class Fluent::Plugin::Buffer

def add_metadata(metadata)
  log.on_trace { log.trace "adding metadata", instance: self.object_id, metadata: metadata }
  synchronize do
    if i = @metadata_list.index(metadata)
      @metadata_list[i]
    else
      @metadata_list << metadata
      add_timekey(metadata)
      metadata
    end
  end
end

def add_timekey(metadata)
  if t = metadata.timekey
    @timekeys[t] += 1
  end
  nil
end

def chunk_size_full?(chunk)
  chunk.bytesize >= @chunk_limit_size * @chunk_full_threshold || (@chunk_limit_records && chunk.size >= @chunk_limit_records * @chunk_full_threshold)
end

def chunk_size_over?(chunk)
  chunk.bytesize > @chunk_limit_size || (@chunk_limit_records && chunk.size > @chunk_limit_records)
end

def clear_queue!
  log.on_trace { log.trace "clearing queue", instance: self.object_id }
  synchronize do
    until @queue.empty?
      begin
        q = @queue.shift
        log.trace("purging a chunk in queue"){ {id: dump_unique_id_hex(chunk.unique_id), bytesize: chunk.bytesize, size: chunk.size} }
        q.purge
      rescue => e
        log.error "unexpected error while clearing buffer queue", error_class: e.class, error: e
        log.error_backtrace
      end
    end
    @queue_size = 0
  end
end

def close
  super
  synchronize do
    log.debug "closing buffer", instance: self.object_id
    @dequeued.each_pair do |chunk_id, chunk|
      chunk.close
    end
    until @queue.empty?
      @queue.shift.close
    end
    @stage.each_pair do |metadata, chunk|
      chunk.close
    end
  end
end

def configure(conf)
  super
  unless @queue_limit_length.nil?
    @total_limit_size = @chunk_limit_size * @queue_limit_length
  end
end

def del_timekey(metadata)
  if t = metadata.timekey
    if @timekeys[t] <= 1
      @timekeys.delete(t)
    else
      @timekeys[t] -= 1
    end
  end
  nil
end

def dequeue_chunk
  return nil if @queue.empty?
  log.on_trace { log.trace "dequeueing a chunk", instance: self.object_id }
  synchronize do
    chunk = @queue.shift
    # this buffer is dequeued by other thread just before "synchronize" in this thread
    return nil unless chunk
    @dequeued[chunk.unique_id] = chunk
    @queued_num[chunk.metadata] -= 1 # BUG if nil, 0 or subzero
    @dequeued_num[chunk.metadata] ||= 0
    @dequeued_num[chunk.metadata] += 1
    log.trace "chunk dequeued", instance: self.object_id, metadata: chunk.metadata
    chunk
  end
end

def enqueue_all(force_enqueue = false)
  log.on_trace { log.trace "enqueueing all chunks in buffer", instance: self.object_id }
  if block_given?
    synchronize{ @stage.keys }.each do |metadata|
      return if !force_enqueue && queue_full?
      # NOTE: The following line might cause data race depending on Ruby implementations except CRuby
      # cf. https://github.com/fluent/fluentd/pull/1721#discussion_r146170251
      chunk = @stage[metadata]
      next unless chunk
      v = yield metadata, chunk
      enqueue_chunk(metadata) if v
    end
  else
    synchronize{ @stage.keys }.each do |metadata|
      return if !force_enqueue && queue_full?
      enqueue_chunk(metadata)
    end
  end
end

def enqueue_chunk(metadata)
  log.on_trace { log.trace "enqueueing chunk", instance: self.object_id, metadata: metadata }
  chunk = synchronize do
    @stage.delete(metadata)
  end
  return nil unless chunk
  chunk.synchronize do
    synchronize do
      if chunk.empty?
        chunk.close
      else
        @queue << chunk
        @queued_num[metadata] = @queued_num.fetch(metadata, 0) + 1
        chunk.enqueued!
      end
      bytesize = chunk.bytesize
      @stage_size -= bytesize
      @queue_size += bytesize
    end
  end
  nil
end

def enqueue_unstaged_chunk(chunk)
  log.on_trace { log.trace "enqueueing unstaged chunk", instance: self.object_id, metadata: chunk.metadata }
  synchronize do
    chunk.synchronize do
      metadata = chunk.metadata
      @queue << chunk
      @queued_num[metadata] = @queued_num.fetch(metadata, 0) + 1
      chunk.enqueued!
    end
    @queue_size += chunk.bytesize
  end
end

