      :user => @jdbc_user,
      :password => @jdbc_password.nil? ? nil : @jdbc_password.value,
      :pool_timeout => @jdbc_pool_timeout
    }.merge(@sequel_opts)
    begin
      Sequel.connect(@jdbc_connection_string, opts=opts)
    rescue Sequel::PoolTimeout => e
      @logger.error("Failed to connect to database. #{@jdbc_pool_timeout} second timeout exceeded.")
      raise e
    rescue Sequel::Error => e
      @logger.error("Unable to connect to database", :error_message => e.message)
      raise e
    end
  end

  public
  def prepare_jdbc_connection
    require "java"
    require "sequel"
    require "sequel/adapters/jdbc"
    require @jdbc_driver_library if @jdbc_driver_library
    begin
      Sequel::JDBC.load_driver(@jdbc_driver_class)
    rescue Sequel::AdapterNotFound => e
      message = if @jdbc_driver_library.nil?
                  ":jdbc_driver_library is not set, are you sure you included 
                  the proper driver client libraries in your classpath?"
                else
                  "Are you sure you've included the correct jdbc driver in :jdbc_driver_library?"
                end
      raise LogStash::ConfigurationError, "#{e}. #{message}"
    end
    @database = jdbc_connect()
    @database.extension(:pagination)
    if @jdbc_validate_connection
      @database.extension(:connection_validator)
      @database.pool.connection_validation_timeout = @jdbc_validation_timeout
    end
    @database.fetch_size = @jdbc_fetch_size unless @jdbc_fetch_size.nil?
    begin
      @database.test_connection
    rescue Sequel::DatabaseConnectionError => e
      #TODO return false and let the plugin raise a LogStash::ConfigurationError
      raise e
    end

    @sql_last_start = Time.at(0).utc
  end # def prepare_jdbc_connection

  public
  def close_jdbc_connection
    @database.disconnect if @database
  end

  public
  def execute_statement(statement, parameters)
    success = false
    begin 
      parameters = symbolized_params(parameters)
      query = @database[statement, parameters]
      @logger.debug? and @logger.debug("Executing JDBC query", :statement => statement, :parameters => parameters)
      @sql_last_start = Time.now.utc

      if @jdbc_paging_enabled
        query.each_page(@jdbc_page_size) do |paged_dataset|
          paged_dataset.each do |row|
            yield extract_values_from(row)
          end
        end
      else
        query.each do |row|
          yield extract_values_from(row)
        end
      end
      success = true
    rescue Sequel::DatabaseConnectionError, Sequel::DatabaseError => e
      @logger.warn("Exception when executing JDBC query", :exception => e)
    end
    return success
  end

  # Symbolize parameters keys to use with Sequel
  private 
  def symbolized_params(parameters)
    parameters.inject({}) do |hash,(k,v)| 
      case v
      when LogStash::Timestamp
        hash[k.to_sym] = v.time
      else
        hash[k.to_sym] = v
      end
      hash
    end
  end

  private
  #Stringify row keys and decorate values when necessary
  def extract_values_from(row)
    Hash[row.map { |k, v| [k.to_s, decorate_value(v)] }]
  end

  private
  def decorate_value(value)
    if value.is_a?(Time)
      # transform it to LogStash::Timestamp as required by LS
      LogStash::Timestamp.new(value)
    else
      value  # no-op
    end
  end
end