package spark

import org.slf4j.Logger
import org.slf4j.LoggerFactory

/**
 * Utility trait for classes that want to log data. Creates a SLF4J logger
 * for the class and allows logging messages at different levels using
 * methods that only evaluate parameters lazily if the log level is enabled.
 */
trait Logging {
  // Make the log field transient so that objects with Logging can
  // be serialized and used on another machine
  @transient private var log_ : Logger = null

  // Method to get or create the logger for this object
  def log: Logger = {
    if (log_ == null) {
      var className = this.getClass().getName()
      // Ignore trailing $'s in the class names for Scala objects
      if (className.endsWith("$"))
        className = className.substring(0, className.length - 1)
      log_ = LoggerFactory.getLogger(className)
    }
    return log_
  }

  // Log methods that take only a String
  def logInfo(msg: => String) = if (log.isInfoEnabled) log.info(msg)

  def logDebug(msg: => String) = if (log.isDebugEnabled) log.debug(msg)

  def logWarning(msg: => String) = if (log.isWarnEnabled) log.warn(msg)

  def logError(msg: => String) = if (log.isErrorEnabled) log.error(msg)

  // Log methods that take Throwables (Exceptions/Errors) too
  def logInfo(msg: => String, throwable: Throwable) =
    if (log.isInfoEnabled) log.info(msg)

  def logDebug(msg: => String, throwable: Throwable) =
    if (log.isDebugEnabled) log.debug(msg)

  def logWarning(msg: => String, throwable: Throwable) =
    if (log.isWarnEnabled) log.warn(msg, throwable)

  def logError(msg: => String, throwable: Throwable) =
    if (log.isErrorEnabled) log.error(msg, throwable)
}