def generate_chunk(metadata)
  raise NotImplementedError, "Implement this method in child class"
end

def initialize
  super
  @chunk_limit_size = nil
  @total_limit_size = nil
  @queue_limit_length = nil
  @chunk_limit_records = nil
  @stage = {}    #=> Hash (metadata -> chunk) : not flushed yet
  @queue = []    #=> Array (chunks)           : already flushed (not written)
  @dequeued = {} #=> Hash (unique_id -> chunk): already written (not purged)
  @queued_num = {} # metadata => int (number of queued chunks)
  @dequeued_num = {} # metadata => int (number of dequeued chunks)
  @stage_size = @queue_size = 0
  @timekeys = Hash.new(0)
  @metadata_list = [] # keys of @stage
end

def metadata(timekey: nil, tag: nil, variables: nil)
  meta = new_metadata(timekey: timekey, tag: tag, variables: variables)
  add_metadata(meta)
end

def metadata_list
  synchronize do
    @metadata_list.dup
  end
end

def metadata_list_clear!
  synchronize do
    @metadata_list.clear
  end
end

def new_metadata(timekey: nil, tag: nil, variables: nil)
  Metadata.new(timekey, tag, variables)
end

def persistent?
  false
end

def purge_chunk(chunk_id)
  synchronize do
    chunk = @dequeued.delete(chunk_id)
    return nil unless chunk # purged by other threads
    metadata = chunk.metadata
    log.on_trace { log.trace "purging a chunk", instance: self.object_id, chunk_id: dump_unique_id_hex(chunk_id), metadata: metadata }
    begin
      bytesize = chunk.bytesize
      chunk.purge
      @queue_size -= bytesize
    rescue => e
      log.error "failed to purge buffer chunk", chunk_id: dump_unique_id_hex(chunk_id), error_class: e.class, error: e
      log.error_backtrace
    end
    @dequeued_num[chunk.metadata] -= 1
    if metadata && !@stage[metadata] && (!@queued_num[metadata] || @queued_num[metadata] < 1) && @dequeued_num[metadata].zero?
      @metadata_list.delete(metadata)
      @queued_num.delete(metadata)
      @dequeued_num.delete(metadata)
      del_timekey(metadata)
    end
    log.trace "chunk purged", instance: self.object_id, chunk_id: dump_unique_id_hex(chunk_id), metadata: metadata
  end
  nil
end

def queue_full?
  synchronize { @queue.size } >= @queued_chunks_limit_size
end

def queued?(metadata=nil)
  synchronize do
    if metadata
      n = @queued_num[metadata]
      n && n.nonzero?
    else
      !@queue.empty?
    end
  end
end

def queued_records
  synchronize { @queue.reduce(0){|r, chunk| r + chunk.size } }
end

def resume
  # return {}, []
  raise NotImplementedError, "Implement this method in child class"
end

def start
  super
  @stage, @queue = resume
  @stage.each_pair do |metadata, chunk|
    @metadata_list << metadata unless @metadata_list.include?(metadata)
    @stage_size += chunk.bytesize
    add_timekey(metadata)
  end
  @queue.each do |chunk|
    @metadata_list << chunk.metadata unless @metadata_list.include?(chunk.metadata)
    @queued_num[chunk.metadata] ||= 0
    @queued_num[chunk.metadata] += 1
    @queue_size += chunk.bytesize
    add_timekey(chunk.metadata)
  end
  log.debug "buffer started", instance: self.object_id, stage_size: @stage_size, queue_size: @queue_size
end

def statistics
  buffer_space = 1.0 - ((@stage_size + @queue_size * 1.0) / @total_limit_size).round
  stats = {
    'stage_length' => @stage.size,
    'stage_byte_size' => @stage_size,
    'queue_length' => @queue.size,
    'queue_byte_size' => @queue_size,
    'available_buffer_space_ratios' => buffer_space * 100,
    'total_queued_size' => @stage_size + @queue_size,
  }
  if (m = timekeys.min)
    stats['oldest_timekey'] = m
  end
  if (m = timekeys.max)
    stats['newest_timekey'] = m
  end
  { 'buffer' => stats }
end

