# Base logger
#
#   Abstract base class for loggers
#
#   Implements common behavior such as log level, default text formatter etc
#
#   Note: Do not create instances of this class directly
#
module SemanticLogger
  class Base
    # Class name to be logged
    attr_accessor :name, :filter

    # Set the logging level for this logger
    #
    # Note: This level is only for this particular instance. It does not override
    #   the log level in any logging instance or the default log level
    #   SemanticLogger.default_level
    #
    # Must be one of the values in SemanticLogger::LEVELS, or
    # nil if this logger instance should use the global default log_level
    def level=(level)
      @level_index = SemanticLogger.level_to_index(level)
      @level = level
    end

    # Returns the current log level if set, otherwise it returns the global
    # default log level
    def level
      @level || SemanticLogger.default_level
    end

    # Implement the log level calls
    #   logger.debug(message, hash|exception=nil, &block)
    #
    # Implement the log level query
    #   logger.debug?
    #
    # Parameters:
    #   message
    #     [String] text message to be logged
    #     Should always be supplied unless the result of the supplied block returns
    #     a string in which case it will become the logged message
    #     Default: nil
    #
    #   payload
    #     [Hash|Exception] Optional hash payload or an exception to be logged
    #     Default: nil
    #
    #   exception
    #     [Exception] Optional exception to be logged
    #     Allows both an exception and a payload to be logged
    #     Default: nil
    #
    # Examples:
    #    require 'semantic_logger'
    #
    #    # Enable trace level logging
    #    SemanticLogger.default_level = :info
    #
    #    # Log to screen
    #    SemanticLogger.add_appender(STDOUT)
    #
    #    # And log to a file at the same time
    #    SemanticLogger.add_appender('application.log')
    #
    #    logger = SemanticLogger['MyApplication']
    #    logger.debug("Only display this if log level is set to Debug or lower")
    #
    #    # Log semantic information along with a text message
    #    logger.info("Request received", :user => "joe", :duration => 100)
    #
    #    # Log an exception in a semantic way
    #    logger.info("Parsing received XML", exc)
    #
    SemanticLogger::LEVELS.each_with_index do |level, index|
      class_eval <<-EOT, __FILE__, __LINE__ + 1
        def #{level}(message=nil, payload=nil, exception=nil, &block)
          if level_index <= #{index}
            log_internal(:#{level}, #{index}, message, payload, exception, &block)
            true
          else
            false
          end
        end

        def #{level}?
          level_index <= #{index}
        end

        def benchmark_#{level}(message, params = {}, &block)
          if level_index <= #{index}
            benchmark_internal(:#{level}, #{index}, message, params, &block)
          else
            block.call(params) if block
          end
        end
      EOT
    end

    # Dynamically supply the log level with every benchmark call
    def benchmark(level, message, params = {}, &block)
      index = SemanticLogger.level_to_index(level)
      if level_index <= index
        benchmark_internal(level, index, message, params, &block)
      else
        block.call(params) if block
      end
    end

    # Add the supplied tags to the list of tags to log for this thread whilst
    # the supplied block is active
    # Returns nil if no tags are currently set
    #   To support: ActiveSupport::TaggedLogging V3 and above
    def tagged(*tags)
      push_tags(*tags)
      yield
    ensure
      pop_tags(tags.size)
    end

    # Previous method for supplying tags
    alias_method :with_tags, :tagged

    # Returns a copy of the [Array] of [String] tags currently active for this thread
    # Returns nil if no tags are set
    def tags
      # Since tags are stored on a per thread basis this list is thread-safe
      t = Thread.current[:semantic_logger_tags]
      t.nil? ? [] : t.clone
    end

    # Add tags to the current scope
    def push_tags *tags
      # Need to flatten and reject empties to support calls from Rails 4
      new_tags = tags.flatten.collect(&:to_s).reject(&:empty?)
      t = Thread.current[:semantic_logger_tags]
      Thread.current[:semantic_logger_tags] = t.nil? ? new_tags : t.concat(new_tags)
    end

    # Remove specified number of tags from the current tag list
    def pop_tags(quantity=1)
      t = Thread.current[:semantic_logger_tags]
      t.pop(quantity) unless t.nil?
    end

    # Thread specific context information to be logged with every log entry
    #
    # Add a payload to all log calls on This Thread within the supplied block
    #
    #   logger.with_payload(:tracking_number=>12345) do
    #     logger.debug('Hello World')
    #   end
    #
    # If a log call already includes a pyload, this payload will be merged with
    # the supplied payload, with the supplied payload taking precedence
    #
    #   logger.with_payload(:tracking_number=>12345) do
    #     logger.debug('Hello World', :result => 'blah')
    #   end
    def with_payload(payload)
      current_payload = self.payload
      Thread.current[:semantic_logger_payload] = current_payload ? current_payload.merge(payload) : payload
      yield
    ensure
      Thread.current[:semantic_logger_payload] = current_payload
    end

    # Returns [Hash] payload to be added to every log entry in the current scope
    # on this thread.
    # Returns nil if no payload is currently set
    def payload
      Thread.current[:semantic_logger_payload]
    end

    # Semantic Logging does not support :unknown level since these
    # are not understood by the majority of the logging providers
    # Map it to :error
    alias :unknown :error
    alias :unknown? :error?

    # DEPRECATED See SemanticLogger.default_level=
    def self.default_level=(level)
      warn "[DEPRECATION] `SemanticLogger::Logger.default_level=` is deprecated.  Please use `SemanticLogger.default_level=` instead."
      SemanticLogger.default_level = level
    end

    # DEPRECATED See SemanticLogger.default_level
    def self.default_level
      warn "[DEPRECATION] `SemanticLogger::Logger.default_level` is deprecated.  Please use `SemanticLogger.default_level` instead."
      SemanticLogger.default_level
    end

    ############################################################################
    protected

    # Initializer for Abstract Class SemanticLogger::Base
    #
    # Parameters
    #  klass [String]
    #   Name of the class, module, or other identifier for which the log messages
    #   are being logged
    #
    #  level [Symbol]
    #    Only allow log entries of this level or higher to be written to this appender
    #    For example if set to :warn, this appender would only log :warn and :fatal
    #    log messages when other appenders could be logging :info and lower
    #
    #  filter [Regexp|Proc]
    #    RegExp: Only include log messages where the class name matches the supplied
    #    regular expression. All other messages will be ignored
    #    Proc: Only include log messages where the supplied Proc returns true
    #          The Proc must return true or false
    def initialize(klass, level=nil, filter=nil)
      # Support filtering all messages to this logger using a Regular Expression
      # or Proc
      raise ":filter must be a Regexp or Proc" unless filter.nil? || filter.is_a?(Regexp) || filter.is_a?(Proc)

      @filter    = filter.is_a?(Regexp) ? filter.freeze : filter
      @name      = klass.is_a?(String) ? klass : klass.name
      self.level = level unless level.nil?
    end

    # Write log data to underlying data storage
    def log(log_)
      raise NotImplementedError.new("Logging Appender must implement #log(log)")
    end

    # Return the level index for fast comparisons
    # Returns the global default level index if the level has not been explicitly
    # set for this instance
    def level_index
      @level_index || SemanticLogger.default_level_index
    end

    # Struct Log
    #
    # level
    #   Log level of the supplied log call
    #   :trace, :debug, :info, :warn, :error, :fatal
    #
    # thread_name
    #   Name of the thread in which the logging call was called
    #
    # name
    #   Class name supplied to the logging instance
    #
    # message
    #   Text message to be logged
    #
    # payload
    #   Optional Hash or Ruby Exception object to be logged
    #
    # time
    #   The time at which the log entry was created
    #
    # duration
    #   The time taken to complete a benchmark call
    #
    # tags
    #   Any tags active on the thread when the log call was made
    #
    # level_index
    #   Internal index of the log level
    #
    # metric [Object]
    #   Object supplied when benchmark_x was called
    Log = Struct.new(:level, :thread_name, :name, :message, :payload, :time, :duration, :tags, :level_index, :exception, :metric)

    # Whether to log the supplied message based on the current filter if any
    def include_message?(struct)
      return true if @filter.nil?

      if @filter.is_a?(Regexp)
        (@filter =~ struct.name) != nil
      elsif @filter.is_a?(Proc)
        @filter.call(struct) == true
      end
    end

    # Log message at the specified level
    def log_internal(level, index, message=nil, payload=nil, exception=nil, &block)
      if exception.nil? && payload && payload.is_a?(Exception)
        exception = payload
        payload = nil
      end

      if block && (result = block.call)
        if result.is_a?(String)
          message = message.nil? ? result : "#{message} -- #{result}"
        elsif payload && payload.respond_to?(:merge)
          payload.merge(result)
        else
          payload = result
        end
      end

      # Add scoped payload
      if self.payload
        payload = payload.nil? ? self.payload : self.payload.merge(payload)
      end
      struct = Log.new(level, Thread.current.name, name, message, payload, Time.now, nil, tags, index, exception)
      log(struct) if include_message?(struct)
    end

    # Measure the supplied block and log the message
    def benchmark_internal(level, index, message, params, &block)
      start     = Time.now
      begin
        rc = block.call(params) if block
        exception = params[:exception]
        rc
      rescue Exception => exc
        exception = exc
      ensure
        end_time = Time.now
        # Extract options after block completes so that block can modify any of the options
        log_exception = params[:log_exception] || :partial
        min_duration  = params[:min_duration] || 0.0
        payload       = params[:payload]
        metric        = params[:metric]
        duration      = if block_given?
          1000.0 * (end_time - start)
        else
          params[:duration] || raise("Mandatory block missing when :duration option is not supplied")
        end

        # Add scoped payload
        if self.payload
          payload = payload.nil? ? self.payload : self.payload.merge(payload)
        end
        if exception
          case log_exception
          when :full
            struct = Log.new(level, Thread.current.name, name, message, payload, end_time, duration, tags, index, exception, metric)
            log(struct) if include_message?(struct)
          when :partial
            struct = Log.new(level, Thread.current.name, name, "#{message} -- Exception: #{exception.class}: #{exception.message}", payload, end_time, duration, tags, index, nil, metric)
            log(struct) if include_message?(struct)
          end
          raise exception
        elsif duration >= min_duration
          # Only log if the block took longer than 'min_duration' to complete
          struct = Log.new(level, Thread.current.name, name, message, payload, end_time, duration, tags, index, nil, metric)
          log(struct) if include_message?(struct)
        end
      end
    end

  end
end