def storable?
  @total_limit_size > @stage_size + @queue_size
end

def takeback_chunk(chunk_id)
  log.on_trace { log.trace "taking back a chunk", instance: self.object_id, chunk_id: dump_unique_id_hex(chunk_id) }
  synchronize do
    chunk = @dequeued.delete(chunk_id)
    return false unless chunk # already purged by other thread
    @queue.unshift(chunk)
    log.trace "chunk taken back", instance: self.object_id, chunk_id: dump_unique_id_hex(chunk_id), metadata: chunk.metadata
    @queued_num[chunk.metadata] += 1 # BUG if nil
    @dequeued_num[chunk.metadata] -= 1
  end
  true
end

def terminate
  super
  @dequeued = @stage = @queue = @queued_num = @metadata_list = nil
  @stage_size = @queue_size = 0
  @timekeys.clear
end

def timekeys
  @timekeys.keys
end

def write(metadata_and_data, format: nil, size: nil, enqueue: false)
  return if metadata_and_data.size < 1
  raise BufferOverflowError, "buffer space has too many data" unless storable?
  log.on_trace { log.trace "writing events into buffer", instance: self.object_id, metadata_size: metadata_and_data.size }
  staged_bytesize = 0
  operated_chunks = []
  unstaged_chunks = {} # metadata => [chunk, chunk, ...]
  chunks_to_enqueue = []
  begin
    # sort metadata to get lock of chunks in same order with other threads
    metadata_and_data.keys.sort.each do |metadata|
      data = metadata_and_data[metadata]
      write_once(metadata, data, format: format, size: size) do |chunk, adding_bytesize|
        chunk.mon_enter # add lock to prevent to be committed/rollbacked from other threads
        operated_chunks << chunk
        if chunk.staged?
          staged_bytesize += adding_bytesize
        elsif chunk.unstaged?
          unstaged_chunks[metadata] ||= []
          unstaged_chunks[metadata] << chunk
        end
      end
    end
    return if operated_chunks.empty?
    # Now, this thread acquires many locks of chunks... getting buffer-global lock causes dead lock.
    # Any operations needs buffer-global lock (including enqueueing) should be done after releasing locks.
    first_chunk = operated_chunks.shift
    # Following commits for other chunks also can finish successfully if the first commit operation
    # finishes without any exceptions.
    # In most cases, #commit just requires very small disk spaces, so major failure reason are
    # permission errors, disk failures and other permanent(fatal) errors.
    begin
      first_chunk.commit
      if enqueue || first_chunk.unstaged? || chunk_size_full?(first_chunk)
        chunks_to_enqueue << first_chunk
      end
      first_chunk.mon_exit
    rescue
      operated_chunks.unshift(first_chunk)
      raise
    end
    errors = []
    # Buffer plugin estimates there's no serious error cause: will commit for all chunks eigher way
    operated_chunks.each do |chunk|
      begin
        chunk.commit
        if enqueue || chunk.unstaged? || chunk_size_full?(chunk)
          chunks_to_enqueue << chunk
        end
        chunk.mon_exit
      rescue => e
        chunk.rollback
        chunk.mon_exit
        errors << e
      end
    end
    # All locks about chunks are released.
    synchronize do
      # At here, staged chunks may be enqueued by other threads.
      @stage_size += staged_bytesize
      chunks_to_enqueue.each do |c|
        if c.staged? && (enqueue || chunk_size_full?(c))
          m = c.metadata
          enqueue_chunk(m)
          if unstaged_chunks[m]
            u = unstaged_chunks[m].pop
            if u.unstaged? && !chunk_size_full?(u)
              @stage[m] = u.staged!
              @stage_size += u.bytesize
            end
          end
        elsif c.unstaged?
          enqueue_unstaged_chunk(c)
        else
          # previously staged chunk is already enqueued, closed or purged.
          # no problem.
        end
      end
    end
    operated_chunks.clear if errors.empty?
    if errors.size > 0
      log.warn "error occurs in committing chunks: only first one raised", errors: errors.map(&:class)
      raise errors.first
    end
  ensure
    operated_chunks.each do |chunk|
      chunk.rollback rescue nil # nothing possible to do for #rollback failure
      if chunk.unstaged?
        chunk.purge rescue nil # to prevent leakage of unstaged chunks
      end
      chunk.mon_exit rescue nil # this may raise ThreadError for chunks already committed
    end
  end
end

def write_once(metadata, data, format: nil, size: nil, &block)
  return if data.empty?
  stored = false
  adding_bytesize = nil
  chunk = synchronize { @stage[metadata] ||= generate_chunk(metadata).staged! }
  enqueue_chunk_before_retry = false
  chunk.synchronize do
    # retry this method if chunk is already queued (between getting chunk and entering critical section)
    raise ShouldRetry unless chunk.staged?
    empty_chunk = chunk.empty?
    original_bytesize = chunk.bytesize
    begin
      if format
        serialized = format.call(data)
        chunk.concat(serialized, size ? size.call : data.size)
      else
        chunk.append(data, compress: @compress)
      end
      adding_bytesize = chunk.bytesize - original_bytesize
      if chunk_size_over?(chunk)
        if format && empty_chunk
          log.warn "chunk bytes limit exceeds for an emitted event stream: #{adding_bytesize}bytes"
        end
        chunk.rollback
        if format && !empty_chunk
          # Event streams should be appended into a chunk at once
          # as far as possible, to improve performance of formatting.
          # Event stream may be a MessagePackEventStream. We don't want to split it into
          # 2 or more chunks (except for a case that the event stream is larger than chunk limit).
          enqueue_chunk_before_retry = true
          raise ShouldRetry
        end
      else
        stored = true
      end
    rescue
      chunk.rollback
      raise
    end
    if stored
      block.call(chunk, adding_bytesize)
    end
  end
  unless stored
    # try step-by-step appending if data can't be stored into existing a chunk in non-bulk mode
    #
    # 1/10 size of original event stream (splits_count == 10) seems enough small
    # to try emitting events into existing chunk.
    # it does not matter to split event stream into very small splits, because chunks have less
    # overhead to write data many times (even about file buffer chunks).
    write_step_by_step(metadata, data, format, 10, &block)
  end
rescue ShouldRetry
  enqueue_chunk(metadata) if enqueue_chunk_before_retry
  retry
end

def write_step_by_step(metadata, data, format, splits_count, &block)
  splits = []
  if splits_count > data.size
    splits_count = data.size
  end
  slice_size = if data.size % splits_count == 0
                 data.size / splits_count
               else
                 data.size / (splits_count - 1)
               end
  slice_origin = 0
  while slice_origin < data.size
    splits << data.slice(slice_origin, slice_size)
    slice_origin += slice_size
  end
  # This method will append events into the staged chunk at first.
  # Then, will generate chunks not staged (not queued) to append rest data.
  staged_chunk_used = false
  modified_chunks = []
  get_next_chunk = ->(){
    c = if staged_chunk_used
          # Staging new chunk here is bad idea:
          # Recovering whole state including newly staged chunks is much harder than current implementation.
          generate_chunk(metadata)
        else
          synchronize{ @stage[metadata] ||= generate_chunk(metadata).staged! }
        end
    modified_chunks << c
    c
  }
  writing_splits_index = 0
  enqueue_chunk_before_retry = false
  while writing_splits_index < splits.size
    chunk = get_next_chunk.call
    chunk.synchronize do
      raise ShouldRetry unless chunk.writable?
      staged_chunk_used = true if chunk.staged?
      original_bytesize = chunk.bytesize
      begin
        while writing_splits_index < splits.size
          split = splits[writing_splits_index]
          if format
            chunk.concat(format.call(split), split.size)
          else
            chunk.append(split, compress: @compress)
          end
          if chunk_size_over?(chunk) # split size is larger than difference between size_full? and size_over?
            chunk.rollback
            if split.size == 1 && original_bytesize == 0
              big_record_size = format ? format.call(split).bytesize : split.first.bytesize
              raise BufferChunkOverflowError, "a #{big_record_size}bytes record is larger than buffer chunk limit size"
            end
            if chunk_size_full?(chunk) || split.size == 1
              enqueue_chunk_before_retry = true
            else
              splits_count *= 10
            end
            raise ShouldRetry
          end
          writing_splits_index += 1
          if chunk_size_full?(chunk)
            break
          end
        end
      rescue
        chunk.purge if chunk.unstaged? # unstaged chunk will leak unless purge it
        raise
      end
      block.call(chunk, chunk.bytesize - original_bytesize)
    end
  end
rescue ShouldRetry
  modified_chunks.each do |mc|
    mc.rollback rescue nil
    if mc.unstaged?
      mc.purge rescue nil
    end
  end
  enqueue_chunk(metadata) if enqueue_chunk_before_retry
  retry
end